Submitted to: Journal Of Arboriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 10, 1998
Publication Date: N/A
Interpretive Summary: Although a number of conventional insecticides are registered for and used against the gypsy moth by arborists and nurserymen, Bacillus thuringiensis (Bt) is the only biological/reduced-risk insecticide that is currently in wide use. Arborists and nurserymen face a variety of situations when dealing with the gypsy moth in nurseries and on shade trees in urban and suburban settings. Control materials might not be equally suitable for all situations or compatible with all treatment philosophies. In a continuation of studies designed to improve ground-based control tactics against the gypsy moth, we compared the residual activities of insecticides that are either registered or are candidates for registration for use by nurserymen, or by arborists in IPM programs for gypsy moth management in urban settings. The study compared 5 biological insecticide treatments (one Bt and 4 gypsy moth nuclear polyhedrosis virus (NPV) treatments) and 2 reduced-risk insecticides (neem and tebufenozide) against 2 commonly used standard insecticides (Diflubenzuron and cyfluthrin). Significant details pertaining to the use of the specific control materials were clarified in support of a decision matrix around which an IPM system can be formulated for use by arborists and nurserymen.
The direct and residual efficacy of selected traditional, safer, and biological insecticides were evaluated for use by arborists and nurserymen. The standard insecticides cyfluthrin and diflubenzuron, and the ecdysone agonist tebufenozide, demonstrated excellent activity against all instars in both a 1-hour residue study and a 35 day residue study. Bt was clearly more effective against second instar larvae than against fourth instar larvae, and lost significant activity against the gypsy moth after 7 days. The efficacy of the neem product was similar to that of Bt in that it controlled younger instars better than it did older instars. Although its speed of action was slower than that of Bt, it remained highly active against gypsy moth 21 days after treatment. NPV without the activity enhancer Blankophor BBH gave significant levels of control for all 4 larval instars fed on 1-hour residues, although mortality was higher for younger instars than for older instars. Residual effectiveness was significantly reduced after 1 day. The addition of Blankophor BBH to the NPV tank mix led to improved kill in the 1-hour study and to vastly improved residual activity (up to 35 days).