Kentucky Pest News, August 28, 2012

7/31/2019 Kentucky Pest News, August 28, 2012

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Online at:www.uky.edu/KPN

Number 1316 August 28, 2012

CORN

-Corn Earworm Moths Captures Increasing in

Vegetables

SOYBEAN

-Soybean Vein Necrotic-Associated Virus

Common in Soybean

FRUIT CROPS-Bluberry Mosaic Virus Detected in Kentucky

-Fungicide-Resistant Downy Mildew Detected

in Kentucky Vinyard

SHADE TREES AND ORNAMENTALS

-Sawflies-Late Season Pine Defoliators

LAWN AND TURF

-Leaf Rusts are Apparent

PEST OF HUMANS

-Stinging Caterpillars

-Dealing with Mosquitoes

DIAGNOSTIC LABORATORY HIGHLIGHTS

INSECT TRAP COUNTS

CORN

Corn Earworm Moths Captures Increasing inVegetablesBy Ricardo Bessin

As corn earworm pheromone trap catches increase

in late summer, sweet corn and tomato growers

may need to step up their surveillance and

management of this pest. Corn earworm is knownby several common names including tomato

fruitworm, soybean podworm, and cotton

bollworm. Generally it is a fruit feeder and can

attack a wide variety of crops including tomatillo,

pepper, okra, and green beans.

Figure 1. Corn earworms are less sensitive to pyrethroid

insecticides than a decade ago.

At this time of the year we usually experience

much larger populations of this pest. The female

moth is attracted to fields that are flowering or

fruits. Field corn that is beginning to dry drown is

one source of the adult moths as they complete

their development in corn ears, the other source is

through migration from southern areas. Storm

fronts from approaching from southern states can

bring large numbers of corn earworm moths andother pests.

Sweet corn producers and growers of fruit

vegetables may need to step up their game to

prevent damage from this insect. Over the pastseveral years, entomologists in the Midwest have

noted reduced susceptibility to the pyrethroid

insecticides (IRAC group 3) by corn earworm, but

are hesitant to call it resistance. Because of this,growers should be ready to evaluate the level of

control after an insecticide spray. Sweet corn

growers need to carefully manage corn earwormwhile the ears are silking to prevent the larvae

entering ears. Generally commercial growers willneed to spray an insecticide targeting corn

earworm on three to five day intervals until the

silks dry. Sprays need to be directed to the center

third of the plant. With tomatoes and other fruit

vegetables, growers should monitor plants anddeveloping fruit for signs of fruitworm activity

Lexington, KY 40546
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and spray as needed. Fruitworms do not enter the

fruit but will chew up to -inch cavities in the

fruit.

Figure 2. Yellow-striped armyworm numbers also

increasing.

Yellow-striped armyworm numbers are also

increasing and they will cause similar damage to

tomato fruit. The young larvae are foliage feeders

while the larger larvae attack the fruit. In terms of

management, they can be treated as tomato

fruitworm when scouting or for selecting controls.

SOYBEAN

Soybean Vein Necrotic-Associated Virus

Common in SoybeanBy Don Hershman

A new virus disease of soybean, soybean vein

necrotic-associated virus (SVNaV), is fairly

widespread throughout Kentucky at this time. We

have seen symptoms of SVNaV at low levels inKentucky for the last 15 years, but the disease has

only recently been named and characterized (I.

Tzanetakis and co-workers, 2009; J. Zhou and co-

workers, 2011). The original description of

SVNaV was from field-grown soybeans collected

in Tennessee in 2008. SVNaV is thought to be

transmitted to soybean by soybean thrips, which

were quite common this season due to the drought.

Thus far, SVNaV has been confirmed in 12 states:

AR, DE, KY, KS, IL, MD, MO, MS, NY, PA, TN,

and VA.

Although SVNaV is easy to find in many fields, I

would be surprised if the disease is severe enough

in any field to result in measurable yield losses. Infact, I am not aware of any instances in the U.S.

where measurable yield losses have been

attributed to SVNaV. It is, however, an emerging

disease that merits additional study and

monitoring.

