kentucky pest news may 15, 2012

7/31/2019 Kentucky Pest News May 15, 2012

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Online at:www.uky.edu/KPN

Number 1302 May 15, 2012

CORN

-Fungicides Best Used at Reproductive Stage

TOBACCO-Disease Update for the Week of May 15

VEGETABLES

-Leaf Mold on Greenhouse Tomatoes

-Spring Vegetable Insect Management

SHADE TREES

-Arthropod-Induced Galls Becoming Evident

CORN

Fungicides Best Used at Reproductive StageBy Paul Vincelli

Some corn growers feel that fungicides are an

important part of their production system,

especially for fields with significant diseasepressure. If using a fungicide, one of the most

important decisions is, when to apply it? If

applying an herbicide anywhere during V4-V8, it

certainly would be tempting to include a fungicide,

since there are no additional application costs to

including the fungicide. However, the clear

pattern of research trials so far is that significantly

better results are obtained by applying that same

fungicide at VT through R1 instead of earlier.

The growth-promoting effects of strobilurin

fungicides like Headline, Quadris, etc., are tooinconsistent and unpredictable to justify using a

fungicide for that reason. This is true whether

applying during vegetative stages or at VT/R1.

What about disease control? If that is your

objective, studies typically show that the single

application around silking gives you the most

bang for your buck. Early applications just

FRUIT CROPS

-San Jose Scale Crawler Emergence

LAWN & TURF

-Dramatic Rust Activity on Kentucky Bluegrass

PASTURES

-Thistle-feeding Insects Play Role in Biocontrol

LIVESTOCK

-Face Flies

DIAGNOSTIC LAB HIGHLIGHTS

INSECT TRAP COUNTS

dont seem to have much impact on disease

development during grain fill.

What about two applications, one at V4-V8 and

another at reproduction? Again, the research Ive

seen shows no consistent benefit to the early

application. It is much better to use oneapplication at VT-R1, then any other timing

program.

TOBACCO

Disease Update for the Week of May 15By Kenny Seebold

Current situationOver the past week, the most commonly reported

diseases in the float system have been target spot

and Pythium root rot. At this time of year, the

diseases most likely to cause serious problems are

blackleg and Pythium root rot. In the case of

Pythium, we now can use Terramaster up to 5 days

before transplanting so long as seasonal limit for

Lexington, KY 40546
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the fungicide (3.8 fl oz/100 gal of float water) is

not exceeded. Managing blackleg will be more

challenging under the current weather conditions.

Theres no sure-fire way to keep this disease out,

but there are several things that can be done toreduce the overall threat from blackleg:

1. Allow the N levels to drop to around 75ppm or a bit lower in float beds. This will

slow plant growth, and reduce the

likelihood during clipping of accumulating

debris in trays. The blackleg pathogen

often infects leaf debris first and then

bridges to otherwise healthy plants, and

can explode from this point during humid

and hot weather. The bacteria that cause

blackleg are almost always present, and

are opportunistic. Successful management

of blackleg hinges on reducing the

conditions that favor their ability to infectand spread.

2. Clip carefully. Dont take off more than to 1 inch of growth at a time, and empty

baggers regularly to avoid deposition of

leaf matter in trays. Sanitize mowers after

each use with a solution of 1 part bleach to

9 parts water.

3. Get as much air moving on plants aspossible. Excessively damp conditions atthe tray-surface level are a big factor in

promoting blackleg during warm weather.

4. Raise water levels in beds so that the topsof trays are above the sideboards of floatbays to improve cross-flow of air andbetter drying.

5. Apply agricultural streptomycin at a rateof 1 tsp / gallon of spray mix to help

suppress blackleg. In conjunction with

good ventilation, this practice will reduce(although not eliminate) the occurrence of

blackleg. If disease is found, take

aggressive measures to get air moving

through plants, and treat them with 2 tsp

of agricultural streptomycin per gallon.Drying the plants down after blackleg is

found is critical it may be necessary to

move affected trays onto wagons or racks

and place them outside (or in a protectedarea if rain threatens) to get things dry at

tray-surface level.

6. Dont forget about target spot. Maintain afungicide program to keep this disease

under control. Leaves damaged by target

spot, particularly ones lower on the plant,

will be prone to attack by the blackleg

pathogen.

