Pesticides including weedicides, insecticides, fungicides, acaricides are basically used to manage the weeds, insects, diseases (fungal and bacterial) and mite population respectively in agriculture as well as horticulture crop protection along with production. However, continuous use of these chemicals may have the potential to generate environmental/ecological/behavioral problems including resistance in pest, outbreak of secondary pest and pest resurgence. Therefore, for the purposes of crop protection, application of alternative pest management strategies is acceptable so as to reserve existing chemicals.
When we talk about alternate control of pests, one option of them is biological control which includes the use of predators, parasites and parasitoids. The major problem associated due to reliance on pesticide control is chemical resistance development in respected pest species. This encourages the use with an increase in dose and number of pesticide which extends the adversely effects on these natural enemies. Due to decrease in predators and parasitoids pests might be resurging of pest. The impact of chemicals may range over long periods and areas if the often use of pesticides to be continued, the standard balance may not ever be attained. Pesticides show toxicity against both pest and natural enemy due to their similarities in physiology as well as both belongs to arthropods. These chemical affects the biology, development, production of eggs of insects and ability to find the prey or host. No doubt, our primary aim is to control the pest population from economical plant not natural enemies, but natural agents come in interaction with applied chemicals by a variety of means such as:
- direct exposure during application,
- by contact with the chemical residues,
- through food chain,
- while moving on treated plant parts or soil surfaces,
- through predation,
- through feeding of host by parasitoids
- and immature consuming the host body
All classes of insecticides affect the natural enemies by reducing:
- egg lying,
- egg hatching emergence rate,
- prey searching efficiency,
- prey acceptance,
- prey consumption,
- the developmental rate extended,
- repellency effect more,
- and changed the sex ratio which results the production of fewer females.
Pesticides differ according to their action, which influences the eradication of insect pests in addition to these chemicals may indirectly effect the population of natural enemy. If we classify the pesticides on their mode of action, they may be contact poison, stomach poison, systemic/translaminar, nerve and fumigants. Furthermore, the method of application is also very important which may be foliar, drench and granular cause indirect effects on natural agents in addition to the mode of action of chemicals.
Likewise, the type of chemical may significantly have to indirect influence on these biological agents such as the use of broad spectrum chemicals, nerve pesticides are most of them belongs to older classes while organophosphate, carbamate and pyrethroid have direct and indirect effect/harmful to natural agents other than nerve poison chemicals such as insect growth regulators (IGR’s), plant extracts, selective feeding blockers, insecticidal soaps and bio-pesticides.
These are considered to the selective pesticides against pests. The effective combination of pesticide and natural agents in an Integrated Pest Management (IPM) program is dependent on awareness of the ecology and behavior of pests and biological enemies than the accessibility of techniques and tools. The best methodology to conserving biological control is a combination of strategies including knowledge of the biology and behavior of pests, monitoring of life history of pests and natural enemies, choice of selective chemicals, use of the least disrupting formulation of the pesticide, application only when absolutely necessary, basing pesticides on reaching economic injury levels (EIL)/(ETL). By can save our agricultural environment and get residues free end product by conserving and protecting natural agents through providing them suitable environment.
*Nawaz Haider Bashir, **Muhammad Ismail, ***Usman Wali Muhammad, ****Naveed mushtaq and *****Adeel Raiz *, **, ***Department of Entomology ****, *****, Department of Plant Breeding and Genetics University of Agriculture, Faisalabad.