However, its yield per acre here is lower than in most of the sugar cane producing countries. Among many reasons behind this low production such as poor management practices, weeds, water shortage etc, insect pests also play a negative role in decreasing the yield. According to rough estimates, insect pests cause almost 20 to 40 per cent reduction in yield of the crop resulting in huge losses to growers. Amongst sugar cane pests, borers cause more damage to the crop. Moths of sugar cane stem borers lay their eggs underside the leaves. Within 36 to 48 hours larvae come out of the eggs and start feeding on tender parts of the plant. After some time, the larvae find their way into the stem. They keep feeding inside the cane and render it unfit for consumption and milling. Weight of cane and sucrose percentage is drastically reduced. In case of root borer attack, the central whorl of leaves dry up and form dead hearts.

Another harmful pest of cane is the leaf hopper (pyrilla), which causes serious damage to the crop. Its attack is reported to have been increasing for the last couple of years in Sindh. Pyrilla is an insect pest which sucks juice from the leaves as a result they dry up. In addition, it also emits a sweet substance (honey dew) which serves as a medium for a fungus namely sooty mould, which turns the leaves black and photosynthetic activity of plants is badly affected. Plants get weakened and sucrose percentage also drops. Both the adults and nymphs suck the sap from leaves. The leaf hopper is very agile and jumps around in large numbers, making a faint noise when a person walks through a heavily infested field. This pest breeds through out the year and migrates from one crop to another in search of fresh food.

Chemical control: Chemical method is generally used for controlling the pests. But it has lot of side effects. Its continuous use causes resistance problems in insects and is also harmful for insects which are beneficial. Sugar cane borers are difficult to be controlled with pesticides, owing to their stealthy habit of feeding. And at the time of leaf hopper attack, the crop attains considerable size, therefore spray operations can not be easily performed for controlling the pest.

Biological control: In 1930, after a lot of research, entomologists succeeded in finding an alternative method of pest control -- the biological control. This method involves predators and parasites to control harmful insect pests. This is a safe method of pest control. In Sindh, this method has been tried in sugar cane crop growing areas of Mehran Sugar Mills, Tando Allahyar, Al-noor Sugar Mills, Moro, Matiyari Sugar Mills, Matiari, Habib Sugar Mills, Nawabshah, and Fauji Sugar Mills, Khoski.

Biological control is very successful in cane crop and is gaining popularity among growers. Natural enemies of sugar cane pests like trichogramma and Chrsoperlla cornea are periodically released in the field. The females of trichogramma trace the eggs of the cane borers and lay their eggs among them. From these eggs tinny larvae of the parasite emerge which eat up the embryo of borer’s eggs. Within seven days the parasite completes its life-cycle and adults of trichogramma emerge from cane borer’s eggs.

This process continues and the population of trichogramma keeps increasing and population of borers keep decreasing, and thus the cane crop remains protected from borers’ attack. Some times due to unfavourable weather conditions or spray of pesticides population of trichogramma is drastically reduced and chance of borer’s attack is increased. In such conditions to maintain an adequate population of trichogramma in the field, scientists have evolved a technique.

Through this technique trichogramma is reared in laboratory on the eggs of angomous grain moth (Sitotroga cerealella).The eggs of this moth are glued on 2×2.5 inch paper card and are then got parasitised by female trichogramma. After six days of parasitisation these cards are tagged in cane crop at the rate of 10,000 eggs per acre, each card having 2,000 eggs. Just after second day of tagging, 10,000 adults of trichogramma emerge from these eggs and spread in field in search of sugar cane borer’s eggs and check the borers’ population.

Another, natural enemy of sugar cane pests is the Chrysoperlla carnea which is used for the control of cane leaf hopper. It is also reared in laboratory on the eggs of angomous grain moth. Sugarcane leaf hopper’s attack starts in the end of July or in the beginning of August. During this time Chrysopa cards at the rate of five cards per acre should be tagged periodically in the field. Chrysopa cards are applied fortnightly where as those of trichogramma are repeated six to seven times per season to keep the pest population below economic injury level.

Precautionary measures: For achieving better control these cards should be tagged preferably on the underside of leaves and tagged early in the morning or evening, so that it may not face heat or sun as soon as they emerge. Trichogramma cards should be regularly tagged each month from March to September. Chrysopa cards should be tagged every month from July to November.

Advantages of biological control: By this method sugarcane pests like root borer, stem borer and top borer can be successfully controlled without application of pesticides. This method is not harmful for other beneficial insects and is safe for environment and easy to apply.

Expenditures involved: This method is very cheap as compared to chemical control method. It costs Rs200 to Rs300 per acre annually whereas a cost of Rs1,500 to Rs2,000 per acre is incurred on chemical control method.