washington alfalfa seed - the ir-4 projectir4.rutgers.edu/fooduse/perfdata/1949.pdf · orthene...

Progress Reportand Proposal for the

WASHINGTONAlfalfa Seed

COMMISSION

Presented October 25, 2006by

Doug Walsh, Washington State UniversityRick Boydston, USDA Agricultural Research Service

George Vandemark, USDA Agricultural Research ServiceSally O’Neal Coates, Washington State University

WASHINGTON

Alfalfa SeedCOMMISSION

Progress Reports

Arthropod Management ......................1

Disease Management ...........................8

Weed Management ............................ 11

Proposals

Arthropod Management ....................15

Pollinator Protection .........................17

Weed Management ............................19

Report 1 • Arthropod Management

early spring in three separate Washington State geographic locations. Plots were established in or near the towns of Prosser, Othello, and Touchet. At each location, treatments were replicated 4 times in a complete random block design.

We applied insecticides at the times growers would apply them: at pre-bloom, at bloom, and after the bloom period of the alfalfa. Treatments were applied using a CO2-powered backpack sprayer equipped with a four-nozzle boom, using 25 gallons of water per acre as a carrier. Following treatments, we used sweep nets to sample Lygus abundance, making five 180° sweeps per plot.

Arthropod Pest Management on Alfalfa SeedProgress Report for 2005 and 2006

PI: Douglas Walsh, Associate Entomologist WSU ProsserCooperators: Holly Ferguson, Extension IPM Coordinator/Specialist

Timothy Waters, Extension Educator, Benton & Franklin CountiesJohn Kugler, Extension Educator, Grant & Adams CountiesRick Boydston, Research Agronomist, USDA-ARS, Prosser

George Vandemark, Geneticist, USDA-ARS, ProsserSally O’Neal Coates, Extension IPM Specialist, WSU Tri-Cities

Activities Detailed in This Report1. Lygus Insecticide Efficacy Trials 20052. Lygus Insecticide Efficacy Trials 20063. Lygus Pyrethroid Resistance Studies 20054. Lygus Migratory Patterns 20065. Miticide Efficacy Trials 20056. Miticide Efficacy Trials 20067. Leafcutting Bee Pesticide Safety 2006

1. Lygus Insecticide Efficacy Trials 2005In 2005, we screened a number of

insecticides for their ability to control Lygus nymphs in alfalfa seed fields (Table 1). To begin, we established 18-foot-by-20-foot field plots in

Table 1: Insecticides Tested for Efficacy Against Lygus on Alfalfa Grown for Seed In Washington State

Trade Name Chemical Formulation Manufacturer

Rimon novaluron 0.83 EC Chemtura

Assail acetamiprid 70 WP Cerexagri, Inc.

Provado imidacloprid 1.6 F Bayer Crop Science

Actara thiamethoxam 25 WDG Syngenta Crop Protection, Inc.

Calypso thiocloprid 4 SC Bayer Crop Science

Orthene acephate 75 S Valent Agricultural Products

Lorsban chlorpyrophos 4 E Dow AgroSciences LLC

Dimethoate dimethoate 4 EC Helena Chemical Company

Avaunt indoxicarb 30% WDG DuPont Ag.

Capture bifenthrin 2 EC FMC Corporation

Warrior lambda-cyhalothrin 1 lb./ gallon Syngenta Crop Protection, Inc.

MSR Spray Concentrate

oxydemeton methyl methoxylchlor

2 lbs./ gallon Gowan Co.

MSR + Captureoxydemeton methyl

methoxylchlor bifenthrin2 lbs./gallon + 2 EC Gowan Co./ FMC Corporation

HGW86 proprietary 10% SC DuPont Ag.

HGW86 proprietary 20% SC DuPont Ag.

Dibrom naled 8 E Helena Chemical Company

Dipel 2xBacillus thuringiensis

subsp. Kurkstaki6.4% WP Valent Agricultural Products

Lannate methomyl 90% SP DuPont Ag

1

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Report 1 • Arthropod Management • continued

During the pre-bloom period, we applied more treatments to the Prosser plots than we applied to the Touchet and Othello plots. At the Prosser location, the Orthene, Lorsban, Dimethoate, Capture, and Warrior treatments provided significantly better Lygus control than did the untreated check. At the Othello location, Rimon, Orthene, Lorsban, Avaunt, Capture, and Dibrom treatments provided significantly better Lygus control than did the untreated check. At the Othello location, Dibrom was substituted for the Warrior treatment at the Prosser location. Pre-bloom treatment results are summarized in Table 2.

A variety of circumstances unrelated to our experimental protocols rendered the Touchet plots unacceptable for data analysis, therefore results for those plots were not taken or calculated for the pre-bloom period.

During the bloom period of the alfalfa maturity, we applied identical treatments in all three locations. A summary of results is shown in Table 3. At the Prosser and Touchet locations, none of the treatments applied provided significantly better control than the untreated check. At the Othello location, Assail was the only treatment that controlled Lygus nymphs significantly better than the untreated check. At all three loctions, the

Table 3: 2005 Bloom Treatments

Product RateMean Lygus/5 Sweeps ± Std. Error

Prosser Touchet Othello

Rimon 0.83 EC 12 oz./A 3.1 ± 0.9 1.8 ± 0.6 2.8 ± 1.5

Assail 70 WP 0.05 lb/A 4.6 ± 1.6 2.5 ± 1.3 2.0 ± 1.1*

Calypso 4 SC 4.0 oz./A 2.6 ± 0.8 5.5 ± 1.5 5.5 ± 1.3

Beauvaria bassiana 1e13 (conidia) 3.4 ± 0.9 6.0 ± 1.1 4.9 ± 0.7

HGW86 10% SC 4.8 fl oz/A 6.7 ± 2.2 4.0 ± 0.4 7.8 ± 1.5

HGW86 10% SC 10.3 fl oz/A 7.8 ± 1.7 1.5 ± 0.5 12.0 ± 4.0

HGW86 10% SC 20.6 fl oz/A 1.5 ± 0.4 1.3 ± 0.1 4.8 ± 2.9

HGW86 20% SC 10.3 fl oz/A 5.3 ± 1.5 2.3 ± 0.8 8.0 ± 1.6

Dibrom 8 E 1 pint/A 3.8 ± 1.1 2.3 ± 1.1 4.3 ± 1.5

Dipel 2x 6.4% WP 8 lb/A 5.4 ± 1.8 3.5 ± 1.2 6.0 ± 1.0

Untreated check 2.5 ± 0.4 3.5 ± 1.3 7.8 ± 3.0

* Asterisk indicates treatment exhibiting control that was better, by a statistically significant margin, than the untreated check.

Table 2: 2005 Pre-bloom Treatments

Product Rate

Mean Lygus/5 Sweeps ± Std. Error

Prosser Othello

Rimon 0.83 EC 12 oz./A 4.0 ± 0.7 1.4 ± 0.4*

Assail 70 WP 0.05 lb/A 5.0 ± 1.5 ---------

Provado 1.6 F 3.8 oz./A 3.5 ± 0.9 3.3 ± 0.8

Actara 25 WDG 4.0 oz./A 2.0 ± 0.6 ----------

Calypso 4 SC 4.0 oz./A 4.8 ± 1.4 ----------

Orthene 75 S 1.33 lb. ai/A 0.4 ± 0.1* 0.4 ± 0.2*

Lorsban 4 E 2 pt/A 0.3 ± 0.2* 0.1 ± 0.1*

Dimethoate 4 EC 1 pt/A 1.2 ± 0.4* ----------

Avaunt 30% WDG 3.5 oz./A 4.1 ± 0.9 0.9 ± 0.6*

Capture 2 EC 6 oz./A 0.1 ± 0.1* 0.1 ± 0.1*

Warrior 1lb./gal. 3.84 oz/A 0.7 ± 0.3* ----------

MSR spray con-centrate, 2 lbs/gal.

