kentucky pest news may 8, 2012

8/2/2019 Kentucky Pest News May 8, 2012

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Online at:www.uky.edu/KPN

Number 1301 May 8, 2012

TOBACCO

-Managing Bacterial Soft Rot on Tobacco

Seedlings

-Disease Update for the Week of May 7

VEGETABLES

-Sclerotinia sclerotiorum on Lettuce and Tomato

SHADE TREES AND ORNAMENTALS

-Caught Holding the Bag

TOBACCO

Managing Bacterial Soft Rot on Tobacco

SeedlingsBy Kenny Seebold

After a period of weather conditions that were

cooler and drier than normal, warm temperatures

and rains picked up in Kentucky at the beginning

of May. One of the biggest threats to tobacco in

float beds during warm weather is bacterial softrot, or black leg. This disease is fast-moving and

can cause quite a bit of damage in a very short

time frame. Careful management of tobacco float

beds can prevent serious losses or delays in

setting.

BACKGROUND. Warm, humid conditions in the

float bed are the ideal environment forErwinia

carotovora subsp. carotovora and other bacterial

species that cause blackleg. Initially, leafclippings (debris) or wounded tissue are colonized

by the blackleg pathogen. Debris and leavesinfected byErwinia appear necrotic and slimy

(Figure 1). Systemic infections, which arise when

Erwinia moves from debris or wounded tissuesinto healthy plants, result in darkening of the stem

that tends to move up one side of the seedling

primarily, hence the name blackleg (Figure 2).

Affected areas of the stem may also show

splitting, and in advanced stages, seedlings will

LAWN AND TURF-Rolling Putting Green Reduces Dollar Spot

INSECTS

-Brown Marmorated Stink Bug Found in Bell

County

DIAGNOSTIC LAB HIGHLIGHTS

INSECT TRAP COUNTS

collapse. Under favorable conditions, blackleg

will spread rapidly, causing significant loss of

useable transplants in as few as 1-2 days (Figure

3).

The bacteria that cause blackleg are essentially

parasites of wounded or stressed tissue, and are

plentiful in soil and on leaf surfaces. Because the

pathogens are always present, development of

disease is dependent on a favorable environmentand plentiful food (in the form of plant debris or

wounded/stressed tissue). Factors that may lead to

outbreaks of blackleg include: high nitrogen

levels (> 150 ppm), warm temperatures (>75 F),

high humidity, long periods of leaf wetness, and

plant injury (stress and wounding). The latter

occurs routinely during clipping and can lead to

rapid spread of bacterial soft rot if carried out

when plants are wet.

MANAGEMENT. Cultural practices are the most

important ways to prevent of bacterial diseases.Provide adequate ventilation to shorten the length

of time that foliage stays wet this may be the

most important of all management practices toreduce the incidence of blackleg. Most outbreaks

we see in Kentucky are associated with warm

temperatures and excessive moisture on float

plants. Avoid over-fertilizing, a practice referredto as pushing seedlings, as this leads to dense,

Lexington, KY 40546
http://www.uky.edu/KPNhttp://www.uky.edu/KPNhttp://www.uky.edu/KPNhttp://www.uky.edu/KPN


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lush growth that is more susceptible to disease and

takes longer to dry. Clip and handle plants only

after they have been allowed to dry properly. Leaf

debris left behind after clipping can serve as a

starting point for the pathogens that cause blacklegand should be removed promptly. Along with

maintaining good airflow in the float system,keeping as much leaf debris out of the beds as

possible is a key to holding blackleg in check.

Chemical options for control of blackleg are

limited. Agricultural streptomycin can be used in

outdoor plant beds to suppress bacterial diseases,

but is not specifically labeled for use in transplant

facilities. Because the use of agricultural

streptomycin is not expressly prohibited in

transplant production, however, EPA rules allow

its use in the float system. Streptomycin provides

only moderate suppression of blackleg, though,and growers who choose to apply the material in

the greenhouse must accept all liability. Apply 3-

5 gallons of a 100-200 ppm solution of

streptomycin to 1000 sq. feet of float bed. This

use rate translates to 0.5-1 lb per 100 gallons of

water, or 1-2 teaspoons per gallon. Apply

streptomycin before symptoms appear for best

results, using the lowest rate. Use the 200-ppm

rate immediately after the appearance ofsymptoms of blackleg. Some plant injury may be

observed when applying the higher rate. Refer to

the product label and the 2011-2012 Kentucky-Tennessee Tobacco Production Guide (ID-160)

for more information. The guide can be foundonline at

www.uky.edu/Ag/TobaccoProd/pubs/id160.pdf.

