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8/7/2019 Kentucky Pest News April 19, 2011
http://slidepdf.com/reader/full/kentucky-pest-news-april-19-2011 1/4
Online at: www.uky.edu/KPN
Number 1264 April 19, 2011
WATCH FOR
-2011 Armyworm1 Populations appear to be
Following 2006 & 2008 Outbreak Levels
CORN
-SmartStax Refuge in the Bag Receives
Approval
WATCH FOR
2011 Armyworm1
Populations appear to be
Following 2006 & 2008 Outbreak Levels By Doug Johnson, Extension Entomologist &
Patty Lucas, Extension IPM Specialist
2011 captures
of armyworm
moths in UK-
IPM
pheromone
baited traps so
far mimicthose seen in
recent
outbreak years
(2006 &
2008). An“outbreak”
year is simply
one when the
populationreaches a size
that requires control and/or produces crop
damage that exceeds the cost of control.Armyworms overwinter in Kentucky and are
found in fields every year. They usually do notreach damaging populations but producers and
consultants should be careful not to overlook
them until it is clear that damaging levels are not
present.
FRUIT CROPS-Scab Infections Are Likely On Apple and
Crabapple
DIAGNOSTIC LAB HIGHLIGHTS
INSECT TRAP COUNTS
The UK-IPM monitoring system provides amethod of developing some degree of risk
assessment. Because there are many years of
trap capture data available and information onwhen populations resulted in crop loss, we can
compare the current year to what has happened
on a recurring basis in past years. See graphs of
UK-IPM trap captures at:
http://www.uky.edu/Ag/IPM/ipm.htm
Select the insect of interest from the list at the
bottom center of the screen.
How the Graphs are Presented: Each graph
contains at least two lines. The Blue line is a
rolling five year average. This line does NOT
include outbreak years; so it indicates a
population trend that has little risk of cropdamage. Weekly trap catches from the current
year appear in Green. Capture from an outbreak
year is plotted in Red and also in Black if there
is a second outbreak year shown.
Using The Graphs: The risk from thesepopulations can be viewed as follows. If the
Green line appears to be occurring at about the
same levels as the BLUE there is no evidence of
elevated risk. The damage potential increases
with the separation of the Green line above the
Blue line. Increased scouting for armyworm
damage will be needed if the Green line
approaches or exceeds the Red outbreak line.
Lexington, KY 40546
Figure 1. AW Moths in trap.
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Applying the Information : Insect-trap graphs,
provide a quick and simple way to assess risk
from the current population trend each week and
to adjust scouting priorities. At present, graphsare updated on Friday afternoon.
Restrictions:
• These data do not predict occurrences in
specific fields. They only tell you when
risk is elevated so you can target thattime period for sampling.
• The absence of elevated risk does not
mean there will be no damage.
Armyworms are present in most fields
every year so there is ALWAYS some
level of risk. These data only describewhen risk is greater than one would
normally expect.
• The presence of elevated risk does not
mean that damage will occur in an
individual field. The graphs are only a
snap shot in time of what is ordinary or
out of the ordinary.
• These graphs represent the capture of
adult moths. Moths are not the
damaging stage.
• The larval (juvenile) or caterpillars are
the damaging stage. Caterpillars will
occur at some time after the moths are
flying. This why the graphs provide an
“Early Warning” before the damageoccurs.
Scouting for the Damaging Stage: The graphs
only show moth flight, one must scout for the
caterpillars or damage to assess the damage
potential. Using the moth capture as a beginningpoint (BioFix) one can use temperature data to
make a general prediction as to when feeding
damage can be expected. This is the stage that
important to scout. This prediction has not yetbeen mechanized. So if the population continues
to follow the outbreak year data, a prediction of
the dates when caterpillars are expected to be
present will be published in each Kentucky Pest
News at:
http://www.ca.uky.edu/agcollege/plantpathology
/extension/kpnindex.htm,
and the Grain Crops Blogspot at:
http://graincrops.blogspot.com/
Crops at Risk: Armyworms can feed on all grass
crops including corn, timothy, millet, bluegrass,
small grains and some legumes. In Kentuckythe crops most commonly infested are corn,
wheat and grass hay. Major damage is unusual,
but this pest occasionally can inflict major
losses.
See Entfact-111 Armyworms in Small Grains at:
http://www.ca.uky.edu/entomology/entfacts/entf
actpdf/ef111.pdf andEntfact – 109 Armyworms in Corn at:
http://www.ca.uky.edu/entomology/entfacts/entf
actpdf/ef109.pdf
These fact sheets will give a general overview of
the insect’s description, biology and damage.
Controls: Insecticides registered for use against
armyworms may be found in Ent-16, 17 or 47;
Insecticide Recommendations for Corn or Small
Grains or Alfalfa and Pastures & Hay), available
at:
http://pest.ca.uky.edu/EXT/Recs/welcomerecs.html
Future Plans: It is hoped that in future the
current graphs will also display estimations of
when the caterpillar stage is likely to occur. At
present this information is provided in Kentucky
Pest News articles.
