Over the past three years, two graduate students have devoted time to studies of two species of Entomopthora fungi that are parasitic on the spruce budworm. These students have worked largely under the direction of Dr. Richard Soper, USDA, Agricultural Research Service, Orono. Dr. Soper's major research goal is the development of Entomopthora and other fungi for control of aphids on potatoes and other agricultural pests. He has been devoting some time, largely though graduate students, to those Entomopthora species which attack the budworm.
A major step was the development of the ability to mass-culture these fungi on artificial media, with production of large masses of resting spores. The resting spore is the means by which these fungi overwinter, and is the most practical stage by far to store and spread into the environment, in hopes of creating epidemics among pest insects.
Unfortunately, the earlier attempts of our graduate students to create epidemics in budworm, by spraying more suspensions on trees, have failed. The resting spores have failed to germinate and spread disease. The next step is to return to the laboratory and attempt to devise means that will enhance germination of these spores. In addition, a small amount of further field study is contemplated in hopes of locating more virulent strains of these fungi in natural budworm infestations.
The dynamics of some species of insects, including such forest insect pests as tent caterpillars and the gypsy moth, are affected by changes in the quality or vigor of populations. These changes are often associated with changes in the appearance of individuals, or by differences in size, behavior, or biochemistry.
Observable changes in population quality have been useful indicators of population trends, and can be used in predictive indices. The current epidemic of spruce budworm in Maine is currently being treated with insecticide in an effort to keep trees alive. The ability to predict population levels could affect control strategies. Accurate forecasts that populations of budworm will decline would provide a means to determine the number of years that treatments would have to be applied, and a possible means of reducing the amount of acreage to be treated. Although the research could be considered exploratory, if successful, the reduction in a very small percentage of areas treated with insecticide would underwrite the cost of the research.