Sticky traps are a standard tool for monitoring alate arthropod pests in greenhouses. However, in practice, evaluation of traps over the whole growing season is rarely done. For decision making by growers, sticky traps are often only used for detection of pest presence. The reason behind is that although many studies show that pest population densities can be estimated using sticky traps under experimental conditions, validation under growing conditions and monitoring of beneficials are often lacking. In the current study, we evaluated whether trap densities recommended for practice are sufficient to estimate pest population densities of Trialeurodes vaporariorum (Hemiptera: Aleyrodidae) and its natural enemy Encarsia formosa (Hymenoptera: Aphelinidae) in protected tomato cultures throughout the growing season. Our results show that trap catches provide reliable information about pest densities, in which correlations differed for specific developmental stages, i.e. adults \ nymphs \ nymphs (previous week). A single yellow sticky trap provided reliable information on nymphal density in the tomato crop on an area of at least 170 m 2 . A rapid increase of parasitoid trap catches indicated high parasitism. In our experiments, a total trap catch of C6 parasitoids/trap was a suitable threshold for sufficient natural enemy activity in the tomato crop. The implementation of these results in practice and the transferability to other cropping systems are discussed.
The development and morphology of the immature phases of Pachycrepoideus vindemmiae (Rondani, 1875) (Hymenoptera, Pteromalidae) are described from a laboratory rearing culture maintained on Ceratitis capitata (Wiedemann, 1824) (Diptera, Tephritidae) using microscopic techniques, including light and scanning electron microscopy. The surface of the chorion of the egg is granulated, and the micropyle occurs at the anterior end. The labrum of the first instar larva does not have sensilla, and the second to fourth instar larvae have setae on the head. The mature larva is characterized by the position and number of the integumental differentiations (sensilla and setae). On completion of larval development, an adecticous and exarate pupa is produced. As for the adult, the mandibles of the pupae are toothed. Five larval instars are recorded, based on statistical analyses of the sizes of the larval mandibles in combination with characters such as the number of exuviae and excretion of the meconium. Developmental time from egg to adult emergence was 18-20 days for males and 21-23 days for females at 21-26 degrees C, 55-85 relative humidity, and a 16L:8D photoperiod. The results show that the eggs and different larval instars of this parasitoid can be unambiguously identified only by scanning electron microscope.
Parasitoid fitness strongly depends on the availability and quality of hosts, which provide all resources required for larval development. Several factors, such as host size and previous parasitation, may affect host quality. Because self-superparasitism induces competition among a female's offspring, it should only occur if there is an imperfect recognition of self-parasitized hosts or if there is a fitness advantage to self-superparasitism. Against this background, we investigated self-superparasitism and offspring production in Spalangia cameroni (Hymenoptera: Pteromalidae) in relation to the abundance of a novel host, Ceratitis capitata (Diptera: Tephritidae). Individual pairs of parasitoids were provided with either two (low host abundance) or ten (high host abundance) pupae per day. Under high host abundance, lifetime fecundity (number of eggs laid), offspring number, number of pupae parasitized and hosts killed were greater than under low host abundance, whereas the number of eggs per host was lower; and the proportion of hosts that did not produce offspring tended to be lower. The latter suggests the occurrence of ovicide, when hosts are scarce due to an at least imperfect recognition of previously self-parasitized hosts. Offspring production per parasitized pupa was higher when hosts were scarce and levels of self-superparasitism high, suggesting the existence of beneficial effects of self-superparasitism.
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