2 pints/A 2.4 ± 0.8 ----------

MSR + Capture 2 pt + 6 oz/A 7.5 ± 1.3 ----------

HGW86 10% SC 4.8 fl oz/A 4.9 ± 0.9 ----------

HGW86 10% SC 10.3 fl oz/A 3.8 ± 0.8 2.4 ± 1.1

HGW86 10% SC 20.6 fl oz/A 6.4 ± 1.7 ----------

HGW86 20% 10.3 fl oz/A 5.5 ± 1.4 ----------

Dibrom 8 E 1 pint/A ---------- 1.5 ± 0.5*

Untreated check 4.5 ± 1.1 4.0 ± 1.2

* Asterisks indicate treatments exhibiting control that was better, by a statistically significant margin, than the untreated check.

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HGW86 10% applied at the high rate tended to provide the next best level of control of Lygus nymphs, but the results were never statistically significant.

Due to time and harvest constraints, post-bloom alfalfa maturity applications were only made at the Prosser location. In this case, all products tested with the exception of the HGW86 10% at the moderate rate provided significantly better control of Lygus nymphs than the untreated check. These results are summarized in Table 4.

2. Lygus Insecticide Efficacy Trials 2006

We continued screening insecticides in 2006, again using 18-foot-by-20-foot plots established in Prosser, Othello, and Touchet fields. Treatments were replicated 4 times in a complete random block design.

The pre-bloom insecticide treatments were applied on June 1, 2006, and the bloom treatments were applied on July 3, 2006. Applications were made using a CO2-powered backpack sprayer equipped with a four-nozzle boom, using 25 gallons of water per acre as a carrier. Following treatments, we used sweep nets to sample Lygus abundance, making five 180° sweeps per plot.

All of the treatments provided effective control of Lygus nymphs pre-bloom when examined one week after treatment at the Othello location. Nymph populations crashed the following week. Adult populations were not suppressed by pre-bloom treatments at the Othello location. Othello site results for the pre-bloom period are summarized in Table 5.

Table 4: 2005 Post-bloom Treatments

Product RateMean Lygus/5

Sweeps ± Std. Error

Prosser

Rimon 0.83 EC 12 oz./A 1.9 ± 0.8*

HGW86 10% SC 4.8 fl oz/A 6.6 ± 4.2*

HGW86 10% SC 10.3 fl oz/A 7.3 ± 1.7

HGW86 10% SC 20.6 fl oz/A 3.8 ± 0.9*

HGW86 20% 10.3 fl oz/A 2.5 ± 0.9*

Orthene 75 S 1.33 lb. ai/A 1.1 ± 0.5*

Capture 2 EC 6 oz./A 1.1 ± 0.6*

Warrior 2 EC 1lb./gal. 3.84 oz/A 2.5 ± 1.2*

Lannate 90% SP 2 pints/A 3.6 ± 2.4*

Dibrom 8 E 1 pint/A 1.4 ± 0.7*

Lorsban 4 E 2 pt/A 1.6 ± 0.6*

Dimethoate 4 EC 1 pt/A 2.3 ± 1.1*

Untreated check 14.0 ± 7.3

Table 5: 2006 Pre-bloom Treatments, Othello

ProductProductper acre


Adults Nymphs8 June

Assail 70 WP 1.1 oz 10.25±3.15 2.25±0.48

Baythroid 2.8 oz prod 7.25±2.06 1.50±1.19

Belief 3.0 oz prod 13.50±1.32 4.75±2.25

Capture 2 EC 6.4 oz./A 5.00±2.12 0.25±0.25

Dimethoate 4 EC 1 pt/A 13.00±1.96 2.75±0.63

Rimon 0.83 EC 12 oz./A 11.50±1.19 2.00±0.70

Untreated check 14.25±3.33 21.75±6.93

Venom 3.0 oz 9.75±1.11 2.50±0.50

15 JuneAssail 70 WP 1.1 oz 16.25±1.55 0.50±0.29


Belief 3.0 oz prod 15.75±2.48 0.50±0.29

Capture 2 EC 6.4 oz./A 8.75±1.80 0


Rimon 0.83 EC 12 oz./A 9.50±2.53 0.25±0.25

Untreated check 11.25±2.10 0

Venom 3.0 oz 14.75±3.25 0

22 JuneAssail 70 WP 1.1 oz 6.50±2.40 0

Baythroid 2.8 oz prod 8.50±2.40 0

Belief 3.0 oz prod 9.75±2.30 0.25±0.25

Capture 2 EC 6.4 oz./A 10.75±1.80 0

Dimethoate 4 EC 1 pt/A 10.00±1.80 0

Rimon 0.83 EC 12 oz./A 10.75±2.87 0

Untreated check 10.75±2.39 0.25±0.25

Venom 3.0 oz 8.00±1.78 0.50±0.29

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At the Prosser location, the pre-bloom treatment results were inconsistent at the Prosser location. Nymph populations were low following treatment, but adult populations remained consistent at an average of about 2 to 3 adults per sweep sample, as outlined in Table 6.

The bloom treatments (Table 7, below) were very effective at the Prosser site and relatively effective at the Othello site.

We again experienced problems with the Touchet plots that were beyond our control and unrelated to our experimental protocols, rendering those plots unacceptable for data analysis.

