A GROWER SURVEY OF DISEASES, INVERTEBRATE PESTS, AND PESTICIDE USE ONPOTATOES GROWN IN SOUTH-AUSTRALIA

In 1991, a survey was distributed to 251 potato growers in South Austr alia 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 re sults were summarised for the State and by district (Adelaide Hills, A delaide Plains, Murray Lands, South East). The most prevalent diseases encountered by respondents in all districts were target spot caused b y Alternaria solani, and rhizoctonia canker caused by Rhizoctonia sola ni. Other diseases of concern to growers included late blight caused b y Phytophthora infestans, seed piece decay caused by various pathogeni c and saprophytic microorganisms, common scab caused by Streptomyces s cabies, and leaf roll caused by potato leaf roll virus. The most commo nly 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 ma ncozeb (51% of respondents), tolclofos methyl (24%), and lime (20%). G reen peach aphid (Myzus persicae), potato aphid (Macrosiphum euphorbia e), potato moth (Phthorimaea operculella), and jassids and leafhoppers (Jassidae, Cicadellidae) were the pests of greatest concern to the gr owers. Others included Rutherglen bug (Nysius vinitor), redlegged eart h mite (Halotydeus destructor), and thrips (Thripidae). The most commo nly used insecticides were methamidophos (40% of respondents), monocro tophos (22-28%), and dimethoate (7-13%).