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Abstract
Western Corn Rootworm is a pest of maize that mostly damages roots. Many alternative strategies have been explored to control this species, with little or non-lasting success, and it remains a threat to maize production worldwide. Gaeolaelaps aculeifer, a soil-dwelling predatory mite that inhabits the first few centimeters of the soil, showed high predatory potential against WCR larvae in the laboratory. In this study, we explored the efficiency of G. aculeifer against WCR in more realistic contexts. First, we infested maize plants isolated in pots in a greenhouse with WCR, and tested the impact of different densities of mites on plant protection. Using standard indicators of WCR population presence and impact, we confirmed that G. aculeifer has the potential to control WCR at densities starting from 100 mites/plant. Then, considering that the release of a large amount of biocontrol agents at WCR emergence might be too costly and constraining for large-scale implementation, we tested the efficiency of a predator-in-first strategy in a maize field infested by WCR. The goal was to introduce fewer G. aculeifer combined with Aleuroglyphus ovatus eggs as an alternative food source in order to let the mite population grow in the field and reach sufficient density at the critical stage for protection. This strategy gave comparable results to pesticide on all indicators examined in our field trial, highlighting the potential to sustainably manage this pest.
Highlights
With 1068 million tons produced in 2017 [1], Maize (Zea Mays L., 1753) is the first cereal produced in the world
The impact of the mites presence has been detected and in order to identify which density of predatory mite is necessary to control WRC populations with a limited impact on plant quality under the same conditions, we tested the impacts of the mite density (100, 500 or 1000 individuals per plant) in the maize + Western Corn Rootworm (WCR) + mites treatment on the number of WRC emerged, chlorophyll index per plant and the 1-3 IOWA ranking scale
Our results provide the first empirical demonstration of the ability of soil-dwelling predatory mites to prevent WCR damages on maize plants
Summary
With 1068 million tons produced in 2017 [1], Maize (Zea Mays L., 1753) is the first cereal produced in the world. Most species are mobile predators feeding on collembola, nematodes, insect larvae, insects eggs and other microarthropods [32,33] Their effectiveness as biological control agents in regulating soil pest populations have contributed to their use both in the field and in the greenhouse [34,35]. The predators-in-first (PIF) strategy, first suggested by McMurtry et al [46], aims to let the predators establish before the targetable pest or stage is present This method relies on generalist predators’ capacity to feed, survive and reproduce on an alternative food source provided by the environment [46,47,48,49]. To establish a proof of concept of this PIF strategy in realistic conditions before a wider experimental plan, we led the trial in one maize field and compared it with pesticide treatment and a negative control
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