Biological control of natural enemies

By Bhai Khan Solangi 

In Sindh and other provinces of Pakistan, farmers spray toxic chemicals (pesticides) on cotton, vegetables, oilseeds and fruit crops. The pesticides have brought positive results in boosting production but many chemicals have caused resistance in pest species.

Biological control of natural enemies Its intensive and indiscriminate use has caused diseases such as cardiac, diabetics, indigestion, and kidney failure etc. It has also resulted in the environmental pollution, besides, contaminating food.

Pesticides have been accumulating in the soil, air and water which calls for safe and cheap control methods. This can only be achieved through the Integrated Pest Management (IPM) practice.

Pest control through environmentally safe ways is considered an integral part of balanced agro ecosystem management and protection. An effective management requires monitoring of insect population and observance of scientifically-based threshold values.

Pesticides use is one of the most common and effective methods for controlling pests and plant diseases. One of the safest biological methods is through predators and parasites. 

All insect populations are affected to a greater or lesser extent by natural enemies, meaning the “balance of nature” and natural regulation. Actually, Darwin’s term “struggle for existence” is what we call natural enemies. These are the primary regulating force in the dynamics of their populations.

It is important to know what natural enemies are affecting an insect pest population and to obtain an estimate of their impact. Such information may be the basis for explaining pest population density and predicting outbreaks.

Since the establishment of canal system in Sindh, many important crops are cultivated round the year. Due to regular cultivation of land, hundreds of insect pests appear that reduce the quality and quantity of crops.

Development of the predator population depends on the availability of prey. A number of beneficial insects are found in fields, where their food habits are different. A high reproductive rate is important so that populations of natural enemy can rapidly increase when hosts are available.

In Pakistan some experiments have proved that many insect predators naturally occur on the agro-ecosystem and feed on different pests. Amongst those predators, Coccinellid beetles occupy a unique position as a biological controlling agent.

Ladybird beetles belong to the family Coccinellidae, order Coleoptera class insecta. The Coleoptera comprises largest group of insects. These vary in size from 0.25mm to 150mm. The wing structure is quite characteristic. The front pair of wings are known as elytra.

Biological control of natural enemies Elytra are hard and thick sheath serving as a cover for their body and hind membranous wings. Hind wings are used for flight and during flight the front elytra are kept stretched on each side. The Coleoptera is the largest order in class insecta having 220,000 described species.

The Ladybird beetles are widely distributed throughout the world and feed on many insect species which occur on trees, shrubs, weeds, grasses and cultivated crops. Therefore, Ladybird beetles are known as one of the most beneficial and recognizable groups of insects.

The bright colours of Ladybird beetles warn enemies that they have a bitter taste. The spots of each species are arranged in a different pattern. They are carnivorous characterized by the mandibles having simple or bifid apices and each jaw being armed with a basal tooth for grasping and chewing their hosts.

The common species of Ladybird beetles, which occur in our agro-ecosystem are; 7-spotted beetle, coccinella septempunctata L., 11-spotted beetle, Coccinella undecumpunctata L., Zigzag beetle, Menochilus sexmaculatus Fab., Coccinella transversals and Brumus suturalis F. These are most important of all predators, both adults and larvae are voracious predators of many insect species.

Scientifically, it has been proved that the above mentioned beetles, each can consume about 40-60 individuals/day of aphids, jassids, white flies, mites, scale insect and eggs of various moths.

Looking at the efficiency of Ladybird beetles, we have to promote these insect species to control the noxious pests and to avoid the use of pesticides, which will keep our environment safe and healthy.

Courtesy:The DAWN