Intraguild predation and competitive displacement between Nesidiocoris tenuis and Dicyphus maroccanus, two biological control agents in tomato pests

Dicyphus maroccanus Wagner and Nesidiocoris tenuis Reuter （Hemiptera： Miridae） are 2 biological control agents in tomatoes. Through the crop seasons, a natural shift in the occurrence of both mirids in favor ofN. tenuis has been observed at the end of the cropping cycle in eastern Spain. To better optimize their conservation, the reasons for the observed change, such as intraguild interactions （IGP） or the influence of environmental conditions, are worth elucidating. To do this, we first studied the IGP of adult females on heterospecific nymphs in the laboratory. We next studied exploitative competition between adults and nymphs of each species when feeding on Ephestia kueniella Zeller （Lepidoptera： Pyralidae） eggs in the laboratory. Finally, to analyze the competitive displacement between both mirids, we conducted a semifield experiment in which both predators were released together. All experiments were conducted at 2 temperature regimes （20 and 25~C）. Adult- to-nymph intraguild interactions occurred only at 25 ~C at very low levels, showing that N. tenuis attacked and consumed a greater proportion ofheterospecific nymphs. Nesidiocoris tenuis was a better competitor than D. maroccanus when feeding on the shared prey in the presence of its heterospecific nymph at 25 ~C. In semifield conditions, N. tenuis showed a competitive advantage over D. maroccanus at both temperatures. We conclude that there is not direct interference between both species, however, N. tenuis has a greater ability to outcompete, since it is best adapted to higher temperatures and it is able to remove food sources for D. maroccanus.

When do predatory mites (Phytoseiidae)attack? Understanding their diel and seasonal predation patterns

Predatory mites of the Phytoseiidae family are considered one of the most important groups of natural enemies used in biological control.The behavioral patterns of arthropods can differ greatly daily and seasonally;however,there is a lack of literature related to Phytoseiidae diel and seasonal predation patterns.The predatory activity of three phytoseiid species (two Tetranychidae-specialists,Phytoseiuluspersimilis and Neoseiulus californicus,and one omnivore,Euseius stipulatus)that occur naturally in Spanish citrus orchards was observed under laboratory conditions in winter and summer.The temperature and photoperiod of the climatic chamber where the mites were reared did not change during the experiment.Our study demonstrates that phytoseiids can exhibit diel and seasonal predatory patterns when feeding on Tetranychus urticae (Acari:Tetranychidae).Neoseiulus californicus was revealed to be a nocturnal predator in summer but diurnal in winter.In contrast,P.persimilis activity was maximal during the daytime,and E.stipulatus showed no clear daily predation patterns.The predatory patterns described in this study should be taken into account when designing laboratory studies and also in field samplings,especially when applying molecular techniques to unveil trophic relationships.