1The armyworm, Mythimna interpunctella
(Haworth), may be found listed in earlier publications
as armyworm or true armyworm, Pseudaletia
unipuncta (Halworth). The insect is the same, only
the names have been changed.
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CORN
SmartStax Refuge in the Bag Receives
ApprovalBy Ric Bessin
This past week the EPA approved SmartStaxrefuge in the bag which is being sold as Genuity
SmartStax Refuge Complete by Monsanto and
SmartStax Refuge Advanced by DowAgrosciences. This is the first approved refuge
in the bag technology that controls both above
and below ground pests. No additional refuge
needs to be planted. The seed in each bag is a
blend of 95% SmartStax protected seed and 5%
refuge seed. SmartStax controls a wide range of
pests including rootworms and above ground
caterpillars and uses dual modes of action (gene
pyramiding) and the refuge seed todelay/prevent resistance by insect pests.
FRUIT CROPS
Scab Infections Are Likely On Apple and
CrabappleBy John Hartman
Apple scab, caused by the fungus Venturia
inaequalis, is the most common and destructivedisease of Kentucky apples. Apple scab affects
several different hosts including: apples and
flowering crabapples ( Malus spp.), hawthorn
(Crataegus spp.), mountain ash (Sorbus spp.),
firethorn (Pyracantha spp.), and loquat( Eriobotrya japonica). Pear (Pyrus spp.) is
infected by a related fungus, Venturia pirina,
which causes nearly identical symptoms.
Infections occur on leaves, fruits, and blossomsand first appear as velvety brown to olive
colored spore-filled lesions that turn black with
age (Figure 2). Infected apple leaves eventually
turn yellow and drop (Figure 3). Fruit scablesions develop a corky appearance (Figure 4).
Overwintering apple leaves provide the spores
that initiate primary infections on new growth in
early spring. For newly emerging leaves to
become infected, spores on the leaf surface must
be bathed in a film of moisture produced by rain
or dew for enough time as is necessary for the
spores to germinate and penetrate the leaf. Thelength of time needed depends on the
temperature. The temperature and leaf wetnessrelationship to heavy infection levels is
presented in the following table, sometimes
referred to as Mills table.
Approximate minimum number of hours of leaf wetting required for a
heavy apple scab infection at various
temperatures (Mills table, modified).
Average
temperature
(F)
Leaf
wetness
hours
Lesions
visible
(days)
78 26 -63-75 18 9
60 20 11
57 22 13
54 24 14
51 27 16
48 30 17
45 41 17
42 60 17
In April 2011, there have already been several
prolonged leaf wetness events. Using datacollected from mesonet weather stations located
in almost half of Kentucky’s counties, heavy
scab infection likely occurred on susceptibleunsprayed trees at least once and in some
locations, up to three times during the period of
April 8-18. The wettest periods appeared to be
April 9-10, April 11-13, and April 15-17.Although temperatures were mainly in the 50's
leaf wetness duration often continued for well
over 24 hours. Leaf wetness duration estimated
times of 27, 30, 32, or even 41 hours were found
at some locations. Scab threats during this timewere highest throughout eastern Kentucky and
gradually diminished at weather stations farther
west.
After primary infections occur in early spring,
scab lesions develop and conidia are produced in
the lesions, providing secondary inoculum for
continued infections of new leaves. Leaf
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wetness and temperature relationships for
secondary scab infection are similar to the
primary infection values presented in Mills
table. Look for scab lesions (source of
secondary inoculum) on susceptible andunsprayed apples and crabapples to appear by
about April 21 or 22.
DIAGNOSTIC LAB HIGHLIGHTSBy Julie Beale & Paul Bachi
Recent agronomic samples in the PDDL have
included Sclerotinia crown/stem rot on alfalfa;
Stagonospora leaf blotch and Ascochyta leaf
spot on wheat; and Rhizocotonia damping off ontobacco seedlings. We have seen a fewproblems on greenhouse vegetables, including
thrips injury on squash; Sclerotinia stem rot,
oedema and thrips injury on tomato; and
intumescence (physiological condition) on
sweetpotato.
From landscapes, we have seen black root rot on
holly; leaf curl on peach; white pine decline; and
winter drying on holly, magnolia andrhododendron.
INSECT TRAP COUNTSApril 8 - 15
Graphs of insect trap counts for the 2011 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 7 0
Armyworm 206 485
Corn earworm 2 0
European corn
borer
0 0
Southwesterncorn borer
0 0
Fall armyworm 0 0
Figure 2. New scab lesions on flowering crabapple
leaves. Note that lesions are often positioned along
the veins where leaves remain wet for the longest
time.
Figure 3. Scab-infected apple leaf beginning to
turn yellow.
Figure 4. Fruit scab on apple.