Hostname: page-component-586b7cd67f-l7hp2 Total loading time: 0 Render date: 2024-11-30T20:19:55.507Z Has data issue: false hasContentIssue false
  • English
  • Français

Some factors affecting numbers of Empoasca lybica (De Berg.) (Homoptera: Cicadellidae) infesting cotton in the Sudan Gezira

Published online by Cambridge University Press:  10 July 2009

R. J. V. Joyce
R. J. V. Joyce
Affiliation:
Desert Locust Suruey, Nairobi, Kenya.
Get access Rights & Permissions [Opens in a new window]

Extract

The Cicadellid, Empoasca lybica de Berg, is an important pest of cotton in the Sudan Gezira, where over 300,000 acres of cotton are grown annually under irrigation. Cotton is sown in mid-August, and the plants are uprooted and burnt the following May. The life-cycle of E. lybica from egg to gravid adult takes 16–24 days, and the adults live for up to 40 days. There is no diapause. During the 100 days from late August to early December when breeding on cotton is of economic importance, a single male and female could give rise to some 50,000 progeny.

During May to July, when crops are confined to irrigated gardens and river banks, E. lybica is widely distributed in such places and can be found also on tree hosts, which are numerous especially in the southern Gezira and along river banks. There is circumstantial evidence of displacement over long distances, and the great majority of catches of E. lybica in sticky traps were made before the increase in population on cotton that occurs from September onwards.

Of the 53 species of host-plants that have been recorded, only Solanum dubium, Rhynchosia memnonia, Hibiscus spp. and Abutilon spp. are of importance in the ecology of E. lybica. The first two especially are common weeds in fallows, which comprise more than half the land under rotation. Populations of E. lybica in Gezira fallows at the time of cotton germination tended to be greatest where pre-sowing rains (i.e., those falling from 1st July to 15th August) were highest. Correspondingly, initial infestation of cotton was highest in seasons and places receiving the most pre-sowing rains, although density of infestation in any place was affected by sowing date and proximity to irrigated fields and gardens which supported weed host-plants.

In order to develop a system of sampling for infestations of E. lybica in the cotton crop, the distribution of nymphs on cotton plants was examined. It was found that nymphs were most numerous in the leafiest zones of the plant and a random choice of leaves seemed an appropriate means of sampling for infestation. The distribution of nymphs within and between cotton fields was also investigated and a standard sampling procedure adopted.

Peak infestations on cotton could not be predicted from the level of initial colonisation, or from surveys a month later. Peak infestations were usually inversely related to the level of initial colonisation, especially when comparisons were made between seasons, as at the Gezira Research Farm. That is to say, high levels of initial infestation, which occurred in seasons of good pre-sowing rains, tended to be followed by low rates of increase, and in years of poor pre-sowing rains, initial infestations tended to be low and rates of increase high.

The relationship of these findings to those of Cowland & Hanna (1950) and Hanna (1950) are discussed; the hypothesis that pre-sowing mud-splash is a major factor controlling numbers of E. lybica in the Sudan Gezira is discounted, although it is accepted that this factor temporarily reduces populations.

The rate of increase of infestations of E. lybica was found to be positively correlated with the concentration of nitrogen recorded 2–4 weeks previously in the cotton leaf. This concentration affected not only the rate of increase of the initial colonisers, but also the rate of recovery of populations during November and December after spray-applications of DDT. The nitrogen concentration in the leaf was increased by nitrogenous fertiliser, with a corresponding increase in infestations of E. lybica. It was also found to be negatively correlated with pre-sowing rains, which, if low, prevent the nitrate in the top 12 in. of Gezira soil being washed to lower levels, but the data presented provide no evidence that the relationship is causal.

It is concluded that localities and seasons of poor pre-sowing rains favour a high rate of increase of small populations of E. lybica because of high nitrogen concentration in cotton leaves during September and October. This tendency is augmented by application of nitrogenous fertiliser. A regression equation relating the peak infestations of E. lybica with pre-sowing rainfall and with nitrogenous fertiliser is given and the infestations computed from this are shown not to differ significantly from those recorded in the Gezira as a whole, and in the four main divisions of it separately, during the eight years 1949–1956.

Type
Research Paper
Information
Bulletin of Entomological Research , Volume 52 , Issue 1 , April 1961 , pp. 191 - 232
Copyright
Copyright © Cambridge University Press 1961

