REDUCTION OF DAMAGE TO MAHOGANY BY MAHOGANY SHOOT BORER AND MAHOGANY LEAF MINER BY USE OF AZADIRACHTIN

Abstract

In a study conducted in Florida in the spring of 1993, after initial attack of West Indies mahogany [Swietenia mahagoni (Meliaceae)] by mahogany shoot borer [Hypsipyla grandella (Pyralidae)], frass production, used as an indicator of larval development with accompanying internal damage to shoots, did not progress on 22 trees treated with azadirachtin, but did progress in shoots in 49.9% and 22.9% , of 22 untreated trees on two different observation dates, May 26 and June 18 respectively. On these untreated trees, 73.9% and 88.2% of the attack sites observed on May 20 and June 10 respectively, showed significant frass development within about a week. Damage by mahogany leaf miner [Phyllocnistis meliacella (Gracillariidae)] was observed in samples from 5 of 22 trees treated with azadirachtin and from 17 of 22 trees in the controls. There were more than 4 times as many mines in the controls than in the trees treated with azadirachtin (p < 0.01). Because in Florida the period of mahogany shoot borer and mahogany webworm (Macalla thyrsisalis) attack coincides with the spring flush of West Indies mahogany, azadirachtin applications timed with spring flush could reduce damage of both pests, plus the spring populations of mahogany leaf miners. The potential of this method for situations outside of Florida is discussed.