Table 6: 2006 Pre-bloom Treatments, Prosser

ProductProductper acre


Adults Nymphs

5 JuneAssail 70 WP 1.1 oz 4.00±1.68 7.50±0.87


Belief 3.0 oz prod 2.75±0.95 3.25±1.88

Capture 2 EC 6.4 oz./A 1.00±0.70 0.25±0.25


Rimon 0.83 EC 12 oz./A 4.75±1.18 6.00±1.58

Untreated check 3.25±1.37 8.25±1.62

Venom 3.0 oz 2.25±1.44 4.75±1.37

9 JuneAssail 70 WP 1.1 oz 1.25±0.63 0.50±0.29


Belief 3.0 oz prod 2.50±0.29 1.00±0.41

Capture 2 EC 6.4 oz./A 2.50±0.64 0


Rimon 0.83 EC 12 oz./A 1.50±0.64 0.25±0.25

Untreated check 2.50±0.64 1.00±0.70

Venom 3.0 oz 2.75±0.63 0.75±0.48

19 JuneAssail 70 WP 1.1 oz 2.50±1.26 0.25±0.25


Belief 3.0 oz prod 1.75±0.85 0.50±0.50

Capture 2 EC 6.4 oz./A 2.75±1.11 0.25±0.25


Rimon 0.83 EC 12 oz./A 3.50±0.96 1.00±0.41

Untreated check 6.75±0.85 0

Venom 3.0 oz 3.00±1.78 2.75±1.80

Table 7: 2006 Blooom Treatments

ProductProduct per acre

Othello ProsserAdults Nymphs Adults Nymphs

13 JulyAssail 70 WP 1.1 oz 8.00±3.00* 9.00±3.03 1.25±0.63 0.25±0.25

Belief 3.0 oz prod 9.50±1.50 5.00±2.20 4.50±1.19 0.75±0.75

Dibrom 1 pint/A 25.75±6.62 13.00±4.06 6.25±0.95 1.00±0.57

Rimon 0.83 EC 12 oz./A 8.25±2.39 6.00±0.91 4.50±0.65 0.25±0.25

Untreated check 26.25±2.53 11.25±3.06 15.50±4.29 5.00±4.36

20 JulyAssail 70 WP 1.1 oz 13.00±6.63 9.00±3.03 3.50±1.71 0.50±0.50

Belief 3.0 oz prod 8.0±02.45 4.25±1.93 3.50±1.19 1.00±0.71

Dibrom 1 pint/A 23.50±6.85 13.00±4.06 6.75±3.20 3.50±1.32

Rimon 0.83 EC 12 oz./A 9.75±2.39 8.25±2.72 5.50±1.26 2.75±1.25

Untreated check 34.00±6.12 13.50±5.20 16.25± 4.03 11.00±4.30

* Mean Lygus/5 Sweeps ± Std. Error

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Figure


3. Lygus Pyrethroid Resistance Studies 2005

Dr. Bill Brindley from Utah State University documented in 1990 that Lygus populations quickly developed tolerance to bifenthrin if the population was exposed to bifenthrin several times during the course of a season. This is shown graphically in Figure 1 in that the dose response of Lygus populations to bifenthrin in Washington was elevated compared to populations in Utah or Oregon. Bifenthrin (Capture) had been registered in Washington State under a 24C and had been used extensively in the previous year, 1989. The populations in Utah and Oregon had no history of exposure to bifenthrin.

Subsequently, bifenthrin use expanded in alfalfa-seed growing areas throughout the early 1990s. After several years of overuse, localized Lygus populations developed resistance and treatment failures ensued.

Washington State alfalfa seed growers began expressing concern about this issue and trying to use the product more judiciously. Figure 2, showing dose-response results for four Lygus populations in 2005 demonstrates that the growers have indeed been using bifenthrin more judiciously in recent years.

To acquire this data, we mimicked Dr. Brindley’s baggie bioassay technique and exposed populations of Lygus from WSU IAREC, Touchet, WSU Othello, and Warden to bifenthin. Lygus adults were field captured and placed into plastic ziplock baggies with several concentrations of bifenthrin. Lygus were held at 70º F in our portable growth chamber (see photo) for 8 hours after placement in the baggies. We assessed mortality at 8 hours by the Lygus failing to respond to tactile stimulation with coordinated movement. Mortality data was log transformed and is presented graphically in Figure 2. Our data demonstrates that the dose response of Lygus populations to bifenthrin in 2005 were similar to when the product first came on the market in 1989. The judicious use of bifenthrin over the past several years has helped preserve the effectiveness of this product.

Figure 1: Comparison of Lygus/Bifenthrin Contact Bioassays in Washington to Those of Oregon and Utah in 1990 (Simko OSU, Mayer WSU, Brindley USU)

Figure 2: Dose Response of Lygus Populations in South-Central

Washington to Bifenthrin June 2005

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6. Miticide Efficacy Studies 2006We established research plots of the same

size and general location as the previous year to evaluate acaracides against spider mite. Treatment took place on July 28, 2006. This year, we added spiromesifen at two different application rates. We sampled leaves for pest presence 11 days after treatment on August 8, 2006. All of the treatments suppressed mite populations compared to the untreated control, but the non-registered products Acramite, Oberon, Fujimite, and Zeal provided the most effective control, as shown in Table 9.

Table 9: July 2006 Miticide Trials in Alfalfa Seed

Product lb ai/A Mites*Abamectin/Agrimek+oil† 0.019 10.000

Bifenazate/Acramite 4SC‡ 0.75 2.500

Bifenazate/Acramite 50WS‡ 0.50 3.250

Bifenthrin/Capture 2EC 0.100 10.000

Etoxazole/Zeal 0.135 2.500

Fenpyroximate/Fujimite 0.15 2.250

Hexathiozox/Onager 1E+oil† 0.125 11.750

JMS Stylet Oil 2% sol. 10.000

Methidathion/Supracide 2E 3 pt/A 10.500

Propargite/Comite 1.00 7.000

Spiromesifen/Oberon 0.187 4.000

Spiromesifen/Oberon 0.25 1.500

Untreated Control -- 25.500

* Mean number of mites per 10 leaflets ± std. error. † Added oil at 0.5% v/v solution. ‡ Added Ad-Wet to solution at label rate.

4. Lygus Migration StudiesEighteen windowpane flight traps were placed in three draws

from the valley floor adjacent to alfalfa seed fields near Gardena up into the foothills to determine if Lygus adults were migrating down into the valley from the foothills. No migration of Lygus adults was documented in weekly surveys either up or down the draws between April and August 2006. Windowpane flight traps were also placed on the valley floor to monitor the movement of Lygus adults among fields from April through August. Lygus adults were detected moving between fields in mid-April and then throughout the rest of the growing season. Higher trap counts corresponded to dates that forage alfalfa fields in the vicinity were being cut. We conclude that the Lygus populations that infest alfalfa seed fields in the Gardena area are resident populations that overwinter on the Valley floor and do not migrate in from the adjacent dry foothills.

5. Miticide Efficacy Studies 2005We set up 6-foot-by-15-foot research

plots in an alfalfa seed field at WSU Prosser to test candidate acaricides for their ability to suppress pest spider mites. We sprayed on July 14, 2005 and conducted pest surveys fourteen days later, selecting 10 leaflets at random from each plot and quantifying mites under a dissecting microscope. All of the treatments suppressed mite populations compared to the untreated control. Bifenthrin, hexthiozox, and stylet oil were the least effective treatments in this trial. Table 8 shows treatments utilized and abbreviated results.

Table 8: July 2005 Miticide Trials in Alfalfa Seed

Product lb ai/A Mites*Abamectin/Agrimek+oil† 0.019 4.500

Bifenazate/Acramite 4SC‡ 0.75 2.500

Bifenazate/Acramite 50WS‡ 0.50 2.250

Bifenthrin/Capture 2EC 0.100 11.000

Etoxazole/Zeal 0.135 3.750

Fenpyroximate/Fujimite 0.15 0.750

Hexathiozox/Onager 1E+oil† 0.125 12.500

JMS Stylet Oil 2% sol. 12.500

Methidathion/Supracide 2E 3 pt/A 4.500

Propargite/Comite 1.00 2.500

Untreated Control -- 24.750

* Mean number of mites per 10 leaflets ± std. error. † Added oil at 0.5% v/v solution. ‡ Added Ad-Wet to solution at label rate.

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Report 1 • Arthropod Management • conclusion

7. Leafcutting Bee Pesticide Safety Trials 2006Because of the economic importance of the alkali bee,

Nomia melanderi, and the alfalfa leafcutting bee, Megachile rotundata, to our state’s alfalfa seed industry, it is imperative that we know whether the crop protection compounds we might use are toxic to these pollinators. Washington State University’s Dr. Dan Mayer was one of very few entomologists who conducted safety studies on these Pacific Northwest pollinators. Dr. Mayer’s retirement in 2000 created a subsequent information gap

Products in our 2006 trials were tested at the maximum label rate for registered products or at the maximum rate the registrants suggested for the use of their product for insect or mite control on alfalfa seed. They were applied with a R&D CO2-pressurized sprayer at a rate of 26 gallons per acre using a hand-held boom applied to 0.01-acre plots of first- or second-growth alfalfa. Field-weathered residual test exposures were replicated 4 times with 4 foliage samples per treatment and time interval. Samples consisting of about 400 cm of foliage were taken from the upper 15 cm portions of plants, clipped to 1-inch lengths, and placed into 15-cm Petri dishes with tops and bottoms separated by a wire screen (6.7 meshes/cm) insert (45 cm long and 5 cm wide).

Alfalfa leafcutting bees were collected and chilled at 35 degrees F. to facilitate handling. Residual test exposures were replicated 4 times by caging 20 LB with each of four foliage samples per treatment and time intervals. Bees in cages were fed syrup 91:1 ratio) in a wad of cotton (5 x 5 cm), and the bees held at 75 degrees F. for 24 hour mortality counts.

