The control of stored products pests in the South Island of New Zealand : a two part study

Abstract

This study is in two parts. The first reports the results of a mail questionnaire which was sent to 180 companies storing agricultural produce in the South Island of New Zealand. Sixty-eight percent were returned and showed that most respondents had at some time had pest infestations. Ten percent of respondents suffered regularly from pests and most stores took control measures. Annual expenditure for pest control ranged from zero to $4,800 per company.

The second part was a laboratory trial where the new insecticides pirimiphos-methyl and difluron were compared with the traditional maldison, to control the stored products weevil Sitophilus granarius (L.). A range of concentrations of each insecticide dust was mixed into wheat in 500 ml Jars. Adult S. granarius were added, and their mortality and the number of progeny hatching for two generations was found. Weight changes in the wheat were also measured.

Pirimiphos-methyl was the most toxic and the cheapest insectivide to use. Concentrations of 0.5 ppm and above controlled the infestation. Difluron was half as toxic as pirimiphos-methyl and was the most expensive of the three insecticides to use. Maldison was one-fifth as toxic as pirimiphos-methyl and about twice as expensive to use.