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Eastern New York Field Crops Pest Report, 2004

This is a seasonal scouting report giving growers in the Eastern New York area information on the presence of agricultural pests. The report is written by Ken Wise, IPM Extension Area Educator for Livestock and Field Crops.

July 8, 2004 Alfalfa

Potato Leafhopper Over Threshold

Terry Lavigne (Albany County) reports high populations of potato leafhopper (PLH) adults and nymphs in alfalfa fields. He was finding 100 PLHs for 3 sets of sweeps in 15-16" stands. This was about 25% over threshold and management action needs to be taken within a week monitoring. Potato leafhopper infestations over threshold in alfalfa can reduce the plant protein by 5% and yield by a ½ ton per acre per cutting. If you see V-shaped yellowing on the tips of the leaves you have a good chance potato leafhopper has been in your alfalfa. It gets even worse, if V-shaped yellowing has appeared you have already lost protein and yield, plus the alfalfa will have slower re-growth after harvest and increased chance of winter kill. For management information check our on-line IPM guides: IPM for Potato Leafhopper in Alfalfa.

Field Corn
European Corn Borer Opens the Door for Anthracnose Stalk Rot

While scouting, I observed signs of European corn borer (ECB) in field corn. There were broken leaf midribs, frass in the whorls, and holes in the stalks. European corn borer damage, can on occasion cause localized problems for field corn producers. However, while it's damage may be conspicuous, it more typically does not cause significant economic losses in NYS. If a field has had a history of ECB problems producers might consider crop rotation or the use of an ECB resistant (Bt) hybrid. In addition to direct feeding damage the holes bored by ECB larvae can provide a means for the anthracnose fungus to enter the plant. Conditions that favor anthracnose stalk rot are continuous corn, surface corn residue (minimum & no tillage) and wet, humid, warm weather. Anthracnose stalk rot symptoms may appear after tasselling. Look for vertical, tan to reddish brown, water-soaked lesions (streaks) in the rind. Lesions become large, dark brown to shiny black. The best management practices to minimize or avoid anthracnose require action before or at the time of planting, i.e. the use of diseases resistant hybrids and hybrids with a good standability rating. Crop rotation with non-grass crops and plow under infected residue are also recommended. Fields with high amounts of anthracnose leaf blight should be checked for indications of anthracnose stalk rot. If stalk rot is found you may wish to target that field for early harvest to avoid losses associated with premature lodging. For more information on corn diseases checkout our online publication: Diseases of Corn Management Guide 234k pdf file

Start Thinking CORN ROOTWORM: What Fields are at risk?
Corn rootworm populations build in a cornfield from year to year. Fields that are not rotated and remain in corn for several years are most at risk from corn rootworm damage. A two to three year rotation reduces the risk that a corn field will reach an action threshold for this pest. This spurs the question, “Do you scout a 1st year cornfield after sod for corn rootworm?” Yes, because any pollinating cornfield can attract corn rootworm. Even worse, late pollinating corn can attract many hungry corn rootworm beetles from fields where they did not get enough pollen. After the beetles eat their fill on late season pollen they will lay eggs in the soil. So yes, you have to scout all cornfields for corn rootworm that are going to be planted to corn next year. You do not need to scout fields that will be rotated out of corn next year. For more information on corn rootworm checkout our online publication: Corn Rootworm Management Guide 972 pdf file

Check next week’s pest report for when and how to scout for corn rootworm in field corn!

Weeds of the Week: Wild Buckwheat, Field Bindweed and Hedge Bindweed?

While scouting this week I stumbled over some wild buckwheat in a corn field. As you know they can easily trip a person up! After brushing off the dust I did have to go and check my weed guide to make sure it really was wild buckwheat. It's fairly easy to get Wild Buckwheat, Field Bindweed and Hedge Bindweed mixed up. Some call them all bindweed. The following table is a guide to help distinguish between the weed species:

Plant Characteristic

Field Bindweed

Hedge Bindweed

Wild Buckwheat

Leaves

Leaves are 1 to 2” long, smooth and shaped like an arrowhead. The leaf sides are generally parallel. Single point basal lobe.

Generally triangular shaped and somewhat pointed. Double point basal lobe.

Heart-shaped leaves with a pointed tip.

Flower

White or pale pink, about 1” across

White or pinkish,

1.5 to 2” across

Very small and green

Roots

Deep rooted

Roots are relatively shallow but very extensive

Root are shallow

Life Cycle

Perennial

Perennial

Annual

Other features

 

 

Wild buckwheat has an ochrea(membranous sheath) at each node.

Website for more information: Field Bindweed, Hedge Bindweed, Wild Buckwheat

Wheat

Fusarium Head Blight (Scab) Found In Oneida County

Jeff Miller (Oneida County) reports Fusarium head blight (FHB) at 4 to 8 percent infection in some fields. One of the most devastating diseases of wheat is FHB also called Scab. This disease infects the grain head at flowering. The disease builds up in corn, wheat and other grain residues. During the day the spores are carried up into the atmosphere and at night settle out across the landscape. If it rains at flowering and spores are present there is a good chance the grain will become infected with the disease. The first symptoms of FHB occur shortly after flowering. Diseased wheat heads exhibit premature bleaching as the pathogen progresses. One or more spikelets located in the top, middle, or bottom of the head may be bleached. Over time, the premature bleaching of the spikelets may progress throughout the entire head. If the environment is warm and moist, aggregations of light pink/salmon colored spores may appear on the rachis and glumes of individual spikelets. Later in the season, bluish- black spherical bodies may appear on the surface of affected spikelets. As symptoms progress, the fungus colonizes the developing grain causing it to shrink and wrinkle inside the head. Often, the infected kernels have a rough, wilted appearance, ranging in color from pink, soft-gray, to light-brown.

File written by Adobe Photoshop¨ 4.0

Grain infected with Fusarium can contain mycotoxins, vomitoxin and zearalenone. These can be toxic to many different livestock animals and humans. For information on feeding scab infected grain please refer to this website: http://www.cce.cornell.edu/programs/nw-ny-dairy-fieldcrops/Library/WheatVomitoxin.pdf

Leaf Rust

While scouting a wheat field in Oneida County we discovered that 100 percent of the flag leaves had 50 to 60% of the leaf area covered with rust. While in this case it was too late to control the disease the rust normally appears from Late April to June. Rust lesions are small, circular, and vivid orange in color. They may occur on stems, but are most common on the upper surface of leaves. Leaf rust can develop very rapidly so it should be treated as soon as possible. Leaf rust is favored by warm and humid weather with thunderstorms in June. Leaf rust is disseminated by winds which carry the airborne spores great distances. Temperatures between 600 and 800 F are optimal for disease development. To scout for leaf rust assess the upper three leaves for symptoms and signs of leaf rust in early to mid-May, before flag leaf emergence. If the disease (any amount) is observed on approximately 50 percent of main tillers, averaged across the field, a spray should be considered.

Thanks to: Jeff Miller (Oneida County), Terry Lavigne (Albany County) and Keith Waldron and Julie Stavisky (NYS IPM) for contributing to this week's report.

Cheers
Ken Wise