Look for leaves with faint to distinct oak leaf

patterns that range from a whitish to bright yellow

(Fig. 1). Over the course of 2-3 weeks, the oak

leaf symptom will turn yellow to brown (Fig. 2).

Older lesions (Fig. 3) are commonly infected by

saprophytic/secondary fungi, especiallyCercospora spp. Symptoms tend to be most

evident in the upper 1/3 of the canopy. I have

been seeing symptoms of this disease for well overa month, but their frequency and intensity are now

peak. My preliminary observations suggest that

some soybean cultivars may be more susceptible

to SVNaV than others. To date, no resistance to

SVNaV has been identified. No control measurestargeting thrips or SVNaV are warranted.

Figure 3. Typical initial oak leaf pattern symptom caused by

soybean vein necrotic-associated virus (photo by D.

Hershman).


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(Soybean photos continued from previous page)

Figure 4. Range of symptoms caused by soybean vein

necrotic-associated virus (photo by D. Hershman).

Figure 5. Old lesions of soybean vein necrotic-associated

virus colonized by a host of secondary fungi, especially

Cercospora spp. (photo by D. Hershman).

FRUIT CROPS

Blueberry Mosaic Virus Detected in KentuckyBy Nicole Ward, UK Extension Plant Pathologist

Blueberry mosaic virus was confirmed in ablueberry orchard in central Kentucky this

summer. This is the first report of blueberry

mosaic in the state. The virus has not previously

been found in southern states, but it has been

reported in Michigan, Indiana, New Jersey, NewYork, Oregon, Washington, and British Columbia.

Formerly considered a disorder, blueberry

mosaic has only recently been classified as a virus.

Not much else is known about it. Highbush

cultivars Bluecrop, Pioneer, Concord,

Earlibule, and Jersey are among the susceptible

cultivars. Virus symptoms have not been reportedin rabbiteye blueberry. Limited research has beenconducted thus far, but it is under evaluation by a

team of researchers at the USDA-ARS Marucci

Center in New Jersey.

SymptomsFoliar symptoms include mottling and mosaic-

patterned characteristics on leaves. Patterns rangefrom mild to brilliant with yellow, orange, and/or

red colorations (see figures 6 through 9). Mosaic

symptoms are not always produced each year, and

environmental conditions may affect symptomdevelopment. It is possible that during cool

seasons, symptoms are more pronounced. Thus,

under ideal conditions, symptoms may appear

suddenly, and it may appear that spread is rapid.

Infected plants often result in reduced fruit load.

Yield losses of 15% have been reported on

Bluecrop in Michigan. Fruit on infected plants

have been shown to ripen later than noninfected

fruit, and fruit quality is low.

SpreadThe vector (carrier) of the virus is not known.

Researchers report that blueberry mosaic is not

transmissible by mechanical means (i.e. pruners).

However, the virus is graft transmitted. Becausevirus particles are systemic (dispersed throughout

the vascular system), once infected, all plant parts

are infected, even when symptoms are absent.


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Thus, cuttings should never be taken from a virus-

infected plant.

As mentioned above, the vector of blueberry

mosaic virus is not known. Therefore, growers areencouraged to destroy infected plants until it is

clear on how the virus spreads. Whether an insectvector is involved is yet to be determined.

Current research indicates that the virus is slow-spreading (if at all) under field conditions.

However, in Michigan, spread is rapid. So far, the

reason is unknown.

TreatmentThere is no cure for plant viruses, including

blueberry mosaic. Growers should remove

infected plants and destroy them by burning or

burying. Remove all roots within soil, as well.Scout orchards, especially nearby plants, several

times during the growing season. Contact a local

extension agent if a plant appears suspicious.

Most importantly, purchase plants from a

reputable grower. Visit nurseries before plantpurchase and ask to inspect parent plants.