Figure 1. Early symptoms of blackleg include soft-rotting of

lower leaves and leaf material; a foul odor can often be

detected even before symptoms can be seen.

Figure 2. Blackened, water-soaked lesions on the lower

stems of affected plants are typical of later-stage blackleg.

Figure 3. In severe cases of blackleg, large numbers of

plants can be lost in a matter of a few days.

Disease Update for the Week of May 7By Kenny Seebold

As we move into the month of May, the potential

for diseases in tobacco float beds tends to increase.Scattered cases of target spot, collar rot, and

Pythium root rot cropped up around the state in

April, but the disease situation was fairly mild

overall. However, over the past week I have

gotten a good number of calls regarding collar rot

and have learned that bacterial soft rot (black leg)

is active in some areas. Outbreaks of disease just

before setting time can be challenging and can
http://www.uky.edu/Ag/TobaccoProd/pubs/id160.pdfhttp://www.uky.edu/Ag/TobaccoProd/pubs/id160.pdfhttp://www.uky.edu/Ag/TobaccoProd/pubs/id160.pdf


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cause delays in getting to the field, stand losses

after setting, and even outbreaks of disease after

setting. Careful management of float beds at this

point in the season can help prevent serious

problems in the coming weeks. Here are a fewquick tips to help keep diseases from getting out of

hand.1. Keep plants well-ventilated. Excessive

leaf wetness promotes diseases like target

spot, collar rot, and bacterial soft rot.

Make sure that side-curtains are lowered

and fans are running before temperatures

exceed 85F in the greenhouse, and raise

water levels in beds so that tray tops are

even with side boards to promote good

cross ventilation.

2. Keep an eye on bed fertility. High levelsof nitrogen promote black leg, while very

low levels (below 50 ppm) favor targetspot.

3. Maintain a regular fungicide program forleaf disease control. For target spot,

plants should be treated on a 5-7 day

schedule with a mancozeb fungicide such

as Dithane DF, Manzate Pro-Stick, or

Penncozeb 75DF at a rate of 0.5 lb/100 gal

of spray mixture (1 tsp / gal). After the

first or second clipping, the best optionwould be Quadris applied at a rate of 4 cc

per 5 gal of spray solution. The solution

should be sprayed onto 1000 sq. ft. of floatbead (roughly 400 trays) so as to achieve

good leaf coverage and stem rundown.Quadris can be used only once on

seedlings in the float system, so growers

must switch back to a mancozeb fungicide

if additional treatments are required. As

air temperatures rise, consider treatingwith AgriMycin 17 to prevent black leg.

The rate is 1 tsp per gallon of spray mix

for prevention, and 2 tsp per gallon for

suppression after symptoms are found.

Use enough spray mixture to get coverageof lower stems and leaves as much as 7-

10 gallons per 400 trays on larger plants.

Do not tank-mix AgriMycin and Quadris

to avoid injury.4. Dont forget about Pythium root rot. As

float bed water warms, the Pythium risk

increases dramatically and the disease can

spread very quickly. Terramaster

fungicide is the only labeled product for

this disease and should be applied around

3 weeks after seeding (when roots first

enter float water) at a rate of 1 fl oz/100

gal of bed water. Follow up treatmentscan be made at 2-3 week intervals, and are

advised for growers using trays that aremore than 3 years old. If disease is found

before the first Terramaster application,

use 1 to 1.4 fl oz/100 gal of float water

(higher rate for severe outbreaks).

Terramaster cannot be applied later than 5

days before transplanting, and use no

more than 3.8 fl oz/100 gal per crop of

plants. If Pythium root rot is found on

plants just before setting, consider adding

Ridomil Gold SL to the transplant water.

The recommended rate is 4 fl oz/A in the

setter barrel, which can be increased to 8fl oz/A for black shank suppression.

Ridomil Gold SL is the only fungicide

labeled for setter-water use (do not use

Ultra Flourish, Meta Star 2E, or Ridomil

Gold EC in this manner), and growers

should use a setter-water volume of at

least 200 gal/A to reduce the potential for

plant injury. If using Ridomil Gold SL in

setter-water for black shank, do so only ifa variety with good (7-level or better)

resistance is being planted AND disease

pressure is low to moderate. In all othercases, make a broadcast application of

Ridomil or similar product beforeplanting.

