Functional Synchronization of Biological Rhythms in a Tritrophic System

In a tritrophic system formed by a plant, an herbivore and a natural enemy, each component has its own biological rhythm. However, the rhythm correlations among the three levels and the underlying mechanisms in any tritrophic system are largely unknown. Here, we report that the rhythms exhibited bidirectional correlations in a model tritrophic system involving a lima bean, a pea leafminer and a parasitoid. From the bottom-up perspective, the rhythm was initiated from herbivore feeding, which triggered the rhythms of volatile emissions; then the rhythmic pattern of parasitoid activities was affected, and these rhythms were synchronized by a light switch signal. Increased volatile concentration can enhance the intensity of parasitoid locomotion and oviposition only under light. From the top-down perspective, naive and oviposition-experienced parasitoids were able to utilize the different volatile rhythm information from the damaged plant to locate host leafminers respectively. Our results indicated that the three interacting organisms in this system can achieve rhythmic functional synchronization under a natural light-dark photoperiod, but not under constant light or darkness. These findings provide new insight into the rhythm synchronization of three key players that contribute to the utilization of light and chemical signals, and our results may be used as potential approaches for manipulating natural enemies

Prospects for predatory mirid bugs as biocontrol agents of aphids in sweet peppers

In recent years, biological control strategies to control many major horticultural pests have been successfully implemented in the Eastern Mediterranean basin. However, the management of some pests, such as aphids in sweet pepper crops, can still be improved. The goal of this study was to examine the potential of the omnivorous predatory mirids Nesidiocoris tenuis, Macrolophus pygmaeus, and Dicyphus maroccanus as biocontrol agents of aphids in sweet pepper crops. First, the capacity to detect Myzus persicae-infested and un-infested plants was studied in a Y-tube olfactometer. Females of the three species of predatory mirids were strongly attracted to the odor of infested M. persicae plants. Second, the prey suitability of young and mature nymphs of M. persicae for these three mirid species was studied. The three species actively preyed on M. persicae, although D. maroccanus resulted the most voracious species preying both young and mature nymphs. Finally, the capacity of the three omnivorous predators to reduce M. persicae in heavily infested plants was determined in semi-field conditions. The three species of mirids could reproduce on aphids and establish on sweet pepper plants. Mirids significantly reduced the number of M. persicae per leaf, reaching levels of aphid reduction close to 100 % when compared to the untreated control. These results suggest that mirids might play a major role in aphid management in sweet peppers. The potential implementation methods of predatory mirids for the biological control in sweet peppers are discussed