Key points
- Farmers should regularly monitor storage facilities for pests and treat as required.
- A random survey was carried out to determine the range and frequency of insect species in stored grain in Canterbury.
- 90% of storage facilities had been treated with insecticides prior to filling, and 79% of grain was treated with an insecticide during storage. In most cases that insecticide was the organophosphate pirimiphos-methyl.
- Overall 77% of grain samples were infected with one or more species of insect or mite.
- Key insects found were saw-toothed grain beetles (33% of samples), flat grain beetles (18%) and psocids (55%). Weevil species were identified in one sample.
- Psocids are only considered important when present in high numbers, typically when grain has high moisture and mould is present.
- Mites were found in 14% of samples and thrips (a likely contaminant from harvest) in 12% of samples.