VEGETABLES

Sclerotinia sclerotiorum on Lettuce and Tomato

By Kenny Seebold

Over the past few weeks, timber rot (or white

mold), caused by S. sclerotiorum, has been found

on tomatoes around the state. On lettuce, weveseen white mold (also called drop) caused by the

same pathogen. These diseases have affected

tomatoes (Figs. 4 and 5) and lettuce (Fig. 6) in


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greenhouses and high tunnels mainly, but a few

cases have been confirmed on field-grown

tomatoes. Cucurbits are also affected by S.

sclerotiorum, particularly in greenhouses or high-

tunnels.

Managing diseases of vegetables caused by S.sclerotiorum can be difficult when conditions

favor the pathogen (cool and damp weather),

particularly in the greenhouse. Emphasis in the

greenhouse should be placed on sound cultural

practices (plant spacing, fertility, and ventilation)

and sanitation. Remove any plant debris promptly

and destroy it, as this material often is colonized

by Sclerotinia first and allows the pathogen to

become established. Remove affected plants and

fruit and bury them or discard in compost or cull

piles that are located at least 100 yards from where

susceptible crops are being grown. Sclerotia (Fig.7) produced by S. sclerotiorum can survive the

winter easily in cull piles and will generate fruiting

bodies the following spring. These fruiting bodies

will release spores that can travel short distances,

and will infect susceptible crops if encountered.

In the case of tomato and lettuce, there are no

fungicides labeled specifically for control of

Sclerotinia in greenhouses. Fontelis can be

applied to tomatoes in greenhouses for control ofBotrytis gray mold, and may suppress timber rot.

The rate of application for Fontelis on tomato is 1

to 1.5 tablespoons per gallon of spray (applied to1,360 sq ft). Botran 75W or Fontelis can be

applied to cucurbits to manage white mold. Referto ID-36 (2012-2013 Vegetable Production Guide

for Commercial Growers) for rates of Botran.

Fontelis may be applied to cucurbits at a rate of

to 1 tablespoon per gallon (sprayed over 1,360 sq

ft), and should be alternated with a differentfungicide such as copper, mancozeb, or Catamaran

(active ingredient = chlorothalonil).

In the field, remove and destroy infected plants as

described for greenhouses. Additionally, croprotation can be effective in preventing buildup of

inoculum in soil. Deep-turning of crop residues

following an outbreak ofSclerotinia will reduce

the amount of viable sclerotia that survive overtime. Fungicide options are limited on tomato, but

lettuce producers can apply Rovral (or Iprodione

50W, etc.), Endura, or Fontelis to manage

Sclerotinia diseases. Refer to ID-36 to learn more

about use rates, and always refer to product labels

for specific use and safety guidelines.

Figure 4. Timber rot of tomato.

Figure 5. Mycelium ofSclerotinia sclerotiorum on tomato

stem.


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Figure 6. White mold or "drop" of lettuce.

Figure 7. Sclerotia ofSclerotinia sclerotiorum formed inside

a tomato stem affected by timber rot.

SHADE TREES AND ORNAMENTALS

Caught Holding the BagBy Lee Townsend

Bagworm egg hatch usually occurs in late May incentral Kentucky but, as with most things, is well

ahead of schedule this year. Eggs survive the

winter in the bags that contained last years

females. Hatch occurs following the accumulation

of 650 to 750 degree days (base 50F); that targetwas reached in Fayette County between May 1 and

May 5 this year, about three weeks ahead of

schedule. Eggs hatch over a 4 to 5 week period

which means that the insect will be active for

some time and one control measure may not be

enough. Bagworms commonly catch people off

guard; the infestation is not recognized until

significant damage is done. That is even more

likely with the early onset of feeding this year.

Figure 8. This newly hatched bagworm caterpillar has

already started its shelter and is feeding on an oak leaf.

Early damage is confined to the upper leaf surface.

