kentucky pest news june 28, 2011

8/6/2019 Kentucky Pest News June 28, 2011

1/11

Online at:www.uky.edu/KPN

Number 1274 June 28, 2011

WATCH FOR

-Far Western Kentucky Producers Need to Check

for Corn Earworm!

CORN

-Watch for Fall Armyworm in Late Corn

-Recognizing Gosss Wilt of Corn

TOBACCO-Disease Update

VEGETABLES-Corn Earworm (aka Tomato Fruitworm) and

Vegetables

WATCH FOR

Far Western Kentucky Producers Need to

Check for Corn Earworm!By Doug Johnson Extension Entomologist, Cam

Kenimer Fulton Co ANR Agent, and Patty

Lucas IPM Specialist

Cam Kenimer is capturing very large numbers of

corn earworms in his Fulton Co. KY trap. (See:

http://ces.ca.uky.edu/fulton/InsectTraps)

Although these large numbers have not been seen

in the Princeton or Lexington traps, the pest is

being reported in states to our south and west. This

can be a very destructive pest and producers

should be on the lookout for its presence.

This insect,Helicoverpa zea, variously called the

corn earworm, cotton bollworm, and tomatofruitworm, and in KY, the soybean podworm,

attacks a wide range of field and garden plants

including corn, cotton, soybeans, tomatoes, and

tobacco. It may also be occasionally found on

alfalfa and garden beans. Do not confuse the corn

earworm with the tobacco budworm,Heliothis

virescens. They are related pests but often respond

very differently to insecticides. Additionally, the

FRUIT CROPS

-Peach Fruit Diseases-Blackberry Rosette (Double Blossom) Disease

Appearing

LANDSCAPE PLANTS

-Landscape Plant Problems Observed with TurfHerbicide Applications

INSECT TRAP COUNTS

DIAGNOSTIC LAB HIGHLIGHTS

budworm is a much more destructive pest in

tobacco.

Corn earworm adults are buff to light green mothswith a wingspan at rest of about . Eggs are

white to pink about 1/30 wide and laid singly.

Larvae (worms) are small to 1 in length whenfull grown. They are usually tan to pale green with

several dark stripes down the back. However,

color may be quite variable, with some individuals

almost black.

Lexington, KY 40546

Figure 1. Corn earworm red phase.
http://www.uky.edu/KPNhttp://www.uky.edu/KPNhttp://www.uky.edu/KPNhttp://ces.ca.uky.edu/fulton/InsectTrapshttp://ces.ca.uky.edu/fulton/InsectTrapshttp://ces.ca.uky.edu/fulton/InsectTrapshttp://www.uky.edu/KPN


2/11

Photos courtesy of Marlin Rice and Iowa StateUniversity.

CORN

Watch for Fall Armyworm in Late CornBy Ric Bessin

With the late corn planting, growers need to be

watching their corn for fall armyworm feeding.

With this insect it is important to catch infestationsearly as later stages of the insect are more difficult

to control. While many fields have been planted to

corn hybrids expressing Bt genes that provide

partial to high levels of fall armyworm control,

non-Bt corn planted in refuge fields should be

monitored regularly.

Corn is most attractive to fall armyworm while it

is in the vegetative stages. Late planted fields that

remain vegetative later into the season will bemost likely to experience some level of fall

armyworm infestation. As the larvae increase insize while feeding they begin to form a frass

plug in the whorl and feed underneath its

protection. The plug can limit the penetration ofinsecticides into the whorl. For this reason, it is

always much easier to control younger fall

armyworm larvae rather than older larvae.

Begin checking corn at the mid whorl stage for fall

armyworm activity. Survey 20 consecutive plants

(selecting the first randomly) from at least 5

locations in the field. Small larvae cause "window

pane" damage to leaves similar to European corn

borer. A few days before tasseling, look for large

larvae in the whorls which will be pushed out

when the tassels emerge. These larvae may attack

young ears. Continue to check for this insect until

silks begin to dry. Control needs to be considered

when egg masses are present on 5% of the plants

Figure 2. Corn earworm brown phase.

