Interference by Western Flower Thrips in rearing Asian citrus psyllid: Damage to host plants and facultative predation

• Ten adult Western Flower Thrips (WFT) per shoot caused significant damage to jasmine.
• In a separate study, 10 WFT per shoot caused little damage to sweet orange.
• Five adult WFT per 90 eggs of the Asian citrus psyllid (ACP) caused 87% egg mortality.
• A pirate bug, Orius insidiosus, at 5 adults per 90 ACP eggs caused 100% egg mortality.
• This bug is a good thrips predator but would be incompatible with rearing ACP.

An infestation of Western Flower Thrips (WFT), Frankliniella occidentalis (Pergande), recently developed on young citrus trees in a greenhouse devoted to rearing Asian citrus psyllid (ACP), Diaphorina citri Kuwayama. Large numbers of young flush leaves were killed which negatively impacted ACP, as ACP is dependent on flush for oviposition and nymph development. Further, WFT predated on immature ACP killing a large proportion of young nymphs. Two experiments were subsequently conducted to assess WFT damage to two ACP rearing host plants, orange jasmine [Murraya exotica (L.)] and sweet orange [Citrus sinensis (L.) Osbeck]. Direct comparisons of WFT damage to the two host plants were not made because the plants were not studied at the same time and the age of adults used in the experiments was not known. An infestation of ten adult WFT per flush shoot caused significant damage to orange jasmine: most (73%) flush shoots were killed, and shoots not killed were significantly growth retarded. Ten adult WFT per flush shoot caused little damage to sweet orange. A third experiment showed that five adult WFT per 90 ACP eggs predated on large numbers of eggs and 1st instar ACP − only 13% of the eggs hatched and developed beyond the 1st nymphal instar (WFT did not attack later instars). Predation on ACP immatures in this experiment included an evaluation of a minute pirate bug [Orius insidiosus (Say), regarded as effective against WFT] also at five adults per 90 ACP eggs. All ACP eggs were killed by this predator before eclosion. O. insidiosis might be useful for reducing infestations of WFT on citrus or other ACP host plants, but the predator would be incompatible with rearing ACP.