kentucky pest news april 19, 2011

8/7/2019 Kentucky Pest News April 19, 2011

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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.

http://www.uky.edu/KPN









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.

http://www.ca.uky.edu/agcollege/plantpathology/extension/kpnindex.htm





http://www.ca.uky.edu/entomology/entfacts/entfactpdf/ef111.pdf




















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



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.

kentucky pest news april 19, 2011

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