Biological Control of Mole Crickets by Fungal Pathogens
Fungal, protozoan, viral, and bacterial pathogens have been found associated with mole crickets in North and South America. Two of the fungal pathogens, both of them native to the USA as well as to many other countries, have received most attention by researchers; they are Beauveria bassiana and Metarhizium anisopliae. Both of these fungi have been found in nature as pathogens of a long list of insect species, but normally few insects in any population are killed by them because the concentration of the pathogens in nature is low. These pathogens can be, and are, produced industrially and marketed as biopesticides. When applied at high concentrations, they kill a high proportion of insects that they contact in the area targeted. Two things can improve the kill of the inset
pests targeted.
Mole cricket infected with Beauveria bassiana, "white muscardine".
First, the method of application can improve contact of the pathogen with the insect pests targeted. Application methods for some insect pests have been devised. Methods for subterranean insect pests (such as mole crickets) still need development because broadcast application on the soil surface is likely to be prohibitively expensive as well as leading to the rapid demise of the pathogen when it encounters bright sunlight. Alternative methods are injection into the soil, or incorporation of the pathogen into an attractant such as a bait. Materials used to make the bait obviously are important, because it must be very attractive to the target pest while preserving the pathogen.
Mole cricket infected with Metarhizium anisopliae, "green muscardine".
Second, each of these fungal pathogens has been collected from various insect species from various places. Capabilities of these various collections of pathogens, called strains, differ. Under experimental comparison using Scapteriscus mole crickets in the laboratory, some strains have been found to kill all mole crickets they contacted, whereas others killed a much smaller proportion. Many strains of Beauveria bassiana have been designated by code numbers and letters; they are not distinct species. Speed of kill by these various strains also differs, though in general all are slower than chemical pesticides now in use.
Mole cricket infected with Aspergillus.
Development of a method of applying fungal pathogens against Scapteriscus nymphs is a worthwhile project because biological control agents now in use (Steinernema scapterisci, Ormia depleta, and Larra bicolor) have little or no effect against nymphs. If successful, it could replace use of chemical pesticides now used against the nymphs, with greater safety to non-target organisms.
Mole cricket infected with Sorosporella - Syngiocladium.
The University of Florida sells color sheets depicting adult mole crickets, mole cricket life cycle, mole cricket damage (Turfgrass Insects Sheet 1) as well as photos of nematodes and a fungus attacking mole crickets (Beneficial Insects Sheet IV). These are just two of forty-three color sheets currently developed by the Department of Entomology and Nematology covering a wide range of beneficial and harmful insects. You can order these sheets through the UF/IFAS Extension Bookstore by calling (800) 226-1764 or order them online at http://ifasbooks.ufl.edu/.
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