Blue Mold

Blue mold has yet to be found in the United Statesas of the first of the week. I will continue to

consult with my colleagues at the North American

Plant Disease forecast center and send an alert ifthis situation changes.

VEGETABLES

Leaf Mold on Greenhouse TomatoesBy Kenny Seebold

Leaf mold (Figs. 1 and 2), caused by Fulvia fulva,

is a fairly common disease of tomatoes grown in

greenhouse and high tunnels in Kentucky. Over

the past few weeks, the number of reports of this

disease has increased steadily and in some cases

severe outbreaks have been documented. High

humidity and moderate-to-high temperatures favor

development of leaf mold. Spores or sclerotia of

the leaf mold fungus can survive in debris and onsurfaces (greenhouse walls, stakes, tools) for as

much as a year.

Successfully managing leaf mold hinges on

keeping humidity levels as low as possible inside

greenhouses. Good air movement also helps to

keep periods of leaf wetness as short as possible,

reducing the risk of infection. Routine fungicide

applications will help suppress leaf mold. Begintreatments after plants are 18-24 inches in height

and spray on a 7-14 day schedule. The following

fungicides can be used in greenhouses and hightunnels to manage leaf mold:

1. Mancozeb: products include Dithane,Manzate, Penncozeb, and

Koverall. Moderately effective, PHI=5 d,

REI=24 h.


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2. Fixed copper: products include Badge,Badge X2, Champ, Cueva, Kocide,

Nordox, and Nu-Cop. Mildly-to-

moderately effective, PHI=0 d, REI=24 h.

3. Chlorothalonil: Catamaran is the onlychlorothalonil fungicide for greenhouse

vegetables. Moderately effective, PHI=0d, REI=12 h.

4. Azoxystrobin + difenoconazole: QuadrisTop (cannot use Quadris SC in

greenhouses, only Quadris Top). Very

effective, PHI=0d, REI=12 h.

5. Cymoxanil + famoxadone: Tanos (mustbe tank-mixed with fixed copper or

mancozeb). Moderately-to-very effective,

PHI=3-5 days (depends on tank-mix

partner), REI=12 h.

Sanitation is another important tool formanagement of leaf mold. After the season ends,

sanitize tools with a 10% bleach solution.

Greenhouses and high tunnels should be closed

tightly and allowed to reach daytime temperatures

of at least 135 F over the course of 2-3 weeks.

This will help reduce carryover of the leaf mold

pathogen inside structures. For more information

on leaf mold and its management, refer to ID-172

(IPM Scouting Guide for Common Pests ofSolanaceous Vegetables in Kentucky).

Figure 1. Symptoms of leaf mold on upper surfaces of

tomato leaves appear as circular, yellow blotches.

Figure 2. Circular, olive-colored masses of spores on lower

surfaces of tomato leaves are a key diagnostic feature of

leaf mold.

Spring Vegetable Insect ManagementBy Ric Bessin

Several key pests of vegetables need to be

controlled in the late spring, as control during thisperiod will also help with their management later

in the summer. Early in the season it is important

to get the seedlings and vegetable transplants off

to a good start. There are some of the early-season

insects that need to be managed to ensure healthy

stands.

Cabbage and Broccoli

Early this spring there were some reports of

seedcorn/cabbage maggots that were related to

fields that were set immediately after the soil was

turned in the spring. Typically when we allow twoweeks or more between field preparation and

setting of plants we can reduce issues with thesemaggots as they are strongly attracted to the fields

with decaying organic matter. Striped flea beetles,

imported cabbageworm and diamondback moth

larvae are the pests that attack the spring crop.

With flea beetles on seedling plants, less than 4 to5 true leaves, use a threshold of an average of two


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beetles per plant when deciding whether or not to

spray. A threshold of 15 percent infested plants

can be used with worms until either head-fill or

crown formation, then the threshold drops to 5

percent infested plants. While the type of mixtureof worms it is not important when deciding if to

spray, the types of worms will determine whichinsecticides are used. Page 131 inID-36has a

table that shows the relative efficacy of the

different insecticides against the common insect

pests.

Figure 3. Imported cabbagworm larva.

