A simple, inexpensive, permanent method for individually marking Colorado potato beetle is presented. The method consists of puncturing the elytra within the cream-colored longitudinal bands using a minuten nadeln; the wound response produces intense melanization at the point of puncture. Division of a band into three zones, each potentially receiving a dot, produces an octal digit. If all eight bands are employed, more than 16 million beetles can be uniquely marked. No significant survival effects of marking were seen in teneral, post-teneral, or post-diapause adult beetles. Propensity to fly in mid-summer beetles was generally unaffected by marking. Probabilities of mismarking and misreading are negligible if sufficient care is employed.

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Five weekly applications of Beauveria bassiana (Balsamo) Vuillemin, a genetically engineered isolate of Bacillus thuringiensis Berliner (Raven®), and aldicarb (Temik®) were compared for control of Colorado potato beetle, Leptinotarsa decemlineata (Say) in an irrigated desert cropping system. B. thuringiensis was applied using low and high label rates (1.17 and 7.0 l ha−1). B. bassiana was applied at 5×1013 spores ha−1. Aldicarb (Rhône‐Poulenc), applied at 3.37 kg a.i. ha−1 provided the greatest beetle control and potato yields (45 metric tons ha−1), but overall lowest biodiversity in nontarget organisms, particularly predatory Heteroptera. Low and high rates of B. thuringiensis produced fair to excellent beetle control, yielded 33 and 40 metric tons ha−1 and enabled good survival in predatory Heteroptera and other nontargets. Plots treated with B. bassiana resulted in poor control of beetles prior to row closure after which fair to good control was achieved. Yield in the Beauveria‐treated plots was 33 metric tons ha−1 and effect on biodiversity was comparable to the Bt‐treated plots. The lowest number of overwintering adult L. decemlineata was found in the plots treated with bacteria and fungi (0.68–0.84 adults/0.03 m−3 of soil) and the highest was found in control and aldicarb plots (3.44 and 1.84 adults/0.03 m3 of soil). Aphids and leafhoppers showed higher densities in plots treated with microbial control agents, but were eliminated from plots treated with aldicarb.

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The Colorado potato beetle is a major worldwide pest of potato and several other solanaceous plants. Insecticidal resistance is a serious problem in the northeastern and mid-Atlantic regions of the United States and a developing problem in other potato production areas of the United States and Canada (Forgash 1985; Johnson and Sandvol 1986; Boiteau et al. 1987). In the northwestern United States, insecticides applied to control the green peach aphid also control Colorado potato beetle, but these insecticides are likely to become ineffective due to the development of resistance or unavailable because of restricted use and environmental concerns. Biologically based management strategies are needed to reduce dependency on insecticides; these strategies require new basic knowledge including understanding prolonged diapause in populations of the Colorado potato beetle. Krysan et al. (1986) established that the occurrence of prolonged or repeated diapause can influence management strategies for insects, especially with respect to crop rotation.