The Big Sandy Mountaineer -

Green Acres


November 18, 2020

If we continue to have drought conditions, grasshopper pest populations will explode this spring. One insecticide available is Dimilin 2L. Below are a few facts about Dimilin 2L.

• Dimilin 2L is an insecticide that interferes with molting. This insect growth regulator does not poison the grasshoppers, but it controls immature grasshoppers by interfering with their normal shedding of skin as they grow. As a result, it takes time to see mortality.

• Dimilin 2L is an insect growth regulator which is effective on a wide variety of insect pests, predominately from the families Lepidoptera and Diptera. Because of its mode of action, which results in a disruption of the normal molting process of the insect larvae, the action of Dimilin 2Lis slow and several days may elapse before the full effect is seen. Because of its specificity, DIMILIN is an excellent product for use in IPM programs.

• Dimilin 2L interferes with formation of a grasshopper’s exoskeleton, which leads to loss of body fluids. Three to seven days after Dimilin 2L has been applied, grain growers will notice reduced feeding. Maximum control usually is achieved in 10 to 14 days. For cereal grains, If a large influx from neighboring fields should occur, the time to reduce that population may not be short enough to minimize extensive foliage feeding; a tank mix with a knockdown insecticide is recommended under these conditions.

• Because Dimilin 2L does not act by toxicity, it is safer for beneficial insects. It is important to apply Dimilin 2Lwhen grasshoppers are second to fourth stage nymphs, which is when they measure about three-fourths of an inch in length, and do not have fully formed wings. It is not effective to control adults, because as they have completed their development.

• Minimize exposure of this product to bees and other insect pollinators when they are foraging on pollinator attractive plants around the application site.

• Minimize drift of this product on to beehives or to off-site pollinator attractive habitat. Drift of this product onto beehives or off-site to pollinator attractive habitat can result in bee kills.

• For cereal grains, do not make more than one application per season. Do not exceed four fluid ounces (one ounce active ingredient) per acre per season. Do not apply after the boot stage of growth.

Information for this article came from Kevin Wanner (MSU Extension Entomologist), the Dimilin 2L Label ( and Sue Blodgett (Previous MSU Extension Entomologist).

MSU Extension is an equal opportunity/affirmative action provider of educational outreach Montana State University U.S. Department of Agriculture and Montana Counties Cooperating.


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