Commercial cotton growing in the Sudan dates from 1867. At present, about 400,000 ha of various cotton cultivars are grown under different irrigation systems. The production of this main cash crop has been faced with a multitude of entomological and pathological problems, some of which were tackled through the adoption of specific cultural practices or enforcement of legislative regulations.

When cotton treatment with synthetic organic insecticides was initiated in the mid 1940s against Empoasca lybica de Berg, the impressive preliminary results have encouraged over-reliance on chemical control at the expense of other measures. This rather limited approach of control strategy has contributed partially to the appearance of new pests in damaging levels e.g. Heliothis armigera (Hbn.), Bemisia tabaci (Genn), Aphis gossypii (Glov) and Spodoptera littoralis. The principal measure for their control is insecticide application.

The cost of crop protection soared to ten-fold during the last 20 years. The annual number of sprays applied to cotton increased from one to seven sprays. To overcome the ever increasing use and high costs of pesticides on cotton growing, the Agricultural Research Corporation undertook intensive research programmes to find answers to major crop protection problems. Since 1978 researchers are directing their efforts towards the development and implementation of integrated pest management strategies to include cultural and legislative measures, as well as the use of more selective insecticides.

As a background to an IPM project, this paper describes pesticide treatment of cotton in Sudan Gezira, starting in 1945/46. Until the end of the 1950's, one treatment per season was sufficient to control the only important pest, the jassid, Empoasca lybica, but the number of treatments increased during the 1960's (from 3 to 5) and has since the early 1970's been 6–9.

The continuous use of pesticides has resulted in changes of the pest complex, ultimately creating “hyper” pests such as the whitefly (Bemisia tabaci), cotton bollworm (Heliothis armigera) and aphids (Aphis gossypii). The increase in number of applications of pesticide is coupled with the rising costs of pest control and a stagnant yield. The stickiness problem created by the honey dew of whitefly and aphids increased with the rising number of sprays. The exclusive use of chemical control not only failed to improve the quality or quantity of the yield, but put a great strain on the national economy as well.

The Sudan therefore requested the FAO to initiate an IPM project starting in 1979, with financial support from the Netherlands. During the past 2 years support has also been given by the World Bank. The IPM approach has given very valuable results during the last two seasons when large (more than 100 acres) plots in the Gezira and Rahad Schemes were left unsprayed with the objective of investigating the potential of the natural enemies in the absence of pesticides, and to compare findings with population trends of pest and beneficial organisms in the fields subjected to conventional chemical control.

The first significant finding was that Bemisia tabaci and Aphis gossypii can be managed at desirable levels by their indigenous natural enemies, and that their outbreaks are attributed to the decimation of these natural enemies by chemical treatment. Populations of beneficial arthropods were consistently much lower in the fields which received regular pesticide applications.

The result of the large-scale experiments indicate that Empoasca lybica is the only really damaging pest (“key pest”) in the Gezira because of the absence of natural enemies to regulate its population. Control of E. lybica in the 1940's and 1950's resulted in the creation of Heliothis armigera as a major pest. This situation necessitated early season applications of pesticides to suppress H. armigera, which further reduced the role of the natural enemies of B. tabaci and A. gossypii. Both have developed into major pests of regular occurrence.

Cotton farmers in Gezira are now faced with a complex of very serious pests. In order to solve this problem, we will have to make drastic changes in pest control strategies and to adopt an IPM approach as soon as possible. The biological control H. armigera is considered as first priority in order to avoid the early season application of pesticides. Trichogramma pretiosum was introduced from the USA and released in the Rahad Scheme in 1988/89. The preliminary results are very promising.

Cultural and biological control of E. lybica will be attempted in order to further reduce pesticide applications. The control of this pest by the use of “milder” pesticides is also included in the programme.

The presently used threshold levels for all major pests are very low, and are under revision through properly conducted large-scale experiments.