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Cotton growing and IPM in China and Egypt Graham Matthews describes integrated pest management programmes in two areas of irrigated cotton

There ts increasing concern about the use of pestk'ides on crops such as cotton and efforts are being made to develop IPM programmes. Although considerable research has been carried out. there has been criticism that very few such programmes have been implemented. This note illustrates how IPM programmes have been used on two areas of irrigated cotton and have successfully reduced the use o f insecticides.

in contrast to the situation in some cotton-growing areas where farmers are applying many insecticides too frequently, there is an area of cotton (4200 ha) north of Shihezi (State Farm 148) in N.W. China, on land being reclaimed from the Gobi Desert and irrigated with water from the Tian Shan mountains, where an average of only 1.5 insecticide sprays were required during 1990. Over 10 years ago, more sprays (~< 10) were applied but the number has been reduced by the implementation of an integrated pest management programme. At pre- sent the main pest is the red spider mite, although some aphids and boll- worm (Helicoverpa armigera) are recorded. Acid-delinted seed coated with a fungicide is sown under poly- thene film in twin rows 30cm apart with 60cm across the intervening furrow. The polythene allows the cotton crop to be sown early before the maize which may act as a trap crop for boilworm at a critical period when the cotton is flowering. Plants, thin- ned to 150,000 per hectare, are irri- gated four times and sprayed with a plant growth regulator, mepiquat chloride, at the 7/8-leaf stage, start of flowering and at peak flowering.

Crop monitoring in China

The crop is examined for pests every five days and insecticide sprays are

Dr G. A. Mar'thews is Director of IPARC, Imperial College at Silwood Park, Ascot, Berks. SL5 7PY, UK. Received 26 Novem- ber 1990; accepted 2 January 1991.

0261/2194/91/02/0083-02 ~'i: 1991 Butterworth-Heinemann Ltd

based on locally devised thresholds, the level of which depends on how many natural enemies are also pre- sent. Cotton is sown in rotation in strips usually no more than 120m wide with other crops such as wheat, alfalfa, sugar beet or maize in the adjacent strips, so that if an insecticide spray has to be applied, predators can reinvade from these other crops, which are not sprayed. Poplar trees have been extensively planted over the last 5 years along the edges of fields to act as windbreaks and provide refuges for natural enemies in the under- growth below the snow cover in the winter.

Insecticides

Dicofol, propargite and hexythiazox are among the acaricides used. Wherever possible, insecticide or acaricide treatments are applied locally by knapsacks to avoid treat- ment of a whole block using a tractor- mounted boom sprayer. Although there are large blocks of cotton, they have used tractor sprayers rather than aerial application of insecticides. Traps baited with molasses and vine- gar are used to stop early-season cut- worm moths. After harvesting the seed cotton (yields>3000kg seed cotton per ha), the stalks arc also removed from the fields and used for the manufacture of hardboard.

Temperatures

The low pest incidence may be due in part to the isolation of the relatively

small area and extreme cold winter weather (sub-zero temperatures between November and March). However, the hot summer provides conditions conducive to an increase in pest populations which could signifi- cantly reduce yields if the natural enemies were not conserved.

Cotton-growing in Egypt

In Egypt, the number of insecticide spray applications has also been reduced on the irrigated crop in the Nile Delta (overall an area of 420 000 ha), another area surrounded by desert. However, winter temper- atures are not as low as in China, and vegetables and other crops continue to be grown throughout the year. The succession of crops allows natural enemies to survive, so insecticides need to be applied only when pink bollworm populations cause more than 5% damage to bolls (in 1990 on average < 4 sprays were applied in most areas). In the 1950s the leafworm Spodoptera littoralis (Boisduval) was sprayed with many insecticides and this led rapidly to the build-up of populations highly resistant to insecti- cides. The leafworm is at present con- trolled by hand-picking of egg masses (Salama, 1983) and when sprays are required later in the season against pink bollworm different chemical groups are used in succession, mainly an insect growth regulator plus organophosphate (OP), a pyrethroid, a carbamate, and then an OP. In 1990 the use of a pyrethroid was avoided.

Application methods

At present about 70% of the cotton is sprayed by aircraft (mostly helicop- ters in 1990) but there are plans to change to more ground spraying.

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Trials are in progress to evaluate the use of reduced volumes of water- based sprays to replace the existing high-volume hand-carried lance and hose system. It is hoped that increased use of the pheromone gossyplure will decrease further the need for insecti- cide sprays, especially if all the farms destroy the crop residues after har- vest. The Natural Resources Institute, Chatham, have been studying the effects of pheromones over many years in Egypt. Different formulations of gossyplure have been applied by air late in June or July but recent experi- ments have shown good results by earlier application in May.

Successful IPM

The scale of these two areas is, of course, quite different, but the suc- cessful limitation of the use of insecti- cides in these examples is probably due to the area-wide implementation of alternative control tactics, notably conservation of natural enemies by avoiding large-scale early-season sprays of broad-spectrum chemicals and timing later sprays in relation to crop monitoring. In view of the increasing concern about insecticide resistance, where some insecticides

have been over-used, further attention is clearly needed to the control pro- gramme used on all crops by every farmer within a defined agro- ecosystem to determine what changes need to be made and how all those involved can collaborate in an IPM programme.

Reference

Salama, H. S. (1983) Cotton-pest management in Egypt. Crop Prot. 2, 183-191

CROP PROTECTION Vol. 10 April 1991