Forestry News

Nematodes to Control Black Army Cutworm

Black army cutworm (Actebia fennica) is an occasional late spring pest of newly established conifer plantations. During the day larvae hide in leaf litter, and move onto the plants in the evening to feed. Steinernematid nematodes may be a good alternative to chemical controls for this pest, since the larvae are frequently in contact with soil, the nematode's natural environment.

The infectivity of three strains of Steinernema carpocapsae and one strain of S. feltiae, alone and in combination, were assessed in the lab and under field conditions in a black spruce plantation in Canada.

Infection in petri dish tests was highest among third, fourth and fifth instar larvae, and generally over 60%. First and second instars were able to avoid contact with nematodes by escaping to the underside of the petri dish lid, while sixth instars were just not as susceptible; infection in these groups was less than 30%.

In field tests, black army cutworms were caged for 1 week over black spruce seedlings treated with spray (1st year only) or soil-plug inoculations (both years) of nematodes. The different nematode strains were applied individually and in combination. Nematode applications protected both current and year-old foliage from damage by the larvae. In 1993 no larvae were left alive in the treatments containing S. carpocapsae "All" strain, whereas in 1994 it did not work as well because soil temperatures were cooler.

S. feltiae provided the best protection when soil temperatures were cool (45-52F), while the All strain of S. carpocapsae was best at slightly warmer soil temperatures (60-62F). A mixture of these two strains should provide protection under a wide range of temperatures. Although nematodes performed well under experimental conditions, efficacy during a natural infestation remains to be demonstrated.

Source:

West, R. J. and T. C. Vrain, 1997. Nematode control of black army cutworm under laboratory and field conditions. Can Entomol. 129:229-239.


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