Expanding scope of evaluation of insecticides beyond efficacy and cost to including environmental impact assessment

 

 Research Planning meeting at Dr PDKV, Akola-seen from left seated: Dr KV Kharche, Director [Res]; Dr Sharad Gadakh, Vice-Chancellor; Dr GT Gujar and Dr DB Undirwade, HoD Entomology and Director [Ext Edu]

A few days ago, I attended a research planning meeting in the discipline of entomology at the Dr Panjabrao Deshmukh Krishi Vidyapeeth, Akola. This is like a project formulation for studying various aspects, especially effective management tactics against the key insect pests damaging the important crops grown in the area under the University’s jurisdiction. The project proposals mostly focussed on the evaluation of insecticides at two different locations in each of two years’ period under the field conditions. The results of evaluation of management tactics are then discussed at the joint AGRISCO meeting which is an annual feature of the agricultural universities in the state of Maharashtra. And on the basis of recommendations arising out of the AGRISCO meeting, these are approved for implementation in the albeit entire state. Since most of the crops are common to other regions viz., Marathwada, western Maharashtra and Konkan, falling under the respective jurisdiction of the Vasantrao Naik Marathwada Agricultural University, Parbhani and the Mahatma Phule Krishi Vidyapeeth, Rahuri and Dr Balasaheb Sawant Konkan Krishi Vidyapeeth, Dapoli; it is likely that similar studies are carried out there too leading to overlaps or even repetitions.

Going back to the meeting content, I found that topics were relevant to the needs of the farmers. For instance, these included evaluation of management tactics against the fruitfly in Nagpur mandarin, the stemfly in soybean, podfly in Pigeonpea, aphids in cowpea and sucking pests in sugarcane. Insecticide-centric integrated pest management [IPM] modules dominated the studies to be undertaken. Of course, these are not only projects. Many others were in different stages of implementation. The Department of Entomology has also worked on the biopesticides including biological control and advocated their use in the context of integrated approach to crop protection. Besides, this Department is undertaking studies on use of drones for crop protection, biotechnological approaches to improving biopesticides, development of sericulture and bee keeping along with other basic studies.

Evaluation of insecticides is undertaken at the field-recommended doses and at time intervals taking into consideration crop growth under local conditions. It is often supposed that at the specific time interval or at a phenological stage of crop, pest infestation is good enough to cause significant crop damage and hence, necessary tactics may manage the pest, reduce crop damage and ensure commensurate yield increase. Since this approach is not based upon the attainment of economic threshold level [ETL] of pest insect, it could lead to incurring unnecessary expenditure on crop protection, as pest infestation or crop damage does not always translate into significant yield decline. Some time, compensation mechanisms predominate over the crop damage thereby reducing need for use of insecticides. Evaluation of insecticides should therefore be based upon the ETL of pest species, so that economics of crop protection favours the farmers. Hence, these studies must also estimate incremental cost-benefit ratios [ICBR], besides usual observations on reduction of pest infestation and of crop damage, and concomitant yield increase. Since crops suffer from other biotic stresses, field studies should also include observations on other pests and appropriate steps to contain them.And also estimates of natural enemies in different treatments.

Furthermore, evaluation of pesticides should also include concerns of consumers on the quality of produce. In recent times, consumer has become acutely aware of environmental pollution as well as health hazards posed by misuse of insecticides and other pesticides. Just few years ago, some farm labours spraying insecticides on cotton in the district of Yavatmal lost their lives and many more suffered ill-effects due to pesticide poisoning. Besides, farm produce is reportedly found to be contaminated with pesticide residues, as often pesticides are sprayed until harvest. Unfortunately, cases of unapproved pesticides being used on crops lead to unforeseen health hazards directly or indirectly. Although the Insecticide Act, 1968 prescribes waiting period of pesticides for harvest of crops, the agro-ecological conditions differ a lot, as these conditions influence dissipation of pesticide and its residues to level below maximal permissible limit in the harvested produce. Sometimes, anomalies are found between waiting period of pesticide and the duration of crop, if the latter matures earlier than the normal or in crops where periodic harvesting occurs. The waiting period prescribed for pesticide in a crop is based upon its estimates of pesticide residues in the grain harvest at the end of crop maturity. However, this is not true for many crops where grains are harvested in the grain formation [milky/immature] stage to be used for culinary purpose. Vegetable crops being short duration and with multiple harvests are sometime sprayed indiscriminately. Hence, studies must also include estimation of pesticide residues at harvest as well as at times when grains or produce are harvested for culinary purposes. Such an approach will help in allaying fears of citizens who are concerned with extraneous chemicals present in food, leading to “poison in my food plate” syndrome.

In India, 859 pesticide formulations are registered, and these include 267 synthetic insecticide formulations. In view of environmental concerns expressed, there is a need for authentic information in the public domain in the form of “fact sheets” of pesticides registered in the country. The information available online about these pesticides is not relevant in the Indian context and hence unreliable. As a part of evaluation of pesticides under field conditions, there is a need to include estimate of environmental impact quotient [EIQ] of each pesticide as an additional objective. The concept of EIQ was advocated many years ago by Kovach et al. [1992] which could be suitably modified and adapted. In brief, EIQ, pesticide residue estimates and conventional evaluation including ICBR could go a long way in assuring the people that recommended pesticide use is based upon the least adverse environmental impact for the people, high safety for the consumers, and optimal cost-benefit ratio for the farmers, respectively.

 Thanks to Drs Sharad Gadakh, VC of PDKV, V K Kharche, Director of Research, PDKV and D B Undirwade, Head, Department of Entomology, PDKV and other participants for interesting discussion.

Kovach, J., Petzoldt, C., Degni, J., and Tette, J. 1992. A method to measure the environmental impact of pesticides. New York’s Food and Life Sciences Bulletin 139:1–8.