Delaware County Cooperative Extension

Grass Hoppers: Coming To a Field Near You?

Grass Hoppers: Coming To a Field Near You?
Brian C. Pugh, NE Area Agronomy Specialist


When is treatment warranted in a forage setting? If grasshoppers are robbing the forage or hay you
need to get your herd through the winter then treatment should be considered. The real question
becomes, can you apply insecticide for less money than what the lost forage would be worth? If
hay is scarce and tops $75 per bale, the answer would be yes.
Actual thresholds for treating grasshopper infestations are higher than what you might think. For
small grasshoppers (1/2 inch), treat when populations are 24-100 per sq. yard. For adult hoppers,
treat at populations of 8-40 per sq. yard. Walk randomly through the field to determine if they are
concentrated in certain areas, whereby reducing insecticide needed. Common chemical controls
include:
Carbaryl (Sevin):

  •  0.5-1.0 lb/acre for small grasshoppers, 1.25-1.875 lbs/acre for adults.
  •  14 day pre-harvest interval (PHI) for grazing or haying

Malathion:

  •  1.5-2 pts/acre (0.75 – 1.25 lbs/acre)
  •  0 day PHI for grazing or haying

Dimilin:

  •  2 fl oz./acre (0.0075 – 0.0156 lbs/acre) at 2nd to 3rd instar (1/2” or less)
  •  0 day PHI for grazing or haying

Lambda cyhalothrin (Warrior, Karate)- Restricted Use:

  •  2.56- 3.54 oz/acre (0.2-0.3 lb ai/acre)
  •  0 day PHI for grazing, 7 day PHI for hay

Contact your County Educator for many other chemical options.
Producers should consider withdrawal times and chemical cost before deciding on an active ingredient.
If they have a private applicator license, many of the lambda cyhalothrin products have
shown acceptable control of grasshoppers up into the adult stages at a reduced cost when compared
to traditional products such as carbaryl. Just remember if using generics, many have a reduced
concentration and achieving the desired application of active ingredient will be crucial.
(Many generic lambda cy products are 1 lb instead of 2 lb/gallon products, this doubles the required
application rate).
Also remember to always read the label before spraying and good luck with the grasshoppers!

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