Search

Several pyrethroid insecticides provided nearly 100% mortality of army cutworm, Euxoa auxiliaries (Grote), populations under field conditions in central Kansas. Performances of endosulfan and chlorpyrifos were variable, but they displayed adequate insecticidal activity against army cutworms. Bacillus thuringiensis var. kurstaki , carbofuran, ethyl parathion, malathion, and methyl parathion did not provide satisfactory control. Variation in vegetative growth and eventual wheat yields were not caused solely by larval populations of army cutworms. Moisture availability favoring vigorous plant growth was an important factor for plants to withstand army cutworm feeding. Use of insecticides to control army cutworms was found to be of variable profitability depending on the circumstances.

A mixture of Z -5-tetradecen-1-yl acetate and E -7-tetradecen-1-yl acetate in ratios of 1:99 to 11:89 were found through behavioral bioassays in the laboratory and field testing to be a specific attractant for the adult male army cutworm, Euxoa auxiliaris (Grote). The optimum ratio of these chemicals was about 5:95 and the pure chemicals alone were nonattractive in the field. The greatest trap catches were to 1 mg of attractant on rubber band dispensers and the males were only attracted during their 2nd flight period of August to October. The attractant was more effective in attracting males than one unmated female per trap. It was strongly inhibited by low percentages of Z 7-14:Ac or Z 7-14:OH.

Alkenals have recently become known as components of the sex pheromones of a few lepidopterous specis. A field survey of aldehydes and aldehyde-acetate mixtures as candidate lures for moths revealed general attractant activity in straight olefinic aldehydes of carbon number 12, 14 and 16. The numerous species captured by baited traps indicated that aldehydes may be as important in sex attractants as the better known acetates and alcohols. The main species captured were Acronicta sperata Grote, Ceramica picta (Harris), Agrotis volubilis Harvey, Cry modes devastator (Brace), Eurois astricta Morrison, Euxoa acornis Smith, Euxoa obeliscoides Guenee Faronta diffusa (Walker), Feltia ducens (Walker), Fishia derelicta Hampson, Lithomoia solidaginis Hubner, Nephelodes emmedonia (Cramer), Polia tacoma Strecker and Schinia bina Guenee.

The calling behavior of 3 closely related, interfertile species of cutworm moths, E. declarata (Walker), E. campestris (Grote), and E. rockburnei Hardwick, was studied in the laboratory. The temporal pattern of calling activity by virgin females differs for each species with a peak of calling in scotophase at 2.3 h for declarata, 7.7 h for campestris, and 10.3 h for rockburnei. The calling period of declarata is exclusive from that of rockburnei and nearly exclusive from that of campestris. There is overlap between the calling periods of campestris and rockburnei but the initial and peak phases, which under natural conditions with males present would be by far the most important, are separated by 2.5 h. Differences in calling rhythm are probably sufficient to account for the strong conspecific mating tendency exhibited by these species in laboratory tests, although such differences may not be the only isolating mechanism involved.

The morphology of the internal reproductive system of the adult female army cutworm, Euxoa auxiliaris (Grote) (Lepidoptera: Noctuidae), and the spermatophore, is described and illustrated. The study shows the basic similarities and differences between the army cutworm and some other noctuid species previously studied.

The effectiveness of the attractant blend, Z -5- and E -7-tetradecenyl acetates in a microgram ratio of 50:950 for adult males of army cutworm, Euxoa auxiliaris (Grote), was enhanced by the addition of trace quantities (0.13–2.5 eg or 0.013–0.25%) of Z -7-tetradecenyl acetate, but the addition of 2% of this isomer reduced the trap catches. An alternate specific attractant, developed by field testing highly purified chemicals, consisted of a 3-component blend of Z -5-, Z -7-, and Z -9-tetradecenyl acetates. In a microgram ratio of 100:1:10 on rubber septa, this attractant was effective in the field for at least 24 days. The trap catches. were reduced as the quantities of the Z -7- or Z -9-tetradecenyl acetates in this blend were increased to 8 and 33%, respectively. The 3-component attractants for the army cutworm were both strongly inhibited by less than 0.4% Z -5-dodecenyl acetate which is the main component of the redbacked cutworm pheromone.

This paper is an account of an outbreak of the cutworm, Euxoa Auxiliaris Grote, on alfalfa at Vernal, Utah, in 1916, which seemed, but was not conclusively proven, to be controlled by parasites, of which about a dozen species were reared as follows: Berecyntus bakeri Howard, A panteles laeviceps Ashmead, Meteorus vulgaris Cresson, Amblyteles nuncius Cresson, Habrobracon erucarum Cushman, Paranomalon sp., Ernestia sp., Anthrax alternata Say, Anthrax willistonii Coquillet, Aphiochaeta . sp., and Phorichaeta cinerosa Coquillet. It contains some data on the life history, habits and occurrence of both the host and its principal parasites as observed in the field and while rearing them in an improvised insectary.

Euxoa auxiliaries (Grote) was reared successfully on a semi synthetic diet for 10 generations without any apparent change in morphology, fecundity, or egg viability. Eggs hatched in 5 days when they were incubated at 26.5 and 80% RH. The 7 larval stages obtained with this rearing method were completed in 29-33 days, and 97% of the larvae survived. The pupal stage lasted 19-24 days, and 88% emerged as adults.

When incidence of parasitism and diseases of insects are to be determined by recovering the organisms, large numbers of field-collected insects often must be brought into the laboratory. Parasites can be recovered by rearing their hosts until the parasites emerge either as adults or as mature larvae. At the Northern Grain Insects Research Laboratory at Brookings, S. Dak., we developed a collecting technique for use in field studies to recover parasites and to determine incidence of parasitism in the armyworm, Pseudaletia unipuncta (Haworth); the army cutworm, Euxoa auxiliaris (Grote); and the pale western cutworm, Agrotis orthogonia Morrison.