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8/8/2019 Kentucky Pest News September 21, 2010
http://slidepdf.com/reader/full/kentucky-pest-news-september-21-2010 1/4
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.
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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.
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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.
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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.