Dr. Mayer concluded that materials or rates of materials that cause less than 25% mortality with 2-hour residues can probably be applied during early morning with little or no hazard to bees and those that cause less than 25% mortality with 8-hour residues can probably be applied during late evening with little or no hazard to bees.

as new miticides, insecticides, fungicides, and herbicides came down the pipeline for registration. In 2005, we developed a protocol to conduct pollinator safety bioassays and resume this important work.

In 2006, we screened a series of insecticides and miticides for their toxicity to alfalfa seed pollinators. Part of this information is shown in Table 10. The data we gathered and analyzed in 2006 will be used to pursue 24C registrations for spiromesifen and or fenpyroximate for mite control and acetamiprid for Lygus and aphid control and to alter a contingency 24C for novaluron to include bloom sprays for Lygus control.

Table 10: Mortalities of alfalfa leafcutting bee (LB) exposed to

different age residues of pesticides applied to 0.01 acre plots of alfalfa. Prosser, WA. 2006. Percent mortality

after 24 hours of exposure

TreatmentAge of Residues

2 h 8 h

bifenazate/ Acramite 4SC 11.25 16.25

thiamethoxam/ Actara 5.00 2.50

abamectin/ Agrimek w/oil 15.00 6.25

acetimiprid/ Assail 70 WP 1.25 5.00

flonicamid/ Beleaf 2.50 7.50

thiacloprid/ Calypso 12.50 5.00

bifenthrin/ Capture 2EC 93.75 77.50

propargite/ Comite 25.00 11.25

naled/ Dibrom 22.50 15.00

fenpyroximate/ Fujimite 27.50 13.75

HGW 86 10% SC 22.50 16.25

spiromesifen/ Oberon 1.19 16.25

imidacloprid/ Pravado 8.75 2.38

novaluron/ Rimon 3.75 3.75

etoxazole/ Zeal 4.70 4.25

Untreated Control 2.38 3.46

Leafcutter bee (Megachile sp.)

Photo by David Cappaert,

http://www.insectimages.org.

7

Report 2 • Disease Management

8

Disease Management on Alfalfa SeedProgress Report for 2006

PI: George J. Vandemark, Research GeneticistUSDA Vegetable and Forage Crops Research Unit, Prosser, WA 99350

Cooperators: Douglas Walsh, Associate Entomologist WSU ProsserRick Boydston, Research Agronomist, USDA-ARS, Prosser

Introduction

The primary interaction between plants and soil involves the relationship between the plant and the microorganisms present in the soil. These include detrimental soilborne plant pathogens such as Sclerotinia spp., Fusarium spp., and Verticillium spp. as well as beneficial soilborne microroganisms such as Bacillus spp. Pseudomonas spp. that confer advantages to plants by producing compounds promoting plant growth or suppressing the growth of fungi that cause plant disease. These plant-microbe interactions are especially important to perennial crops such as alfalfa, which often suffer from disease complexes due to infection of the plant over time by multiple organisms. Besides causing plant death, these disease complexes result in premature stand decline and reduced yields. Other soilborne diseases, such as alfalfa wilt caused by Verticillium albo-atrum, are transmitted via seed. Seed-transmitted diseases can adversely impact the marketability of alfalfa seed for export markets.

In this report we describe research we conducted to survey, identify, and quantify soilborne fungi as well as research to determine the effects of several field treatments on both the incidence of soilborne diseases and soil populations of beneficial microorganisms. These treatments (freezing, tilling, mowing, and pesticide application) are considered to be candidate alternatives to field burning for the management of alfalfa seed fields.

Objectives

1. Survey and identify plant pathogenic soilborne fungi present in the research plot.

2. Quantify soilborne microbes such as Bacillus spp., Pseudomonas spp., and actinomycetes (filamentous bacteria) that are associated with suppression of soilborne diseases caused by fungi.

Methods

Alternatives to burning: 7 treatmentsIn cooperation with weed scientist Rick

Boydston and entomologist Doug Walsh,plots were established in a grower-cooperator’s alfalfa

Figure 3

Examples of disease-causing fungi and bacteria isolated from alfalfa plants.

Report 2 • Disease Management • continued9

seed field in Touchet, Washington. We then initiated a series of post-harvest (dormant season) treatments that might be considered alternatives to burning. The treatments were as follows:

1. leaving stubble and heating with steam2. leaving stubble and flash freezing, which

was accomplished by a combination of nitrogen gas (N2) and/or dry ice (solid carbon dioxide/CO2)

3. removing stubble via mowing4. burying stubble via tilling5. leaving stubble and applying pesticide

and, in order to make relevant comparisons, two additional plots:

6. leaving field stubble and not burning (control)

7. burning stubble Burning, freezing, mowing, tilling, and

pesticide application took place on February 14, 2006. The steam treatment was performed on March 15, 2006, as the steaming equipment was unavailable at the earlier date.

Isolation of fungi from plant tissueWe removed a single plant from each

of the seven aforementioned plots. We rinsed each plant sample, scrubbed it, and disinfected its surface with a 10% bleach solution for one minute followed by two sterile water rinses. We then plated samples of tissues representing the various parts of the plant on a variety of media. Crown, taproot, fine root, and crown bud tissue was plated onto acidified potato dextrose agar. The use of this general media would likely reveal Fusarium spp., Sclerotinia spp., Rhizoctonia solani and some oomycete fungi if present. Stem and petiole sections were plated on 1.5% water agar to detect the presence of Verticillium spp. Additionally, cornmeal agar amended with antifungal and antibiotic compounds (pimaricin, vancomycin, benomyl and PCNB) was used to preferentially isolate Phytophthora and Pythuim spp. using crown tissue, fine roots, lateral roots, and taproot/fine root junction.

Soil baiting for fungi and sieving for sclerotia

Six-inch-by-six-inch by one-inch deep soil samples were also collected from each plot for soil sieving and baiting. Entire soil samples were wet sieved through 2-mm and 0.84-mm sieves to separate sclerotia of Sclerotinia spp. For soil baiting, 4 g of sampled soil was added to approximately 25 ml of sterile water containing 3 to 5 sterilized cracked cucumber seeds. This general isolation method is useful in recovering oomycete fungi as well as chytrid fungi from soil.

Quantifying soil bacteriaFinally, we collected

a single soil core sample at a depth of 12 inches

from each plot. The soil was homogenized and serial dilutions were made in ddH

2O. Serial

dilutions (50 μl) were plated on Pseudomonas-selective media and incubated for 3 days at 28oC to detect Pseudomonas spp. To detect Bacillus spp. and actinomycetes, we heated soil samples for 10 minutes in a water bath 85oC. Serial dilutions were plated on LB agar and incubated for 3 days at 28oC.

Results

Soilborne plant pathogens implicated in the crown rot complex of alfalfa were present at some frequency in the plants we sampled from each of the treatments. Cortical-rotting Fusarium spp. (F. oxysporum and F. solani, primarily) were absent in the burning and stubble removal treatments but were identified at 25% frequencies in all other treatments (Figure 3, page 8). Serratia marcescens, a bacterium often associated with the crown rot complex, was present in samples of steaming,

Figure 4

“Baiting” soil with cucumber seeds

to detect soilborne fungi.

10Report 2 • Disease Management • conclusion

burning, and stubble removal treatments as well as in the control plot (Figure 3, page 8). The soil baiting technique illustrated in Figure 4 recovered Pythium spp. in steaming, insecticide/herbicide, stubble removal and control plots. Phytophthora spp. were identified in flash freezing and pesticide plots. Soil sieving did not reveal the presence of sclerotia of Sclerotinia sclerotiorum although visual assessment of the field indicated its presence. S. sclerotiorum was not observed in the stem blight phase in the field and could not be isolated from plant material. Verticillium albo-atrum, the causal agent of Verticillium wilt, was not detected in any of the plants sampled.