Sweet Corn

Corn flea beetles and cutworms are the two

primary pests that will attack seedling corn. Therehave been some reports of cutworm activity in

field corn, so this is an indication that we will needto monitor sweet corn carefully until plants reach

18 inches in height. Use 3 percent cut plants with

cutworms actively feeding as the guideline for

treating cutworms. Flea beetles can transmit the

bacterium that causes Stewart=s Wilt, so wilt

resistant cultivars may be needed in years

following mild winters, such as this past winter.

Otherwise the threshold for direct feeding by corn

flea beetles is 50 percent of the plants with leaf

scars and some leaves turning white.

Figure 4. Corn flea beetle on leaf.

Tomatoes and Peppers

There have been numerous reports of thrips on

greenhouse grown tomatoes and transplants this

spring. This is a result of the mild winter. Thripsare a concern as they attack the bud of the plants

and cause distorted leaves to emerge, they are alsoa vector of two common viruses, Tomato Spotted

Wilt and Impatiens Necrotic Spot. Thrips can also

cause a defect on tomato fruit called gold flecking.

Tobacco and potato flea beetles will attack both

tomato and pepper plants. Usually, the plants will

quickly outgrow moderate damage. Occasionally,

serious damage can occur to plants less than six

inches. Use 4or more beetles per plant and plants

less than 6 inches as the guideline for treatment.

Colorado potato beetle can also do serious damageto tomato plants less than 8 inches. Use 10 beetles

per 20 plants as the guideline for treatment when

the plants are less than 8 inches in height.

Figure 5. European corn borer is the key pest attacking

pepper.


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Eggplant and Potato

As with tomato, flea beetles and Colorado potato

beetle are serious early season pests of potato and

eggplant. Use the same threshold for tomatoes

above. Resistant to insecticides continues to be aserious problem for Colorado potato beetle. While

we are fortunate to have several effectiveinsecticides, Colorado potato beetle has shown a

tremendous ability to adapt and become resistant

to new insecticides. Because of this, producers

should not use insecticides with the same mode of

action for consecutive generations of this insect.

Often local populations of this insect may be

resistant to one group of insecticides, and in other

areas they may be resistant to others. For this

reason, what works well in one county may not

work at all in another. The new IRAC codes on the

labels should help producers identify products that

can be used in rotation.

Figure 6. Colorado potato beetle continues to be a serious

pest of potato, eggplant and tomato.

Squashes, Cucumbers and Melons

Cucumber beetles have been active since early

April in the Lexington area due to the mild winter.

While cucumber beetles feed on cucurbits, they

transmit the bacteria into the wounds that can

cause bacterial wilt of cucurbits. Melons,

cucumbers and some squashes are very susceptible

to this disease. The most effective technique to

limit the disease is to prevent the beetles from

feeding on the plants. Growers have used row

covers, regular foliar sprays or an at-planting, soil

drench of a systemic insecticide for cucumber

beetle and bacterial wilt management. If the

correct insecticide is selected, these treatments

also provide control of squash bug on squash and

pumpkins. With the systemic treatments, the

duration of control for squash bug is only about

2/3 of the duration cucumber beetle control.

Figure 7. Squash bugs nymphs can be very difficult to

control late in the season, early management is very

important.

SHADE TREES

Arthropod-Induced Galls Becoming EvidentBy Lee Townsend

Figure 8. Leaf galls often are green early, then change to red

and eventually black before the insect or mite emerges(photo by G. Huffman).

Some galls are irregular plant growths which arestimulated by the reaction between plant hormones

and powerful growth regulating chemicals

produced by some insects or mites. Galls may

occur on leaves, bark, flowers, buds, acorns, or

roots. Leaf and twig galls are most noticeable. The


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inhabitant gains its nutrients from the inner gall

tissue. Galls also provide some protection from

natural enemies and insecticide sprays. Important

details of the life cycles of many gall-makers are

not known so specific recommendations to timecontrol measures most effectively are not

available.

Gall makers must attack at a particular time in the

year to be successful. Otherwise, they may not be

able to stimulate the plant to produce the tissue

which forms the gall. Generally, initiation of leaf

galls occurs around "bud break" or as new leaves

begin to unfold in the spring.

Galls are becoming evident on many trees now,

especially oaks. Heavily galled leaves may drop

prematurely but this generally does not affect the

health of established trees. Several Entfacts covercommon galls oaks

http://www.ca.uky.edu/entomology/entfacts/ef408.

asp; maples -


asp; general galls -


asp.

