Processes within pasture and crop ecosystems: Some effects of weather on aphids in crops and pastures in Canterbury, New Zealand
- Department of Scientific and Industrial Research, Lincoln
- Postal address: C/- Crop Research Division, Private Bag, Christchurch, New Zealand
Pest insects are frequently held in check by natural means. The level of this control is influenced by the supply of food, the activity of parasitic organisms, including entomophagous insects and disease pathogens, and weather. Any enquiry into the importance of weather in insect ecology must include an examination of the effects of temperature (including freezing), humidity, wind (direction and velocity), precipitation (rate and amount), light (intensity and duration), and evaporation. The effects of these factors are interrelated and all react on other controlling influences. The importance of weather in this connection is well illustrated by the work of Andrewartha and Birch (1954). In a 14–year census of thrips in a garden in Adelaide they showed that 78 percent of the variation in annual peak numbers was correlated with meteorological variations.