Sorghum XV-7

Grasshoppers

John B. Campbell

Grasshopper.

Identification (and life cycle/seasonal history)

Most species of grasshoppers deposit eggs in the fall in grassy areas along the edges of fields in grassy ditches and waterways or in range and pastureland adjacent to fields. Grasshoppers that damage crops have only one generation per year. Eggs are deposited in the fall in pods. The eggs hatch in late spring or early summer. Grasshoppers have gradual metamorphosis, which means the nymphs resemble the adults. Most species go through five molts before they become adults. Generally, the nymphs feed on the same plant species as adults. However, by the time grasshoppers develop to adults, the grass may be maturing or drying up. Adults will then migrate to more desirable vegetation which is usually field crops. Grasshoppers are strong fliers so they are capable of migrating considerable distances to find a suitable food source.

Management Approaches

Chemical Control

Sampling/Surveying/Timing of Sampling

Grasshopper surveys should begin in late spring and continue into early summer since the various species that may effect crops hatch at different times. Scout field margins.

Economic Thresholds

If numbers of nymphs reach 15 to 20 per square yards around field margins, treat the margins before the nymphs move into the sorghum field. For adults, the 15 to 20 nymph density is equal to eight adults per square yard. But, control measures should be taken before the nymphs become adults. When the grasshoppers become adult, they are much more difficult to control. They are larger thus becoming more difficult to control and treatment has to encompass much larger areas.

Product List for Grasshoppers

	Insecticide	Product Per Acre (Fl oz. or oz. product)	Preharvest interval, remarks
	Cyfluthrin (Baythroid)	2-2.8 fluid oz per acre	See label for restrictions.
	Dimethoate (Cygon)	^1/2 lb A.I.	Do not apply after heading.
	Chlorpyrifos (Lorsban 4E)	^1/4-^1/2 lb A.I.	Do not treat sweet varieties of sorghum. Limit 1.5 lb/season.
	Lambda-cyhalothrin^R (Warrior 1 lb/EC)	2.56 to 3.84 fl.oz.	See label for restrictions.
^RRestricted Use Pesticide.
The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies.  State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.

Categories: Sorghum, Insects, Grasshoppers

Date:12/18/06