FRUIT CROPS

San Jose Scale Crawler EmergenceBy Ric Bessin

While most of our fruit trees don't have much of a

crop to manage this year due to the late freeze in

April, there are a few insect pests that can affect

the health of the trees and should be managed. San

Jose is one of those pests. While feeding thesescale insects inject enzymes into the wood that are

toxic and can cause limb dieback or even death of

some peach and apple trees. Late May and early

June is when the eggs of the first generation hatch

and crawlers emerge in a typical year, but with the

early warmer weather this year we are likely to

have emergence 10 or more days earlier. For this

reason, growers should use black tape applied with

the sticky surface outward around infested scaffold

limbs. The tape is checked twice a week for the

presence of scale crawlers which will appear as

fine tan specks on the tape. This will signal the

time to treat for the first generation of the summer.

Figure 9. San Jose scale crawlers stuck to black tape.

During most of the year, the scale nymphs and

adults are protected from most insecticides

underneath a waxy cap. During the motile crawler

stage they are more vulnerable. This is one of the

key periods for control of the scale. There is an

emergence of crawlers later in the summer, but

that generation is not synchronized, emerging overseveral weeks making control difficult.

LAWN & TURF

Dramatic Rust Activity on Kentucky BluegrassBy Paul Vincelli

Leaf rust activity is very severe on some swards of

Kentucky bluegrass in Central Kentucky. It maybe showing up on perennial ryegrass and other

cool-season grasses as well.

RecognitionThe disease is readily recognizable from the tiny,orange pustules of powdery spores that erupt from
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within the leaf blade (Figs. 10-11). These pustules

eventually cause leaf blades to turn yellow and dry

up. The disease does not kill turf outright but can

weaken it if severe.

Why so much, so early?

More frequent occurrence of mild winters ispredicted by the theory of global warming. Many

plant pathologists agree that the increasing

occurrence of mild winters will result in increasedseverity of a number of diseases, because of

increased overwintering by pathogens. We may

be seeing an example of that with these rust

outbreaks.

Management notesUnder Kentucky conditions, these leaf rusts of

turfgrasses usually are significant problems only in

swards that are growing slowly, such as those thatare low in nitrogen or low in soil moisture.

Normally, maintenance of adequate soil moisture

and autumn fertilization are sufficient for

managing this disease. However, some outbreaks

observed this spring are quite severe, so for certain

high-value swards, there may be interest in

spraying fungicides. Effective products are listed

in the Extension publication, Chemical Control of

Turfgrass Diseases 2012, available at

http://www.ca.uky.edu/agc/pubs/ppa/ppa1/ppa1.pd

f. Many of the most effective products will only

be available to commercial pesticide applicators.Also, keep in mind that certain products listed are

not labeled for home lawn use; those products are

included in the publication for the benefit of those

managing golf courses and other specialized

turfgrasses.

Figure 10. Rust of Kentucky bluegrass, showing pustules

containing thousands of spores.

Figure 11. Microscopic view, looking down on two pustules

with spores. Courtesy of David Williams.

PASTURES

Thistle-feeding Insects Play Role in BiocontrolBy Lee Townsend

Plant-feeding insects are generally viewed as pestsbut some feed exclusively on noxious weeds such

as musk or nodding thistle. Since its introductionfrom Europe in the mid- to late 1800's, musk

thistle has spread over much of North America and

has become a significant problem in pastures andalong rights- of-way. Fortunately, some insects

from the home range of this weed have been used

successfully to help to manage it in the US.

Figure 12. Thistlehead weevil and egg insertion sites on flower

bracts.
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Two insects from this program are established

over much of Kentucky and have had an impact on

management of the weed. Both can be found now

on musk thistle along with another insect that has

a distinct visual impact but probably more limitedeffectiveness.

The thistlehead weevil is about 3/8-inch long; its

oblong body is dark with small patches of golden

scales. This beetle feeds a little on foliage and

stems of second-year plants but its major

contribution to thistle control comes from larval

feeding on the seeds in the thistle seed head.

