How bad will grasshoppers be this summer in Colorado? The 2018 grasshopper hazard map based on the 2017 survey of adult grasshopper activity conducted by United States Department of Agriculture - Animal and Plant Health Inspection Service - Plant Protection and Quarantine, shows that there will be low grasshopper populations in Colorado in general with the exception moderate and high populations of grasshoppers in the southeastern counties.

The map shows that there will be low populations of grasshoppers in the Front Range (except central Weld County), northeastern, west and southwestern Colorado counties.

Courtesy of USDA

Weather conditions will determine how much of the damage potential will be realized in those areas with moderate populations of grasshoppers too. For example, cool wet conditions after egg hatch can result in enough mortality in immature grasshoppers to prevent outbreak. In addition, if adequate moisture is available, forage regrowth will offset much of the grasshopper damage. Most grasshopper outbreaks occur when drought conditions are prevalent.

The simple economic threshold for grasshoppers in rangeland is 15-20 grasshopper nymphs per square yard. An economic threshold is the insect's population level or extent of crop damage at which the value of the crop destroyed exceeds the cost of controlling the pest.This number is equivalent eight to ten adult grasshoppers per square yard.  However, the economic importance of an infestation is affected by such factors as range condition, cattle prices, and treatment costs.

Strategies for managing grasshoppers in crops as well as rangelands and recommendations for specific conditions can be found in the High Plains Integrated Pest Management (IPM) Guide.

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