(F38) PASTURE (GRASSES): Phalaris arundinacea L., Lolium perenne L., Dactylis glomerata L. Amy Peters Department of Rangeland Resources Oregon State University 631 Alder St Myrtle Point, OR 97458 Tel: (541) 572-5263 Fax: (541) 572-5963 email: firstname.lastname@example.org Glenn C. Fisher Amy J. Dreves Department of Crop and Soil Science Oregon State University 3017 ALS Bldg Corvallis, OR 97331 Tel: (541) 737-5576 Fax : (541) 737- 3479 email: email@example.com email: firstname.lastname@example.org Armyworm (AW): Pseudaletia unipuncta (Haworth) Two experiments were conducted in Aug 2005 to evaluate carbaryl, Javelin® WG biological insecticide, and Success® Naturalyte® insecticide for control of AW infesting grass pastures in Coos County, OR. Experiments were located at two dairy sites managed for pasture and hay production: site I (a conventional dairy) was a pasture of mixed grasses consisting primarily of perennial ryegrass, reed canary grass and white clover; site II (an organic dairy) was a reed canary grass pasture. At the time of application, larval populations were large and uniformly distributed among plots (> 30 larvae/sq ft). At site I, application of products was made to predominantly second and third instar larvae; at site II, application of Success and Javelin was made to third and fourth instar larvae. AW populations were low and consisted of younger instars at site I compared to site II. In fact, AW populations were sufficiently greater by the time treatments were applied to site II, so all but the plot area in the experiment was harvested. Treatments were applied on 9 Aug at site I in the late afternoon and were concluded at site II at dark. Plots at both sites were 20 x 20 ft and replicated three times in a RCB design. Treatments were applied in a 6.5 ft swath using a CO backpack sprayer equipped with a 5 nozzle boom (8002 flat fan nozzles with a 50 mesh screen) to deliver 40 gpa at 30 psi. On 15 Aug (6 DAT), plots in both sites were evaluated by taking ten, 5 ft straight-line sweeps with a standard 15-inch diameter sweep net in the middle area of each plot, leaving 5 ft between sampled area and plot borders. Site I was sampled again on 24 Aug (15 DAT). The numbers of live AW were counted and recorded in each plot. Data were subjected to analysis of variance (ANOVA) and means were separated using the Fisher Protected (LSD, P = 0.05). All values were transformed using square root transformation to equalize the variance. Actual means are presented in tables. At both sites, Success at both 3 and 6 oz rates gave significantly better AW control than the other treatments (Table 1 & 2). Also, the low rate of Success was comparable in performance to the high rate. Neither Javelin nor carbaryl at the rates tested significantly reduced AW numbers below those of the untreated check at site I. And although the Javelin treatment significantly reduced numbers of AW below those of the untreated check at site II, the approximate 50% control observed was inadequate. No foliar symptoms of phytotoxicity were observed with any treatment. Collections of AW larvae from site II in late Aug indicated that nearly 25 were parasitized by Tachinid flies (Table 3). Table 1 No. AW larvae/10 sweeps Treatment/ Rate formulation 1b (AI)/acre 6 DAT 15 DAT Success 0.047 1.7b 1.3b Success 0.094 3.0b 1.3b Javelin WG 0.85 26.7a 15.7a Javelin WG 1.3 20.3a 18.3a Carbary l4L 1.0 30.7a 20.7a Untreated check --- 25.3a 18.7a F 13.48 19.75 P < 0.001 < 0.001 Means followed by the same letter are not significantly different (P = 0.05; Fisher LSD). Data were transformed using (square root (x + 0.5)) to reduce variation - actual means are presented in table. Table 2 No. AW larvae/10 sweeps Treatment/ Rate formulation 1b (AI)/acre 6 DAT Success 0.047 20.0c Success 0.094 19.0c Javelin WG 0.85 72.3b Javelin WG 1.3 107.3ab Untreated check --- 141.3a F 10.10 P 0.002 Means followed by the same letter are not significantly different (P = 0.05; Fisher LSD). Data were transformed using (square root (x + 0.5)) to reduce variation - actual means are presented in table. Table 3 Percent AW mortality factors parasitism Tachinid fly 22.6 Braconid wasp (Meteorus spp.) 1.7 Unknown causes of mortality 32.1 A total of 230 AW larvae collected from pasture grass in Myrtle Point, OR. One Tachinid fly emerged from AW puparium instead of larva.
Arthropod Management Tests – Oxford University Press
Published: Jan 1, 2007