According to a systemic survey undertaken by the department of plant protection, during 1976-77, there are 120 species of grasshoppers in the country. However, in the rice-growing belt of upper Sindh and Balochistan rice grasshoppers, particularly, Hieroglypus and Oxia species are the dominating ones.
Under conducive climatic condition, grasshoppers assume serious proportion, thus inflicting significant damage not only to the rice crop in its milky grain stage, but also, to early sown wheat crop soon after its germination stage and canola oilseed crop, especially when its cultivation is undertaken as dobari crop viz: crop sown on residual soil moisture left after the paddy harvest.
Among the oilseed crops traditional rape and mustard, toria, jhambho, etc., are the common ones grown in rice belts as a dobari crop. However, during 1996, in pursuit of achieving self-sufficiency in the edible oil production, the Pakistan Oil Seed Development Board introduced an exotic variety of oilseed crop- Canola in upper Sindh rice growing districts of Larkana, Jacobabad and Shikarpur, as a dobari crop. But unfortunately, the entire cultivation of canola on thousand of acres was wiped out by the rice grasshoppers.
Here, it would be proper to mention that canola leaves being very much succulent and sweet are susceptible to grasshoppers, contrary to rape and mustard and jambho leaves which are hairy and bitter in taste. Again in 1998, canola was tried as a dobari crop in the rice belt of Balochistan by the PODB. Here too, this very exotic oilseed crop was wiped out by rice grasshoppers.
As per agriculture department source this year again, the PODB has supplied 40 tons of canola seeds to the growers of Balochistan free of cost to undertake its cultivation as a dobari crop. Since a survey undertaken by this scribe during the month of October had indicated high grasshoppers on rice crop, it is apprehended that the fate of canola cultivation in the rice belt of Balochistan may not be different than that of 1998 when after damaging canola, grasshoppers had migrated on early sown wheat crop and had caused significant damage to wheat and sorghum crop in districts Jaffarabad, Nasirabad and Jhal Magsi. Yet the irony is that to handle the menace of grasshoppers in the rice growing area, neither the agriculture extension department of government of Sindh nor that of Balochistan has taken any step.
Under the mistaken belief that more water would enhance productivity, our ignorant growers, particularly in Sindh, indulge in excessive use of irrigation water through kutchha water-courses. This attitude results into water-logging and salinity because of the seepage from kuchha water-courses.
Here, it would be proper to mention that water-logging is a state when the soil becomes heavily saturated with water. Soil affected by it stops producing crop due to suffocation, and thus land becomes barren. Whereas, salinity means the presence of excess soluble, as well as exchangeable, salt in the soil. Among its solutions foremost is the judicious use of irrigation water and the lining of irrigation canals and watercourses. For controlling water-logging on large scale, improved drainage is essential. Besides, the forest department has recommended plantation of eucalyptus trees on both sides of the canals, watercourses and all sides of the fields. According to it, a full-grown eucalyptus tree can drain 25 gallons (112.5 litres) of water per day from the soil to the atmosphere through transpiration. However, this practice has boomeranged in the rice growing belts of upper Sindh and Balochistan. This is because following the eucalyptus plantation, insurgence of some insect pests, particularly whitebacked plant hopper and rice leaf-folder, have enhanced manifold requiring extra expenditure on the control of these insect pests menace.
Lining of watercourses: Since water management, tillage, crop varieties, etc., have strong correlation with insect pests’ development, the lining of watercourses may play a vital role in reducing the grasshopper problem in the rice growing area, particularly, in upper Sindh and Balochistan, where grasshopper is impeding canola cultivation. Study of the life-cycle has revealed that there are three stages in the grasshopper’s life-cycle, the egg, nymph, and adult. Under conducive climatic condition each female lays up to 300-400 eggs during summer and fall. Egg pods are deposited in the upper few inches of undisturbed soil such as the grassland, pastures, ditches, bunds around field margins and watercourses.
In the rice growing area of upper Sindh and Balochistan, it has been observed by this scribe during his long crop pests surveillance, that field margins do allow the insurgence of grasshoppers but massive soil on either side of kutchha watercourses, harbouring dense grass cover play a vital role in the development and proliferation of grasshopper population in the rice agro ecosystem. Due to conducive factors like adequate soil moisture and grass cover, grasshoppers prefer to lay eggs in the soil surrounded by roots of grasses. Since pakka (cemented) watercourse will be devoid of these conducive factors it is quite likely that the lining of watercourses may become a limiting factor in minimizing the grasshopper problem in rice growing belts of upper Sindh and Balochistan.
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