Weather conditions

Weather conditions can play a major role in pest occurrence:

  • Weather fronts can assist migratory pests (such as helicoverpa, mirids, and armyworm) to move into regions
  • Heavy or excessive rainfall may dislodge or drown some pests.
  • Above average rainfall encourages slugs and snails.
  • Abnormally high or low temperatures may result in a decline or absence of some pests.
  • Cold conditions can make crops more susceptible to pest damage (slower to compensate).
  • Weather conditions that favour plant growth will also favour growth of weeds, including those that are hosts for insect pests.
  • The speed of insect development is often temperature-related. Under warm conditions, pests may develop to damaging sizes more rapidly and/or cycle through additional generations within a season.

Weather conditions should also be taken into consideration when planning control measures:

  • Rain can reduce effectiveness of applied sprays.
  • Temperatures that reduce pest activity are also likely to reduce the effectiveness of chemicals that rely on ingestion or direct contact (e.g. insects will not get a lethal dose if they stop feeding/moving due to cold weather).
  • Lower temperatures may reduce the activity/effectiveness of some beneficials.
  • Fungal pathogens work best under higher humidities.
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