Pg. 17-21 Integrated management of litchi pests

Damage surveys of the coconut bug in the Nelspruit and Onderberg areas were completed for the second season. Abortion of stink bug damaged fruit in the Nelspruit region remained constant at ± 45 – 50% while very little damage was observed for the second consecutive year on a number of farms in the Onderberg area. A new stink bug (Leptocoris hexophthalma [Thunberg], Rhopalidae) was observed on litchis in the Onderberg, Nelspruit, Kruger National Park and Hazyview areas. Currently it is expected that incidence of this bug will be of a sporadic nature and no specific precautions are therefore recommended. An application during early October of Cypermethrin 200 g/L EC against the coconut bug significantly reduced early abortion of infested fruit, but final yields of treated trees were not statistically significant different from untreated trees. It was postulated that litchi trees were able to compensate for early crop damage or that Coconut bugs only migrated into the orchards at a later stage. A follow-up trial during the 2010 season when lower yields are anticipated is therefore suggested. Isomate reduced the incidence of the litchi moth significantly during the early season, but when insect numbers increased towards the end of the season, differences between treatments were no longer significant.

Summary:

• The article focuses on integrated pest management (IPM) strategies for controlling major pests in litchi orchards, particularly the coconut bug (Pseudotherapthus wayi), litchi moth, and a newly observed stink bug (Leptocoris hexophthalma).
• Damage surveys showed that coconut bug damage (fruit abortion) was consistently around 45-50% in the Nelspruit region, but very low in the Onderberg area, likely due to different climatic and host plant conditions.
• Cypermethrin insecticide applied in early October significantly reduced early fruit abortion from coconut bug infestation, but did not statistically improve final yields, suggesting litchi trees compensate for early damage.
• Leptocoris hexophthalma was found sporadically on litchis, often causing black moldy patches; it is suspected to be a sporadic pest with localized trees potentially needing spot spraying, though fruit from sprayed trees should not be exported due to residue concerns.
• Mating disruption using Isomate pheromone dispensers reduced litchi moth damage early in the season, but control diminished as insect pressure increased toward the end of the fruit development cycle.
• The study emphasizes timing pesticide applications closer to harvest in November with minimal residue risks and advocates biological control and environmentally friendly methods to maintain sustainable insect management.
• The succession of different pests over the season was observed: coconut bug dominates early, litchi moth mid to late season, and fruit flies are expected at the season end, with little direct interaction between these pests.
• Future pest management should consider the potential spread of coconut bugs linked to nearby cultivation of other host crops like mangoes, avocados, and macadamias, especially in the Nelspruit area.
• Secondary fungal infections transmitted by pests during feeding may impact shelf life of fruit and require further investigation.
• Overall, the article presents practical recommendations for integrated litchi pest management balancing economic benefit, environmental impact, and export quality standards.