Ethyl m-digallate from red maple, Acer rubrum L., as the major resistance factor to forest tent caterpillar, Malacosoma disstria Hbn.

An ethanolic extract of red maple (Acer rubrum L.) leaves (RME) applied to trembling aspen (Populus tremuloides Michx.) leaves reduced feeding in choice test assays with forest tent caterpillar larvae (Malacosoma disstria Hbn.) (FTC), whereas a trembling aspen foliage extract, similarly applied, stimulated feeding. Compounds isolated from the RME were gallic acid, methyl gallate, ethyl gallate, m-digallate, ethyl m-digallate, 1-O-galloyl-beta-D-glucose, 1-O-galloyl-alpha-L-rhamnose, kaempferol 3-O-beta-D-glucoside, kaempferol 3-O-beta-D-galactoside, kaempferol 3-O-beta-L-rhamnoside, kaempferol-3-O-rhamnoglucoside, quercetin 3-O-beta-D-glucoside, quercetin 3-O-beta-L-rhamnoside and quercetin 3-O-rhamnoglucoside, (-)-epicatechin. (+)-catechin and ellagic acid. All of the gallates, (-)-epicatechin, and kaempferol 3-O-beta-L-rhamnoside deterred feeding on trembling aspen leaf disks when applied at 0.28 mg/cm2. The two digallates deterred feeding by 90% and were the most effective. HPLC analysis indicated that ethyl m-digallate is present in amounts 10-100 x higher in RME (approximately 2.5-250 mg/g) than any other compound. Thus, ethyl m-digallate appears to be the major compound protecting red maple from feeding by FTC, with a minor contribution from other gallates.

Efficacy of cypermethrin for the control of mosquito larvae and pupae, and impact on non-target organisms, including fish.

In laboratory tests, cypermethrin was highly toxic to mosquito larvae and pupae. It was more toxic at low temperatures after a 24 hr exposure. Larvae of Aedes stimulans were less susceptible than Culex restuans. Technical cypermethrin was more toxic than an emulsifiable concentrate formulation. In outdoor simulated pools cypermethrin 40% EC was consistently effective against larvae and pupae of Ae. stimulans at 10 g AI/ha and Culex spp. at 50 g AI/ha. When stickleback fish were tested, no mortality occurred at the lowest effective dosage in each trial. The residual toxicity of cypermethrin increased with dosage and was much higher in a test at 8 degrees C than at 20 degrees C. In natural snowmelt pools, cypermethrin at 20 g AI/ha provided 92-100% control of Aedes spp. larvae and pupae by 7 days after treatment. Non-target amphipod, anostracan, cladoceran and insect populations were usually reduced 80-100% while copepods, ostracods and hydracarinid mites were generally less affected. No significant mortality of caged stickleback fish occurred in these pools.