Pg. 18-22 Progress with litchi moth research

Quantification of peak oviposition is crucial for litchi moth control as it will determine the application timing of contact
insecticides. First eggs were observed during mid November 2007, but the majority of oviposition took place when the
fruit began to color noticeably. The best time for a contact insecticide would therefore be towards the end of November
annually. Due to Last Cali’s mode of action, an earlier application is suggested. Last Call was evaluated on a 10 ha Wai
Chee litchi farm, just outside Nelspruit. Infestation on the farm was significantly less than the previous season. The
probability of the pheromone plume emanating from the treated plot (8 ha) affecting adjoining untreated plots is a distinct possibility and this trial should probably be repeated for another season to confirm these results. The insecticide trial was replicated in both the treated (Last Call) and untreated plots and despite a very low infestation, triflumuron SC appeared to be the superior product. It was positively proven that the coconut bug fed on litchis. While mature fruit are apparently not affected, significant abortion of immature fruit was recorded (averagee ±21%; range 16 – 32%). While the ability of subtropical fruit trees to compensate for early crop loss is unquestionable, the amount of early bug induced abortion that can be tolerated before economic losses ensue, still has to be determined experimentally. For macadamias it has been proven that mouthparts of the bugs introduce an array of opportunistic saprophytic fungi into the kernels. The effect of coconut bug feeding on post-harvest shelve life of the fruit is also a factor that needs clarification. A gross margin analysis revealed that significant infestation (±1 – 6%) of the litchi moth could be tolerated before the application of any corrective spray is economically justifiable on fruit destined for the internal market.

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