Abstract
Simple SummaryWasps, generally referred to as “farmers friends” because of their ability to control devastating fruit flies, were imported from Hawaii and released in Kenya for the management of the invasive Oriental fruit fly Bactrocera dorsalis. It was noted that the introduced wasp had developed a liking for the native fruit fly species Ceratitis cosyra which already has a native wasp controlling it. We therefore undertook a study to understand the interaction of the introduced and native wasp on the invader Oriental and native fruit flies. Our results show that when the native wasp attacks the invader fruit fly, the wasp is killed because of the strong immune system of the oriental fruit fly. The good news is that the introduced wasp efficiently controls both the invader and the native fruit flies. We have discussed these findings based on various scientific principles which favor the co-existence of the two wasps without any detrimental effect on their survival. We have also suggested that more studies be conducted in open field conditions where both fruit flies occur in abundance and choices regarding which fruit fly species to attack are much wider.The braconid wasp, Diachasmimorpha longicaudata (Ashmead), was introduced in Kenya from Hawaii for classical biological control of the invasive tephritid, Bactrocera dorsalis Hendel. Following reports that D. longicaudata had formed new associations with Ceratitis cosyra, laboratory experiments were conducted to assess the interaction between the introduced and the native parasitoid of C. cosyra; Psyttalia cosyrae (Wilkinson) under three scenarios: B. dorsalis only, C. cosyra only and mixed populations of the two species. Parasitoids were introduced to the host as sole, sequential and simultaneous releases. Host searching and probing events were five times higher for D. longicaudata than P. cosyrae with both hosts. Total parasitism was highest (78%) when D. longicaudata was released alone on C. cosyra, compared to 20% for P. cosyrae released on the same host. Releases of P. cosyrae on B. dorsalis resulted in 0% parasitism, compared to 64% parasitism by D. longicaudata. Specific parasitism for P. cosyrae was three times higher when P. cosyrae was released first in sequential releases on C. cosyra compared to when it was released after D. longicaudata. These findings suggest that the two parasitoids can both suppress C. cosyra but B. dorsalis acts as a reproductive sink for P. cosyrae. Our findings should form the basis of field investigations where options are much wider for both parasitoids.
Highlights
The Tephritidae have a worldwide distribution and comprise approximately 4000–4500 described species in 500 genera [1,2,3]
Diachasmimorpha longicaudata was reared on late second instar larvae of B. dorsalis while P. cosyrae was raised on C. cosyra larvae of the same age following a procedure similar to that described by Mohamed et al [54] and Ekesi et al [72]
Diachasmimorpha longicaudata wasps were faster than Psyttalia cosyrae in landing, probing and initiating oviposition in all host combinations tested (Figure 1A–F)
Summary
The Tephritidae have a worldwide distribution and comprise approximately 4000–4500 described species in 500 genera [1,2,3]. The need for cost effective, environmentally friendly and sustainable approaches to fruit fly management has greatly pushed pest management in the direction of strategies fitting this category or creating new prospects for tactical combinations in an integrated pest management (IPM) approach [32] One such strategy is the use of parasitoids. Within the Braconidae is the subfamily Opiinae, a diverse group of koinobiont endoparasitoids of various cyclorrhaphous Diptera constituting about 1500 to 1900 species worldwide [35,36,37] Out of this number, more than 100 species have successfully been reared on fruit-infesting Tephritidae [38] and several have been effective in controlling most fruit flies of economic importance [31,39,40,41,42,43,44,45,46,47]. Opiinae are the most preferred natural agents for fruit fly suppression because of their host specificity and high parasitism rates [48,49,50]
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