Functional response of Diachasmimorpha longicaudata (Ashmead) over Ceratitis capitata (Wiedemann): Influence of temperature, fruit location and host density

Abstract

To establish a successful Biological Control (BC) program, exotic parasitoids should be proven to be targeted species, capable of surviving in a new environment, inducing pest population reduction. Moreover, to achieve this aim, imported exotic parasitoids should usually adapt to a new host (the target pest), which usually results in practical improvements. The determination of the functional response of the imported parasitoid was recognized as a key requirement prior to its introduction. In this work, we determined the functional response of the parasitoids, Diachasmimorpha longicaudata, against the medfly, Ceratitis capitata, under two different scenarios, one in the laboratory and another in the greenhouse. In both scenarios, we determined D. longicaudata parasitism percentage, fertility, sex ratio, and induced host mortality, considering temperature, fruit location, and host density. In laboratory conditions, when the medfly host larvae were provided within an artificial diet, our results demonstrated that the two different temperature ranges (20-24 and 25-29 degrees C) were suitable for the activities and development of D. longicaudata. Parasitism, fertility, and medfly population reduction corresponded to a Type II functional response with a male-biased offspring sex-ratio (females/males + females; 33-46%), while induced mortality decreased with an increase in host density. Similarly, when the hosts were provided inside fruits, parasitism and fertility also corresponded to a Type II functional response, and the offspring sex ratio was also male-biased (34-37%). However, in greenhouse conditions, our results showed no significant differences regarding fruit position. For host density, the only significant differences were found for fertility and a slightly female-biased offspring sex-ratio at higher ratios (38-58%) with the same Type II response, as in laboratory conditions. The information reported here about the key demographic parameters and the functional response of D. longicaudata using C. capitata as its host under various environments and situations will assist in the evaluation of its potential as a biological control agent against this pest. Our results show that this parasitoid can search efficiently for host individuals even at low host densities, irrespectively of their spatial location (infested fruits in the canopy or as ripened fruits fallen to the ground) or independently of the temperature of the environment.