Seasonal development, Insect vectors, and host range of bacterial wilt of sweet corn

Elliott, C. and Poos, F.W. (1940) Seasonal development, Insect vectors, and host range of bacterial wilt of sweet corn. Journal of Agricultural Research, 60 (10). pp. 645-686.

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A detailed account is given of further work on bacterial wilt of sweet maize caused by Aplanobacter stewarti [cf. R.A.E., A 24 603], including studies on the seasonal development, host range and insect vectors of the bacterium, of which the most important is the Halticid, Chaetocnema pulicaria, Melsh. The results are based on records made from 1934 to 1937 at Arlington Experiment Farm (in Virginia, near Washington, D.C.) and for shorter periods at 4 localities in New York, 1 in Indiana and 1 in Ohio. The following is based on the authors' summary. At Arlington, winter temperatures were well above 32°F. in 1933-34, 1934-35 and 1936-37, adults of C. pulicaria were numerous early in the following seasons, and bacterial wilt was abundant and destructive, whereas in the winter of 1935-36 the average temperature was below 32°F., adults of C. pulicaria were not plentiful early in 1936, and there was little infection in the early leaf stage. Although infection became general as the season advanced, most of the lesions did not develop beyond local leaf infections and the crop was good. Similar observa-tions were made in the other localities, and it is concluded that the numbers of wilt-infected plants are closely associated with winter temperatures. Where mean winter temperatures are well below 32°F., fewer beetles survive than where they are above 32°F. During 1934-37, 28, 769 insects representing 94 species in 76 genera were tested to determine which species and what proportion of each carry A. stewarti internally and may be vectors of the bacterium under field conditions. Tests of 18, 613 individuals of C. pulicaria during the 4 years indicated that it is the only species of importance in harbouring the bacterium over winter and in spreading it during the growing season. C. denticulata, III., may possibly play some part in dissemination, but it is not so abundant at Arlington and feeds preferably on Panicum dichotomiflorum. Although A. stewarti sometimes occurs in abundance in it and it ranks next to C. pulicaria in the numbers of adults from which the bacterium was isolated, it is doubtful whether the latter ever overwinters in it. None of the other insects from which A. stewarti was isolated is considered a vector of any importance under field conditions. It seems possible for insects casually feeding on maize to pick up A. stewarti from infected plants, but the type of culture obtained indicates that such insects do not furnish a favourable environment for the bacterium and are of no importance in its spread. In the species of Chaetocnema, the percentage of beetles infected was usually greater among those caged on infected maize than among those collected from the field. In 1934 and 1935, A. stewarti was isolated from 56-68 and 60-95 per cent. of examples of C. pulicaria caged on infected maize and from 48 and 61 per cent. of those of C. denticulata. Further proof of the overwintering of A. stewarti in adults of C. pulicaria was obtained. Seven beetles collected on the 16th March 1936 were fed on maize plants in the greenhouse, and typical wilt symptoms developed. A. stewarti was isolated from adults of this species collected at Arlington in every month of the year except February during the four years, and one isolation was made from some collected on the 26th February 1936 at Norfolk, Virginia. Early-and late-season isolations from C. pulicaria from other localities have shown that the overwintering adults are more or less infected with A. stewarti in all sections of the country in which wilt is prevalent and isolations have been made. In studies of the host range of A. stewarti, Euchlaena perennis, E. mexicana and Coix lacrymajobi have been found to be susceptible [cf. 24 604], but Tripsacum spp. were immune.

Item Type: Article
Author Affiliation: Associate pathologist, division of ceral crops and diseases, bureau of plant industry senior entomologist, division of ceral and forage insect investigations, bureau of entomology and plant quarantine, United states department of agriculture
Subjects: Plant Production > Production Practices
Plant Protection
Divisions: General
Depositing User: Library ICRISAT-InfoSAT
Date Deposited: 12 Apr 2012 15:10
Last Modified: 12 Apr 2012 15:10

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