Figure 3. Corn earworm green phase.

Figure 4. A fall armyworm larva showing the inverted

"Y"-shaped mark on the front of the head.

Figure 5. Fall armyworm egg masses are covered

with moth scales and fine bristles.


3/11

or when 25% of the plants show damage

symptoms and live larvae are still present.

Controlling larger larvae, typically after they are

hidden under the frass plug, will be much more

difficult.

Recognizing Gosss Wilt of CornBy Paul Vincelli

Gosss Wilt is an emerging bacterial disease ofcorn (dent corn, popcorn, sweet corn) in the

Midwest. For decades, this disease has caused

problems in several Plains states, especially in

Nebraska, Colorado and Wyoming. In the pastfew years, the disease has also been found in

scattered fields in Indiana and Illinois, causing

losses as high as 60 bu/acre. Although Kentucky

may be too far south for serious outbreaks, it is

worth keeping a watch out for this disease.

SymptomsInfection of corn by the Gosss wilt bacterium

(Clavibacter michiganensis subsp. nebraskensis)

produces necrosis of leaves (Figure 7). The

disease results in long, tan spots of dead tissue

anywhere on leaves. Infected leaves usuallyexhibit blighting of leaves. These symptoms can

be easily confused with other diseases and

disorders. However, there are a few distinctive

features to look for. The main symptom that

distinguishes Gosss wilt from other problems is

the presence dark green, water-soaked flecks or

freckles (Figures 8-9). Also, on wet leaves, only

might be able to observe a cloudy bacterial

exudate on infected tissues. When these exudates

dry, they leave a faint shiny cast on lesions.

Infections can also result in the stalk (Figure 10-

11). Vascular infection often results in symptoms

of drought stress and premature plant death.

Management NotesThe bacterium that causes Gosss wilt survives

between seasons in infested corn residue.

Therefore, the risk of disease is higher under

conservation-tillage and/or continuous corn.

Rotation of even one year away from corn reduces

disease pressure substantially. Hybrids of yellow

dent corn with resistance to Gosss wilt are

available. The bacterium also survives in

association with corn seed. Seed producers may

be required to obtain phytosanitary certificates forcorn seed export.

Fungicides do not provide protection against a

bacterial disease like Gosss wilt. Crops other

than corn are not affected by this disease.

Figure 6. A fall armyworm larva and the frass used to

plug the whorl.

Figure 7. Goss's wilt of corn (photo by Alison Robertson,

Iowa State University).


4/11

TOBACCO

Disease UpdateBy Kenny Seebold

The first reported case of blue mold in the U.S.

was found in Chester County, PA on June 23. The

outbreak occurred on burley seedlings in float

beds, and all plants were destroyed; no blue moldhas been found to date on field-grown tobacco in

the area. For Kentucky producers, the PA source

does not pose a serious risk at this time. The

North American Plant Disease Forecast Center is

projecting that spores from areas with blue mold

will move up the eastern coast of the U.S. Even

though the threat is low from blue mold at this

time, our weather has been favorable for disease

Figure 8. Goss's wilt of corn, showing dark green flecks and

"freckles" (photo by Carl Bradley, University of Illinois).

Figure 9. Goss's wilt of corn, showing dark green flecks and

"freckles" (photo by Alison Robertson, Iowa State

University).

Figure 10. Stalk and leaf symptoms of systemic Goss's wilt

(photo by Howard F. Schwartz, Colorado State University,

Bugwood.org).

Figure 11. Stalk symptoms of systemic Goss's wilt (photo

by Howard F. Schwartz, Colorado State University,

Bugwood.org).


5/11

development so growers should scout fields

regularly and be prepared to act if the disease is

found.

