Assessing the Potential for Biological Control of Field Bindweed, Convolvulus arvensi, with the Gall Mite Aceria malherbe, and the Moth Tyta luctuosa
Field bindweed (Convolvulus arvensis) is a severe competitor with crops and may cause yield losses of 20-80 percent, depending on the crop and farming system. It is a deep-rooted, perennial weed capable of reproducing from root or rhizome fragments, or from seed, which may remain dormant for up to 50 years. Because of these characteristics, field bindweed is extremely difficult to control. Traditional control practices, including cultivation and the use of herbicides, are expensive, environmentally hazardous, and have only a short-term effect in reducing populations. For these reasons, the development of new bindweed management strategies that are cost effective, self-sustaining, environmentally safe, require low inputs, and provide long-term control, is essential. A management approach that satisfies all these criteria is biological control, which involves the use of living organisms to feed on, and thereby reduce, field bindweed populations.
1) To evaluate the overwintering potential of the gall mite A. malherbe, and the moth T. luctuosa, in different climatic zones within the North Central region.
2) To determine the dispersal ability of the moth (T. luctuosa) at several release sites.
3) To determine the effects of moth (caterpillar) introductions on field bindweed growth, and determine the infestation levels necessary to ensure detrimental effects to field bindweed.
4) To investigate and quantify field bindweed population reduction by the moth (caterpillar).
5) To train and involve farmers with on-farm releases, surveying, and monitoring of the biological control agent, and in the evaluation of success.
6) To disseminate knowledge of the ecology and biology of moth to farmers and farmer organizations, extension personnel, other researchers, and those concerned with noxious weed control.
The bindweed moth, Tyta luctuosa, overwintered successfully for the second straight year in Kansas. However, survival in 1994-95 varied greatly among and within locations. The average rate of survival, from the cocoon stage in the soil to fully emerged adult moths capable of flight, ranged from 0 to 23 percent. The highest survival in a single cage was 64 percent. Moth survival was no higher at southern sites than at northern ones. The approximate chemical makeup of a sex attractant was determined and being synthesized to use as a monitoring tool for assessing dispersal and establishment of bindweed moths. A field experiment revealed that moderately high densities (about 75/m2) of large T. luctuosa caterpillars are necessary for complete defoliation of bindweed in the field. Educational efforts, such as presentations, tours, radio shows, press releases, and individual on-farm training sessions, have increased awareness of nonpesticide alternatives for managing weeds and the potential of using natural enemies to control field bindweed, an extremely serious pest in the Midwest and throughout the United States.