kentucky pest news may 10, 2011

8/6/2019 Kentucky Pest News May 10, 2011

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Online at:www.uky.edu/KPN

Number 1267 May 10, 2011

CORN

-More Pest Risk with Late Planted Corn

CUCURBITS-Planning for Cucumber Beetle Management

Should Start Early

TOBACCO

-Disease Update for the Week of May 9

CORN

More Pest Risk with Late Planted CornBy Ric Bessin

With the delayed start to the corn season, the risk

of economic losses to insect pests increases

significantly. Probably the most important factor

affecting insect pest pressure in corn is planting

date. When we plant early or even on time we

escape much of the more serious mid- and late-

season insect pressure. The reason for this is that ittakes time for local insect populations to build in

numbers and for southern pests to reinvade the

state. For each pest there are corn stages that are

more attractive than other stages and with some

pests like corn earworm only certain stages are

vulnerable to losses.

FRUIT CROPS-Apple, Peach, Blackberry and Grape Diseases

Appearing Now

SHADE TREES

-Arthropod-Induced Galls Beginning to Appear

DIAGNOSTIC LAB HIGHLIGHTS

INSECT TRAP COUNTS

So producers need to plan on how to manage these

pest problems and anticipate these infestations.

One solution is to use Bt corn with these later

plantings. The table below compares the relative

effectiveness against many of the more common

insect pests in Kentucky. With late plantings the

risk increases significantly with corn earworm

(CEW), fall armyworm (FAW) and corn borers

(ECB and SWCB). The table also includes the

minimum refuge requirement with each

technology. Note that with some of the refuge inthe bag technologies, no additional external refuge

requirement is needed. These external refuges are

sometimes referred to as structured refuges.

Relative Efficacy of Bt corn Technologies

Against Insect Pests in Kentucky

Corn Types

ECB

SWCB

BCW

CEW

FAW

WCRW

Min.

Refuge

Requir

ement

YieldGardCB

++++ ++++ ++ ++ 20%block

Herculex 1 ++++ ++++ ++ + +++ 20%

block

Agrisure CB ++++ ++++ ++ ++ 20%

block

YieldGard

RW

++ 20%

block

Herculex

RW

++ 20%

block

Agrisure

RW

++ 20%

block

YieldGard ++++ ++++ ++ ++ ++ 20%

Lexington, KY 40546

Figure 1. Evidence of stalk tunneling with corn

borers.
http://www.uky.edu/KPNhttp://www.uky.edu/KPNhttp://www.uky.edu/KPNhttp://www.uky.edu/KPN


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Plus block

Herculex

Xtra

++++ ++++ ++ + +++ ++ 20%

block

Agrisure

3000GT

++++ ++++ ++ ++ ++ 20%

block

YieldGard

VT3

++++ ++++ ++ ++ +++ 20%

block

YieldGard

VT2 Pro

++++ ++++ ++ +++ ++++ 5%

block

YieldGardVT3 Pro

++++ ++++ ++ +++ ++++ +++ 20%block

SmartStax ++++ ++++ +++ +++ ++++ +++ 5%

block

Optimum

Intrasect

++++ ++++ ++ 5%

block

Agrisure

Viptera 3110

++++ ++++ +++ ++++ ++++ 20%

block

Agrisure

Viptera 3111

++++ ++++ +++ ++++ ++++ ++ 20%

block

AcreMax 1 ++++ ++++ ++ + +++ ++ RIB +

20%

block

AcreMax

RW

++ RIB

SmartStax

Refuge

Advanced/C

omplete

++++ ++++ +++ +++ ++++ +++ RIB

ECB = European corn borer = Little or no activity

SWCB = Southwestern corn borer + = Poor to fair control

BCW = Black cutworm ++ = Good control

CEW = Corn earworm +++ = Very good control

FAW = Fall armyworm ++++ = Excellent control

WCRW = Western corn rootworm

Even when using Bt corn, growers may still need

to manage insect pests on the late planted refuges.

My experience is that losses due to insect damage

can range from 10 to 25 bushels in late panted

corn when pests are not managed. Last year, a

research plot in Princeton that was planted in mid

June showed more than 40 bushel difference

between Bt and non-Bt corn.

We do have effective foliar insecticides for corn

pests. In terms of timing of foliar insecticide

applications, it will depend on the pest targeted. If

corn earworm is the target, then the start of silking

would be the most beneficial timing, but a single

application only provides partial control at best as

egg laying will occur over a 10 to 12 day period

before silks dry. In addition, sprays are best

directed at the central third of the plant. For this

reason, foliar control of corn earworm has not

been practical or economical.

