Upload
awpmaint
View
216
Download
0
Embed Size (px)
Citation preview
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/KPN8/6/2019 Kentucky Pest News June 28, 2011
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.
8/6/2019 Kentucky Pest News June 28, 2011
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).
8/6/2019 Kentucky Pest News June 28, 2011
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).
8/6/2019 Kentucky Pest News June 28, 2011
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.pdf8/6/2019 Kentucky Pest News June 28, 2011
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.
8/6/2019 Kentucky Pest News June 28, 2011
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.
8/6/2019 Kentucky Pest News June 28, 2011
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.
8/6/2019 Kentucky Pest News June 28, 2011
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).
8/6/2019 Kentucky Pest News June 28, 2011
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.html8/6/2019 Kentucky Pest News June 28, 2011
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