For recommendations on the control of tobaccodiseases, please consult past issues of the

Kentucky Pest News, or the Kentucky-TennesseeTobacco Production Guide (ID-160), available at

http://www.ca.uky.edu/agc/pubs/id/id160/id160.pd

f. For up-to-date reports on the status of blue

mold and other tobacco disease information, checkthe KY Blue Mold Warning System online at

www.uky.edu/Agriculture/kpn/kyblue/kyblue.htm.

VEGETABLES

Corn Earworm (aka Tomato Fruitworm) and

VegetablesBy Ric Bessin

As reported by Doug Johnson and Patty Lucas

earlier in this issue of the KPN, record corn

earworm moth captures were noted in the

Purchase Area last week. While corn earworm can

be a pest of field corn and soybeans, it is also a

serious pest of sweet corn and tomato. Besides

corn and tomatoes it will also attack okra, peppers,

and some other vegetables. The numbers capturedlast week in the Purchase Area were significant

not only because of the exceptionally high

numbers, but also because these levels are

occurring so early in the season. In addition tothat, many crops are behind because of the late

planting due to rain-soaked fields this spring.

The corn earworm is potentially the mostdamaging insect pest of sweet corn and tomato.

The larvae are highly variable in color, ranging

from pale yellow, to red, to green, to brown with

pale stripes running lengthwise. The larvae havefour pairs of prolegs and are densely covered withmicroscopic spines that make the larvae feel

rough.

The moths lay eggs at night on leaves near green

fruit at the outer edges of the plant. The dome-shaped eggs are white when first laid and develop

a reddish brown band before hatching. After the

egg hatches, the larva feed for a short period of

time on the foliage before attacking the fruit. Theyprefer to feed on green fruit and usually do not

enter ripe fruit. Damage consists of deep watery

cavities frequently in the stem end of the fruit.

During its development, one larva may injureseveral fruit.

Sweet corn producers need to begin managing

corn earworm at silking. The adult females areattracted to volatiles emitted by the fresh silks. Sothe bulk of egg laying occurs during the 10 or so

days that the silks are fresh. It is during this period

that insecticides will have their greatest benefit

controlling corn earworm. Generally the first

insecticide for corn earworm is applied at theinitiation of silking and reapplied every 3 to 5 days

Figure 12. Corn earworm moth.

Figure 13. A group of corn earworm larvae showing

their variability in color.
http://www.ca.uky.edu/agc/pubs/id/id160/id160.pdfhttp://www.ca.uky.edu/agc/pubs/id/id160/id160.pdfhttp://www.ca.uky.edu/agc/pubs/id/id160/id160.pdfhttp://www.uky.edu/Agriculture/kpn/kyblue/kyblue.htmhttp://www.uky.edu/Agriculture/kpn/kyblue/kyblue.htmhttp://www.uky.edu/Agriculture/kpn/kyblue/kyblue.htmhttp://www.ca.uky.edu/agc/pubs/id/id160/id160.pdfhttp://www.ca.uky.edu/agc/pubs/id/id160/id160.pdf


6/11

until the silks finish drying. Sprays should be

directed to the center third of the plant.

In most years the corn earworm (tomato

fruitworm) is a late-season pest of tomato and

growers often dont need to do anything until the

field corn in their area begins to dry down. This

year, with the early high numbers in the Purchase

Area, growers in those counties should begin to

monitor their field for any signs of fruitwormdamage. The early signs are small to medium

sized holes in the developing fruit, occasionally

tomato fruitworm will produce a series of holes or

attack more than one fruit in a cluster. While this

pest tunnels into the tip of the corn ear, withtomato it remains on the outside of the fruit

producing holes that extend up to inch in depth.

At the first signs of fruitworm activity, growers

should use an insecticide for fruitworm control.

There are a number of recommended insecticides

for corn earworm and tomato fruit worm control

that come from several insecticide different

classes. Entomologists in the Midwest have noted

reduced sensitivity (note that I avoid saying

resistance) of corn earworm to pyrethoid

insecticides in small plot sweet corn trials. Where

growers feel they are not getting the level of

control that expect, other modes of action (IRACgroupings) are available. However, before

blaming the insecticide, growers also need to make

certain that timing, coverage, and calibration

where correct. A complete listing of insecticides

recommended for Kentucky vegetable production

is listed in ID-36.

