No abstract

Our search for a suitable biological agent to control the tomato russet mite (TRM), Aculops lycopersici, was initiated in 2013. Neoseiulus californicus, Amblyseius andersoni, and Neoseiulus fallacis showed a promising pest reduction potential in a curative control strategy. Although these beneficials had a low survival on tomato and were not able to eradicate the pest, plants did not present typical TRM damage. However, their inability to establish in the tomato crop means that their commercial use would require repeated introductions, making their use too expensive for growers. Other predatory mites in the survey, such as the iolinids Homeopronematus anconai and Pronematus ubiquitus, showed the potential for a preventative strategy as they can establish and reach high densities on tomato with weekly or biweekly provision of Typha angustifolia pollen as a food source. When the tomato crop was adequately colonized by either iolinid, the development of TRM and any damage symptoms could be successfully prevented. The potential of iolinid predatory mites for biological control of eriophyids is discussed.

The evolutionary origin of queen pheromones (QPs), which regulate reproductive division of labor in insect societies, has been explained by two evolutionary scenarios: the sender-precursor hypothesis and the sensory exploitation hypothesis. These scenarios differ in terms of whether the signaling system was built on preadaptations on the part of either the sender queens or the receiver workers. While some social insect QPs—such as cuticular hydrocarbons—were likely derived from ancestral fertility cues and evolved according to the former theory, the honeybee’s queen mandibular pheromone (QMP) has been suggested to act directly on preexisting gene-regulatory networks linked with reproduction. This is evidenced by the fact that QMP has been shown to also inhibit ovary activation in fruit flies, thereby implying exploitation of conserved physiological pathways. To verify whether QMP has similar effects on more closely related eusocial species, we here tested for QMP cross-activity in the bumblebee Bombus terrestris. Interestingly, we found that the non-native QMP blend significantly inhibited egg laying in both worker and queen bumblebees and caused accompanying shifts in ovary activation. The native bumblebee QP pentacosane, by contrast, only inhibited the reproduction of the workers. Overall, these findings support the hypothesis that honeybee QMP likely evolved via a route of sensory exploitation. We argue that such exploitation could allow social insect queens to produce compounds that manipulate the workers to remain sterile, but that a major hurdle would be that the queens themselves would have to be immune to such compounds.