Pest resurgence
- 1. RMD Collage of Agriculture and research station, Ambikapur (C. G.) Course Title - Toxicology of Insecticides Course No - ENT – 508 Credit hrs - 2(1+1) Assignment on Pest resurgence – meaning and definition, its brief history, type causes and management of pest resurgence. Submitted to Dr. K. L. Painkra Submitted by (Ast. Prof. of Ag. Entomology) Birjhu karunik M. Sc. Ag. (Entomology )
- 2. Pest resurgence is the rapid reappearance of a pest population in injurious numbers, usually brought about after the application of a broad-spectrum pesticide has killed the natural enemies which normally keep a pest in check. A well-known example in rice cultivation is the resurgence of brown plant hopper (BPH). Pest resurgence is a situation in which a population, after having been suppressed, rebounds to attain a higher population density than was before suppression occurred.
- 3. increasing in the pest populations fallowed by the applications of insecticides which kill some pests and their natural enemies. (According to De Bach) The residual activity of the insecticide then expires and the pest populationis able to increase more rapidly and to a higher abundance when natural enemies are absent . Population after having been suppressed rebounds to numbers greater than before suppression occurred (Pedigo, 1989) It is defined as an abnormal increase of pest population often exceeding the economic injury threshold, following insecticide treatment (Chelliah, 1979). Heinrich et al 1982 defined resurgence as a statistically significant increase in the insect population or damage in insecticide treated plots over that of untreated plots.
- 4. ◦ The first instance of resurgence in rice was noticed in Brown plant hopper in the experimental fields of the IRRI. ◦ where the plots treated with gamma HCH @ 2 kg ai/ha recorded approximately three times higher population of BPH than the untreated control (IRRI, 1969). ◦ Resurgence has become a wide spread phenomenon in the past 2 decades (Bhathal et al., 1991).
- 6. 1) Primary pest resurgence 2) Secondary pest resurgence Primary pest resurgence = Pest populations which were initially suppressed by the applications of pesticides bounce back to excessive levels within short time. Primary pest resurgence occurs when the target mite population responds toan acaricide treatment by increasing to a level at least as higher than the population level observed before the treatment.
- 7. The type of resurgence where minor pests developing into major pests. Development of secondary pest resurgence occurs when an acaricide treatment controls the primary pest and destroy natural enemies of minor pests elevating the secondary pest to primary pest status. The successful control of one primary pest can lead to an outbreak of a second primary pest when the two pest species feed on the same plant part. A secondary pest was in such small numbers previous to pesticide application that it was not a significant pest. It became an economic pest after the insecticide application as minor pest population numbers shoot up and become major pest
- 8. Suppression of natural enemies: Insecticides, in general, exert adverse effects on the parasites and predators of crop pests and in many instances, this is considered as a major causes for insect pest resurgence to unmanageable proportions. Natural enemy mortality following broad spectrum insecticide application suggested as a important factor for BPH resurgence in rice (Miyashita, 1963
- 10. 1.Reduced Biological Control (Secondary) – most common with insects. 2.Reduced Competition – most common with weeds (mono vs. dicots). 3.Direct Stimulation of Pest – usually due to subacute doses 4.Improved Crop Growth.
- 11. Reduction in Natural Enemy Populations - Direct effects - Indirect effects Hormoligosis. Alteration of plant quality. Induction of insect detoxification enzymes by plant secondary chemicals and/or insecticides. Direct and indirect enhancement of fecundity. Effects of insecticide exposure on insect behaviour. Reduction of competition.
- 12. Avoiding hormoligosis. Avoiding natural enemy destruction. Avoiding competitor destruction. Use physiologically selective control measures. Use ecologically selective control measures. Inoculative release of natural enemies.. Diversification of control methods.