FRUIT CROPS

Peach Fruit DiseasesBy John Hartman

When peach fruits become infected with decayfungi or other pathogens, the losses can be

substantial because by harvest time many of the

expenses for growing the crop have already

occurred. In some Kentucky orchards diseases

affecting peach fruits are beginning to appear.Rainy spring weather this year will have made

many of these diseases more severe than usual.

Growers should recognize the various peach fruit

diseases so that appropriate disease managementmeasures can be implemented for next year.

Peach scab. This disease is a common problem in

Kentucky orchards especially where an earlyprotective fungicide agenda was not strictly

maintained. The scab fungus, Cladosporium

carpophilum, causes primarily an unsightly

spotting of the fruit skin (Figure 15). Scab first

appears as small, round, green to black spots on

the fruit about six or seven weeks after petal fall.

Fruit lesions first appear as small, greenish,

circular spots which later become black and

velvety, primarily on the stem end of half-grown

to mature fruit. When the disease is severe, the

lesions often run together which results in cracked

or deformed fruit. Although the most conspicuoussymptoms of peach scab occur on the fruit, the

disease can also occur on twigs and leaves. Shoot

and twig infections are circular to oval, brown in

the center with slightly raised purple margins. Thefungus overwinters in twig lesions and becomes

active during shuck split (just after petal fall) and

in the weeks following.

Bacterial Spot. This disease, caused by

Xanthomonas arboricola (X. campestris pvpruni)

may appear on some cultivars in years with

stormy, rainy weather. Leaf lesions are brown toblack and generally angular in outline. Often the

centers of spots fall out, and margins have a

reddish coloration; severely infected leaves turn

yellow and drop. Infected fruit develop brown toblack lesions (Figure 16). Lesions may coalesce

and the fruit can become pitted and cracked.

Figure 14. Tomato fruitworm damage to developing fruit.


7/11

Brown Rot. Brown rot disease, caused by thefungusMonilinia fructicola, reduces yields

primarily by decaying the fruits on the tree and

after harvest. All stone fruits are highly

susceptible to brown rot. Warm, wet, humidsummer weather conditions favor infections by the

brown rot fungus. Decay begins as a smallcircular brown spot which rapidly expands to

destroy the entire fruit. Sometimes the brown rot

fungus can be seen sporulating on the surface ofthe decayed fruit (Figure 17). Rotted fruits may

fall or remain on the tree as mummies. The brown

rot fungus also causes blossom blight and twig

blight in the spring.

Anthracnose. Caused by a fungus called

Colletotrichum gloeosporioides, anthracnose is

sometimes referred to as crater rot. This fruit rot

disease appears to affect nearly all peach cultivarsand may appear continuously from June through

August. Anthracnose is characterized by circular,

sunken, tan lesions on ripening fruit (Figure 18).

The sunken lesions have a glistening or slimy

surface, unlike brown rot disease with which it

could be confused. Lesions may begin as smallchlorotic spots on the fruit surface and gradually

enlarge so that the rotted tan spot is visible. The

decay continues to enlarge to an inch or two

inches in diameter by which time the fruit is

significantly damaged. When the decay becomes

quite advanced on the tree or after harvest, thefruit surface eventually takes on a grayish black

color. Leaf and twig symptoms are generally not

seen with this disease. Fungal spores are spread

through splashing rain and infections are favoredby warm, moist weather. Although symptoms are

found primarily on ripe or ripening fruit, infections

could occur during bloom and the fungus could

then remain latent in developing fruit. Outbreaks

of the disease in Kentucky this year could be

related to wet spring weather.

Fungicide suggestions and timing for peach fruitdiseases are found in the U.K. Cooperative

Extension bulletin ID-92, Kentucky Commercial

Tree Fruit Spray Guide 2011, available at County

Extension Offices.

