Wingless grasshoppers and their control

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Nymphal development

Wingless grasshoppers develop through five nymphal stages, or instars, before becoming adults. These five stages can be completed in as little as seven weeks if the spring is warm.

The first instar hoppers feed on prostrate and rosette-forming plants in pasture, particularly capeweed and flatweed. Their limited mobility at this early stage restricts feeding to the hatching site. If suitable food plants are not at the hatching site or are masked by tall pasture grasses such as ryegrass, few first instar hoppers survive.

Subsequent sequence instars (second, third, fourth and fifth) are more mobile and able to disperse from the hatching site. This dispersal is stimulated by the less acceptable dry feed and 'opening up' of the lower storey pasture as annual grasses dry off. Late instar hoppers infest larger areas and feed on a wider variety of plants than early instars.

Moisture is a critical factor for survival of the fourth and fifth instars and adults. In dry pasture the adults depend almost totally on trees for moisture and shade. Isolated trees are the most affected because they act as focal points and attract hoppers from a wide area.

Nymphs begin to develop into adults in late November and most are adult by late December. Mating commences two to three weeks after the adult stage is reached and females start laying eggs about one week after mating.

During this period there are high densities of hoppers on green, perennial pastures, and in home gardens. The females are particularly active in search for green feed as this type of food is essential for development of their eggs.

There is strong evidence that years with unusually high summer/autumn rainfall (as was the case in 1990) allow the development of more feed which results in increased wingless grasshopper populations in the following summer.

Contact information

David Cousins
+61 (0)8 9368 3920