Additional fungi were recovered from plant tissue and soil that are may be incidental, but their presence is nonetheless interesting. Zygomycete fungi (likely Rhizopus and Mucor spp.) were isolated from tissue in all treatments except the pesticide treatment plots. Chytrid fungi were isolated from soil baiting in the steaming burning, pesticide, and stubble removal treatments and while these fungi are rarely pathogenic on alfalfa, they are often implicated as hyperparasites of other fungi, particularly oomycetes such as Phytophthora and Pythium. Gliocladium, Trichoderma, Penicillium, Fusarium and Alternaria species were identified from plant tissue isolations in all treatments. The presence of these “incidental” common fungi is typical although they have in some cases been reported to be hyperparasites of other plant pathogenic fungi.

No significant differences were observed among treatments for the number of beneficial Pseudomonas spp. and Bacillus spp. detected in soil samples (Figure 5, Table 1). Despite the lack of significant differences, a trend

was observed in that the highest number of both types of bacteria were observed in the control plots, while the lowest numbers were observed in the burning and stubble removal treatments. Within a plot, populations of Bacillus spp. tended to be much higher than populations of Pseudomonas. In two plots subjected to burning and in a single plot subjected to stubble removal, no Pseudomonas spp. could be detected. These results suggest that additional controlled experiments should be conducted to unambiguously determine if these two treatments suppress growth of beneficial microorganisms that have been implicated in the control of plant diseases.

Table 11: Means comparison* for Bacillus spp. and Pseudomonas spp. in different treatments

Treatment Pseudomonas (colonies/gm soil)

Bacillus (colonies/gm soil)

Control 71,500 A 987,500 A

Tillage 62,000 A 726,667 A

Flash-freeze 36,500 A 882,500 A

Insecticide/herbicide 29,500 A 937,500 A

Steaming 24,000 A 940,000 A

Stubble removal 14,500 A 722,500 A

Burning 16,500 A 772,500 A

†LSD (a = 0.05) 68,703 388,270

*Means calculated based on the results of four replicated plots for each treatment.†LSD = Least Significant Difference

Figure 5

Isolation of beneficial microorganisms from soil.

11

Report 3 • Weed Management

Weed Management in Alfalfa SeedProgress Report for 2005 and 2006

PIs: Rick Boydston, USDA-ARS, and Ray Baker, WSU ProsserCooperators: Douglas Walsh, WSU Prosser, and George Vandemark, USDA-ARS

Activities detailed in this report:1. Small Pot Study on Prickly Lettuce2. Field Trial on Prickly Lettuce3. Effect of Stubble Removal Alternatives on

Prickly Lettuce Seed Germination Three trials were initiated on weed control

in alfalfa seed production. The first two trials involved prickly lettuce control and/or alfalfa tolerance with several herbicide treatments. The third trial investigated the effects of various stubble treatments on prickly lettuce seed viability.

Karmex + Gramaxone

Sencor + Gramaxone

Gramaxone

Nontreated

Sinbar + Gramaxone

Chateau + Gramaxone

Nontreated Karmex + Gramaxone

Sinbar + Gramaxone Sencor + Gramaxone

Chateau + Gramaxone Gramaxone

Above: Prickly lettuce 6 days after treatment.Below: Prickly lettuce 2 weeks after treatment.

1. Small Pot Study on Prickly Lettuce Control

Flumioxazin (Chateau) at 0.09 and 0.188 lb ai/a, diuron (Karmex) at 1 and 2 lb ai/a, terbacil (Sinbar) at 0.5 and 1 lb ai/a, metribuzin (Sencor) at 0.38 and 0.75 lb ai/a, and norflurazon (Zorial or Solicam) at 1 and 1.5 lb ai/a were tested at two application timings for prickly lettuce control. Prickly lettuce seed was planted October 5, 2005 in pots placed outdoors.

Preemergence treatments were applied October 6, 2005 and early postemergence (1 inch prickly lettuce) treatments were applied November 16, 2005. All postemergence applications at the 1 inch stage of prickly lettuce included paraquat (Gramoxone) at 0.5 lb ai/a and nonionic surfactant. All herbicide treatments totally controlled prickly lettuce and pots were reseeded to determine if any residual herbicide activity remained in the soil to control a later flush of prickly lettuce. In early May, all treatments were still controlling prickly lettuce well and the trial was ended. Among the postemergence treatments, the paraquat alone and flumioxazin plus paraquat killed the prickly lettuce seedlings the quickest.

Karmex, Sinbar, Sencor, and Solicam are all labeled for use in alfalfa seed production and controlled prickly lettuce well at these early stages of application in late fall. Chateau also controlled prickly lettuce well and is being considered for labeling in alfalfa seed production.

12Report 3 • Weed Management • continued

2. Field Trial on Prickly Lettuce Control

A prickly lettuce trial was initiated on a sprinkler-irrigated alfalfa seed field belonging to a grower-cooperator near Touchet, Wash-ington, on November 21, 2005. Fall herbicide applications were compared to spring herbi-cide applications that followed field burning on February 14, 2006. Prickly lettuce was 1inch diameter with 1 to 2 leaves at the time of the first herbicide applications in Novem-ber. Treatments included paraquat (Gramox-one) plus flumioxazin (Chateau) at two rates, paraquat plus diuron (Karmex), paraquat plus norflurazon (Zorial) and a nontreated check. In mid-December, the paraquat plus flumioxazin treatments and the paraquat plus norflurazon treatment were controlling the target weed 97 to 99%, whereas the paraquat plus diuron treatment was controlling prickly lettuce 90%.

The entire field was burned on February 14, 2006. Emerged prickly lettuce seedlings were only partially suppressed by the burning treatment. Spring herbicide treatments were applied March 1, 2006. Very little alfalfa injury was noted in March, April, and June from all herbicide treatments tested (Table 12). Prickly lettuce control from all fall-applied herbicide treatments was 99 to 100%. Control from all

spring-applied herbicide treatments was 99 to 100% except with norflurazon, which controlled prickly lettuce 94%.

Karmex and Solicam, both labeled for use in alfalfa seed production, controlled prickly let-tuce well applied in fall or spring. Chateau also controlled prickly lettuce well, did not injure alfalfa appreciably, and is being considered for labeling in alfalfa seed production. Fall treat-ments of all the herbicide treatments had less prickly lettuce escapes than spring applications. Field burning had limited effect on prickly let-tuce seedlings that had already emerged.

Table 12: Prickly lettuce control in alfalfa seed production following seven herbicide treatments near Touchet, WA

Herbicide Treatment

Rate(lb ai/a)

Prickly LettuceDensity 2/7/06

(no./ft2)

PricklyLettuce Control4/24/06

(%)

PricklyLettuce Control6/21/06

(%)

WesternSalsify6/21/06

(no/plot)

Alfalfa Injury6/24/06

(%)

Nov. 21 Application

Chateau + Gramoxone 0.125 + 0.5 0 b 99 a 100 a 0 b 1.8 a

Chateau + Gramoxone 0.25 + 0.5 0 b 99 a 100 a 0 b 2.0 a

Karmex + Gramoxone 1.5 + 0.5 0 b 99 a 100 a 0.5 a

Solicam + Gramoxone 1.5 + 0.5 0 b 100 a 99 a 0.5 b 3.0 a

Mar. 1 Application

Chateau + Gramoxone 0.125 + 0.5 13 a 98 ab 99 a 1.8 b 3.8 a

Karmex + Gramoxone 1.5 + 0.5 17 a 99 a 99 a 4.0 b 2.5 a

Solicam + Gramoxone 1.5 + 0.5 12 a 94 b 94 b 5.0 b 0 a

Nontreated check 13 a 0 0 26.3 a 0

Field burned Feb. 14, 2006. Means followed by the same letter within columns are not significantly different according to Fischer’s Least Significant Difference test at the 5% level.