Furthermore, a virus-free certification is always

worth the extra cost.

Figure 6. Foliar symptoms include mottling and mosaic-

patterned characteristics on leaves.

Figure 7.

Figure 8. . Patterns range from mild to brilliant with yellow,

orange, and/or red colorations.

Figure 9.


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Fungicide-Resistant Downy Mildew

Detected in Kentucky VineyardBy Nicole Ward, UK Extension Plant Pathologist

This summer, a grape grower in central Kentucky

reported persistent downy mildew in his vineyard.He noted that regular applications of Abound andPristine fungicides failed to manage the disease.

After laboratory analysis, the pathogen was

deemed completely resistant to the two fungicides

at the lowest recommended rates and 85%

resistant at the highest recommended rates.

What is fungicide resistance?In the simplest terms, pathogens become resistant

to fungicides when the chemical no longer

manages disease symptoms. However, even the

most effective fungicides fail to completelyeradicate a pathogen population. There are always

a few fungal spores or other fungal inoculum that

survive the pesticide application. Those survivors

may be the result of ineffective spray coverage,but individual pathogens may have a trait that

provides some type of resistance to the fungicide.

Think back to high school biology when we

learned the theory of survival of the fittest.

Unfortunately, a single survivor can multiply into

thousands of individuals while passing that

resistance gene onto its offspring, much the way

our parents passed on eye color to us.

How did resistance develop?Consider that it is highly unlikely that a fungalpopulation will incur resistance to more than one

chemical type, at least over the short term. As a

fungal population can become resistant to a single

chemical, growers should rotate sprays with a

different chemical group. These chemicalrotations can become confusing, and many

growers do not fully understand the concept of

chemical groups.

Chemical groups are classified by biochemical

mode of action, not necessarily by active

ingredient. For example, within the strobilurin

group of fungicides, active ingredients include

azoxystrobin, pyraclostrobin, trifloxystrobin, and

kresoxim-methyl, all of which are quinone-outside

inhibitors. Because information on biochemical

modes of action can be confusing for growers, the

Fungicide Resistance Action Committee (FRAC)

developed numeric codes that represent these

chemical groups. Strobilurins are classified as

FRAC group 11. These codes appear on the top

right side of all pesticide labels. Thus, growers

may simply refer to the coded chemical group

number on labels as opposed to depending uponcomplex information such as mode of action.

Considering that all fungicides within the same

group have the same mode of action, it is clear that

if a grower fails to properly rotate fungicide

groups, fungicide resistance risk is high.Additionally, fungicide labels indicate the

maximum number of applications allowed per

growing season. A maximum of four applications

of strobilurins are allowed per growing season.The grower mentioned above used Abound and

Pristine fungicides consistently over a two-yearperiod, exceeding the maximum number of

applications and failing to rotate with a different

chemical group. This rapidly induced thedevelopment of a resistant population of the

downy mildew pathogen.

Figure 10. Abound fungicide is classified as a FRAC Group

11 fungicide. The chemical group code appears on the top

right corner of fungicide labels.


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How does a grower know if a resistant population

developed?Pathogen populations do not begin as 100%

resistant. In fact, resistance develops gradually.

Thus, growers should be aware of efficacy anddisease control. If a product(s) begins to become

less effective over time, he should contact his localExtension agent immediately.

What next?If resistant pathogen populations develop within avineyard, growers should immediately stop using

the fungicide in question and all others in the same

FRAC group. With the assistance with an

Extension agent or specialist, growers should

identify other fungicides that will effectively

manage disease. In the aforementioned case, the

grower stopped using strobilurin fungicides and

substituted a phosphorous acid fungicide (ProPhyt,Rampart, etc.) for management of downy mildew.If strobilurins are used for management of other

diseases, tank-mix with another product (within a

different FRAC group) that provides downy

mildew control.

More InformationFungicide resistance can appear complicated, so

growers should not hesitate to seek assistance in

development of a spray program. Contact

University of Kentucky Cooperative Extension

agents or specialists for assistance.