Bagworms are a nemesis because damage can be

significant unless a good control strategy is

followed. Four important elements are 1) Effective

spray timing which is now, egg hatch is

underway statewide. 2) Thorough coverage means

being sure that an insecticide application reaches

deep into the canopy or shrub. Treatment of just

the outer foliage will not reach bagworms feeding

deeper in the plant structure. 3) Treat all infested

trees and shrubs, not just ones that are heavily

infested. 4) Finally, apply a follow-up or clean-uptreatment about 3 weeks later to control bagworms

from late-hatching eggs.

A number of effective products are available for

bagworm control. Using them effectively provides

the best results.


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LAWN AND TURF

Rolling Putting Greens Reduces Dollar SpotBy Paul Vincelli, Extension Plant Pathologist

And Gregg Munshaw, Extension Turfgrass

Agronomist

In recent years, some of the research emerging

from Michigan State University has shown that

lightweight rolling of creeping bentgrass putting

greens resulted in reduced dollar spot pressure.Anything that reduces dependence on the frequent

application of fungicides is of wide interest to golf

courses and golfers. A recently published paper*

has looked deeper into this practice on a sand-based

soil mix (90:10 sand:peat v/v). This article

summarizes the state of the science on this topic.

Key points from the research are as follows:

Reductions in disease pressure varied,although rolling significantly reduced

disease pressure most of the time.

Reductions were as great as 90%. But

overall turf quality in turf not receiving

fungicide was improved significantly byrolling.

Reductions in disease pressure generallyoccurred when lightweight rolling was

done consistently on a schedule of five

days per week. (Earlier studies showed

more inconsistent benefits when greenswere rolled 2-3 times per week.

The greatest benefit (up to 90% diseasereduction) occurred when rolling was

done twice per day following morning

mowing (five days a week, as noted

above).

Time of day for rolling was of littleimportance. Rolling once in the afternoon

was no different than rolling once

following morning mowing.

The mechanism involves more than dewremoval. It makes sense to think that

rolling might somehow speed the dryingof leaf surfaces, reducing disease pressure

in that way. However, the recent paper

suggests it may not be that simple.

Rolling appears to slightly enhance the

volumetric water content of the top 1.5

inches of root-zone, providing more

moisture that may help improve host

resistance. It has also been speculated that

rolling reduces turf stress by creating more

prostrate growth that is less subject to

scalping during close mowing, thereby

increasing host resistance. There may alsobe benefits that relate to increased

microbial antagonism, as suggested by

higher bacterial activity in rolled plots.

In summary, lightweight rolling clearly has

benefits in reducing dollar spot pressure on putting

greens. Exactly why this happens is complex. But

whatever the mechanism, rolling seems to work

pretty darn well under field conditions.

Thanks to Paul Giordano for reviewing a draft of

this article.

*Giordano and others. 2012. Timing and Frequency Effects of

Lightweight Rolling on Dollar Spot Disease in Creeping

Bentgrass Putting Greens. Crop Science 52:13711378.

https://www.crops.org/publications/cs/abstracts/52/3/1371

Figure 9. Dollar spot control from lightweight rolling. 1X and

2X refer to number of passes after AM mowing. Image

courtesy of Paul Giordano.
https://www.crops.org/publications/cs/abstracts/52/3/1371https://www.crops.org/publications/cs/abstracts/52/3/1371https://www.crops.org/publications/cs/abstracts/52/3/1371


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INSECTS

Brown Marmorated Stink Bug Found in BellCountyBy Ric Bessin

Last month, Stacy White submitted brown

marmorated stink bug (BMSB) for identification

from Bell County, this represents the 11th county

where it has been found. This pest was first

confirmed in Kentucky in October of 2010 inBoyd County and has been appearing in several

other eastern and Central Kentucky counties. The

BMSB may become one of the more serious insect

pests in Kentucky in the coming years. It has a

very wide host range attacking many field and

horticultural crops as well as ornamental plants.

During the off season it is home invader

gathering in large numbers on and in homes.Information from other states indicates that thisinsect becomes active in the field sometime in mid

to late April.

BMSB has been identified in several Kentucky

counties. It has now been confirmed in Jefferson,Fayette, Boyd, Carter, Rowan, Lawrence, Floyd,

Maggofin, Lewis, Greenup, and Bell counties and

a half dozen other counties have reported stink

bugs invading homes but have not submitted

samples for identification. This pest is a very

capable hitchhiker and has the ability to rapidlymove to new areas on vehicles and freight.

Among the stink bug species we have in

Kentucky, BMSB is large. It has a mottled

charcoal colored appearance and it quite flattened.

