Forages: Grasshoppers

Excerpt from Agronomy Guide for Field Crops (Chapter 5)

Order OMAFRA Publication 811: Agronomy Guide for Field Crops

Table of Contents

1. Description
2. Life History
3. Damage
4. Scouting Technique
5. Action Thresholds
6. Management Strategies
7. Updates on Forages: Grasshoppers
8. Related links...

Description

There are several species of grasshopper that may attack forages. They vary in colour from green to brown. Nymphs look similar to adults but are smaller and have incomplete wings. Both stages feed by chewing. All species have enlarged hind legs for jumping.

Life History

Grasshoppers overwinter as eggs in the soil, usually in uncultivated fields and pastures. Nymphs hatch from the eggs in early June and begin feeding on emerging plants. Nymphal stages last for approximately 2 months with adults appearing later in the season to feed, mate and oviposit their eggs in the soil for next year's population. Grasshoppers prefer to lay eggs in sandy soils with grassy, undisturbed areas. Drought conditions for 1-2 years favour egg and nymph survival.

Damage

Both adults and nymphs feed on the leaves. In alfalfa grown for seed, grasshoppers may become destructive by feeding on blossoms and seed pods. High infestations can defoliate fields and cause yield loss. Feeding damage usually begins around the borders of fields, adjacent to grassy fencerows. High risk factors include no-till, grassy fields, dry, open autumn seasons and mild winters.

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Scouting Technique

Begin scouting in late June when grasshoppers are still young. Scout adjacent fencerows and grassy borders.

Action Thresholds

An average population of 15-20 nymphs/m2 in the spring may warrant control.

Management Strategies

Early-season control should be concentrated on the boundaries of the field in those areas with high nymphal populations. Refer to OMAFRA Publication 812, Field Crop Protection Guide, for insecticide recommendations. It should be noted that spraying insecticides on alfalfa will also kill beneficial insects, the natural enemies of potato leafhopper, alfalfa weevil and lygus bug. Several natural enemies, including ground beetles and crickets, feed on the egg stage while birds and spiders feed on the nymph and adult stage, helping to reduce the populations. The fungus Entomophthora grylli can reduce the populations when weather conditions are warm and humid. Removal of grassy weeds in fields and borders by tillage helps reduce nymphal numbers that require these plants to survive. Tillage buries eggs deeper in the soil, hindering nymphal emergence. Chemical control is more effective on nymphal stages than adults.

(Order OMAFRA Publication 812, Field Crop Protection Guide)

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Updates on Forages: Grasshoppers

• Field Crop Protection Guide - Publication 812
  • Forages: Grasshoppers

Related links...

• Insects
• Forages

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