kentucky pest news september 21, 2010

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Online at: www.uky.edu/KPN

Number 1248 September 21, 2010

VEGETABLES

-Not All Whiteflies are the same

-Tips on Harvesting and Handling Pumpkins

FIELD CROPS

-X-Large Fall Armyworm Caterpillar Population

Should be Past

VEGETABLES

Not All Whiteflies are the Same By Ric Bessin

As usual, it has been a challenging year for

vegetables in Kentucky, wet early and dry the

end of the growing season. Summer is now

slowly releasing its grip and reluctantly giving

way to more typical fall weather patterns. So

what does this have to do with insect problems?

Well, nearly everything. One of the more

notable and unusual problems can be large

numbers of whiteflies, particularly the silverleaf whitefly, Bemisia argentifolii . This past week I

received a report of high numbers in the Green

River area on tomatoes and fall cole crops. What

was notable was that the producer noted that

they very not responding at all to neonicotinoid

insecticides (IRAC Group 4A) which would

include imidacloprid, thiamethoxam, and

clothianidin.

SHADE TREES & ORNAMENTALS

-Rhododendron Canker and Dieback

INSECT TRAP COUNTS

Silverleaf whitefly can cause some unusual

problems in vegetables. On tomatoes it cancause irregular ripening on some varieties. There

are a number of causes of irregular ripening of tomatoes that includes yellow shouldering, gray

wall and blotchy ripening. The causes of these

are often attributed to nutrients

(potassium/nitrogen) balances and

environmental conditions (soil compaction,cool-wet weather, or very hot weather).

However, the irregular ripening caused by

silverleaf whitefly appears a bit different than

the other types of ripening disorders. What we

observed is that if one looked at the fruit fromabove, a section of the fruit did not ripen and

remained green to the core, while the rest

ripened normally. In some instances, one half of

the fruit would be ripe while the other side wasgreen. On squash it causes silverleaf, where the

uppersurface of the leaf is almost white while

the underside of the leaf remains the normal

green color. With broccoli, silverleaf whitefly

has been reported to cause a condition calledwhitestalk, but we have yet to observe this in

Kentucky. What is apparent is that it does not

take large numbers of this whitefly to causethese problems. Where we have seen these

problems on squash and tomatoes, only

moderate infestation of silverleaf whitefly were

found. Research in Florida noted that densities

of 5 to 10 nymphs per leaflet may be used as a

threshold for management of silverleaf whitefly

and irregular ripening on tomato.

Lexington, KY 40546

Figure 1. Silverleaf caused by whiteflies to squash.

http://www.uky.edu/KPN






Silverleaf whitefly has many recognized strains

or biotypes. Different strains may differ in their

ability to vector plant diseases (such as Tomato

Yellow Leaf Curl Virus), and differ enormously

in their sensitivity to some insecticide classes.

For example, the Q-biotype is not controlled

with neonicotinoid insecticides. The Universityof Florida provides a through set of whitefly

management recommendations, including

sanitation and crop-free periods, when the Q

biotype of the silverleaf whitefly is suspected

(http://www.mrec.ifas.ufl.edu/LSO/BEMISIA/v

egetable.htm). Non-neonicotinoid insecticides

that can be used as foliar sprays for silverleaf

whitefly include Oberon (cucurbit vegetables,

fruiting vegetables, leafy green vegetables and

brassica leafy vegetables), Portal (melons,

watermelon, and fruiting vegetables), Knack

(brassica leafy vegetables, cucurbit vegetables,and fruiting vegetables), and Courier (cucurbit

vegetables, leafy green vegetables, head and

stem brassicas, and fruiting vegetables).

As homeowners prepare to bring in houseplants

prior to the first killing frosts this fall, care

should be taken to avoid bringing whitefly

infested plants indoors.

Tips on Harvesting and Handling PumpkinsBy Kenny Seebold

For most of us, pumpkins are the symbol of the

fall season. We are heading into the harvest

season, and local markets are being stocked with

pumpkins for sale. Whether a person grows or

buys pumpkins, it’s important to realize that

careful harvesting and handling will help them

last throughout the season. No one wants to

pick or buy the perfect jack-o’-lantern only to

have it collapse in a heap of mush before it canbe carved!

Let’s start with harvesting. Pumpkins should be

harvested as soon as they are ripe and showgood color. Ripe pumpkins can be left in thefield for a time and they can tolerate a light frost.

A heavy frost can damage pumpkins, so they

need to be taken from the field and stored

properly. Try not to harvest pumpkins when the

fruit and vines are wet, since this can lead to the

development of fruit rots. The best time to

harvest is during sunny and dry weather. Cut

vines with a pair of shears and leave 4 to 5

inches of stem, or handle, attached to the fruit tofurther reduce the chances of rot. Leave

pumpkins with any sign of rot in the field –these won’t store for very long. Handle

pumpkins carefully to avoid bruising or

puncturing the rind. Damaged pumpkins aremuch more likely to rot. Store pumpkins in a

cool and dry location – avoid exposure to direct

sunlight as much as possible to prolong the life

of the fruit. Store pumpkins in single layer to

promote good movement of air; this keeps the

environment less favorable to the fungi and

bacteria that rot pumpkins.

