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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.

For 5/11/04:


Alfalfa Weevil Eggs Present
Several adult weevils and eggs laid in alfalfa stems throughout eastern NYS this last week. The predominate question after eggs have been laid in stems is, “When will larvae hatch?” The 1st instar larvae hatch from eggs at 280 degree-days (base temp. 48F). This is just a few days at our typical spring temperatures. Newly hatched larvae are about 1/16 inches long and yellow to light green in color. As larvae feed, grow and molt they become green with white stripes down their back, have a dark brown head. Larvae ultimately grow to reach 3/8 inches long before pupation about early June in New York. Recall that these larger larvae have big appetites and are responsible for 80% of the alfalfa lost to weevil feeding. Check out these websites for correct identification: Alfalfa Weevil Eggs and Alfalfa Weevil Larvae. Check out our on-line publication, IPM for Alfalfa Weevil.

Do you know the number of growing degree-days in your region today?
(Base Temp. 50F)

More Crown and Root Rot Reports

There have been more reports of crown and root rot in Eastern NYS. Remember there are several kinds of rots and symptoms look similar. For more information on crown and root rot check out our on-line guide: Diseases of Alfalfa (Wilts and Rots) Management Guide

Downy Mildew on Alfalfa

During a TAg meeting in Lewis County we discovered many of the plants had downy mildew. Symptoms of downy mildew are leaves become blotched and are light green or yellow. Many times young leaflets can become distorted. Often a dark purplish-gray fungal mat covers the underside of the leaves. This disease is common early in the spring. For more information view are on-line management guide: IPM for Alfalfa Diseases: Leaf Spots

Potato Leafhopper Found in the North Country

While Jennifer Beckman (Lewis County) was conducting a TAg meeting (May 11) this week she discovered one lone potato leafhopper in the sweep net. If potato leafhoppers are that far north already most likely you will find them in many other locations around the state. Do you know what potato leafhopper looks like? Remember adults are bright lime green, 1/8 inch long and can fly. Potato leafhopper nymphs are yellowish-green and look similar to the adult but do not have wings.

Field Corn

Black Cutworm Management
Are grass weeds a problem in your corn? Could be just what a mother black cutworm moth is looking for. Grasses, winter annual broadleaves, and chickweed are favorite targets. If cutworm moths lay eggs in the field and the field is treated with an herbicide, hatching cutworm larvae bail off the dying weeds and look for greener food sources such as emerging corn seedlings. Cutworms can be an annual problem in some fields; particularly those with a history of poor weed control or have low wet areas in the field. Field margins, especially those next to ditch banks, grassy lanes, and hay fields are potential sites for infestation. Doing an early season plant population count is a good way to check corn fields for cutworm damage and other corn emergence problems.

Black Cutworm larvae vary in color from light gray to black with a pale brown to black head. Larvae have a greasy, shiny appearance with coarse granules present over their body. During the day larvae burrow into the soil next to the corn plant. These larvae curl into a C shape when disturbed. Symptoms of damage are leaf feeding, irregular holes in stem, notched and cut or missing plants. No-till fields and those with a lot of grass weeds are at particular risk to black cutworm. Monitor fields to find cutworm larvae when they are less than 1/2 inch long. If there are sufficient numbers and damage present, an insecticide could be justified. Treat only the affected area and a 20 to 40-foot border around the infestation. Rarely does a whole field need to be treated for cutworm. Larger cutworm larvae, greater than 1/2 inch long, are much more difficult to control. If the majority of cutworm larvae are 1/2 inch long or larger their damage is already done. These large larvae are also more tolerant of insecticides, reducing the effectiveness and economic viability of this option.

Check out our on-line publication, Black Cutworm in Field Corn Management Guide 912K pdf file

Weed Emergence in Eastern NYS

NYS IPM has access to emergence predictions models for the State on a few important weeds. Weed emergence models can help with monitoring weeds in the fields, thus when to expect to see them. The following are the ranges in percent weed emergences in Eastern NYS from North to South.

                                    North Country          Oneida/Herkimer C.                       Lower Hudson Valley

Large Crabgrass            5%                               20%                             50%

Pigweed                        5%                               10%                             30%

Giant Foxtail                 20%                             35%                             70%

Common Lambsquarter 20%                             35%                             70%

Velvetleaf                      20%                             30%                             80%

Yellow Foxtail               20%                             40%                             80%

Common Ragweed         70%                             85%                             100%

Birds in Corn
As corn is being planted sometimes we forget that BIRDS can damage corn fields early in the season. Crows, geese, blackbirds and turkeys like to feed on seed and newly emerging plants. There are just a few recommendations for bird control in field corn. Propane cannons may provide some relief by scaring them, however crows, geese, blackbirds and turkeys can adapt to the sound and one should consider community relations when installing a source of regular Ka-Booms. Other suggestions include paying close attention to planter settings for depth and seed slot closure, planting at a higher population on fields where bird feeding is anticipated, setting out alternative or decoy foods for birds such as moistened corn seed.

Thanks to: Jennifer Beckman (Lewis County), Jeff Miller (Oneida County), Julie Stavisky (NYS IPM) and Keith Waldron (NYS IPM) for helping with this week’s report!


Ken Wise