Report 3 • Weed Management • continued13

3. Effect Of Stubble Removal Alternatives on Prickly Lettuce Seed Germination

Our research team conducted a third trial to investigate the effects of various stubble treatments on prickly lettuce seed viability. Prickly lettuce seed was placed in 4 x 4 in. stainless steel wire mesh packets and buried in field plots at two depths (1/8 inch and ½ inch). Each packet contained 100 seeds. A variety of traditional and non-traditional stubble treatments were then employed.Treatments included;

1. leaving field stubble in place (untreated control)

2. burning stubble3. leaving stubble and steaming4. leaving stubble and flash freezing

with CO2

5. leaving stubble and placing dry ice (solid CO

2) on surface

6. mowing stubble7. tilling stubble with rototiller8. leaving stubble and applying

insecticide

Treatments were replicated 4 times in a randomized complete block. Treatments 2 and 4-8 were performed on Feb. 14, 2006. Treatment 3 was performed on March 15, 2006, as the steaming equipment was unavailable at the earlier date.

Prickly lettuce seed packets were retrieved from plots after each stubble treatment and seed was germinated in the laboratory at 23 C in Petri dishes begin-ning on March 20, 2006. Germination of prickly lettuce seed in control plots, mowed, tilled, and insecticide treated plots averaged about 90%. Burning alfal-fa stubble nearly eliminated prickly let-tuce seed germination when seed packets were placed at the shallow depth of 0.125 inches. However, seed buried 0.5 inches was somewhat protected and germina-tion was decreased to 68%. Steam heat

Burning

Freezing

Mowing

Tilling

14Report 3 • Weed Management • conclusion

treatment reduced prickly lettuce germination to 80% and 73% for shallow and deep placed seed, respectively. The partial reduction in germina-tion with the steam treatment could possibly be due to the delayed timing of the seed packet placement in the field inducing a portion of the prickly lettuce into dormancy. Dry ice treatment and CO

2 flash treatments on shallow placed seed

slightly reduced prickly lettuce seed germination to 78% and 86%, respectively. Effect of treat-ments is summarized graphically in Figure 6.

Alfalfa spring growth was similar among all treatments except the tilled plots, which re-duced height by about 40% in late April. The grower applied a blanket herbicide application to the entire trial in early spring and no differences in weeds control among these burn alternatives

were observed throughout the summer. Field burning provided the greatest reduc-

tion in prickly lettuce germination. Prickly let-tuce seed is released in late summer and fall and germinates throughout fall and spring periods. Prickly lettuce is small seeded and does not germinate from deeper depths, so the shallow burial treatment is the likely the most relevant to alfalfa seed producers. Although burning had a positive effect reducing prickly lettuce seed ger-mination, burning had little effect on emerged seedlings in the previously discussed field trial. Field burning likely plays a positive role in reducing prickly lettuce seed viability, but use of effective herbicides probably has more total impact on prickly lettuce populations in alfalfa seed production.

Above Left: Thriving alfalfa seed field, April 24, 2006. Above Right: Tilled plots suffered a loss in height.

Figure 6

Effect of stubble removal treatments on prickly lettuce seed germination.

15

Proposal 1 • Arthropod Management

Background

Lygus bugs, Lygus hesperus Knight (Heteroptera: Miridae), are a native hemipteran (true bug) and are the key pest for alfalfa seed producers in the western United States. Lygus have piercing sucking mouthparts that damage alfalfa seed pods and meristems. Lygus prefer young, developing tissue. They damage alfalfa seed pods and meristems in several ways: direct mechanical destruction of growing tissues by the insect’s mouthparts, chemical destruction of cells by injecting salivary enzymes into plant tissues as they feed, promotion of growth in surrounding tissues by plant-growth-promoting substances in the bug’s saliva, disfigurement of seed pods, and outright blasting of individual seeds within a pod.

Lygus overwinter as adults in plants and plant debris, becoming active as temperatures warm in spring. They mate soon after emerging and females begin laying eggs several days hence. Growers’ decisions on timing and methodology of Lygus control are dictated by the alfalfa plants’ physiological response and bloom cycle in addition to pollinator safety concerns.

Our research team conducted focused on Lygus and spider mites in alfalfa seed in 2006.

Integrated Pest Management for Lygus and Aphid Control on Alfalfa SeedProposal for 2007

PI: Douglas Walsh, Associate Entomologist WSU ProsserCooperators: John Kugler, WSU Extension Agent, Grant County

Holly Ferguson, Extension IPM Specialist, WSU ProsserTim Waters, WSU Extension Agent, Franklin County

Ron Wight, Field Research Director, WSU ProsserSally O’Neal Coates, Extension IPM Specialist, WSU Tri-Cities

Adult Lygus hesperus. Photo by Jack Kelly Clark, UC Statewide IPM Project.

Our work on spider mites was successful to the extent we can say that this pest will be mitigated in alfalfa seed pending the registrations of spiromesifin and or fenpyroximate. Progress was also made against Lygus. As a result of our work in 2006, novaluron (Rimon EC) was registered as a post-bloom Lygus control compound. The pollinator safety data and efficacy data we generated for spiromesifen (Oberon, 1st choice) and fenpyroximate (Fujimite, 2nd choice) will be used to support 24C registrations that will be requested prior to the 2007 growing season.

This year, we hope to turn our attention toward the most damaging aphid species, in addition to continuing our work on Lygus.

Several aphid species are documented pests of alfalfa seed, including blue alfalfa aphid (Acyrthosiphon kondoi), pea aphid (A. pisum), and spotted alfalfa aphid (Therioaphis maculata). However it is infestations of spotted alfalfa aphid that are of the greatest concern for seed producers. The spotted alfalfa aphid is a small, pale yellow or grayish aphid with four to six rows of spined black spots on its back. Mature females may either be wingless or have wings with smoky areas along the veins. This aphid prefers warm weather and is generally found during summer months. Historically it was a pest of the southwest but in recent years it

16Proposal 1 • Arthropod Management • conclusion

has become problematic farther north including here in Washington, particularly in years following mild winter conditions.

Spotted alfalfa aphids inject a toxin into the plant as they feed. Severe aphid infestations stunt plants, reduce yield, and even kill plants. These aphids also secrete large quantities of honeydew, which makes the plants very sticky and encourages the grown of a black fungus, even at relatively low aphid population densities.

All 13,000 acres of alfalfa grown for seed are impacted by Lygus. While aphid infestations vary from year to year, on average, about 25% of the state’s alfalfa seed acreage is impacted to a level justifying insecticide treatment. Alfalfa seed growers in Washington must find a way to cost-effectively and sustainably mitigate the damage caused by Lygus and aphids. Since synthetic pyrethroid insecticides are relatively inexpensive, it is an economic imperative to come up with alternatives that are also relatively inexpensive.

Proposed Project

Objective 1: Develop the necessary data to register acetamiprid for bloom applications and screen other candidate compounds for prebloom and post bloom treatments.

