Suppression of carpenterworm, Prionoxystus robiniae (Lepidoptera: Cossidae), with the entomophagous nematodes, Steinernema feltiae and S. bibionis

Field efficacy of two steinernematid species, Steinernema feltiae (Filipjev) (=Neoaplectana carpocapsae Weiser) and S. bibionis (Bovien) was investigated for suppres sion of carpenterworm, Prionoxystus robiniae (Peck). Two application techniques, gallery injection and bark surface treatment, were used on previously established infestations in oak. Gallery injection of entomophagous nematodes induced high mortality (70-100%) to fifthand sixth-instar carpenterworm. However, bark surface treatments provided variable results. In 1986, nearly 50% mortality was recorded at each of three concentrations, 0.5, 1.5, and 4 x 104 S. feltiae nematodes/gallery. Whereas in 1985, 85% mortality was obtained with a concentration of 2.9 x 104 S. feltiae nematodes/gallery. The carpenterworm, Prionoxystus robiniae (Peck) (Lepidoptera: Cossidae), is a pest of living hardwoods across the entire continental United States. The wood boring larval stage produces injury which ranks it among the most damaging species to oak timber in the southern United States (Donely, 1974; Morris, 1977). Larval feeding produces structural damage and staining of the mined wood. In addition, the gallery, by remaining open 1 to 3 years after adult eclosi?n, presents an infection court for secondary tree pathogens (Solomon and Toole, 1971). Most control efforts on Cossidae and other wood borers involve trunk spray application of chemicals or direct gallery injection of insecticides (Solomon, 1985). The high pathogenicity and mobility of entomophagous nematodes offer a more feasible and environmentally compatible suppression alternative (Gaugler, 1981). Field trials conducted by Cavalcaselle and Deseo (1984), Kaya and Brown (1986), Miller and Bedding (1982), and Lindegren and Barnett (1982) have demonstrated the utility of entomophagous nematodes against lepidopteran wood borers. Prior to the present study, the feasibility of suppressing carpenterworm in southern oaks (Quercus: Fagaceae) with entomogenous nematodes has not been investi gated. Materials and Methods Two temporally separated tests were conducted at the University of Kentucky Robinson Forest in eastern Kentucky. Artificial infestations of P. robiniae were initiated in both tests using a method described by Solomon (1967). Before nema todes were applied, larval survival was determined by observing frass output. Survivorship was increased from 32% in 1985 to 71% in 1986 by cutting a small 1 Scientific paper no. 87-7-172 of the Kentucky Agricultural Experiment Station, Lexington. This research has been conducted (in part) with funds from the U.S. Forest Service, Southern Forest Experiment Station under Cooperative Research Agreement No. 19-85-012. The contents do not necessarily reflect the views and policies of the U.S. Forest Service. Accepted for publication 27 May 1988. This content downloaded from 207.46.13.71 on Fri, 21 Oct 2016 04:54:41 UTC All use subject to http://about.jstor.org/terms VOLUME 61, NUMBER 4 397 Table 1. Field efficacy of Steinernema feltiae and S. bibionis to the carpenterworm, Prionoxystus robiniae, in oak using two application techniques?1985. Dose x io4 Application technique ? (nematodes/gallery) No. rep.b Percent mortality