For fall armyworm control with foliar insecticides

the timing is usually much earlier. This pest is

attracted to vegetative corn and egg laying on

reproductive stage corn is much less common.

Ive seen two leaf corn covered up with eggs while

tasseling corn next to it has no FAW at all.

Because the insect is attacking whorl stage corn

most often and in later stages produces a frass plug

in the whorl to protect against insecticide

applications, when we do need to control it, when

generally time our foliar sprays during mid-whorl

when the larvae are small (less than ). Catching

them small makes control easier as smaller larvae

succumb to a small dose and there is no frass plug.This is also killing them before most of the

defoliation occurs. This insect is relatively easy to

scout for at this stage and we have good thresholds

that can be used to make control decisions. If 5%

of the plants have the hairy egg masses or 25%

of the plants have small larvae, then treatment is

advised. With the strong grain prices likely at the

end of this season, I would consider reducing these

thresholds by about . See Entfact 110, Fall

armyworm in Corn, for more information.

Corn borers, European and southwestern, can also

severely injure late-planted corn. Late planted corn

with escape damage by the first generation of both

Figure 2. Southwestern corn borer.

Figure 3. European corn borer.


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these insects but may still be in the vegetative

stage when the second generations begin their

attacks. So non-Bt late planted corn will need to be

scouted from mid-July onward for corn borers. See

Entfact 108, Southwestern Corn Borer, EntFact106, Predicting Corn Borer Development, and

Ent-16,Insecticide Recommendations for Corn 2011, for more information on these pests, their

thresholds for control, and recommended

insecticides. At the end of the season, heavilydamaged fields need to harvested as soon as

possible to limit losses due to ear drop and stalk

breakage.

CUCURBITS

Planning for Cucumber Beetle Management

Should Start EarlyBy Logan Minter and Ric Bessin

With field planting of cucurbit crops underway,

Kentucky growers need to begin their management

of cucumber beetles. Our two main species, the

spotted cucumber beetle and striped cucumber

beetle, are perennial pests which can inflict severe

damage through direct feeding, especially on

young plants. These beetles also vector pathogens

that lead to bacterial wilt disease of cucurbits.Muskmelons and summer squash are particularly

susceptible to wilt disease. Beginning the lastweek of April, we began seeing striped cucumber

beetles by the hundreds to thousands feeding on

trays of squash seedlings placed in fields near

Lexington and in southern Ohio (immediately

across the river from Greenup Co., KY). Massivenumbers like this can reduce unprotected seedlings

to stubble in a matter of days. Keep in mind, these

trays were the only cucurbits present in fields at

the time which highlights the risk for earlier

plantings.

Because seedling plants are so vulnerable, early

protection is a must. This can be accomplished by

physically excluding pests with row covers orthrough the use of systemic or even foliar

insecticides. The use of row covers offer growers

an insecticide free option while the covers are in

place; typically until flowering. This method is

also approved for organic production. However,

caution should be taken when employing row

covers. It transplanting in hot weather onto black

plastic, be sure not to pin down the plants

against the plastic as they will burn. Becausenatural enemies are also excluded by the covers,

aphid numbers may also become high on theplants. Releasing lady beetles under the covers

may offer some protection. To allow pollination,

covers need to be removed when female flowers

are present, but additional foliar sprays will be

needed to protect against beetles and other pests.

Alternatively, seedlings can be treated with

systemic insecticides such as imidacloprid (e.g.

Admire) or clothianadin (e.g. Belay). Seedling

application should give decent protection for

several weeks, but additional foliar applications of

pyrethroids will probably also be necessary. Thelast alternative would be through the use of weekly

sprays with foliar insecticides. Care should be

taken with foliar sprays to avoid impact on

pollinators; impact can be minimized by applying

sprays late in the afternoon when pollinators are

not active. Hubbard squash varieties are

particularly attractive to beetles, and may be used

as treated trap crops. As always, be sure to use

any insecticides in accordance to product labelsand directions.

Figure 4. Striped cucumber beetles and damage.


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TOBACCO

Disease Update for the Week of May 9By Kenny Seebold

Current ProblemsOver the past week, weve seen a large uptick in

the numbers of reports of Rhizoctonia damping-off

and, more importantly, target spot. The cool and

rainy weather that finally lifted has favored the

development of collar rot as well. Blackleg, orbacterial soft rot, is showing up and may become

worse as the temperatures begin to rise. We

should also expect to see Pythium root rot become

more evident than it has been up to this point.

Compounding the growing threat from diseases is

the likely delay in transplanting that we will see as

growers wait until fields are ready to set the crop.

Plants that are ready for the field now may have tobe held for a few weeks, and can be sitting

ducks for diseases during this period.

