Deal With fungus

English Title: Effects of growing media containing diatomaceous earth on the fungus gnat Bradysia sp. nr. coprophila (Lintner) (Diptera: Sciaridae).
Personal Authors: Cloyd, R. A., Dickinson, A.
Author Affiliation: Department of Natural Resources and Environmental Sciences, University of Illinois, Urbana, IL 61801, USA.
Document Title: HortScience, 2005 (Vol. 40) (No. 6) 1806-1809

Abstract:

Fungus gnats (Bradysia spp.) are major insect pests in greenhouses. The adult stage is primarily a nuisance whereas the larval stage is directly responsible for plant injury by feeding on plant roots or tunneling into stems. Insecticides are used to deal with fungus gnat larvae in growing medium, although sometimes with limited success. This study evaluated the potential of using a soil amendment-diatomaceous earth (DE) incorporated into growing media-for controlling the fungus gnat Bradysia sp. nr. coprophila. Two experiments were conducted by testing a series of growing media containing various concentrations of diatomaceous earth, and several without diatomaceous earth. The effects of the growing media containing diatomaceous earth on both the 2nd and 3rd instars of fungus gnat larvae were determined by recording the number of adults captured on yellow sticky cards (2.5×2.5 cm).

Based on the results obtained from both experiments, the addition of DE to growing medium, at the concentrations tested, did not negatively affect or increase efficacy against both the 2nd and 3rd instars. This suggests that incorporating DE into commercially available growing medium may not be beneficial to greenhouse producers. However, further research is needed to assess whether differential larval susceptibility and moisture content influence the ability of DE to control soil-dwelling arthropods.

Publisher: American Society for Horticultural Science

Plant disease is caused by abiotic and biotic factors. While other chapters deal with the way fungi improve plant health directly, this chapter will ask the question “Can fungi be used to reduce the effects of biotic causes of plant disease?” As most biotic causes are fungi, we will concentrate on fungus to fungus interactions. The topic of fungus to fungus interactions has been reviewed in depth on many occasions from many different points of view. This chapter will not attempt to summarise this work. Rather we will dip into some of the stories.

The interactions between fungi can be manipulated to reduce the damage caused by one fungus on the plant. Essentially, these interactions include:

1. Direct hyphal parasitism
2. Antibiotic interactions
3. Competition for resources

The mechanisms are not mutually exclusive and all may be evident within one interaction at the same or different times.