SHADE TREES AND ORNAMENTALS

Sawflies Late Season Pine DefoliatorsBy Lee Townsend

Sawflies are members of the insect order

(Hymenoptera) that includes ants, bees, and

wasps. The larval stage has a caterpillar-like body

that may be brightly marked with stripes or spots.Some species change significantly in appearance

as they grow, making identification confusing.

Large numbers of sawflies can strip the needles

from a tree in a short period. Several species can

be found on pines in Kentucky.

The European pine sawfly is one that is active at

this time of year. These olive green larvae with

black stripes and shiny black heads can feed on

many pines including Scotch, Eastern white, andAustrian. They feed on the previous year's needles

and do not damage new needles. These sawflies

can feed on twig bark, causing growth deformities.

Trees are seldom killed by the feeding of this

insect during a single season. Full grown larvae

are about 1 inch long.

Figure 11. Introduced pine sawfly larva

The introduced pine sawfly has a black head and

black body that is covered with yellow and white

spots. They prefer the needles of eastern white

pine but also will eat Scotch, red, Austrian, jack,

and Swiss mountain pine. Short leaf and Virginia

pines have been attacked but usually are not

heavily damaged.

Feeding is most severe in the crown to upper half

of the tree but heavily infested trees can be

completely defoliated. If this occurs after the

winter buds have formed, many branches or even

the entire tree can be killed. There are two

generations each year. The second generation ofthis sawfly feeds on both old and new needles

during August and September.

Sawfly populations are usually controlled by

combinations of natural enemies, predators,starvation, disease, or unfavorable weather.

Outbreaks can occur when natural control does not

produce high mortality. Regular inspection of

pines will help to detect sawfly infestations beforethe larvae reach a size that can cause significant

defoliation. Since eggs are laid in clusters, feeding

by groups of larvae can cause unsightly damage to


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ornamental or landscape plantings, as well as

nursery trees

If only a small number of colonies are present and

accessible, they can be handpicked, shaken off, orpruned from the tree and destroyed. Some of the

insecticides that can be used for sawfly control arelisted by the common name of the active

ingredient followed by an example brand name.

Acephate - Orthene Turf, Tree & OrnamentalSpray, bifenthrin- Ortho MAX Lawn & Garden

Insect Killer, carbaryl - Sevin, cyfluthrin - Bayer

Multi-Insect Killer Concentrate, and permethrin -

Ortho Tree, Shrub, and Lawn Spray. Although

sawflies look like caterpillars, they are not

susceptible to Bt sprays.

Stinging CaterpillarsBy Lee Townsend

Late season caterpillars are active now. Many use

camouflage or secretive behavior to avoid

predators, especially birds. A few are protected

and advertise their presence by bright warning

markings. These should be avoided. The

distinctive larva of the white flannel moth is oneof the less common species. They feed on a variety

of deciduous trees and shrubs. These caterpillars

do not actively sting like a bee or wasp. Contact

usually comes as a person accidentally brushes

against a caterpillar that they did not see.

Figure 12. White flannel moth caterpillar. Beware of insects

with bright warning markings.

Stinging caterpillars have some brittle, hollow

spines that are connected to venom glands in the

body. These spines easily penetrate skin and break

off. Then, the irritating venom goes to work.

Reactions to the chemicals vary from slight

irritation to pustules, inflammation, and sometimes

intense pain.

Wide masking tape can be applied to the site to liftthese tiny spines from the skin. To avoid further

injury, the area should not be rubbed until they are

removed. The wound area should then be washedwith soap and water. Place an ice pack or cold

compress on the wound intermittently (15 minutes

on and 15 minutes off). See a physician if there is

a severe or persistent reaction to the toxin.

Figure 13. Close up of stinging spines on spots down the

back of the white flannel moth caterpillar.

More information on stinging caterpillars found in

Kentucky is available in

www.ca.uky.edu/entomology/entfacts/ef003.asp.