We will establish insecticide efficacy trials at three locations (WSU Othello, WSU Prosser, and Touchet) where registered and candidate insecticides will be applied: 1) at pre-bloom, 2) during bloom, and 3) after bloom. Registered compounds tested will include several synthetic pyrethroids and the organophosphate naled. Candidate compounds will include several neonicotinyls, several biologicals, and at least one proprietary numbered compound. Data will be collected on pest efficacy, beneficial and pollinator survivorship, changes in pest populations, and seed set. We will analyze the data by Analysis of Variance (ANOVA), and compared it to untreated controls. Means will be separated between treatment and controls by pairwise t-tests.

Objective 2: Establish a spotted alfalfa aphid colony for bioassay studies.

Aphid adults from this colony will be dipped in test solutions as per the Food and Agriculture Organization protocol (1974) to determine baseline susceptibility and contact activity of acetamiprid, imidacloprid, thiamethoxam, and dinotefuran. Aphid mortality will be corrected against untreated controls. Data will be log transformed and plotted for comparative purposes.

Objective 3: Evaluate insecticide efficacy and the impact of aphid infestation on alfalfa seed yields.

This objective will be conducted opportunistically as we become aware of infestations during the growing season of 2007. Statistical analysis will follow the protocol detailed in Objective 1.

Objective 4. Register acetamiprid for Lygus and aphid control on alfalfa grown for seed.

In addition to pursuing this registration using the data we obtain in Objective 1, we will simultaneously continue moving forward in pursuit of the registration of spiromesifen (Oberon) for use in alfalfa seed fields as an alternative to propargite, using data we collected in 2006.

Budget

Salaries ............................................ $12,117Partial support for IPM Extension Coordinator/ Research Supervisor, Technicians, Communications Specialist

Temporary/Hourly Workers ...............1,800

Benefits ...............................................4,510

Travel .....................................................8011,800 miles @ $0.445/mile

Goods & Services ...................................772Lab supplies and incidentals above and beyond the $2,000 crop protection tools provided by Ceraxagri

Total Request from WASC ......... $20,000

17

Proposal 2 • Pollinator Protection

Background

Pollination is essential for the production of specialty seed crops including alfalfa seed. Most extant pollinator safety studies have been directed toward honeybees, but the honeybee, Apis mellifera, is not an effective pollinator for alfalfa seed in Washington State. The two major pollinators of alfalfa seed in the Northwest are the alkali bee, Nomia melanderi, and the alfalfa leafcutting bee, Megachile rotundata. Washington State University’s Dr. Dan Mayer was one of very few entomologists who conducted safety studies on Pacific Northwest pollinators exclusive of honeybees. Dr. Mayer compiled an extensive list of pesticides that directly characterized the relative safety and or danger of pesticides to leafcutting bees and alkali bees as well as honeybees. This list is online at http://www.beesource.com/pov/traynor/table5. However, pollinator safety studies stalled in Washington State following Dr. Mayer’s retirement in 2000, creating an information gap detrimental to pollinator protection in alfalfa seed.

Insufficient populations of the correct insect pollinator or a reduction in pollinator fitness can result in decreased seed set and grower economic returns. While it is difficult to quantify the precise dollar impact of accidental bee kills, the USDA Regional IPM Centers’ Pest Management Strategic Plan for Western U.S. Alfalfa and Clover Seed Production (http://www.ipmcenters.org/pmsp/pdf/WestAlfalfaCloverSeed.pdf ) estimates that pollinator management represents 20 to 30% of the per-acre costs of alfalfa seed production. It is clear that pollinator safety during bloom is critical and the potential economic impact of accidental bee kills is significant.

Ensuring Pollinator Safety on Alfalfa SeedProposal for 2007

PI: Douglas Walsh, Associate Entomologist WSU ProsserCooperators: Rick Boydston, USDA-ARS, WSU ProsserJohn Kugler, WSU Extension Educator, Grant County

Holly Ferguson, Extension IPM Specialist, WSU ProsserTim Waters, Extension Educator, Franklin County

Sally O’Neal Coates, Extension IPM Specialist, WSU Tri-Cities

It is with this background that our research team embarked on the pollinator protection research described in part on page 7 of this document. We first began investigating pollinator safety in the summer of 2005. Using advice from Washington State Department of Agriculture’s Erik Johansen and the results of a literature search, we developed a protocol to conduct pollinator safety bioassays. In 2006 we screened a series of 14 insecticides and miticides and this data will be used to pursue 24C registrations for spiromesifen and or fenpyroximate for mite control and acetamiprid for Lygus and aphid control and to alter a contingency 24C for novaluron to include bloom sprays for Lygus control.

Proposed Project

The primary objective of this project is to build upon the work we conducted in 2006 to evaluate candidate pest control compounds on alfalfa seed for their relative safety with respect to the primary pollinators, alkali and leafcutter bees. We will do this through a combination of laboratory bioassays and field trials.

Compounds to Be Tested in 2007

fenpyroximate (Fujimite) fluazifop-P (Fusilade)

bifenazate (Acramite) sethoxydim (Poast)

etoxazole (Zeal) clethodim (Select)

oil (Orchex) quizalofop (Assure)

quinoxyfen (Quintec) imazamox (Raptor)

boscalid (Endura) imazethapyr (Pursuit)

fluazinam (Omega) 2,4-DB (Buterac)

Other candidate compounds may be added upon request of the funding entities.

18Proposal 2 • Pollinator Protection • conclusion

Laboratory BioassaysFor our laboratory bioassays, we will

collect treated (and untreated control) samples of alfalfa grown for seed and place them along with specimen bees of the target species into assay cages. After 24 hours, we will calculate percent mortality and subject the results to Analysis of Variance (ANOVA). For compounds that pass the F-test, means will be compared to the untreated controls in pairwise t-tests to determine if statistically significant mortality has resulted from exposure to the compound.

Our assay cages will consist of a plastic Petri dish (15 cm diameter) in which the tops and bottoms are separated by a wire screen (6.7 mesh/cm) that is 45 cm long and 5 cm wide stapled at the ends to form a rigid cage wall.

We will establish 0.01-acre treatment plots in first- or second-year alfalfa fields and replicate each treatment four times. Technicians will apply the various subject pesticides with a CO

2 pressurized sprayer and hand-held 4-nozzle

boom at a standard maximum field rate with 26 gallons of water carrier per acre. We will then take samples of foliage from the treated and non-treated plots at intervals of 2 and 8 hours after application. Samples consisting of about 400 cm3 of foliage will be taken from the upper 15 cm of plants, clipped to 2.5 cm lengths, and placed into each assay cage.

The alkali bee nests in the ground in natural or artificial sites, while the leafcutting bee spends its life above ground in artificial nests and shelters. The two species will be collected from their respective nesting sites then chilled at 35° F to facilitate handling. Twenty-five leafcutting bees or twenty alkali bees will

be placed in each assay cage containing either treated or non-treated alfalfa. The bees will be provided a cotton square that is soaked in a 10% sucrose solution to provide nourishment and held at 75° F for 24-hour mortality counts.

Field Trials on Brood DevelopmentBioassays that determine adult mortality

do not quantify the effect of pesticides on bee larvae. Many of the new soft chemistries employed for pest control can impact larval growth and development. When candidate compounds are targeted for registration in a 1- to 5-year timeframe, grower cooperators will be given enough pesticide product to treat 2.5 acres at peak bloom. Subsequent seed set will be observed and quantified by the grower cooperator and bee boards will be collected at the end of bloom. Larval growth and development will then be observed and measured and the data compared to that of larvae from untreated fields. Candidate compounds that will be tested in 2007 include in these demonstration plots include novaluron, acetamiprid, flonicamid, and spiromesifen. We will use the results of our studies to update the bee safety website and concurrently make that data available to Washington State Alfalfa seed producers. We will also disseminate the results of studies at regional winter short courses and at summer-season field days.

