Effects of Pests and Diseases on the Yield and Quality of Tomatoes in the Port Moresby Area, Papua New Guinea.

Abstract

Studies with tomato variety 'Red Cloud' at Port Moresby showed that the greatest cause of crop loss was fruit damage by the Tomato Caterpillar Heliothis armigera and, to a lesser extent, the Cluster Caterpillar Spodoptera litura. Weekly spraying with 2g/litre of the insecticide 'Septene 80' (Carbary/) reduced the numbers of caterpillars and, consequently, the proportion of fruit insect-damaged. Insecticide effectiveness was greater during the dry season when insect damage was reduced from 71.5% to 25.6% of a// fruit. Application of 1.5g/litre of fungicide 'Dithane M-45' (Mancozeb) did not affect the proportion of fruit damaged by Phytophthora nicotianae and Sclerotium rolfsii rots, which together caused a crop loss N 1.6%. The physiological disorders Blossom End Rot and Growth Cracking occurred on a total of 5.2% of fruit. Flood irrigation during the dry season trial apparently reduced the incidence of Blossom End Rot. Under most favourable conditions a marketable fruit yield potential of 41 t/ha was realized.