We use the antennae to help identify it, as each

antenna has two broad lighter colored areas on an

otherwise dark antenna. The edge of the thorax

between the head and the shoulder is basically

smooth and without noticeable teeth. There is a

small tooth next to the eye, but this is not very

apparent.

Figure 10. A brown marmorated stink bug adult. Note the

antennae with banding and the smooth area between the

eye and shoulder.

While indoors during the winter months, BMSBwill gather in large clusters in hidden places in

buildings. They are also reported to feed in

houseplants in the home. The recommended way

to remove them would be through handpicking or

a vacuum as sweeping them with a broom causesthem to release their stink.

BMSB is a serious pest of garden and crop plants

as it feeds on the fruiting portions of these plants.

While feeding with piercing-sucking mouthparts it

injects enzymes in the wound that damages the

fruits. While BMSB damages the fruiting parts of

plants, they also feed on leaves and stems of some

hosts. BMSB is capable of building to very high

numbers in home gardens in the first years after its

appearance.

Damage to field crops is primarily to soybeans and

field corn. In both of these crops BMSB feeds on

the fruiting part of the plants, the developing

soybean pod or the corn ear. Pod feeding will

result in discolored and shriveled beans similar to

that caused by other stink bugs to soybeans. In

field corn they will feed through the husk withtheir piercing sucking mouthparts causing

shriveled kernels.

In vegetable crops, BMSB will cause damage totomato, pepper, and okra fruit similar to that of the

brown stink bugs. They feed on developing fruit

with the piercing sucking mouthparts causing hard


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corky areas under the skin of the fruit that does not

color properly. Damage to sweet corn is similar to

field corn, except that damaged kernels will

discolor when cooked. With green beans, they

attack the flowers and pods resulting in deformedpods and shriveled and/or missing seeds. With

squash and pumpkins they are reported to attackthe fruit and even kill plants.

In fruit crops, particularly apples, pears, peaches

and nectarines BMSB is reported to attack

developing fruit very early in the season. For this

reason, growers are advised to monitor for BMSB

weekly from fruit set until harvest. Damage to tree

fruits will result in sunken areas on the fruit

surface and discolored corky areas under the skin.

These spots can easily be mistaken for cork spot

on apples. All of our tree fruits and small fruits are

vulnerable to this new pest.

BMSB will also feeds on over 70 species of

ornamental plants including butterfly bush,

redbud, maple, sycamore, princess tree,

honeysuckle, roses, lilac, dahlia, zinnias,

snapdragons, crabapple, and dogwood. If you

suspect BMSB in your area, send a sample to your

county extension service office.

DIAGNOSTIC LAB HIGHLIGHTS

By Julie Beale and Paul Bachi

Agronomic samples during the past week includedbrown stripe on orchardgrass; barley yellow dwarf

virus, stripe rust and cold injury on wheat; loose

smut on barley; and Pythium root rot and cold

injury on tobacco transplants.

On fruit and vegetable samples, we havediagnosed orange rust on blackberry;

Botryosphaeria canker and cedar-apple rust on

apple; fire blight on pear; and Botrytis blight,

Septoria leaf spot, timber rot and Pythium root rot

on tomato.

On ornamentals, we have seen powdery mildew on

petunia; leaf streak on daylily; rose rosette,

powdery mildew, and black spot on rose; powdery

mildew on euonymus; spot anthracnose on

dogwood; Rhizoctonia web blight on crape myrtle;

bacterial spot on cherry; Phyllosticta leaf spot on

maple; and frost injury on various landscapeplants.

INSECT TRAP COUNTS

April 26 May 3

Graphs of insect trap counts for the 2012 season are availableon the IPM web site at -

http://www.uky.edu/Ag/IPM/ipm.htm.View trap counts for Fulton County, Kentucky at -http://ces.ca.uky.edu/fulton/InsectTraps

Note: Trade names are used to simplify the information

presented in this newsletter. No endorsement by the

Cooperative Extension Service is intended, nor is

criticism implied of similar products that are not

named.

Location Princeton,

KY

Lexington,

KY

Black cutworm 11 0

Armyworm 7 38

Corn earworm 17 1

European corn

borer

0 0

Southwestern

corn borer

0 0

Fall armyworm 0 0

kentucky pest news may 8, 2012

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