Efficacy of the Applied Natural Enemies on the Survival of Colorado Potato Beetle Adults.

Vladimír Půža,Jana Konopická,Jiří Nermuť,Oxana Skoková Habuštová

doi:10.3390/insects12111030

Abstract

Simple SummaryColorado potato beetle (CPB) Leptinotarsa decemlineata is the potato plant’s most destructive pest. Recently, resistance to the traditional insecticides has appeared, thus new environmentally friendly control agents are highly needed. In our study, we searched for the most effective entomopathogenic agents that could be used to decrease the emergence of CPB adults from the soil. We selected two entomopathogenic nematodes (Steinernema carpocapsae and S. feltiae) and one strain of fungus (Beauveria bassiana). The suspension application was done on the leaves, plus by watering the pods and the field plots. All the treatments had an obvious effect, but in the field, only the fungal treatment showed a promising result. Further research is needed to develop the most effective application for field usage.Colorado potato beetle Leptinotarsa decemlineata is among the most destructive pests of potatoes quickly developing resistance to traditional insecticides. In the present study, we tested the effect of various species and strains of entomopathogenic nematodes on CPB adults, and subsequently, the most effective nematodes were applied alone and in combination with entomopathogenic fungus B. bassiana in pots with potato plants and in the field and their effect on the number of emerging adults was evaluated. In the experimental infections, both the nematode invasion and pathogenicity were variable, and, in several strains, the mortality reached 100%. In pot experiments, soil application of nematodes S. carpocapsae 1343 and S. feltiae Jakub and fungus significantly decreased numbers of emerging CPB adults, while, after the application on leaves, only fungal treatment was effective. The field application of fungus B. bassiana significantly decreased the number of emerging CPB adults in comparison to control sites by ca. 30% while the effect of nematodes and the nematodes–fungus combination was not significant. In conclusion, we demonstrate the necessity of thorough bioassays to select the most effective nematode strains. Entomopathogenic nematodes have the potential to effectively decrease the emergence of CPB adults, but further research is needed to improve the effectiveness in the field.

Highlights

Colorado potato beetle (CPB), Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae), is among the most destructive pests of potatoes (Solanum tuberosum L.)
In the present study, we focused on adult CPB and we tested a large number of Entomopathogenic nematodes (EPNs) species and strains for pathogenicity to CPB adults in Petri dish assays in order to select the most effective nematodes
The sampling in the potato fields resulted in the isolation of 21 steinernematid strains (Table 1), out of which 13 strains belonged to S. feltiae, 6 strains were identified as S. affine, and 2 strains belonged to S. kraussei

Summary

Introduction

Colorado potato beetle (CPB), Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae), is among the most destructive pests of potatoes (Solanum tuberosum L.). Entomopathogenic nematodes (EPNs) (Steinernematidae and Heterorhabditidae: Nematoda) are ubiquitous lethal insect parasites with global distribution and a wide host range [5]. Due to their ability to infect various insects [6], the possibility of mass production by industrial techniques [7], and their safety to non-target organisms and the environment [8,9], EPNs represent an attractive agent for the biological control of many insect pests [10]. Entomopathogenic fungi (EPFs) represent other promising biocontrol agents Their advantages are that they do not need to be ingested, as they are able to penetrate the host cuticle, and that they can be relatively produced [11]. The fungi are produced either in solid-state fermentation, where they produce aerial conidia, or in a submerged liquidstate fermentation, where they produce blastopores [12], and a number of mycoinsecticide, have been developed in the world [13]

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Conclusion