Integrated Management of Chive Gnats (Bradysia odoriphaga Yang & Zhang) in Chives Using Entomopathogenic Nematodes and Low-Toxicity Insecticides.

Xun Yan,Guoyu Zhao,Richou Han

doi:10.3390/insects10060161

Abstract

Bradysia odoriphaga is a major pest that causes damage to chive production, and which has developed resistance to highly toxic chemical insecticides. Entomopathogenic nematodes (EPN) show a high potential for B. odoriphaga control. This study aimed to develop an effective management method against B. odoriphaga larvae, using EPN with low-toxicity insecticides. Fourteen selected insecticides had no significant effects on the survival and infectivity of Steinernema feltiae SN and Heterorhabditis indica LN2. Synergistic interactions were observed for imidacloprid and osthole with S. feltiae SN against B. odoriphaga larvae. Steinernema feltiae SN was more effective than H. indica LN2 against B. odoriphaga at 15 and 20 °C, and the addition of imidacloprid at 1/10 recommended concentration (RC) significantly increased the efficacy of S. feltiae SN. The year-round occurrence of the B. odoriphaga larvae in chive fields treated by EPN and imidacloprid at 1/10 RC was studied. Results showed that the application of EPN with imidacloprid at 1/10 RC successfully suppressed larval populations of B. odoriphaga in chive fields, thus significantly increasing the yield of chive. The practical method of applying EPN–imidacloprid combinations provided a cost-effective and environmental safety strategy for controlling B. odoriphaga larvae in chive production, which can reduce the usage of toxic chemical insecticides.

Highlights

The chive gnat, Bradysia odoriphaga Yang and Zhang (Diptera: Sciaridae), is a major insect pest in chive production in China [1]
Results showed that the application of Entomopathogenic nematodes (EPN) with imidacloprid at 1/10 recommended field concentration (RC) successfully suppressed larval populations of B. odoriphaga in chive fields, significantly increasing the yield of chive
The practical method of applying EPN–imidacloprid combinations provided a cost-effective and environmental safety strategy for controlling B. odoriphaga larvae in chive production, which can reduce the usage of toxic chemical insecticides

Summary

Introduction

The chive gnat, Bradysia odoriphaga Yang and Zhang (Diptera: Sciaridae), is a major insect pest in chive production in China [1]. Bradysia odoriphaga feeds on plants from seven families and on more than thirty species, and it causes production losses in mushroom sheds [2]. Larvae of B. odoriphaga aggregate in the soil and feed on the roots and stems of the plant, causing plants to stunt or even die [3]. Bradysia odoriphaga has 4–6 overlapping generations per year, and the peak damage occurs in spring and autumn [2,4], which leads to chive production losses of 30% to 80% in North China [5]. Larvae of B. odoriphaga are cryptic in the soil, and much more toxic insecticides are used by the farmer to maintain yields, which has led to heavy insecticide residues in the chives and the soil [6]. Over-use of toxic insecticides has led to the development of insecticide resistance in Insects 2019, 10, 161; doi:10.3390/insects10060161 www.mdpi.com/journal/insects

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