Taxus, Control of Black Vine Weevil (BVW) Larvae, Wooster, Ohio, 1989

Taxus plants, growing in 1 pint (0.47 liter) containers obtained from a nursery in NE Ohio, were used to evaluate conventional insecticides and entomogenous nematodes against BVW larvae. Plants were repotted 27 Jun in 1 gal (3.9 liter) containers with a 3:1 (pine barkipeat) medium mix. Dolomitic lime was added to the mix at 6 lb/cuyd. Plants were fertigated with 200 ppm N, P, K (Peter’s 20-20-20) every Mon, Wed, and Fri. Beginning 7 Aug, water alone was applied via over-head irrigation. BVW eggs were collected from adults held at 22°C and 80%+ RH and a 16 h photoperiod. On 7 Aug, all containers received 75 brown eggs, placed 2.54 cm beneath the surface of the potting medium. An additional 58 brown eggs were placed 16 Aug, as before. Hatchability was 89 and 77 percent, respectively. Treatments were applied 8 Nov when larval head-capsule width averaged 1.63 mm. A nematode stock suspension was made by placing 1 unit of Otinem (50,000,000 nemas) in 10 gallons of water. Nemas were applied volumetrically in 473 ml of water to deliver predetermined numbers of nemas per pot. AgSorb flake (2.4 grams) was added to the finished suspension for each pot of selected treatments. All finished suspensions were mixed thoroughly in a pint jar and poured over the potting medium to achieve even distribution. Other insecticide treatments were applied by mixing the predetermined pot rate in 473 ml of water which was poured over the pot medium, as before. All plants were watered prior to and after application. Plants were then hand watered every Mon, Wed, and Fri. Treatment effects were evaluated 28-29 Nov, when larvae were nearing maturity, by removing the plant and medium from each container and counting the number of larvae and recording their condition. Some pupation was occurring when evaluations were made.