Molecular tracking of insect dispersal to verify arthropod predator movement from an alfalfa field to a peach orchard

Abstract

Implementation of landscape approaches to conservation biological control programs requires the confirmation of putative sources that contribute to predator colonization of crops. Several predator species are known to play an important role in biological control programs in orchards worldwide. This study optimizes a DNA mark-capture procedure based on a topical application of a solution of grinded brine shrimp cysts, Artemia spp. (Anostraca: Artemiidae), followed by a conventional PCR to monitor predator dispersal from an alfalfa field to a neighboring peach orchard.

Orius laevigatus (Fieber) (Hemiptera: Anthocoridae) is a well-known predator present in orchards as well as in arable crops, which was used in this study to optimize the marking procedure. Firstly, the acquisition and the retention time of the Artemia marking method were tested in greenhouse trials either directly by spraying them with the Artemia solution, or indirectly via residual contact on caged plants after the spray. The topical mark remained detectable on O. laevigatus after 6 days, and 50% of the tested predators were positive 3 days after walking on the sprayed plants. Secondly, after spraying the Artemia solution on a 25m2 strip of an alfalfa crop neighboring to a peach orchard, several common predator species were collected using sticky traps placed between both crops after the alfalfa cuts. After PCR analysis with the Artemia specific primers, 32% of the analyzed predators (coccinellids, anthocorids, chrysopids, and mirids) showed their movement from alfalfa to peach. This study confirms the usefulness of this marking method to monitor dispersal of biological control agents between neighboring crops.