No abstract

The emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), an invasive pest discovered in North America in 2002, is now well established and threatens ash (Fraxinus spp.) trees throughout the continent. Experiments were conducted to 1) examine the efficacy of an alternative natural pesticide, azadirachtin, to control emerald ash borer, and 2) determine foliar uptake and dissipation patterns after systemic injections of azadirachtin into trunks of small (2.2 cm diameter at breast height [dbh]), uninfested green ash trees. We found no evidence of mortality of adult beetles. In contrast, fewer larvae completed their development at dose levels > or = 1.7 mg (AI)/cm dbh and development ceased beyond the second instar at dose levels > or = 13.6 mg (AI)/cm dbh. Substantial concentrations (11.2 microg/g dry mass [SD = 7.55]) of azadirachtin were present in leaves within 7 d of treatment. After rapid initial uptake, concentrations in leaves declined logarithmically during the 55 d after injection. A similar pattern was observed in a separate experiment that examined the uptake and translocation of azadirachtin in larger green ash trees (22 cm dbh) treated with 250 mg (AI) /cm dbh with the EcoJect injection system. In another experiment, recently infested plantation green ash trees treated with doses > or = 40 mg (AI)/cm dbh had significant reductions in adult emergence approximately 1 yr postinjection. Given the inhibition of larval development, reduction of adult emergence, and the occurrence of foliar residues at biologically active concentrations, we conclude that azadirachtin is effective in protecting ash trees from emerald ash borer.

The toxicity of the naturally derived insecticide spinosad was tested against the gypsy moth, Lymantria dispar. Bioassays using red oak leaf disks, treated with spinosad in a Potter spray tower, yielded an LC 50 value of 0.0015 mg AIcm À2 (3-day exposure; 13-day evaluation; 2nd instar larvae). Applied to foliage to run-off in the laboratory (potted red oak seedlings) and the ®eld (4 m-tall birch trees), spinosad effectively controlled 2nd instar larvae at concentrations ranging from 3 to 50 mg litre À1 . Toxicity in the laboratory, and ef®cacy and persistence in the ®eld, were comparable to those achieved with the insecticide permethrin. Laboratory studies supported ®eld observations that control was achieved in part by knockdown due to paralysis. In addition, laboratory results demonstrated that crawling contact activity may play an important role in ®eld ef®cacy; 50% of treated larvae were paralyzed 16 h after a 2-min crawling exposure to glass coated with a 4 mg litre À1 spinosad solution.

Culex pipiens entered diapause in early July with more than 90% in diapause by mid-August. Onset of diapause in Culex restuans was in early July with greater than 80% in diapause by late July. The incidence of diapause in C. pipiens increased when larvae were reared at low temperatures or high densities under similar photoperiod conditions. Diapausing adult females of C. pipiens and C. restuans had ratios of follicle:germarium length of less than 2.00:1.00. Ovarioles of recently emerged diapausing C. pipiens developed to the nondiapause stage in 3–4 weeks when held at 25 °C and a photoperiod of 16L:8D. Ovarioles of diapausing C. pipiens in the field did not develop to the nondiapause state before females left their overwintering sites in the spring.

A systemic tree injection tube was designed to introduce the required volumes of neem-based bioinsecticides into conifer trees. The device consists of plastic tubing attached with hose clamps to a maple sap spile at one end and a tubeless automobile tire valve at the other end. A hole is drilled in the tree, the spile is hammered into the hole, the device is filled with the systemic insecticide, and the system is pressurized by attaching a bicycle pump to the tire valve. The parts are readily available, the device is simple to construct and easy and quick to install on a tree, application volumes are adjustable, and the device is reusable. This device has been used successfully to inject 188 trees representing four conifer species in either spring or fall, primarily with neem formulations but also with dimethoate, imidacloprid, and acephate. In most cases, all of the material was injected into the trees without leakage, although neem formulations were characteristically slow to enter the trees and certain neem formulations were not injected completely at volumes above 15 mL per injection tube. Dosages of 0.2 g azadirachtin/cm of diameter at breast height (dbh) or less provided control of pine false webworm, spruce budworm, cedar leafminers, gypsy moth, and introduced pine sawfly on red pine, white spruce, eastern white cedar, white pine, and white pine, respectively. Dosages as low as 0.005 g active ingredient/cm of dbh applied with injection tubes in either one or two holes per tree resulted in a 95% reduction in defoliation of mature (mean dbh ± SD = 23.4 ± 3.3 cm) red pine caused by pine false webworm.