Abstract
To face the environmental problems caused by chemical pesticides, more ecologically friendly alternative pest control strategies are needed. Entomopathogenic nematodes (EPN) have great potential to control soil-dwelling insects that cause critical damage to the roots of cultivated plants. EPN are normally suspended in water and then sprayed on plants or onto the soil, but the inconsistent efficiency of this application method has led to the development of new formulations. Among them is the use of alginate capsules or beads that encapsulate the EPN in favorable conditions for later application. In this study, we evaluated whether alginate beads containing EPN are able to kill larvae of the banded cumber beetle Diabrotica balteata LeConte and thereby protect maize plants from damage by these generalist rootworms. EPN formulated in beads were as effective as sprayed EPN at killing D. balteata. They were found to protect maize plants from D. balteata damage, but only if applied in time. The treatment failed when rootworm attack started a week before the EPN beads were applied. Hence, the well-timed application of EPN-containing alginate beads may be an effective way to control root herbivores.
Highlights
Environmental and public health concerns linked to the use of chemical insecticides have led to pressures to develop alternative strategies for insect pest control
To test the effectiveness of this approach, we carried out two separate laboratory experiments: (1) we evaluated the mortality of D. balteata larvae after application of beads with quiescent entomopathogenic nematodes (EPN) and compared it to EPN applied in water and (2) we evaluated whether maize plants infested by D. balteata larvae benefit from the protection offered by EPN beads
H. bacteriophora applied in alginate beads (EPN beads) and in aqueous suspension (EPN in water) were effective in killing D. balteata larvae
Summary
Environmental and public health concerns linked to the use of chemical insecticides have led to pressures to develop alternative strategies for insect pest control. Biological control using the pests’ natural enemies is commonly recognized as an appropriate alternative [1]. Entomopathogenic nematodes (EPN) are excellent biocontrol candidates. EPN from the Steinernematidae and Heterorhabditidae families are obligate parasites of insects [2]. They are associated mutualistically with pathogenic bacteria of the genera Xenorhabdus and Photorhabdus, respectively, which are lethal to insects [3]. The life cycle of most nematodes includes an egg stage, four juvenile stages, and an adult stage [4]. The only stage that survives outside of a host is the nonfeeding, nondeveloping third stage infective juvenile (IJ), referred to as dauer juvenile [5]
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