Standardization of tree injection procedures of Azadirachtin in coconut (Cocos nucifera L.), mango (Mangifera indica L.) and neem (Azadirachta indica A Juss.)

Abstract

Tree injection is a new technology that is employed to apply fungicides, nutrients and pesticides in large trees in order to avoid drifting of these chemicals and affecting non target organisms. It eliminates the wastage of chemicals to be applied in trees as the quantity used is little compared to other conventional methods of application. This study aimed at standardizing the tree injection procedures in Indian conditions. Stem wood of three species like coconut (Cocos nucifera L.), mango (Mangifera indica L.) and neem (Azadirachta indica A. Juss.) were used in the study along with their leaves after the application of azadirachtin through injection. The depth to which the tree injection can be applied was determined by studying the thickness of the conducting tissues in these species using the software Digimizer. Three size classes like 50-60cm, 60-70cm, 70-80cm were studied. Thickness of high density wood in coconut palm and sapwood in mango and neem does not vary with the change in size class. Average high density wood thickness in coconut palm was 3.5cm and was not more than 4.89cm. Thus a depth of 6 cm was fixed so as to ensure the delivery of chemicals into the most active part of the stem. In case of mango tree, the average sapwood thickness was 6.18cm and was never smaller than 3.27cm. Similarly, average sapwood thickness in neem was 4.38cm and was never smaller than 3.02cm. Thus 3 cm was the depth fixed to inject chemicals in mango and neem. Systemic insecticide, Azajet (50,000ppm) was used to inject the trees. Each tree was marked at a basal height of 20 cm from ground. Holes were made at an angle of 45º to make sure that there was no oozing out of chemicals. The EcoJect pump consisting of a canister, nozzle and a cylinder with compressed air between 100 and 150 PSI was used to inject the chemicals. Two canisters of 20 ml each (40ml/tree) were used to deliver the chemical into the tree trunk. Physiological parameters like photosynthesis, transpiration, leaf temperature and leaf moisture were analyzed using Infrared Gas Analyzer (LI-6400, Portable Synthesis System). Stomatal rate was studied by the replica method. A correlation analysis was conducted between the anatomical and physiological properties of the three tree species. The traces of azadirachtin in the leaves were determined by collecting the leaf samples during specific time intervals like 1hr, 2hr, 6hr, 2 days, 7 days, 14 days, 20 days, 28 days, 40 days and 55 days of tree injection by using High Performance Liquid Chromatography (HPLC). There were no correlations between the anatomical and physiological parameters. Azadirachtin traces were found only in coconut palm on the second day of injection with a peak area of 0.14µg/g. Other trees showed no sign of azadirachtin in their leaves. The traces of the bio pesticide did not last for a week as there was no further detection of azadirachtin in the samples collected after 7 days of injection.