Effect of cold treatment for false codling moth [(Thaumatotobia leucotreta) (Lepidoptera: tortricida)] larvae infesting capsicum

Abstract

Occurrence of false codling moth (Thaumatotobia leucotreta) in export capsicum from Uganda has resulted into horticultural export companies being banned from export. A number of control measures are effective in control at pre-harvest including field sanitation, chemical control,sterile insect techmique, mating disruption, use of insect traps and use of biological control systems. At post-harvest, chemical control using methyl bromide is common but leaves chemical residues and affects the Ozone layer. Cold treatment is a better control option as no residues are left in produce and it is already being used in storage although its effect on false codling moth larva is not known. This study was conducted in a laboratory at the School of Agricultural Sciences, Makerere University to investigate the effect of cold treatment on false codling moths larva mortality and on the quality of fresh sweet pepper. Fruits obtained from an export company were subjected to treatments; 4 0C, 7 0C, 100C and room temperature for 3, 6, 9, 12 and 15 days. Larval mortality (%), weight loss, firmness and decay rate were noted at each day of assessment. Rate of decay was further assessed after shelf period. Data collected was analyzed using Genstat statistical software package 14th edition. Analysis of variance (ANOVA) was performed to determine significant differences within the treatments at 5% (P ≤ 0.05). Significant differences (P < 0.05) were observed among different treatments over the exposure period. Mortality increased with decrease in temperature and increase in duration of exposure. The lowest temperature achieved complete larval mortality after exposure period of 6 days. Quality losses were higher in infested fruits than uninfested fruits. At removal from cold treatment, 4o c exhibited the lowest decay rate (0%) compared to other cold treatment temperatures. However at shelf period, it was higher at 40 c (70%) compared to other treatment temperatures accounted for by chilling injury. weight loss was lowest at 100 c (5.2%) followed by 4 0 c (8.9%) and 7 0 c (13.8%). Firmness was highest at 40 c (4.4) at removal from cold treatment. Holding fruits at 4 0 c for at least 6 days achieved complete larval mortality and quality was not compromised by the time of removal from cold treatment. This study therefore recommends holding the fruits at 40c for at least 6 days and maintaining the fruit under cold treatment to ensure quality.