NY Weekly Field Crop Pest Report, 2005

View From the Field

Western NYS

Julie Stavisky, NYS IPM

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In alfalfa sweeps so far this week, I have observed zero adult alfalfa weevils, and one lone tiny alfalfa weevil larva. Nancy Glazier observed a few alfalfa weevil larvae in western NY. I did not observe any potato leafhoppers yet (and I really want to find them before Ken does!). Predatory insects are abundant in alfalfa. This week, I observed lots of damsel bugs.

In winter wheat, there's hardly a cereal leaf beetle to be found yet.  I saw one adult and a few eggs after much searching. The fields I have observed have been beautifully disease free.

The multi-county buckthorn search has still turned up zero soybean aphids.

Checking Plant Populations-Indication of Pest Issues

Ken Wise, NYS IPM

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As corn starts to emerge it is important to know your corn plant populations. Conducting plant population checks is the first step to determining if there are pest problems in the field.  The pressing question is How do I check my corn plant populations? It is suggested that you sample in units that are one-thousandth of an acre. Please consider developing the habit of sampling rows as they were laid down by the planter. If the field was planted with a six-row planter, then sample the six rows that represent one pass of the planter. Watch tractor wheel tracks and choose your next six-row sample that would correspond to with the same six planter units. This way you would notice any variation or patterns between the units of the planter. Make sure to sample the appropriate length for your row width. Take at least 5 samples as you cross the field.

After you are finished counting plants in each sampling location take the average number of plants and multiply it by 1000. This will give you the number of plants per acre. For example if you had an average of 30 plants you multiply it by 1000 and you would have 30,000 plants per acre. If your plant population is more than10% lower than that expected it may indicate a problem in the field. While many things could cause the population reduction at least two pest related issues might be involved: early season seed or seedling blights and/or seed corn maggot damage. For more information on these pests view our on-line management guides at: Field Corn Diseases. or Early Season Insect Pests in Field Corn

Turkeys - what are they good for?

Keith Waldron, NYS IPM

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Besides being great guests at Thanksgiving, under the right circumstances they can make great field scouts as well. Yes, it is true they can guide you to where your corn “used to be” planted. And they can be effective at breaking up the cow poop habitat that face and horn flies, the scourge of pastured cattle and horses, love to breed in. But wait there’s more…

Mike Stanyard learned earlier this week that the eastern wild turkey (Meleagris gallopavo silvestris) can also be great at monitoring fields for insects. Some local farmer friends recently called Mike to ask “What were those big bugs?” found inside the crops of the wild turkeys they had “harvested” May 1st. The farmers saved the contents of the birds for our intrepid entomologist to check out… Right from the pages of a CCE version of CSI… Sure enough the bugs the birds were feeding on were big and fairly rare… alfalfa snout beetles (ASB). The turkeys were collected in an area where alfalfa snout beetles had been found 2 years ago exiting an alfalfa field. “No wonder we can’t keep alfalfa in there long? “ The location is near the town of South Butler north of the Montezuma Wildlife refuge in Wayne county.

Besides attacking alfalfa, ASB are also fond of red clover, dock, wild carrot, quackgrass and white clover. Plans are to plow under the alfalfa field in question after first harvest and either leave the field fallow for a year or replant to a non-host like corn, wheat, oats, soybeans, potatoes or birdsfoot trefoil.

Turkeys as a bird of prey? Who knew?

A nice thing about turkeys as ASB field scouts?

They work “cheep”….. almost for bird feed…..

Important alfalfa diseases to know!

