Greenhouse investigations on the effect of guava on infestations of Asian citrus psyllid in grapefruit

Reports from Vietnam indicate interplanting guava with citrus reduces infestations of Asian citrus psyllid (ACP) (Diapliorina citri) in citrus. We therefore conducted cage studies in a greenhouse to assess the effect of different guava cultivars on adult ACP mortality and settling behavior on citrus (young potted grapefruit). The effects of cotton and tomato were also evaluated in some tests as non-citrus, neutral host species. Survival of adult ACP confined to potted guava in no-choice situations was reduced as compared to survival on potted grapefruit. However, adult survival was also reduced when they were confined to potted cotton or tomato. Adult ACP released into cages containing only citrus generally moved faster to citrus than when either 'White' guava or cotton was present. Greater numbers of adults were consistently observed on citrus over time in cages with only citrus as compared to in cages with citrus in the presence of guava or cotton. This may have been due to differences in the total plant surface area in cages with citrus alone compared to citrus caged with another plant. Mortality rates of adults were increased in cages containing both citrus and guava in one of two studies. While significant reductions in infestations of adults on young grapefruit sometimes occurred in cages containing both citrus and guava in the greenhouse, the reductions were not enough to verify the Vietnamese guava effect.