Fungi emit a broad spectrum of volatile organic compounds (VOCs), sometimes producing species-specific volatile profiles. Volatilomes have received over the last decade increasing attention in ecological, environmental and agricultural studies due to their potential to be used in the biocontrol of plant pathogens and pests and as plant growth-promoting factors. In the present study, we characterised and compared the volatilomes from four different Trichoderma species: T. asperellum B6; T. atroviride P1; T. afroharzianum T22; and T. longibrachiatum MK1. VOCs were collected from each strain grown both on PDA and in soil and analysed using proton transfer reaction quadrupole interface time-of-flight mass spectrometry (PTR-Qi-TOF-MS). Analysis of the detected volatiles highlighted a clear separation of the volatilomes of all the four species grown on PDA whereas the volatilomes of the soil-grown fungi could be only partially separated. Moreover, a limited number of species-specific peaks were found and putatively identified. In particular, each of the four Trichoderma species over-emitted somevolatiles involved in resistance induction, promotion of plant seed germination and seedling development and antimicrobial activity, as 2-pentyl-furan, 6PP, acetophenone and p-cymene by T. asperellum B6, T. atroviride P1, T. afroharzianum T22 and T. longibrachiatum MK1, respectively. Their potential role in interspecific interactions from the perspective of biological control is briefly discussed.

Interspecific host discrimination and within-host competition between Encarsia formosa Gahan and Encarsia pergandiella (Howard), two endoparasitoids of whiteflies, were studied under laboratory conditions. Interspecific host discrimination was studied at two time intervals (0 h and 72 h after the first species had oviposited). Parasitized and unparasitized Trialeurodes vaporariorum (Westwood) hosts were accepted for oviposition at the same rate by the two parasitoid species. Host type did not affect the handling time of the two parasitoids. The outcome of within-host competition was investigated after females of the two species parasitized the hosts at various time intervals. In four treatments, E. pergandiella was allowed to oviposit 0, 24, 48 and 72 h after E. formosa while in the other two, E. formosa was allowed to oviposit 0 and 72 h after E. pergandiella. In four of these treatments: E. formosa following E. pergandiella at 0 and 72 h, and E. pergandiella following E. formosa at 0 and 24 h, E. pergandiella prevailed. In the host discrimination experiment (72 h interval), 20% of E. pergandiella eggs were killed by E. formosa females. Interspecific ovicide was also observed in the within-host competition experiment, in which 6% of 72-h-old E. pergandiella eggs were killed by E. formosa females.

The occurrence of male antennal glands in three hymenopteran parasitoids belonging to the family Encyrtidae (Leptomastix dactylopii, Rhopus meridionalis and Asitus phragmitis) is reported for the first time. The ultrastructure and function of these glands are described in detail. In all three species the glands consist of clustered unicellular secretory units extending underneath the cuticle. Glandular secretions were released externally and spread onto female antennae by specialized ‘release and spread sites’, appearing as ‘scale-like’ or ‘peg-like’ cuticular structures. These antennal glands play an important role during the complex sequences of courtship behaviour, eliciting female acceptance. The possible behavioural and taxonomical implications are discussed.