Glandular trichomes affect mobility and predatory behavior of two aphid predators on medicinal cannabis

Abstract

Medicinal cannabis (Cannabis sativa L.) is a growing agro-industrial sector with the end product required to be free of pesticides. C. sativa is covered by specialized hairs called trichomes, namely, two types of non-glandular and three types of glandular trichomes. Despite the great importance of biological pest control in medicinal cannabis little is known about the impact of cannabis trichomes on natural enemies mobility and their interaction with prey. In the current study, by employing a video recording set-up, we determined the mobility of Aphidoletes aphidimyza and Chrysoperla carnea larvae and their interaction with the aphid pests Phorodon cannabis and Aphis gossypii on C. sativa leaf disks and inflorescences. As benchmark, we tested the same parameters on sweet pepper leaf disks, a benign host plant for both predators, and without trichomes. It was found, that A. aphidimyza females readily oviposited on P. cannabis colonies developing on C. sativa plants. On C. sativa leaves, covered by non-glandular trichomes, the larvae of both predators were able to move and prey upon aphids. On C. sativa inflorescences, where glandular trichomes prevailed, the larvae of A. aphidimyza were generally inactive while the C. carnea larvae were still able to move and interact with prey albeit to a lesser degree compared to the cannabis leaves. We suggest that the use of A. aphidimyza and C. carnea in augmentative biological control programs in medicinal cannabis should depend on the croṕs growth stage; the former should be employed during the vegetative while the latter during the vegetative and flowering crop stages.