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Allen, M. D. & Selman, I. W. (1955). Egg-production in the mustard beetle, Phaedon cochleariae (F.) in relation to diets of mineral-deficient leaves.—Bull. ent. Res. 46 pp. 393–397.CrossRefGoogle Scholar
Broadbent, L., Doncaster, J. P., Hull, R. & Watson, M. A. (1948). Equipment used for trapping and identifying alate aphides.—Proc. R. ent. Soc. Land. (A) 23 pp. 57–58.Google Scholar
Cowland, J. W. (1947). The cotton jassid (Empoasca libyca, Berg.) in the Anglo-Egyptian Sudan, and experiments on its control.—Bull. ent. Res. 38 pp. 99–115.CrossRefGoogle Scholar
Cowland, J. W. & Edwards, C. J. (1949). Control of Empoasca lybica, de Berg., on cotton in the Anglo-Egyptian Sudan.—Bull. ent. Res. 40 pp. 83–96.CrossRefGoogle Scholar
Cowland, J. W. & Hanna, A. D. (1950). The cotton jassid, Empoasca lybica (de Berg.) during the dead seasons in the Gezira, Anglo-Egyptian Sudan.—Bull. ent. Res. 41 pp. 355–358.CrossRefGoogle Scholar
Crowther, F. (1934). Studies in growth analysis of the cotton plant under irrigation in the Sudan. I. The effects of different combinations of nitrogen applications and water-supply.—Ann. Bot., Land. 48 pp. 877–913.CrossRefGoogle Scholar
Crowther, F. (1941). Studies in growth analysis of the cotton plant under irrigation in the Sudan. II. Seasonal variation in development and yield.—Ann. Bot., Land. (N.S.) 5 pp. 509–533.CrossRefGoogle Scholar
Crowther, F. (1944). Studies in growth analysis of the cotton plant under irrigation in the Sudan. III. A comparison of plant development in the Sudan Gezira and in Egypt.—Ann. Bot., Lond. (N.S.) 8 pp. 213–257.CrossRefGoogle Scholar
Dahms, R. G. (1947). Oviposition and longevity of chinch bugs on seedlings growing in nutrient solutions.—J. econ. Ent. 40 pp. 841–845.CrossRefGoogle ScholarPubMed
Davidson, J. (1925). Biological studies of Aphis rumicis Linn. Factors affecting the infestation of Vicia faba with Aphis rumicis.—Ann. appl. Biol. 12 pp. 472–507.CrossRefGoogle Scholar
Dorst, H. E. & Davis, E. W. (1937). Tracing long-distance movements of beet leafhopper in the desert.—J. econ. Ent. 30 pp. 948–954.CrossRefGoogle Scholar
Evans, A. C. (1938). Physiological relationships between insects and their host plants. I.—Ann. appl. Biol. 25 pp. 558–572.CrossRefGoogle Scholar
Freeman, J. A. (1945). Studies in the distribution of insects by aerial currents. The insect population of the air from ground level to 300 feet.—J. Anim. Ecol. 14 pp. 128–154.CrossRefGoogle Scholar
Fulton, R. A. & Romney, V. E. (1940). The chloroform-soluble components of beet leafhoppers as an indication of the distance they move in the spring.—J. agric. Res. 61 pp. 737–743.Google Scholar
Goodman, A. & Toms, A. M. (1956). Effect of rainstorms upon the cotton jassid in the Sudan Gezira.—Nature, Lond. 178 p. 436.CrossRefGoogle Scholar
Hanna, A. D. (1950). The effect of rainfall on the cotton jassid, Empoasca lybica (de Berg.) in the Gezira, Anglo-Egyptian Sudan.—Bull. ent. Res. 41 pp. 359–369.CrossRefGoogle Scholar
Ireland, A. W. (1948). The climate of the Sudan.—In Tothill, J. D. Ed. Agriculture in the Sudan, pp. 62–83.Google Scholar
Jewitt, T. N. (1953). Seasonal variations in the composition of young cotton leaves in the Sudan Gezira.—J. agric. Sci. 43 pp. 89–91.CrossRefGoogle Scholar
Johnson, C. G. (1950). The comparison of suction trap, sticky trap and tow-net for the quantitative sampling of small airborne insects.—Ann. appl. Biol. 37 pp. 268–285.CrossRefGoogle Scholar
Johnson, C. G. (1951). The study of wind-borne insect populations in relation to terrestrial ecology, flight periodicity and the estimation of aerial populations.—Sci. Progr. no. 153 pp. 41–62.Google Scholar
Johnson, C. G. (1952). The changing numbers of Aphis fabae Scop., flying at crop level, in relation to current weather, and to the population on the crop.—Ann. appl. Biol. 39 pp. 525–547.CrossRefGoogle Scholar
Johnson, C. G. (1956). Distribution and dispersal of aphids in the air.—Mitt, biol. Bundesanst. Berl. no. 85 pp. 22–23.Google Scholar
Joyce, R. J. V. (1952a). The ecology of grasshoppers in east central Sudan.—Anti-Locust Bull. no. 11, 97 pp.Google Scholar
Joyce, R. J. V. (1952b). Entomological Section.—Rep. Res. Div. Minist. Agric. Sudan 1949–50 pp. 81–99.Google Scholar
Joyce, R. J. V. (1956). Insect mobility and design of field experiments.—Nature, Lond. 177 pp. 282–283.CrossRefGoogle Scholar
Joyce, R. J. V. (1959). The yield response of cotton in the Sudan Gezira to DDT spray.—Bull. ent. Res. 50 pp. 567–594.CrossRefGoogle Scholar
Klein, H. Z. (1948). Notes on the green leafhopper, Empoasca lybica, Berg. (Horn. Jassid.) in Palestine.—Bull. ent. Res. 38 pp. 579–584.CrossRefGoogle Scholar
LeRoux, E. J. (1954). Effects of various levels of nitrogen, phosphorus, and potassium in nutrient solution, on the fecundity of the two-spotted spider mite, Tetranychus bimaculatus Harvey (Acarina: Tetranychidae) reared on cucumber.—Canad. J. agric. Sci. 34 pp. 145–151.Google Scholar
Michelmore, A. P. G. (1930). Observations on leafhoppers (Homoptera fam. Jassidae) in the Gezira in 1929.—Bull. Wellcome trop. Res. Lab. (ent. Sect.) no. 31 pp. 64–66.Google Scholar
Snow, O. W. & Taylor, J. (1952). The large-scale control of the cotton jassid in the Gezira and White Nile areas of the Sudan.—Bull. ent. Res. 43 pp. 479–502.CrossRefGoogle Scholar
Thompson, W. R. (1931). On the reproduction of organisms with overlapping generations.—Bull. ent. Res. 22 pp. 147–172.CrossRefGoogle Scholar
Williams, C. B. (1948). The Rothamsted light trap.—Proc. R. ent. Soc. Land. (A) 23 pp. 80–85.Google Scholar
Williams, C. B. (1952). How far do insects travel?—Rep. Rothamst. exp. Sta. 1951 pp. 173–180.Google Scholar