LAWN AND TURF

Leaf Rusts Are ApparentBy Paul Vincelli

Leaf rust diseases are apparent on several cool-

season grasses. Leaf rusts are readily recognizable

in the field by the tiny, orange-colored pustulesthat contain powdery spores which erupt from

within the leaf blade (Fig. 1). 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.
http://www.ca.uky.edu/entomology/entfacts/ef003.asphttp://www.ca.uky.edu/entomology/entfacts/ef003.asphttp://www.ca.uky.edu/entomology/entfacts/ef003.asp


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Under Kentucky conditions, leaf rusts of

turfgrasses are usually most severe in turfgrass

stands that are growing slowly, such as those that

are low in nitrogen or soil moisture. Since autumn

is a very important time to fertilize swards of cool-season turfgrasses in Kentucky in order to help

promote root growth and overall vigor, swards thatare showing substantial levels of rust may simply

need to be fertilized or irrigated. Alleviation of

compaction through aerifying can also help.

For particularly high- value swards where there

may be interest in spraying fungicides, the most

effective products are listed in the UK Extension

publication, Chemical Control of Turfgrass

Diseases, available at

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

f. Be aware that several fungicides labeled for rust

control on turfgrass arenot labeled for home lawnuse (but are labeled for other turf uses). Thus, if

treating a home lawn, be sure the product is

labeled for that particular use.

Figure 14. Highly magnified view of a pustule of leaf rust,

showing orange-colored spores.

.

PESTS OF HUMANS

Dealing With MosquitoesBy Mike Potter and Lee Townsend

Human cases of West Nile Virus have beendetected recently in Kentucky. Reducing exposure

to mosquitoes and eliminating breeding sites, if

possible, are key steps in reducing exposure.

Here are some tips to reduce chances of exposureto mosquitoes:

1. Eliminating breeding sites on your property can

be effective because mosquitoes tend to stay near

them after emerging as adults.

Dispose of old tires, buckets, aluminum cans, and

plastic sheeting or other items that can hold water.

2. Check for stagnant water in drinking troughs

flush out if necessary3. If practical treat water that cant be eliminatedby using products like mosquito donuts or or

granules labeled for that use. Various products

containing the mosquito- specific active

ingredients can be used.

Adult mosquitoes prefer to rest in moist, shady

areas such as dense vegetation during the daytime.

Consequently, homeowners should remove tall

weeds and overgrown vegetation from their yards.

To further reduce intolerable levels of biting adult

mosquitoes, residual insecticides can be applied toshrubs, hedges and other shaded areas, such as

under decks and along foundations.

Recent research by University of Kentucky

entomologists indicates that such treatments

effectively suppress nuisance, biting mosquitoes

for about a month. Residual mosquito sprays are

often best applied by professional pest control

firms. Homeowners opting to try this themselves

should use lawn and garden insecticides

containing permethrin (e.g., Ortho Mosquito B

Gone, Spectracide Mosquito Stop), cyfluthrin(Bayer Advanced Powerforce Mosquito Killer),

bifenthrin (e.g., Ortho Home Defense Max), or

lambda cyhalothrin (Spectracide Triazicide). For

homeowners, a hose-end sprayer is usually most

effective for making such applications.
http://www.ca.uky.edu/agc/pubs/ppa/ppa1/ppa1.pdfhttp://www.ca.uky.edu/agc/pubs/ppa/ppa1/ppa1.pdfhttp://www.ca.uky.edu/agc/pubs/ppa/ppa1/ppa1.pdfhttp://www.ca.uky.edu/agc/pubs/ppa/ppa1/ppa1.pdfhttp://www.ca.uky.edu/agc/pubs/ppa/ppa1/ppa1.pdf


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Exclusion - Mosquitoes can be kept out of homes

by securely screening windows, doors and

porches. The occasional mosquito found indoors

can be eliminated with a fly swatter. Aerosol-type

insecticides labeled for mosquitoes, gnats, andother flying insects seldom provide much relief at

the dosages applied by householders.

