Studies were conducted across the southern United States to characterize the efficacy of multiple Bacillus thuringiensis (Bt) events in a field corn, Zea mays L., hybrid for control of common lepidopteran and coleopteran pests. Cry1F protein in event TC1507 and Cry1A.105 + Cry2Ab2 proteins in event MON 89034 were evaluated against pests infesting corn on above-ground plant tissue including foliage, stalks, and ears. Cry34Ab1/Cry35Ab1 proteins in event DAS-59122-7 and Cry3Bb1 in event MON 88017 were evaluated against the larvae of Mexican corn rootworm, Diabrotica virgifera zeae Krysan and Smith, which occur below-ground. Field corn hybrids containing Cry1F, Cry1A.105 + Cry2Ab2, Cry34Ab1/Cry35Ab1, and Cry3Bb1 insecticidal proteins (SmartStax) consistently demonstrated reductions in plant injury and/or reduced larval survivorship as compared with a non-Bt field corn hybrid. Efficacy provided by a field corn hybrid with multiple Bt proteins was statistically equal to or significantly better than corn hybrids containing a single event active against target pests. Single event field corn hybrids provided very high levels of control of southwestern corn borer, Diatraea grandiosella (Dyar), lesser cornstalk borer, Elasmopalpus lignosellus (Zeller), and fall armyworm, Spodoptera frugiperda (J.E. Smith), and were not significantly different than field corn hybrids with multiple events. Significant increases in efficacy were observed for a field corn hybrid with multiple Bt events for sugarcane borer, Diatraea saccharalis (F.), beet armyworm, Spodoptera exigua (Hübner), corn earworm, Helicoverpa zea (Boddie), and Mexican corn rootworm. Utilization of field corn hybrids containing multiple Bt events provides a means for managing insect resistance to Bt proteins and reduces non-Bt corn refuge requirements.
Several species of Lygus (Hahn) that occur in Saskatchewan are serious and continuing pests of alfalfa grown for seed. They are readily controlled by any one of several insecticides, but the efficiency of this control is dependent upon knowing their seasonal development and occurrence on the crop.In the years 1976 and 1978, at three locations in Saskatchewan, populations of Lygus in alfalfa seed crops were sampled at 5-to 7-day intervals throughout the period of insect activity. In 1979 and 1980 samples of bugs were taken occasionally from the same locations, and in all years from other locations in the province. A sample consisted of 6 7 0 0 specimens collected by either a 38-cm sweepnet in not less than 25 and as many as 200 random sweeps, or a D-Vac sampler in not less than 3 m2 in spring and after harvest when sweep-sampling was not possible. Collected specimens were preserved in alcohol, sorted, and identified. Additional data, not previously published, were available from a similar mid-1950's study of Lygus seasonal occurrence in alfalfa seed crops in the Torch River district of northeastern Saskatchewan.Because the nymphs of the genus Lygus cannot be identified to species, the proportions of the various species collected were determined from the adults, identified according to Kelton (1975).At each sampling date when adults were present, a representative number of not less than 10 and not more than 50 female adults were collected, killed, and dissected. The females were classified as: reproductive-mated, some oogenesis, pre-laying or laying, and non-reproductive-teneral, not mated, absence of oogenesis, fat bodies hypertrophied, in diapause. Male adults were also dissected and classified as above, according to testicular and accessory glandular development.The extensive sampling has shown that Lygus adults generally do not overwinter in alfalfa fields. In the fall as the alfalfa matures they move to more succulent native autumn plants, then hibernate in the shelter of plant litter. In the spring they become active and feed on early-growing plants, and migrate to alfalfa when it becomes suitable for feeding and oviposition.The seasonal occurrence of Lygus nymphs and adults in alfalfa seed crops at three locations are illustrated in Fig. 1. The curves are the means of 4 years' data, expressed as the percent of the total population in nymphal and adult stages throughout the period of activity. Because first-and second-instar nymphs are difficult to distinguish fronl one another they are combined in a single curve. Occurrence can vary by as much as 7 days about these means, due to weather and possibly to species content of the Lygus population.At Moose Jaw, lat. 50°N, long. 105"W, in the shortgrass prairie region, the species composition of the adults was 84% Lygus borealis (Kelton), 13% Lygus desertinus Knight, and 3% Lygus lineolaris (Palisot de Beauvois). Hatch of eggs laid in the alfalfa stems by overwintered females begins about 10 May and is concentrated in a 3-week period. The peak of summer, first-gene...
The alfalfa plant bug, Adelphocoris lineolatus (Goeze), a well-known pest of alfalfa in Europe and the United States, was first recorded in Saskatchewan in 1947, in the Hudson Bay district about 16 miles west of the Manitoba border. By 1959 it had spread westward through the northern agricultural area of the province to within 35 miles of the Alberta border. Economic infestations appeared within two to four years of its initial occurrence in each district.The migratory behaviour of the adult, which is apparently essential for maximum reproduction, effects rapid dispersal of the species. Also, because of this migratory behaviour control measures may have to be undertaken each year, and seedling stands may be infested in the first crop year.The seasonal development of the insect is described. Apparently in the spread of the insect northward a univoltine population is being selected. Eggs that have overwintered in stems hatch in late May and early June. Development proceeds through five nymphal instars, and adults begin to appear toward the end of June. These adults lay eggs during the latter part of July. Most of the eggs enter diapause: less than five per cent of them hatch the same year, and any second-generation adults that do occur do not have time to mate and lay eggs before all activity is halted by freezing weather.The main host plants of A. lineolatus are two cultivated legumes, alfalfa, Medicago media Pers., and red clover, Trifolium pratense L. No native host plants have been found in Saskatchewan.About three per cent of field-collected nymphs from the Nipawin district were parasitized by braconid larvae tentatively identified as Euphorus pallipes (Curtis).
Bran treated with four different insecticides was field-tested as a crop protection measure against mainly third instar grasshopper populations composed mostly of Melanoplus sanguinipes (Fab.). The order of toxicity of these four insecticides was dimethoate 〉 fenvalerate 〉 propoxur 〉 pyridaphenthion. Five dosages of dimethoate were tested against mainly adult grasshopper populations. Rates of mortality due to both aqueous sprays (previously published results) and bran baits were compared. Degradation of both dimethoate and fenvalerate mixed with bran was small when stored in the laboratory at either 1°C or 20°C.
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