Influence of simulated whitegrub damage of roots on water relation parameters in groundnut

White grubs (larval scarbaeids) are important pest of groundnut in many parts of the world. These larvae damage the root system of the plants. A method of simulated whitegrub damage to plants was developed to assess influence of feeding activity of these insects on plant growth. Seeds of groundnut variety Chitra were sown in polythene bags and allowed to grow in a net house. One set was grown under normal water supply and the other set under water stress. Simulated whitegrub damage was created by cutting the roots of plants at 10, 20 and 30 cm from the top soil surface at 30 days after sowing in one set and at 60 days after sowing (DAS) in the other set under both the conditions. Plant leaves were taken at 5, 15 and 25 days after the root cut from both the sets for estimation of proline, peroxidase activity, transpiration rate and relative water content. Simulated whitegrub damage reduced relative water content as well as transpiration and the reduction was highest in plants with roots cut at 10 cm and the lowest in plants with roots cut at 30 cm. Proline content and peroxidase activity increased with the increase in the per cent root cut. The magnitude of increase in proline and peroxidase was almost 2–3 times of the control, in plants whose; roots were cut at 30 or 60 days after sowing. Seed yield was also reduced due to simulated whitegrub damage at both the stages. The roots damaged at 60 DAS reduced the seed yield to a greater extent than the roots damaged at 30 DAS.