Bactra verutana as a Biological Control Agent for Purple Nutsedge1

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Abstract
The effectiveness of Bactra verutana Zeller, a native moth, that is ineffectual in suppressing purple nutsedge, Cyperus rotundus L., was found to be limited by (1) the rapid growth of the host plant—in the field each tuber planted produced an average of 30 shoots after 51 days; (2) intraspecific competition—the larvae are cannibalistic and only rarely does more than one develop per shoot, even though as many as 23 eggs may be laid per shoot; (3) the relatively minor damage that is done to the host plant—in the greenhouse, the feeding of 1 larva per shoot for 30 days resulted in significant growth reductions in 2 of 4 plant characteristics measured, while 2 or 5 larvae caused significant reductions in all 4 of them; (4) parasitism—Apanteles epiblemae Muesebeck attacks about 10% of the larvae in the fall, less during the summer, while Trichogramma pretiosum Riley parasitizes 30–50% of the eggs in the fall after mid-October; and (5) low winter temperatures—only 15 and 11% of the larvae and pupae, located at or below the soil surface, were alive in the field after mid-January, 1973 and 1974, respectively. Nevertheless, results of greenhouse tests suggest that periodic early-season releases sufficient to infest every shoot may significantly reduce nutsedge growth while the crop plant is becoming established.

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