From a general management perspective, growersshould be focusing on providing good ventilationfor their plants (as much as is practical given the

weather), maintaining proper fertility (~ 100 ppm

N), and applying fungicides on regular schedule.

The choice of fungicide to use for things like

Rhizoctonia damping-off and target sot depends

on the age of seedlings in the float bed. Plants that

are dime-sized up to those ready to clip 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 option would be Quadris

applied at a rate of 4 cc per 5 gal of spray solution.

The solution should be sprayed onto 1000 sq. ft. offloat bead (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. Refer to Kentucky Pest News No. 1262

(April 5, 2011) for more information, or consult

the 2011-2012 Kentucky-Tennessee Tobacco

Production Guide (University of Kentucky

Publication No. ID-160). Previous issues of

Kentucky Pest News may also be consulted for

tips on managing problems such as blackleg, collarrot, and Pythium root rot.

FRUIT CROPS

Apple, Peach, Blackberry and Grape Diseases

Appearing Now

By John Hartman

Apple. Frogeye leaf spot and apple scab are

present in unsprayed apple trees. Symptoms of

frogeye leaf spot appeared a few weeks ago on

apple and crabapple leaves while scab symptoms

have appeared more recently. In some plantings,

frogeye leaf spot is more prevalent than other

diseases such as scab. Frogeye leaf spot lesions

are small (1/8 - 1/4 inch) distinct circular, brown

spots (Figure 6). The center portion of the spot

may become tan colored, while the outer edge

remains dark brown, giving it a frogeyeappearance. By contrast, apple scab develops as

dark brown to black diffuse spots (Figure 7) which

lack sharp margins. In both cases, as leaf spots

become more numerous and coalesce, leaves turn

yellow and fall.

Frogeye leaf spot is caused by the fungus

Botryosphaeria obtusa . On apples, in addition to

Figure 5. Striped cucumber beetles and damage.


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frogeye leaf spot,B. obtusa causes black rot of the

fruit and a canker disease of twigs and branches

where the fungus overwinters. Apple scab is

caused by the fungus Venturia inaequalis and it

overwinters on last years fallen leaves. Bothdiseases are well-managed with fungicides, but

with excess rain this spring, some infections likelyoccurred despite fungicide applications.

Peach. Leaf curl symptoms are appearing on

foliage. Peach leaf curl is easily recognized in latespring by the thickened, folded, puckered, and

curled leaf blades (Figure 8). Infected leaves or

parts of leaves soon acquire a red or purplish

coloration, making them especially conspicuous.In severe cases, most leaves on a tree may be

infected. Later, the diseased areas develop a

powdery gray coating (fungal spores) and leaves

may then turn brown, wither, and drop from thetree. Peach leaf curl is caused by the fungus

Taphrina deformans. The fungus can infect

peaches, apricots, and nectarines in commercial

orchards as well as in home landscapes. A single

application of fungicide during the dormant period

is sufficient to control this disease.

Blackberry. Orange rust is now visible on

blackberry shoots and leaves in commercial and

native bramble plantings in Kentucky. Infected

plants can be easily identified shortly after growth

appears in spring when newly formed shootsappear weak and spindly. The new expanding

leaves on such canes are stunted or misshapen and

pale green to yellowish (Figure 9). At this stage,

leaf edges may have a bronze color. The lower

leaf surfaces of these infected shoots bear tiny

orange pustules, visible with a hand lens. Later in

spring, the lower surface of infected, fully

expanded leaves is covered with highly visible

waxy, bright orange blister-like pustules (Figure10). Spores from these pustules, when blown to

nearby healthy plants, will initiate new infections.

Diseased blackberries are infected systemically,even below-ground, and will bear little or no fruit.

Orange rust also affects black raspberry.

Depending on the region and the host, there aretwo different, but almost identical, fungi that cause

orange rust disease. These two fungi,

Arthuriomyces peckianus and Gymnoconia nitens,

cause orange rust, the most important of several

rusts of blackberry and black raspberry. It is

important to remove and destroy plants with

infected canes now. If growers wait a few weeks,

they run the risk of contaminating their healthy

plants and having even more orange rust next year.

Because orange rust is also widespread on wild

blackberries and black raspberries in Kentucky, itis important to not only remove infected plants

from the blackberry planting but also remove

similar plants from wild areas nearby. Fungicides

with proven effectiveness against this disease have

not been found. Thus, timely eradication of

diseased plants is essential. Red raspberries are

immune to orange rust disease.

