ISSUE 2 May 14, 1998
GRASSHOPPER THREAT FOR 1998 IN NORTH DAKOTA
Grasshoppers have been hatching around the state for two weeks plus, now. Localized hot spots, where populations will exceed threatening levels are expected all around the state. So far, the hatch has not resulted in the need for significant insecticide treatments to protect seedling crops. There are reports from the Red River Valley of spraying borders to protect sugar beet seedlings. With the warm spring, hatching has begun about two weeks earlier than observed the past three years. Now, with the temporary change in weather to cool rainy conditions, hatch should slow briefly and may cause some mortality of the young hoppers.
At this time, vigilance is the best recommendation. Scout areas where adult grasshoppers were present last fall. The open fall in 1997 was favorable for egg laying. Inspect infested areas once a week. Newly hatched grasshoppers are small (about the size of a kernel of wheat) and sites require more than a casual inspection. Field crop management decisions are based on the number of grasshoppers per square yard. Estimate populations by moving through an infested area and counting the number of grasshoppers that jump or move within a square foot area. Keep a record of your square foot counts. Divide the total number of grasshoppers counted by the total number of samples taken, then multiply by nine to calculate the number of grasshoppers per square yard. Refer to the table to evaluate damage risk.
Grasshoppers per Square Yard =
|Light||25 - 35||15 - 23||10 - 20||3 - 7|
|Threatening||50 - 75||30 - 45||21 - 40||8 - 14|
|Severe||100-150||60 - 90||41 - 80||15 - 28|
|Rainfall Effects on Grasshoppers
Insecticides Available for Use Against Grasshopper
Field Corn and Sweet corn
Asana XL, Cythion, Diazinon, Penncap-M, Sevin, and Warrior.
Field Corn Only
Dimethoate, Furadan 4F, Lorsban 4E, methyl parathion.
Asana XL, Dimethoate, Furadan 4F, Lorsban 4E, Penncap-M, Scout X-Tra, Sevin, Warrior.
Asana XL, Baythroid, Furadan 4F, Lorsban 4E, Scout X-Tra, Sevin, Warrior.
Asana XL, Dimethoate, Orthene 75S, Sevin.
Asana XL, Dimethoate, Penncap-M, Sevin.
Asana XL, Cythion, Diazinon, Lorsban 4E, Malathion 57EC, methyl parathion, Sevin.
Cythion, Dimethoate, Furadan 4F, Malathion 57EC, methyl parathion, Penncap-M, Sevin, Warrior.
Cythion, Furadan 4F, Malathion 57EC, methyl parathion, Penncap-M.
Furadan 4F, Malathion 57EC, methyl parathion, Penncap-M.
Baythroid, Cythion, Dimethoate, Furadan 4F, Lorsban 4E, Malathion 57EC, methyl parathion, Penncap-M, Sevin,Warrior.
Cythion, methyl parathion, Sevin.
Grass and Grass hay
Pasture and Range
Cythion, Orthene 75S, Penncap-M, Sevin,.
Non-Crop areas with grass cut for hay
Cythion, Malathion 57EC, Sevin.
Non-Crop areas NOT cut for hay
Asana XL, Diazinon, Orthene 75S.
Dimethoate, Lorsban 4E, Sevin, Warrior.
Proso Millet, Lentils, and Flax
methyl parathion (This product is labeled for use on canola, however grasshoppers do not appear on the label. It should provide control at labeled rates.)
Sevin ( in addition, Cythion and methyl parathion are labeled for field peas, however grasshoppers do not appear on the label.)
CUTWORMS AROUND THE STATE
One of the first insect pests we encounter in a season are cutworms. Reports from the valley, north central counties and western sugar beet areas indicate significant activity has been present for one to two weeks. As reported last week from the north central areas, cutworms are feeding on volunteer plants before new crop has been seeded. Last season, significant cutworm injury to later seeded crops (example, sunflower) was reported in many eastern counties.
Of the cutworms that pose problems in North Dakota, the army cutworm and dingy cutworms overwinter as partially grown larvae and are usually the first to cause damage. The pale western, dark sided, and red-backed cutworms, overwinter as eggs. Many cutworm infestations are associated with weedy, wet and reduced tillage areas. Here are brief descriptions and notes on the habits of the key cutworms (size is for full grown larva):
Army cutworm: 1 1/2 to 2 inches; pale greenish-gray to brown with pale stripes and mottled pattern. Larvae hatch in fall, resume feeding in early spring. Important in western North Dakota grain and alfalfa fields. There were reports from South Dakota in April of significant infestations by army cutworm in winter wheat and alfalfa; a few reports from SW ND.
Pale Western cutworm: 1 1/2 inches; generally gray in appearance. Larvae hatch in spring. They feed underground, sometimes damaging plants before they emerge; cut plants are pulled underground. Important in western North Dakota small grain fields.
Dingy cutworm: 1 1/4 inches. Dull, dingy brown color mottled with pale white spotting. Larvae hatch in fall, resume feeding in the spring when soils warm. Damage usually consists of chewed foliage and/or cut stems. Injure corn, sunflower, sugarbeet, and potatoes.
Darksided cutworm: 1 1/4 to 1 1/2 inches. Pale brown on top, lighter on the bottom. Sides have faint stripes. Larvae hatch in spring (mid to late May). Plant feeding same as above.
Red-backed cutworm: 1 to 1/4 inches. Dull gray to brown with dull reddish stripe down back. Larvae hatch in spring (mid to late May). Plant feeding same as above, same hosts.
1998 NORTH DAKOTA INSECT MANAGEMENT GUIDE AVAILABLE ON WORLD WIDE WEB
For your reference, the insect management guide, published annually by NDSU, is available on the internet. You can find it at the following address: