The breeding rate of most field rodents is minimum during summer with lowest numbers occurring during May-June and hence the acceptability of baits will be maximum as there is a paucity of natural food.
Dig burrows and kill the rodents manually. Plough the soil deeply two times a year to a depth of 45 cm so as to break the underground burrows. Maintain burrow bunds around the field so that there will be inadequate space for the rat to construct its burrows.
Avoid keeping hay stacks near the fields as they provide excellent harbourage for the rodent. Inundate the fields to submerge the burrows and kill the rats by asphyxiation. Infuse carbon monoxide poison gas in to the burrows by smoking jute cloth.
Set up bamboo bow traps at 25 numbers per acre to capture the rodents in their pathways.
Rodent control operation should be taken up before sowing the seeds.
Active burrows are to be surveyed and pre baiting is to be done on the first and third day to avoid bait shyness by the rodents.
The baiting formula should contain cereal/flour/garins and nuts 97 parts and vegetable oil 3 parts in the form of one gram ball or lump and this is to be placed at the rate of six grams at mouth of active burrows.
On the fifth day Zinc Phosphide with bait material at rate of 1: 49 (2 per cent) is added to this lump and the poisoned bait is placed at the burrow entrance as usual.
This will take care of 70-80 per cent of the field rodents. Remaining residual population (20-30 per cent) can be controlled by fumigation in the burrows.
On the sixth or seventh day all burrow openings must be closed manually and on the eight day 1.5 gms of Aluminium Phosphide tablets must be dropped at the mouth of newly dug burrow openings.
Time of operation
This operation must be done at the beginning of Khariff and Rabi season.
Besides, it is advisable for farmers to encourage natural predators like rat snakes, owls and birds to freely move in the fields and not disturb or kill them.
Farmers can also erect small wooden tree clumps in their fields for birds like owl perch on.
(R.K. Murali Baskaran, HOD, J. Jayaraj, Associate Prof, Department of agricultural entomology, Agricultural college and research Institute, TNAU, Madurai, email@example.com)