Figure 16. Bacterial spot of peach.

Figure 15. Peach scab disease dark spots on the fruit.

Figure 17. In later stages, shown here, when fruit

is extensively decayed, peach brown rot may

develop heavy fungal growth and sporulation on

the surface.


8/11

Blackberry Rosette (Double Blossom) Disease

AppearingBy John Hartman

Rosette disease, also called double blossom, iscaused by the fungus Cercosporella rubi. This

disease is being observed frequently on

blackberries in the field this summer and is the

subject of recent diagnoses in the plant disease

diagnostic laboratory. Disease symptoms appearthe year after infection occurs, so it is possible that

wet spring weather last year provided conditions

for disease incidence this year. Blackberry rosette

is a very serious disease which can destroy a

blackberry planting by reducing fruit yield and

quality and causing death of canes. Rosette occurs

in all regions of Kentucky.

Symptoms. Blackberry growers will notice

flowers with distorted petals (Figure 19), giving

the appearance of a double flower (hence double

blossom). The mycelium of the fungus growsover the flower pistils and stamens producing a

whitish spore mass (Figure 20). Unopened

flowers are usually elongated and larger, coarser,

and redder than normal. Sepals on infected

flowers enlarge and occasionally become leaf-like.

On some varieties, shoots may appear abnormal

with leafy proliferation (rosette) or witches broom

(Figure 21) while on other varieties the rosette

may fail to develop but infected blossoms are

sterile. Berries do not develop from infected

branches and other parts of the cane may produce

only small, poor quality fruit. Thus, this loss of

yield should concern growers.

How the disease is spread. Blackberries canbecome infected from spores produced on wild

blackberries nearby. The disease begins when the

buds of new canes become infected from fungal

spores produced on infected distorted flowers ofold canes. Symptoms from these infections do not

appear until the next year. Blackberry nursery

stock can harbor the causal fungus in rooted

plants, but not in root pieces, which are commonlysold for blackberry propagation. Successful

growth of disease-free blackberries from root

pieces taken from infected plants is possible while

rooted plants from the same source may becomediseased.

Disease management. Select a site isolated from

wild blackberries or other brambles. In many

parts of Kentucky, this may be difficult. Use

disease-free nursery stock, roots only. If the

disease is not already severe, infected rosettes and

blossom clusters should be picked off and

destroyed before they produce spores. Old canes

should be removed and destroyed immediately

after harvest. Remove and destroy wild

blackberries and other brambles near the planting.

If the disease is serious, application of

azoxystrobin (Abound) from first bloom through

petal fall may be needed. Fungicides may not be

totally effective when disease pressure is high.

Some growers control this disease by harvesting

blackberries in alternate years and destroying the

above ground parts of both the new and old canes

in spring every other year. Splitting the planting

into two fields allows harvest every year with

biennial cropping on each half. There are no

blackberries resistant to rosette (double blossom)disease, but cultivars such as Navaho and Arapaho

may have some tolerance to this fungus. Rosette

rarely occurs on red and black raspberries.

Figure 18. Anthracnose disease on peach may cause a

slightly sunken brown lesion.


9/11

LANDSCAPE PLANTS

Landscape Plant Problems Observed with TurfHerbicide ApplicationsBy J.D. Green, Julie Beale, and John Hartman

During the past few weeks the Plant Disease

Diagnostic Laboratory has received landscape

plants displaying injury symptoms from areas

where Imprelis herbicide had been applied earlierin spring. Imprelis (aminocyclopyrachlor) is a

herbicide product recently introduced for control

of broadleaf weeds in lawns, golf courses, and

other turfgrass situations.

The majority of the trees affected appear to be

spruce (in particular, Norway spruce, but also blue

spruce) and white pine (Figure 22). Visual

symptoms on conifers include dieback beginningat needle tips, needle twisting, and curled andtwisted branches of new growth. Symptoms often

start at the top and outer edges of the tree canopy.

