Oklahoma State University

Critical Insects and Critical Insects and Conservation Tillage in Conservation Tillage in

OklahomaOklahoma

Tom A. RoyerDepartment of Entomology

&Plant Pathology

Conservation Tillage 101, Enid, Conservation Tillage 101, Enid, OK. February 8, 2006OK. February 8, 2006

Oklahoma State University

Topics for Discussion

Critical Insects/Mites Effect of Conservation Tillage

Greenbugs and other aphids Army cutworm White grubs Wheat curl mite Hessian fly

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Topics for Discussion

General lifecycle Management Tools

Effects of tillage on pest Cultural Controls

Rotations Planting date Resistant varieties

Insecticides

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Topics for Discussion

Critical Insects/Mites Effect of Conservation Tillage

Greenbugs and other aphids reduced threat Army cutworm Hessian fly White grubs Wheat curl mite

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Greenbug Lifecycle

Winged adults move into field in fall

Females produce live young soon after becoming adults, produce 35 young in one week at optimal temperatures

Feeding damage visible, and can cause substantial yield loss.

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Greenbug Management Tools for Greenbug Management

Tillage conservation tillage will likely help reduce colonization and

survival of greenbug Crop rotation

Rotation to non-host crops does not directly affect greenbugs Planting Date

Has some influence on greenbug outbreaks, limits fall window of migration, however mild falls can “open” window.

Resistant varieties Greenbug resistance is available

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Greenbug Management Tools for Greenbug Management

Insecticides Seed treatment: effective on fall generations Foliar applications effective tool for active infestations Need to determine applications based upon wasp activity

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Topics for Discussion

Critical Insects/Mites Effect of Conservation Tillage

Greenbugs and other aphids reduce threat Army cutworm reduce threat Hessian fly White grubs Wheat curl mite

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Army Cutworm Lifecycle

Moths arrive in fall from mountain ranges, lay eggs in tilled, thin or newly established stands.

Feed throughout winter, can tolerate very cold temperatures

Become active in early spring, can cause severe damage

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Army Cutworm Management Tools for Army Cutworm Management

Tillage conservation tillage will likely help reduce colonization and

survival of army cutworm Crop rotation

Rotation to non-host crops does not directly affect army cutworm Planting Date

Won’t greatly influence army cutworm outbreaks Resistant varieties

Army cutworm resistance is not useful

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Army Cutworm Management

Tools for Army Cutworm Management Insecticides

Foliar applications effective tool for active infestations

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Topics for Discussion

Critical Insects/Mites Effect of Conservation Tillage

Greenbugs and other aphids reduce threat Army cutworm reduce threat White grubs increase threat Wheat curl mite Hessian fly

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White Grub Lifecycle

May/June beetles arrive in spring, lay eggs in weedy, untilled fields.

1,2, 3-year lifecycles. Grubs feed for one to two years, typically are more of a problem the second year when 3rd instar grubs

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White Grub Management Tools for White Grub Management

Tillage Conservation tillage will slightly increase colonization and re-

colonization of white grubs, especially if fields contain grassy, weedy fallow, and tree stand is nearby (creek bottom)

Crop rotation Rotation to non-host crops can reduce white grub infestations

Planting Date Delayed planting can help with white grub infestations

Resistant varieties No resistance is known

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White Grub Management

Tools for White Grub Management Insecticides

Foliar applications are NOT effective tool for active infestations

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Topics for Discussion

Critical Insects/Mites Effect of Conservation Tillage

Greenbugs and other aphids reduce threat Army cutworm reduce threat White grubs increase threat Wheat curl mite increase threat Hessian fly

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Wheat Curl Mite Lifecycle

Adult mites measure 1/100 inches, are white, cigar-shaped, with 4 legs. They can grow from egg to adult in 8 days at optimum temperatures (77O F)

Hosts: wheat, corn, oats, barley and foxtail millet (and jointed goatgrass)

Transmit wheat streak mosaic virus

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Wheat Curl Mite Management Tools for Wheat Curl Mite Management

Tillage Conservation tillage will likely increase risk of survival of wheat curl mite,

unless volunteer is destroyed at least two weeks before crop is planted Crop rotation

Rotation not a concern, but planting next to other host crops (corn) can serve as a green bridge if corn is late planted.

