A grower survey of diseases, invertebrate pests, and pesticide use on potatoes grown in South Australia

Abstract

In 1991, a survey was distributed to 251 potato growers in South Australia to determine major diseases, insect and other invertebrate pests, and chemicals used to control them. The overall response rate was 48%, but of these, 24 individuals were no longer growing potatoes. The results were summarised for the State and by district (Adelaide Hills, Adelaide Plains, Murray Lands, South East). The most prevalent diseases encountered by respondents in all districts were target spot caused by Alternaria solani, and rhizoctonia canker caused by Rhizoctonia solani. Other diseases of concern to growers included late blight caused by Phytophthora infestans, seed piece decay caused by various pathogenic and saprophytic microorganisms, common scab caused by Streptomyces scabies, and leaf roll caused by potato leaf roll virus. The most commonly used fungicides for disease control were chlorothalonil (33-42% of respondents), mancozeb (30%), and cupric hydroxide (11-13%). The most commonly used seed treatments for control of seed piece decay were mancozeb (51 % of respondents), tolclofos methyl (24%), and lime (20%). Green peach aphid (Myzus persicae), potato aphid (Macrosiphum euphorbiae), potato moth (Phthorimaea operculella), and jassids and leafhoppers (Jassidae, Cicadellidae) were the pests of greatest concern to the growers. Others included Rutherglen bug (Nysius vinitor), redlegged earth mite (Halotydeus destructor), and thrips (Thripidae). The most commonly used insecticides were ethamidophos (40% of respondents), monocrotophos (22-28%), and dimethoate (7-13%).