Lygus Bug Injury and Control on Carrot Seed in Northern California1

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Abstract
Two seasons of investigations with L. hesperus on Red Core Chantenay carrot seed indicate that there are 2 generations of this bud in one season; the 2d generation developing in from 26 to 35 days. The 1954 field cage experiments showed that these bugs cause a blasting or prevent the development of carrot seeds, especially during the blooming period, and that they primarily cause embryoless seed after petal fall. The 1955 cage tests showed that 1 adult bug per 2 seed heads is enough to cause minor economic seed damage, that 1 adult bug per seed head can cause from 44 to 62% of seed loss and reduce germination to as low as 64%, and that nymphs cause about twice as much damage as adults. Field control experiments showed that an insecticide should be applied early in the blooming period of the carrot seed crop; beginning when the 2d stage of bloom of the seed heads is 25-50% in bloom. The investigations have shown that 3 applications of 10% DDT, early in the blooming period of the 2d, 3d, and 4th stages of seed heads, results in the most effective lygus bug control. Under the conditions of these experiments, 2 applications of 10% toxaphene were inferior to one of 10% DDT, were only one-third as residual, and unsatisfactory for control. The predators Nabis sp. and Geocoris sp. were reduced the most by 3 applications of DDT and seemed to be reduced to about the same extent and for the same period as the lygus bugs. Observations and data indicated that the red spider predator, Orius sp., is fairly tolerant to DDT.

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