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Grasshoppers are native insects that attack most food crops and ornamental plants when their native food plants (grasses, forbs) dry up during the summer. There are 4-5 species in the Southern Interior that can reach outbreak numbers after native grasslands have suffered 2-3 consecutive years of hot, dry conditions.
Green native grasses and broadleaf plants; any other green plants in the absence of native hosts.
Under outbreak population levels when native host plants dry up, young flightless grasshoppers will march into nearby green crops including orchards. Winged adults will fly several kilometers in search of green plants required to produce eggs. Once favoured grasses are consumed, hoppers will climb trees and shrubs to feed on green leaves and can damage fruit in search of moisture.
Egg - About 3-4 mm long, elongate, laid in pods in the top 2-3 cm of soil.
Nymph - Newly hatched nymphs are 3-4 mm long and resemble adults except much smaller and wingless; may be variously coloured. They moult five times before reaching the adult stage.
Adult - 2-4 cm long, with strong jumping hind legs and well developed wings; body variously marked with lines and colours that help distinguish the species. (Fig. 1)
|Figure 1. Adult twostripped grasshopper.|
Grasshoppers that attack cultivated drops overwinter as eggs in the soil that hatch in the spring when the soil wrams up. Nymphs will feed where they hatch but will migrate as food runs out. By mid summer they change into adults by acquiring wings which allow them to spread further and faster in search of suitable food. Mating and egg laying begins in late summer and continues into the fall.
If grasshoppers are abundant in the fall, watch to see if females are laying eggs (abdomens stuck in the ground) in or near the orchard. Females generally prefer disturbed soils in which to lay their egg pods. Monitor the site the following spring and take action against the nymphs once they hatch to minimize risk of future problems, and to reduce the amount of insecticide applied. This is a good time to apply Eco Bran. Monitor rangeland or pasture land adjacent to the orchard for grasshopper abundance in order to assess if their numbers pose a potential risk to the orchard.
Grasshopers are attacked by several parasites, predators and diseases that can help lessen the impact of outbreaks and bring outbreaks to an end.
Grasshopper nymphs are susceptible to most sprays used against orchard pests. In extreme situations, Cygon or Lagon sprayed on the orchard floor vegetation will control grasshoppers present. Spray the same products on roadsides, ditches, rangeland or wasteland next to the orchard to control grasshoppers moving in from those areas. Sprays should be applied against the nymphs less than 12 mm long to improve control and reduce the amount of chemical required. A bran-bait formulated product containing carbaryl, Eco Bran Grasshopper Insecticide, is a better alternative for controlling very young hoppers as it is less toxic to non-target species. It must be applied using a special spreader similar to a fertilizer spreader.