Effectiveness of neem extracts and carvacrol againstThecodiplosis japonensis andMatsucoccus thunbergianae under field conditions

The effectiveness of two neem extracts, Neem-Azal (containing 10 mg azadirachtin ml−1) and neem extract (containing 45 mg azadirachtin ml−1, Neem-45) and carvacrol against larvae of Thecodiplosis japonensis and intermediate nymphs of Matsucoccus thunbergianae was field evaluated by the trunk implantation method and compared with that of the systemic insecticide phosphamidon 500 g litre−1 SL. In tests with T japonensis larvae, Neem-Azal (0.3 ml cm−1 diameter at breast height, DBH) and Neem-Azal + phosphamidon (0.15 + 0.15 ml cm−1 DBH) were highly effective compared with phosphamidon alone (0.3 ml cm−1 DBH). With M thunbergianae, Neem-Azal + phosphamidon (0.3 + 0.3 ml cm−1 DBH) and carvacrol + phosphamidon (0.3 + 0.3 ml cm−1 DBH) gave much better control than phosphamidon alone (0.6 ml cm−1 DBH) and Neem-45 alone in spite of the lower effect of Neem-Azal alone (0.6 ml cm−1 DBH). The efficacy of Neem-45 was comparable to that of phosphamidon. These results indicate a possible synergistic effect. As a naturally occurring insecticide, neem extract alone and in mixture with phosphamidon and a mixture of carvacrol and phosphamidon could be useful as a new preventive agent against damage caused by T japonensis and M thunbergianae.