When buying pumpkins, avoid fruit that showany signs of rot. Also steer clear of pumpkins

that don’t have handles, or those that have

handles that are rotting or in poor condition.

Handle pumpkins carefully on the way home,

and store them as discussed earlier. The goal is

to keep pumpkins cool and dry, and out of direct

sunlight so they will last long into the fall. Keep

in mind that once a pumpkin is carved, its days

are numbered. After cutting, exposed surfaces

become colonized by rotting fungi and bacteria.

The warmer the weather after a pumpkin is

carved, the quicker fungi and bacteria will act tobreak it down. For more information on

harvesting and handling pumpkins, refer to UKCooperative Extension Service publication ID-

36, the 2010-2011 Vegetable Production Guide

for Commercial Growers.

Figure 2. Irregular ripening caused by whiteflies.

http://www.mrec.ifas.ufl.edu/LSO/BEMISIA/vegetable.htm








FIELD CROPS

X-Large Fall Armyworm Caterpillar

Population Should be PastBy Doug Johnson

The X-large population of fall armyworm(FAW) caterpillars generated by the X-Large

population of FAW moths in late August (as

indexed by UK-IPM trap counts, See: KPN 1245

Aug 31, 2010) should be past. This does NOT mean that the threat from FAW is over. It simply

means that the large pulse of caterpillars

generated by the extraordinary number of moths

have completed the damaging stage of their life

cycle. We do have evidence (especially forage

fields having to be treated a second time) that

this pulse did cause some producers x-tra

trouble.

My best guess is that the FAW caterpillars

produced from the X-large moth flight are now

in the pupal (resting) stage, from which adult

moths will emerge (See life cycle table below).

So it is possible that another large flight could

occur this fall, depending upon temperature. The

only other large fall occurring FAW population

for which we have record, occurred on Oct. 5,

2007. This led to large numbers of FAW mostly

feeding on volunteer corn (fortunately) in area

wheat fields.

Regardless of whether or not we see another

large surge of moths, FAW caterpillars will be

present until at least the first killing frost and

one should continue to monitor crops at risk. By

now corn and most soybeans and sorghum are

no longer in danger. Grass and alfalfa forages,

especially newly established stands are at

greatest risk. Additionally, any newly

established grass stands including wheat, lawns

and grass covers for construction and

reclamation should be watched.Fall Armyworm Life

Stages

Ave. Length of Life Stage

(Ave. Temp 77oF)

Egg 3 days

Larva (caterpillar –

damaging stage)

14 days

Pupa (resting stage) 12 days

Adult (reproducing and

dispersing stage)

Complete life cycle about

30-32 days.

SHADE TREES & ORNAMENTALS

Rhododendron Canker and DiebackBy John Hartman

Rhododendrons are grown in landscapes

throughout Kentucky. Despite fairly fastidiousgrowing requirements such as a need for moist,

but not wet, acid soil; screening from the hot

sun; and shelter from cold, cutting winds, theyare popular with many gardeners. Onset of hot,

dry weather this year may be having an effect on

Rhododendron canker disease.

Dieback and canker, caused by the fungus

Botryosphaeria dothidea, is often found on

individual rhododendron branches. The first

indication of a problem usually is the appearance

of individual stems with drooping, wilted-looking leaves that are rolled inward. The wilt

symptom may spread until the whole plant is

affected (Figure 3). Closer examination of

affected stems reveals a reddish-brown to black

sunken canker that girdles the stem (Figure 4).

Cankers develop slowly and may appear a

month or two after infection of a pruning wound,

an injury, or a leaf scar. Mature cankers may

produce tiny fungal fruiting structures (pycnidia)

on the stem (Figure 5) which bear spores of the

fungus. Pruning tools have been implicated in

spread of the fungal spores. This disease ismore likely to occur on plants suffering from

heat and drought stress or winter injury. Thus,

recent hot, dry weather may have stressed

Rhododendrons creating conditions favorable

for canker-causing fungi such as

Botryosphaeria.

Figure 3. Rhododendron with rolled leaves

and dead branches due to Botryosphaeria

canker infections on the stem.



INSECT TRAP COUNTS

September 10-17

Graphs of insect trap counts for the 2010 season areavailable 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 0 16

Armyworm 8 14

Corn earworm 0 121

European corn

borer

0 0

Southwesterncorn borer

0 0

Fall armyworm 57 36

Figure 4. Botryosphaeria canker causing browning of

the Rhododendron stem.

Figure 5. Tiny dark pimple-like pycnidia of the

Botryosphaeria fungus on a Rhododendron stem.

kentucky pest news september 21, 2010

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