SOME 80000 acres of cotton crop had to be destroyed in Dera Ghazikhan during the current season on the reports of helio commonly known as “American Sundhi” outbreak in many fields in the cotton belt of Punjab and some areas in Ghotki, Sindh.

Many cultivators in Sahiwal had to remove their crop after an early first picking because the crop had been badly damaged by the pest. Besides, the crop was also damaged in the Nara belt, Sanghar following appearing of a disease locally known as “Garho Pani.”

The persistent drought-like situation has resulted in reduced water discharge in the canals and the lowering of underground water-table. This phenomenon proved a blessing as it rendered thousand of acres of semi waterlogged area — which had become illegal paddy growing area in the cotton belt — fit for cotton crop particularly in Ghotki, Sukkur, Khairpur and Naushero Feroze. But due to water shortage many canals at Sukkur and Guddu Barrage had to be closed for about a month, besides placing some on rotation.

This resulted late sowing of rice and cotton crop in the upper Sindh region during the current Kharif season. Due to the erratic and late supply of water in canals, variation in the stages of cotton crop is rampant. The extent of variation could be gauged from the fact that the early sown crop is under cotton picking, whereas the late sown crop is still under inter-culturing and early boll formation stage requiring two more months to get forfeitable yield, if weather and pests permit.

The pest situation in upper Sindh cotton belt remained normal. All over world, where cotton is produced there are major pest problems and to control it, judicious use of the pesticides is a prerequisite as its irrational use can yield worst results. In Ghotki this year, as per field survey, an estimated 3000 acres of standing cotton crop has come under low to severe “army worm” attack. The cotton field, adjoining forest, orchards, banana and tall trees are the worst victim of this menace.

The survey has indicated that larvae of army worm have eaten off the entire leaves denuding the very cotton plant, besides damaging the young bolls, squares and flowers. A cotton grower at Deh Wadpagya applied 11 different pesticides to control this menace, but in vain.

However, repeated use of methamedophos, either alone or in combination with the other group of pesticides were found rampant in Ghotki. So far, only 15 to 20 per cent damage is expected to the standing early sown crop because majority of bolls have attained maturity. However, late sown crop may sustain severe damage because the majority of bolls are still in the stage of lint development.

Reason of outbreak: The irrational use of pesticides has often created problems, more serious than those for which they were originally applied. These include target pest resurgence, secondary pest outbreak, development of insecticide-resistant pest strains, toxic residues on adjacent crops, adverse impact on non-target organisms, and pesticide biomagnification on ecological food chains. Since army worm is not a regular and major pest of cotton in Sindh, its outbreak may be attributed to aggressive and injudicious use of pesticides in Ghotki.

The army worm: Its female lay eggs in cluster on the lower leaf surface, the young worms are green which on becoming full- grown are nearly 1.5 inches long. Due to their feeding at night, there presence is generally not suspected until the crop is nearly destroyed. This insect fluctuates greatly in abundance. During epidemics it often destroys much of the vegetation over hundreds of square miles.

Suggestions: Since army worm is preyed upon by a number of insects viz: parasitic flies, several ground battles, parasitic wasps etc, the growers should be persuaded to use the natural class of insect control products available in the market, though a bit costly, instead of the OP or the parathroid group of insecticides.

This year many growers may resort to zero-tillage technology for wheat sowing in cotton-wheat rotation, particularly in view of the IRSA’s estimated 51 per cent shortage of irrigation water during Rabi 2001-2002. Since, cotton fields under the army worm epidemic harbour large number of full-grown larvae and pupae in the soil, growers should be advised not to use the zero-tillage technology this year for sowing wheat crop. All fields in the outbreak area should be thoroughly ploughed to expose the hibernating population of army-worm for its natural control by birds. This is necessary because the zero-tillage will enable the hibernating army worm larval/pupae population to continue its next cycle which may in turn pose a serious threat to wheat crop, whose sowing will begin next in November.