Planting Date Can influence wheat curl outbreaks; avoid early planting

Resistant varieties Look for resistant/tolerant varieties to wheat streak mosaic

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Wheat Curl Mite Management Tools for Wheat Curl Mite Management

Insecticides Foliar applications are not an effective tool for active

infestations

Oklahoma State University

Topics for Discussion

Critical Insects/Mites Effect of Conservation Tillage

Greenbugs and other aphids reduce threat Army cutworm reduce threat White grubs increase threat Wheat curl mite increase threat Hessian fly increase

threat

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Hessian Fly Lifecycle

Adult fly is brown, looks like a small mosquito 1/8 inches.

Adults typically live for about 3 days

Mated females can begin to lay eggs about 1 hour after mating and lay about 200 eggs

Larvae feed on stems under leaf sheath, cause stunting or lodging

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Hessian Fly Lifecycle

Over summering generation infests wheat in fall

One to 3 generations from fall to harvest (major one in March)

Emergence is often triggered by favorable temperatures (45 to 50 degrees, and after a rain event).

Wheat at harvest

Volunteer wheat

Early planted wheat (for grazing)

Wheat for grain

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Hessian Fly Management Tools for Hessian fly Management

Tillage conservation tillage will likely allow increased survival of Hessian

fly Crop rotation

Rotation to non-host crops can reduce populations Delayed planting

important tool for reducing H. fly infestations, especially in north Resistant varieties

Important, need to know predominant races of H. fly

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Hessian Fly Management

Removal of volunteer wheat deprives hatching adults from a food source to lay eggs

Plowing old straw to a depth of 4 to 6 inches is a very effective way of reducing over summering Hessian fly

Burning straw will reduce, but many pupae drop to soil surface at harvest, so burning is not nearly as effective

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Hessian Fly Management

Crop rotation Wheat is the preferred host for Hessian fly Use of other crops can reduce the over wintering source of

fly pupae Hessian fly can travel up to a mile from their hatching site

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Hessian Fly Management

Variety Resistance: There are at least 12

Hessian fly biotypes, based upon their susceptibility to identified genes.

A collection of Hessian fly taken from North central OK was screened.

These biotypes can “shift” easily, if a single source of resistance is deployed over a wide area

Biotype A: 41% Biotype B: 16% Biotype C: 22% Biotype D: 13% Biotype F: 4% Biotype I: 1% Biotype L: 2%

H13 resistance gene, present in Molly, was 100% resistant to the sample.

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Hessian Fly Management

Variety Resistance: There are some hard red

winter wheat varieties that have resistance, but the resistance is not put in wheat varieties as a priority.

Susceptible varieties: Custer Jagger Jagalene OK 101

Resistant (Moderate) Chisholm Ike 2137 2145

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Hessian Fly Management Tools for Hessian fly Management

Insecticides Seed treatment: effective on fall generations Foliar applications not tested, and variable in results

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Hessian Fly Management (Chemical Control Seed treatments:

They are effective on fall generations, but not on spring

Gaucho and Cruiser are effectifve

In the SE U.S., spring applications of Warrior, timed to catch adult emergence has had some limited success, but has not been tested in OK.

Kansas greenhouse data: Gaucho 480 @ 48 g/100 kg

seed (1.6 fl oz/cwt) provided 100% control

Cruiser @ 39 g/100 kg (1 fl oz/cwt) provided 92% control

Kansas field data: Gaucho 480 @48 g/100 kg

provided 100% control, no control of spring infestation

Cruiser @34 g/100 kg (0.9 fl oz/cwt) provided 100% control in fall, no control of spring infestation

NT = No till, T = conv. till C= corn, W=Wheat

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Hessian Fly ManagementData Collected from Wheat Fields in Kay County OK 2005

Tillage Crop Rotation

Plant

Date

Seed Treatment

Plants

Infested

Tillers

Infested

NT W/W Early No 61% 41%

NT W/W E Yes 0% 0%

NT W/W E No 89% 40%

T W/W E No 22% 5%

NT CloseClose to wheat stubble

C/W E No 94% 51%

NT Far½ mile from stubble

CW E No 33% 10%

NT C/W L No 0% 0%

Oklahoma State University

Critical Insects and Critical Insects and Conservation Tillage in Conservation Tillage in

OklahomaOklahoma

Tom A. RoyerDepartment of Entomology

&Plant Pathology

Conservation Tillage 101, Enid, Conservation Tillage 101, Enid, OK. February 8, 2006OK. February 8, 2006