Grape. Anthracnose symptoms are being

observed. On young, succulent shoots,

anthracnose lesions first appear as numerous

small, circular, reddish spots that enlarge, becomesunken, and develop gray centers and round or

angular edges (Figure 11). Slightly raised, dark

reddish-brown to violet-black margins eventually

surround the lesions. Lesions may coalesce,

causing a blighting or killing of the shoot. Grape

anthracnose most commonly occurs on shoots andberries, however fruit stems, leaves, petioles and

tendrils are also susceptible. Anthracnose reduces

the quality and quantity of fruit and weakens the

vine. Once the disease is established in a

vineyard, it can be very destructive. Anthracnose

of grape is caused by the fungusElsinoe ampelina.

The fungus overwinters in vineyards as sclerotia

(fungal survival structures) on infected shoots.

Grape growers will have applied lime-sulfur

fungicide while the vines were still dormant to

suppress this overwintering inoculum. In the

absence of fungicide, during prolonged wet

periods, the sclerotia germinate to produce

abundant spores (conidia) which are spread by

splashing rain to new growing tissues. Once the

disease is established, fruiting bodies (acervuli)

form on diseased areas. These acervuli produceconidia during periods of wet weather and the

conidia are responsible for continued spread of the

fungus and the disease throughout the growing

season.


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Figure 6. Frogeye leaf spot lesions on apple leaves.

Figure 7. Apple leaves with apple scab lesions.

Figure 8. Peach leaf curl disease (P. Bachi photo).

Figure 9. Orange rust on blackberry shoot in spring.

Infected shoot (right) is orange and deformed while

healthy shoot (left) is green.

Figure 10. Orange rust pustules on infected

blackberry leaves.

Figure 11. Grape anthracnose

lesions on grape shoots.


7/8

SHADE TREES

Arthropod-Induced Galls Beginning to AppearBy Lee Townsend

The mostcommon

arthropod

gall makersare tiny

wasps, flies,

some aphids

and their

relatives,and mites.

The galls are

irregular

plantgrowths stimulated by the reaction between plant

hormones and powerful growth-regulating

chemicals produced by the gall makers. Galls may

occur on almost anywhere on the plant but leaf

and twig galls are most noticeable.

Gall-dwellers gain

nutrition and protection

from the plant tissue.

They must attack certaintree species at a particular

time of year to be

successful. Otherwise,

they may not be able to

stimulate tree to produce

gall tissue. Initiation of

leaf galls usually occursaround "bud break" as

new leaves begin to unfold in the spring.

Cutting open

a gall may

reveal its

maker. Theelm pouch is

hollow tube

that will

contain one

too many aphids. White legless grubs or maggotscan be found inside many of them. Galls are often

green during early development and turn red or

brown as they mature.

Although heavily galled leaves may drop

prematurely, these growths generally do not harmtrees and only a portion of the leaves are affected.

Natural enemies and weather help to regulate

populations of gall makers so numbers tend tofluctuate from year to year with occasional

outbreaks.

Applying insecticides to galls will neither cause

them to go away nor will it kill the gall makers.Timing is a key factor; a treatment would have to

be applied before gall initiation. Generally, there

is not enough information available to preventive

time treatments. Also, these applications are morelikely to disrupt natural enemies so they would

probably be counter-

productive.

Galls generally do not

harm plant health.

They have been used

for food, as folk

remedies, and as

sources dyes and inks.

Figure 12. Pouch gall on elm caused by an

aphid.

Figure 13. Aphid inside

pouch gall.

Figure 14. Woolly oak fold gall on red

oak, caused by small fly maggots.

Figure 15. Maggot causing

woolly fold gall. Arrow

points to small wasp larva

that will kill the maggot.


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DIAGNOSTIC LAB HIGHLIGHTSBy Julie Beale and Paul Bachi

Agronomic samples this week have included

Pythium root rot, Rhizoctonia damping off and

target spot on tobacco transplants.

On fruits and vegetables, we have seen cane blight

on blackberry; Botryosphaeria canker on

blueberry; anthracnose on grape; frogeye leaf spoton apple; and nutritional problems including

nitrogen deficiency, burn from high soluble salts

and blossom end rot on tomato.

On ornamentals, we have seen Botrytis blight ongeranium and Botrytis crown rot gerbera; injury

from thrips and aphid infestation on gomphrena,

melampodium and zinnia; anthracnose on beech

and maple; Volutella canker on boxwood; blackroot rot on holly; Rhizosphaera and Stigmina

needle casts on spruce; Seiridium canker on

Leyland cypress; powdery mildew on ninebark;

and winter drying/injury on various landscape

shrubs.

INSECT TRAP COUNTS

April 29 May 6

Graphs of insect trap counts for the 2011 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 2 0

Armyworm 46 372

Corn earworm 0 8

European corn

borer

0 0

Southwestern

corn borer

0 0

Fall armyworm 0 0

kentucky pest news may 10, 2011

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