Insect pests in stored grain: a Canterbury example

Abstract

Grain samples were collected from storage facilities of cereal grain producers throughout Canterbury, New Zealand to determine levels of insect pest infestation. Collection followed a preliminary survey in 2015/16 where growers were invited to submit grain samples. It was possible that producers were more likely to send samples if they suspected insect infestation. To eliminate any survey sampling bias in the 2016/17 survey, 42 cereal grain producers were randomly selected. Fifty-eight grain samples were collected from 42 storage facilities, of which 77% were infested with one or more insect species. These were predominantly Coleoptera and Psocoptera. The most frequently encountered beetle species were Orzyaephilis surinamensis and Cryptolestes species. In contrast to the 2015/16 survey, a Sitophilus (weevil) species was recorded for the first time. The proportion of storage facilities infested by insects (77%) was similar to the 2015/16 survey (73%) but higher than two previous surveys in 1971 (38%) and 1979 (50–63%). The proportion of storage facilities treated with insecticides (79%) was similar to the 1979 survey (83%) but greater than the preliminary 2015/16 survey (62%). Results indicate that insect pests of stored grain remain a significant risk for grain producers.