Ken Wise, NYS IPM

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Anthracnose is a disease that occurs in warm and wet weather.  Stems of infected plants wilt and stem tips bend over to form a Shepherds crook. Diamond-shaped lesions can appear on the lower parts of the stem about 1-3 inches above the soil line. Anthracnose may advance from infected stems into the crown tissue. The infected crowns appear bluish-black near the base of stems. Plants can appear straw colored and are scattered throughout the field. For pictures of anthracnose see: Anthracnose Photos

Verticillium wilt can be a serious disease, limiting yield and stand life. An early symptom includes a characteristic V-shaped yellow foliar discoloration similar to potato leafhopper (PLH) injury. One way to tell the difference between PLH injury and verticillium wilt is by using a sweep-net. If you see the yellow V-shaped foliar discoloration and there are no PLHs in the net it is most likely verticillium wilt. As the disease progresses, leaflets wilt, turn yellow or pink, and often curl or twist. Stems of infected plants can remain green for long periods of time. Taproots appear healthy and sound, but in cross section appear to have a dark ring indicating damage to the water-conducting tissues, causing wilt symptoms. Verticillium wilt symptoms may be more obvious in the second cutting. For pictures of verticillium wilt see: Verticillium Wilt Picture

Sclerotinia crown and stem rot usually occurs during cool, moist weather in early spring and late summer. Infected stems become soft and water soaked, the infected plant appears yellow and weak. A characteristic white fluffy mass of mycelium (fungus body) grows over the plants or on the soil surface, infecting new plants as it grows. Seedlings are very vulnerable to this disease. As plants become weak and die, the fungus forms small (1/8 to 1/4 inch), hard black sclerotia (pelletlike balls) on or in the stem or crown tissue. This disease is often associated with fall seedings, seedings into old pastures, or no-till seedings into previous legume sod. For pictures of sclerotinia crown and stem rot see: Sclerotinia on Alfalfa Picture

For more information on alfalfa wilts and crown rots see our online publication: Alfalfa Wilt and Rots Management Guide

Weed scouting in Wheat

Julie Stavisky, NYS IPM

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Except in areas of high weed infestations, winter wheat stands are filling out well, and stem elongation is underway. Heavy weed pressures of winter annuals have been observed (see photo below of chickweed), and annuals are at the 2 to 4 leaf stage.

Herbicide applications are not recommended once wheat plants are in the stem elongation stage. But scouting for weeds continues to be important. Constructing a weed map between now and mid June will help in planning for future use of the field. To practice weed IPM, note where in the field infestations of winter annuals, annuals, and perennial weeds are severe, heavy, or moderate. This information will be crucial for selecting the next crop in the rotation and in implementing weed management options when establishing the next crop.

Growing Degree Days for NYS

Keith Waldron, NYS IPM

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March 1 - May 17, 2005

Clipboard Checklist

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General:

Update field records: variety, planting date/rate, pesticides used, nutrient inputs including manure, other important field observations, etc.

Note wet spots in field for future drainage.

Celebrate end of corn planting? (May 15)

Pest Monitoring Priorities:

Alfalfa:

• alfalfa weevil, alfalfa snout beetle, weeds, crown rot, leaf spot diseases

Small Grain Cereals:

• Winter Wheat: Cereal leaf beetle, virus diseases, powdery mildew, scout for weeds and make a weed map.

• Spring Grains: Cereal leaf beetle, seedling diseases, scout for weeds and make a weed map

Field Corn:

• Monitor corn for weeds, note presence of triazine resistant annual broadleaf weeds. Cultivate or treat if necessary. Pre-emergence herbicide applications by May 20 if conditions allow.

• Review herbicide options for relative control of problem weeds. See Table 3.7.1 Herbicide Effectiveness on Weeds

• Check corn emergence, take stand counts/plant populations, check for signs of damping off / seedling blights, seed corn maggot

Contact Information

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Julie Stavisky:IPM Area Educator, Livestock and Field Crops, Western NY
Phone: (315) 331-8415
Fax: (315) 331-8411
Email: js38@cornell.edu

Keith Waldron: NYS Livestock and Field Crops IPM Coordinator

Phone: (315) 787 - 2432

Fax: (315) 787-2360

Email: jkw5@cornell.edu

Ken Wise: Eastern NYS IPM Area Educator: Field Crops and Livestock

Phone: (518) 434-1690

Fax: (518) 426-3316

Email: klw24@cornell.edu