Thistlehead weevils are common on flower heads

now and egg sites are very easy to see on infested

heads. Each small batch of eggs is covered with a

small amount of chewed plant tissue that the

female pastes over the small hole she chewed onthe flower bract. The grub-like larvae feed on

developing seeds in the flower head. If enough

larvae are present (about 15) no seeds will survive.

Eggs are laid from late April to early July, there is

one generation per year.

The rosette weevil (about inch long) can be

found on plants now, too. This "broad-shouldered"

weevil, a little smaller that the thistle head weevil,has a long, distinct snout, light patches of color,

and short bristles on its body. The grub-like larva

feeds in the center of rosette-stage plants andtaproot severely stunting or killing plants. There is

one generation and finding adults on plants is theeasiest way to see if this beneficial insect is

present.

The thistlehead weevil and rosette weevil pose no

threat to non-target organisms and crops anddisperse on their own to increase their range.

The thistle tortoise beetle is a light green leaf

beetle. The spiny larvae carry a shield of their

feces and shed exoskeltons over their backs. ThisEuropean species chews distinct window-pane

feeding holes in leaves. Some years it can cause

extensive damage to thistle plants.

LIVESTOCK

Face FliesBy Lee Townsend

The face fly is a tough-to-manage pest of pastured

cattle. In addition to the irritation it causes whilefeeding, this fly can play a major role in the spread

of the strains of the bacterium that causes pinkeye

within and between herds.

Female face flies visit cattle for short periods oftime to get the protein they need for egg

production. Sources include tears, mucus, and

saliva. Their sponging mouthparts have small,

abrasive teeth that scratch tender tissue around the

eye to stimulate tear flow; the tears are then

blotted up by the flys specialized mouthparts.

Cattle reacting to face fly annoyance interrupt fly

Figure 13. Rosette weevil, long

dark snout visible at left.

Figure 14. Thistle tortoise beetle on nodding thistle and feeding scar.


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feeding which means that the insect may have to

visit several animals to get a complete meal. Face

flies may pick up the pathogen from an infected

animal and carry it to uninfected animals as they

continue to feed. The pathogen can survive on aface fly for 3 to 4 days, increasing the potential

spread of the infection. While the role of face fliesis important, other eye irritants, such as tall grass,

pollen, and bright sunlight also injury the eye and

can play a role in spread of this disease.

Face fly control is an important part a heard health

program but this is a tough insect to control

because: 1) face flies spend very little time on

animals and 2) they are mostly on the face which

is a difficult keep treated with an insecticide. In

addition, face flies may move several miles so in-

flight of flies from nearby herds can compound

control problems.

Daily access to forced-use dust bags or oilers with

fly strips or bullets generally provide good fly

control because they are used regularly by all

animals in the herd. Some insecticide ear tags also

can reduce face fly numbers significantly. Check

regularly to make sure oilers and dust bags are

charged and that they are dispensing insecticide

properly.

Figure 15. Face flies feeding.

Figure 16. Mineral feeder

with self-application

"mop" to treat cattle for

face flies.

DIAGNOSTIC LAB HIGHLIGHTS

By Julie Beale and Paul Bachi

Agronomic samples during the past week included

thrips injury and magnesium deficiency on corn;

sharp eyespot (Rhizoctonia) on wheat; Rhizoctoniadamping off, target spot and numerous cases of

Pythium root rot on tobacco transplants.

On fruit and vegetable samples, we havediagnosed Botrytis fruit rot on strawberry; fire

blight, frogeye leaf spot and cedar-apple rust on

apple; fire blight on pear; black knot on plum;

bacterial soft rot on potato; and Botrytis blight,

early blight, timber rot, pith necrosis and leaf moldon tomato.

On ornamentals, we have seen bacterial soft rot on

daylily; Mycosphaerella leaf spot on iris; roserosette and black spot on rose; rust on hollyhock;powdery mildew on euonymus; Cryptodiaporthe

dieback on chestnut; Botryosphaeria canker on

Leyland cypress; Dothistroma needle blight on

pine; Pythium root rot on bentgrass; loose smut on

bermudagrass; and brown patch on fescue.


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INSECT TRAP COUNTS

May 3 - 10

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,

KYBlack cutworm 0 0

Armyworm 1 67

Corn earworm 135 2

European corn

borer

3 0

Southwestern

corn borer

7 0

Fall armyworm 0 0

kentucky pest news may 15, 2012

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