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Sampling pulse crops in wet weather

If possible, you should continue to sample your crop in wet weather. The most critical time to sample summer pulse crops is from flowering onwards, through pod set and fill and, for some pests, well into pod ripening.

Heavy rain or flooding may make sampling impossible, which may see your crop suffer damage from pests at critical stages. While not ideal, this should not be too great a cause for concern. In many cases, the crop will be able to compensate for early damage, especially as soil moisture is unlikely to be limiting in a wet summer. You must, however, ensure you minimise any further pest activity.

Learn how to use a beat sheet to sample crops for pests and beneficial insects.

Identifying insect pests

Correctly identifying pests is critical in a wet summer. You may not have time to deal with the consequences of a misdiagnosis and the subsequent pesticide application later in the season.

For example, legume webspinner damage is often confused with damage caused by soybean moth larvae. The latter is usually a minor pest but sometimes occurs in devastating plagues. While soybean moth larvae are readily controlled with a pesticide registered in soybeans, this product is far less effective against legume webspinner. Larvae of these species are easily differentiated by their size and colour.

Read our A-Z guide of insect pests for information on identifying specific pests.

Common wet weather pests

A wetter than average summer will favour some pests more than others.

For example, high helicoverpa and podsucking bug populations are often observed in summer pulse crops in a wet season, and on weed hosts. An abundance of hosts during spring and early summer will boost populations of these pests. However, wetter conditions may eventually act against many caterpillar pests, with major helicoverpa virus outbreaks evident in many sorghum crops, and very likely in peanut crops.

Cooler conditions are also likely to favour soybean aphids, and the red shouldered or Monolpeta beetle often emerges in plague numbers after heavy rain.

In contrast, wet conditions are unfavourable for etiella in peanuts, and damaging populations close to harvest will not threaten crops as they have in recent drought years (when dry soil allowed larvae to reach the underground pods).

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