Ecology of Fungus Gnats (Bradysia spp.) in Greenhouse Production Systems Associated with Disease-Interactions and Alternative Management Strategies.

Raymond A Cloyd

doi:10.3390/insects6020325

Abstract

Fungus gnats (Bradysia spp.) are major insect pests of greenhouse-grown horticultural crops mainly due to the direct feeding damage caused by the larvae, and the ability of larvae to transmit certain soil-borne plant pathogens. Currently, insecticides and biological control agents are being used successively to deal with fungus gnat populations in greenhouse production systems. However, these strategies may only be effective as long as greenhouse producers also implement alternative management strategies such as cultural, physical, and sanitation. This includes elimination of algae, and plant and growing medium debris; placing physical barriers onto the growing medium surface; and using materials that repel fungus gnat adults. This article describes the disease-interactions associated with fungus gnats and foliar and soil-borne diseases, and the alternative management strategies that should be considered by greenhouse producers in order to alleviate problems with fungus gnats in greenhouse production systems.

Highlights

Fungus gnats in the genus Bradysia spp. (Diptera: Sciaridae) are major insect pests of greenhouse production systems feeding on a wide-range of horticultural crops [1,2,3] with the commonly encountered species being Bradysia coprophila Comstock and B. impatiens Johannsen [4,5,6]
Adults do not fly very well and tend to reside near the growing medium, they may still be able to disperse spores of foliar plant pathogens in localized areas of the greenhouse [33]. The potential for both life stages of fungus gnats to transmit diseases means that the tolerance level for the presence of this pest may be very low, which is similar to other insect pests that vector diseases such as the western flower thrips, Frankliniella occidentalis Pergande [36]
It is important to understand that fungus gnats, both larvae and adults, may transmit certain soil-borne plant pathogens to greenhouse-grown horticultural crops, either directly or indirectly potentially resulting in an economic loss

Summary

Introduction

Fungus gnats in the genus Bradysia spp. (Diptera: Sciaridae) are major insect pests of greenhouse production systems feeding on a wide-range of horticultural crops [1,2,3] with the commonly encountered species being Bradysia coprophila Comstock and B. impatiens Johannsen [4,5,6]. A number of insecticides from different chemical classes and various biological control agents including a soil-dwelling predatory mite (Stratiolaelaps scimitus (Womersley)), a rove beetle (Dalotia coriaria Kraatz), and entomopathogenic nematode (Steinernema feltiae Filipjev) have been shown to be effective in suppressing or regulating fungus gnat populations [1,8,14,15,16,17,18,19]. These strategies may only be effective if alternative plant protection strategies are implemented simultaneously. This article will discuss the disease-interactions associated with fungus gnats, and the alternative management strategies that should be considered so as to alleviate problems with fungus gnats in greenhouse production systems

Disease-Interactions

Alternative Management Strategies

Conclusions