In some cases, needle browning will progress

throughout a greater part of the tree. The size and

age of trees affected vary, including younger as

well as older trees with large canopies. On

sensitive deciduous trees and broadleaf plants leaf

epinasty (twisting and cupping) along with

deformed leaf expansion are observed particularly

on new growth (Figure 23).

All variables associated with this problem have

not been fully determined. Furthermore, the long-

term outcome of the plants affected is difficult to

assess at this time. Other factors can also cause

injury to landscape plants and environmental

conditions before, during, and after an application

could contribute to injury. Thus, it is important to

gather as much information as possible to help

with diagnosis of potential herbicide injury

problems. When submitting samples to the Plant

Disease Diagnostic Laboratory, it is helpful when

name(s) of all herbicide products which have beenapplied are indicated for a given site, when and at

what rate applications were made, and when plant

symptoms first appeared.

Herbicide damage to spruce and pine has also been

reported in other areas of the country. Additional

details are highlighted at the following website:

Figure 19. Distorted blackberry flower resulting

from rosette disease infection (APS photo).

Figure 20. Microscopic view of hair-like growth of

Cercosporella rubifungus on the surface of infected

blackberry flower parts (P. Bachi photo).

Figure 21. Bunchy, "witches broom" growth

of blackberry shoots as a result of blackberry

rosette disease (P. Bachi photo).


10/11

http://www.agry.purdue.edu/turf/tips/2011/06172011_Imprelis.html

DIAGNOSTIC LAB HIGHLIGHTS

By Julie Beale and Paul Bachi

Agronomic samples this week have included

deficiencies of potassium, phosphorus and zinc on

corn; potassium deficiency and injury from thripsfeeding on soybean; and Pythium root rot,

Fusarium wilt, tomato spotted wilt virus, soreshin

(Rhizoctonia), temporary phosphorus deficiency

and manganese toxicity on tobacco.

On fruits and vegetables, we have seen

anthracnose and black rot on grape; double

blossom on blackberry; cedar-apple rust on apple;

bacterial spot, oriental fruit moth and plumcurculio injury on peach; bacterial spot and brown

rot on plum; leaf spot (Coccomyces) on cherry;

Rhizoctonia and Fusarium root/stem rots, southern

blight and thrips injury on bean; Fusarium stem roton cabbage; bacterial stalk rot on sweet corn;bacterial wilt on cucumber; Rhizoctonia stem rot

on eggplant; bacterial spot on pepper; Pythium and

Rhizoctonia stem rots on potato; bacterial canker,

early blight and southern blight on tomato; and

Fusarium stem rot on watermelon.

On ornamentals and turf, we have seen black root

rot on wild ginger; southern blight on Jacobs

ladder; Alternaria leaf spot on zinnia; cedar-quince

rust on hawthorn; spot anthracnose on linden;

anthracnose on maple and oak; Rhizosphaeraneedlecast and chemical injury on spruce;

Phyllosticta leaf spot on maple; black spot,

Botrytis bud blight and rosette on rose; brown

patch on fescue; and summer patch and Pythium

root rot on bluegrass.

Figure 22. Brown needles on Norway

spruce.

Figure 23. Leaf distortion on tulip

popular.
http://www.agry.purdue.edu/turf/tips/2011/06172011_Imprelis.htmlhttp://www.agry.purdue.edu/turf/tips/2011/06172011_Imprelis.htmlhttp://www.agry.purdue.edu/turf/tips/2011/06172011_Imprelis.htmlhttp://www.agry.purdue.edu/turf/tips/2011/06172011_Imprelis.htmlhttp://www.agry.purdue.edu/turf/tips/2011/06172011_Imprelis.html


11/11

INSECT TRAP COUNTS

June 17-24

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 3 3

Armyworm 19 716Corn earworm 49 30

European corn

borer

1 0

Southwestern

corn borer

5 0

Fall armyworm 0 0

kentucky pest news june 28, 2011

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