Validation of the usefulness of bovine urine in the control of Oryctes Rhinoceros grub

Abstract

Experienced farmers traditionally applied bovine urine in compost pits and cow dung pits for preventing the larval development of Oryctes rhinoceros, (Linn.), a serious pest of coconut palms. This traditional knowledge was validated in the laboratory by mixing 100 ml of bovine urine with 500 gm cow dung and it was found that presence of urea at a concentration of 1.0 to1.5 % in the bovine urine was the reason behind the insecticidal activity. Aqueous solution of urea at a concentration of 0.3 to 0.4 % in cow dung has resulted 100% mortality of Oryctes rhinoceros larvae in 3-5 days. Toxicity has resulted in hyperproteinemia, elevated total free amino acid and uric acid of hemolymph. Activity of hemolymph aspartate amino transferase, alanine amino transferase and two proteolytic enzymes such as leucine amino peptidase, cathepsin D were decreased, indicating that urea had affected protein turn over and aminoacid metabolism. The carbohydrate metabolism was also affected through elevated activity of trehalase and subsequent decrease in trehalose content. The polysaccaride glycogen showed sharp decrease but the larvae were unable to utilize glucose which resulted hyperglycaemia. SDS-PAGE of hemolymph of urea intoxicated larvae showed sharp changes in the protein profile which was attested through GEL-DOC analysis. Intoxicated larvae showed decrease in total hemocyte count together with selective increase in the population of granulocyte. Urea was the major dissolved constituent of bovine urine and the presence of it was the reason behind its pest control value.