Budget

Salaries ..............................................$5,265Partial support for IPM Extension Coordinator/ Research Supervisor, Technicians, Communications Specialist

Temporary/Hourly Workers ...............1,600

Benefits ...............................................2,048

Travel .....................................................1781,800 miles @ $0.445/mile

Goods & Services ...................................909Lab supplies and incidentals above and beyond the $3,000 crop protection tools provided by Ceraxagri and Bayer

Total Request from WASC ......... $10,000Information will be shared at field days.

19

Proposal 3 • Weed Management

Background

The lack of multiple cuttings and wider row spacing used in alfalfa grown for seed production increase the opportunity for weeds to establish and compete with alfalfa, thereby increasing the need for weed control options. Uncontrolled weeds compete with alfalfa for water, light, and nutrients, lowering the seed yield. Weeds present at seed harvest also contaminate the seed and can increase harvest and seed cleaning costs.

Currently, prickly lettuce (Lactuca serriola), catchweed bedstraw (Galium aparine), and nightshades (Solanum spp.) have been identified as difficult to manage in some alfalfa seed fields. Typically, imazamox (Raptor) herbicide is applied in the fall after planting in August. Raptor misses prickly lettuce but normally controls fall germinated bedstraw if under 3 inches. Bedstraw behaves as both a winter annual germinating in the fall and a summer annual germinating in the spring. The later spring germinating bedstraw germinates after fall-applied imazamox has likely dissipated. Alternatively, catchweed bedstraw resistance to imazamox may be developing.

It is difficult to quantify the total impact of weeds and their control on the productivity and profitability of an alfalfa seed crop, but it is clear that nutrients, water, and light utilized by weeds have negative impacts on the crop. Growers also incur additional costs for seed cleaning (to remove weed contaminants from harvested seed) and the presence of heavy stands of weeds can reduce harvest efficiencies. It is probably not an overstatement to say that weeds and their cost of control can impact some growers’ profitability by 15% or more.

Herbicide Trials in Alfalfa Grown for SeedProposal for 2007

PIs: Rick Boydston, USDA-ARS, and Ray Baker, WSU ProsserCooperator: Douglas Walsh, WSU Prosser

Observations

Alfalfa seed growers must find a way to cost-effectively control these weeds or the problems will likely continue and increase. Our research team tested flumioxazin (Chateau) in

field and pot trials in 2006 and found it to be a promising tool when applied from late fall to early spring on established dormant alfalfa for prickly lettuce and nightshade control in alfalfa seed production. Tolerance of newly seeded alfalfa to flumioxazin applied during the dormant winter period is not known.

Currently, no herbicides with soil residual activity are labeled on newly planted alfalfa. Hexazinone (Velpar) is labeled in alfalfa

grown for hay and in alfalfa seed production in California and was recently allowed for use in alfalfa seed production in the Walla Walla region. Hexazinone applied to dormant alfalfa controls many annual weeds; it provides partial control of prickly lettuce and could be useful if labeled in other production areas.

Carfentrazone (Aim) and fluroxypyr (Starane) control catchweed bedstraw in a number of grass crops, but are not selective when applied to actively growing alfalfa. However, applying these herbicides to dormant alfalfa once bedstraw has germinated may provide selective control of bedstraw without injury to alfalfa. Imazamox (Raptor) normally controls small catchweed bedstraw seedlings,

Comparison between a control plot (above) and treated plot in 2006.

20Proposal 3 • Weed Management • conclusion

but it is unclear why growers are having difficulty controlling this weed (i.e., Is it a function of bedstraw germination time relative to time of herbicide application? Are herbicide resistant weeds a factor?)

Proposed Project We propose to conduct trials with

flumioxazin, hexazinone, carfentrazone, fluroxypyr, and imazamox for prickly lettuce, catchweed bedstraw, and nightshade control in alfalfa grown for seed. We will conduct both field and greenhouse trials.

Field Trial 1One proposed field trial will take place on

plots we will establish on a commercial field near Warden, Washington beginning February 2007. Plots will measure 7.5 to 10 feet wide by 35 feet long. Flumioxazin at 0.125 and 0.25 lb ai/a, hexazinone at 0.75 and 1.5 lb ai/a, carfentrazone at 0.016 and 0.032 lb ai/a, and fluroxypyr at 0.125 and 0.25 lb ai/a will be tested when applied to dormant alfalfa in early February. Each application will be replicated four times for a total of 36 plots including untreated controls. Flumioxazin and hexazinone treatments will include COC at 1% (v/v) and carfentrazone and fluroxypyr treatments will include NIS at 0.25% (v/v).

Field Trial 2The second field trial will be established

near Prosser, Washington and will evaluate the tolerance of newly seeded alfalfa to flumioxazin applied at 0.125 and 0.25 lb ai/a to dormant alfalfa in February. Flumioxazin treatments will include COC at 1% (v/v). Alfalfa will be planted in mid-August, early September, and late September in order to establish three distinct growth stages of alfalfa and to determine if newly seeded alfalfa tolerates flumioxazin and which if any growth stages of seedling alfalfa might tolerate the herbicide. A nontreated check will be included for comparison. Plots will be 10 feet by 30 feet long and treatments will be replicated 4 times for a total of 36 plots.

In both field trials, herbicide applications will be made using a backpack or bicycle

sprayer delivering 20 gpa. Alfalfa injury, growth, and weed control will be measured at 2 weeks after application and at monthly intervals thereafter. Final plant biomass and/or seed production will be determined. All data will be subjected to analysis of variance and treatment means separated using least significant difference test at the 5% level. Field trials will continue into the summer months and data analysis will be concluded by March 2008.

Greenhouse Trial Our proposed greenhouse trials will be

initiated in January 2007 and will take place in Prosser, Washington. Our objective in the greenhouse is to evaluate dose response for catchweed bedstraw to fluroxypyr, carfentrazone, and imazamox. Catchweed bedstraw seed will be planted into a silt loam soil mix. Herbicides will be applied with a bench sprayer over a range of doses: fluroxypyr maximum dose 0.25 lb ae/a, carfentrazone maximum dose 0.032 lb ai/a, and imazamox maximum dose 0.047 lb ae/a at 2-leaf and 4-leaf stages of bedstraw growth. All treatments will include R-11 nonionic surfactant at 0.25% (v/v). Treatments will be replicated five times in a completely randomized design for a total of 65 pots each experiment. The entire experiment will be repeated. Percent control and weed growth will be evaluated 2, 4, and 6 weeks after application. Trials and data collection will continue through January of 2008 and data analysis will be complete by March 2008.

Catchweed bedstraw seed will be collected from at least one site in the Columbia Basin in which poor control has been observed in alfalfa seed production. Seed will be planted as described above seedling response to imazamox applied at a range of doses from 0 to 0.047 lb ae/a will be evaluated as described previously.

Budget

Salaries ............................................ $10,792Partial support for Research Supervisor/Technician

Benefits ...............................................4,208

Total Request from WASC ......... $15,000

Trade names have been used in this report and proposal book for the convenience of the reader, with the intent of simplifying information and product identification; no endorsement is intended. Some products discussed are not registered for use on alfalfa seed. This document describes past, present, and prospective future research, it is not intended to be prescriptive.

Pesticides must always be applied with care and only applied to plants, animals, or sites listed on the label. Individuals mixing and applying pesticides should follow all label precautions to protect themselves and others. It is a violation of the law to disregard label directions. If pesticides are spilled on skin or clothing, clothing should be removed and skin washed thoroughly. Pesticides should always be stored in their original containers and kept out of reach of children, pets, and livestock.

WASHINGTON

Alfalfa SeedCOMMISSION

washington alfalfa seed - the ir-4 projectir4.rutgers.edu/fooduse/perfdata/1949.pdf · orthene...

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