An analysis of the importance of ring spot (Massonina panattoniana) and other related diseases in lettuces with suggested control methods : Thesis for National Diploma of Horticulture (N. Z.)

Abstract

1. Ring spot disease in lettuce is principally a problem in cool wet climates. The Southern half of South Island suffers most from this disease. 2. Regular spraying with a range of recommended fungicides can be very effective in controlling the disease. Research has shown that there is not a wide range in the overall effectivenesss between the recommended fungicides for ring spot. 3. Good crop management techniques are required to minimise the disease. 4, Recommended fungicides can be readily mixed with herbicides or liquid fertiliser, etc. to control ring spot. 5. A Christchurch survey showed that consumers appear to prefer to buy lettuces pre-packed in cellophane in some supermarkets. Some dairy stores retail quality lettuces cheaper than some supermarkets. 6. Auctioneers very seldom accept lettuces infected with ring spot, or other diseases. Growers need to present quality in order to preserve their reputation. Imperfect lettuces can be heavily discounted. 7. There is a good cost-benefit return to growers from the use of fungicides to control diseases, particularly ring spot. 8. Captafol, mancozeb or propineb appear to give the most effective control of ring spot at relatively low cost. There is a trend towards the use of more broad spectrum fungicides.