Topically-Applied Repellents - Repellents will

help prevent bites when spending time outdoors.Traditionally, the most effective mosquito

repellents contained the active ingredient diethyl

toluamide (DEET) ranging from 5% to 40%.

Higher percentages of DEET in the ingredients

provide longer protection. Low -percentage

formulations (10% or less) are suitable for shorter

periods outdoors (e.g., 1 to 2 hrs), and are

recommended for use with young children. Earlier

this year, two new mosquito repellents wereregistered by the U.S. Environmental Protection

Agency and recommended as alternatives to

DEET by the Centers for Disease Control and

Prevention. Picaridin (7% Cutter Advanced) and

Lemon eucalyptus oil (30% Repel Lemon

Eucalyptus) provide relief for about 2 to 4 hrs.

Unlike DEET-based repellents, Picaridin is

essentially odorless and Lemon eucalyptus oil has

a lemon scent. For many people, the new products

will also have a more pleasing feel on the skin.

Both repellents should be appearing on store

shelves soon. Always read and follow directionson the container.

Other Control Possibilities - Many consumer

products claim to attract, repel, capture or kill

mosquitoes. Most of these devices do not

appreciably reduce mosquito abundance or

incidence of bites, or else their claims areunproven. Electrocuting devices or "bug zappers"

using ultraviolet light as an attractant are generally

ineffective in reducing outdoor populations of

mosquitoes and their biting activity. Studies

indicate that mosquitoes make up only a tinypercentage of the insects captured in such traps.

The majority are moths, beetles and other harmless

night flying insects. Other types of mosquito traps

utilize carbon dioxide, warmth, light, and variouschemicals (e.g. octenol) as attractants and claim to

capture tremendous numbers of adult mosquitoes.

Such devices can be quite expensive. Performance

claims to the contrary, such traps seldom have

been shown to reduce populations of biting

mosquitoes on one's property, or the frequency of

bites. In some situations, they could even attract

more mosquitoes into the area they were meant to

protect.

Advertisements for portable electronic devicesusing high frequency, ultrasonic sound routinely

appear in magazines, claiming to keep mosquitoes

and other pests at bay. Some supposedly repel

mosquitoes by mimicking the wing beat frequency

of a hungry dragonfly. Scientific studies have

repeatedly shown these devices to be of negligible

benefit in deterring mosquitoes and reducing bites.

Save your money, as these devices seldom if ever

provide any appreciable measure of protection.

Citronella oil does have mosquito-repelling

properties and the scented candles can providesome protection. For maximum effect, use

multiple candles placed close (within a few feet)

of where people are sitting. A single candle

located at the center or edge of a picnic blanket

probably will not provide much benefit other than

atmosphere. Mosquito-repellent plants, garlic, and

other oft-advertised botanical products generally

are ineffective.

DIAGNOSTIC LAB HIGHLIGHTS

By Julie Beale and Paul Bachi

During the past week we have diagnosed thrips

injury and Rhizoctonia root rot on corn; summer

black stem on alfalfa; frenching on tobacco; brownrot on peach; and Phytophthora fruit rot on

pumpkin.

On ornamentals and turf, we have seen Pythium

root rot and Rhizoctonia root/stem rot on

calibrachoa; downy mildew on impatiens;bacterial soft rot on iris; anthracnose on liriope;

Botryosphaeria canker on rhododendron; rosette

on rose; anthracnose on bentgrass; summer patch

on bluegrass; and brown patch on fescue.


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2012 INSECT TRAP COUNTS

August 16 - 23

Graphs of insect trap counts for the 2012 season

are available on 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 10 0

Armyworm 20 1

Corn earworm 390 3

European corn

borer

0 0

Southwestern

corn borer

422 0

Fall armyworm 91 0

Documents

Kentucky Pest News, August 28, 2012