Taxus, Control of Black Vine Weevil Larvae, Wooster, Ohio, 1990

Abstract

Abstract Taxus plants, growing in 1 pt (0.47 liter) containers obtained from a nursery in NE OH, were used to evaluate conventional insecticides and entomogenous nematodes against black vine weevil larave. Plants were repotted 12 Jul in 1-gal (3.8 liter) containers using two different media mixes. Medium # 1 contained three parts pine bark and one part peat moss (3:1). Dolomitic lime was added to the mix at 6 lb/cuyd. Medium #2 contained three parts pine bark, one part hardwood bark, and one part peat moss (3:1:1). The Dolomitic lime was added to the hardwood bark by the supplier prior to the mixing of the three components. Plants were fertigated with 100 ppm N, P, K (Peter’s 20-20-20) every Mon, Wed, and Fri. Beginning 1 Aug, water alone was applied via over-head irrigation. Black vine weevil eggs were collected from adults held at 22°C and 80%+ RH and a 16:8 LD. On 3 Aug, all containers received 60 brown eggs, placed 2.54 cm beneath the surface of the potting medium. An additional 69 brown eggs were added to each container 10 Aug, as before. Hatchability was 73 and 81 percent, respectively. Nematode treatments were applied 29 Oct when larval head-capsule width avg 1.7 mm and 20 Nov when head-capsule width avg 1.8 mm. A nematode stock suspension was made by placing 1 unit of BIOSYS (10,000,000 nemas) in 10 gal of water. Nemas were applied volumetrically in 473 ml of water to deliver pre-determined no. of nemas per pot. Nema stock suspensions were thoroughly stirred, and 1 liter of the solution was placed in a capped bottle. The bottle was shaken, a pre-determined vol containing a target no. of nematodes was poured into a graduated cylinder. These measured amt of suspension were placed in pt jars, and water was added to bring the vol to 473 ml. This finished suspension was added to each 1 gal pot. All finished suspensions were poured over the potting medium to achieve even distribution. Other insecticide treatments were applied 10 Sep or 29 Oct by mixing the pre-determined 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 received 2.0 cm of over-head irrigation every Mon, Wed, and Fri. Effects of the first nematode treatment were evaluated 11 Dec. The second nematode treatments, along with the insecticide treatments, were evaluated 17 Dec, by removing the plant and medium from each container, counting the no. of larvae, and recording their condition. Some pupation was occurring when evaluations were made.