Journal of Arboriculture 31(4): July 2005 201 Table 2. Mean (± SEM) number of healthy first and second instar Allokermes kingii per four-branch sample. Rate 24 April Treatment Control Acephate Bifenthrin (product/water) — 226.8 g/378 L (8 oz/100 gal) 2.3 L/378 L (0.63 gal/100 gal) Horticultural oil 7.6 L/378 L Imidacloprid Oil + acephate (2.0 gal/100 gal) 5.7 g/7.56 L (0.2 oz/2.0 gal) 7.6 L oil + 226.8 g 49.0 ± 27.5 acephate/378 L (2.0 gal + 8 oz/100gal) F = 0.41 df = 5, 24 P = 0.83 F = 2.77 df = 5, 24 P = 0.04 population outbreaks are unknown. Most scales usually disperse as crawlers and then settle on a host plant, but A. kingii nymphs migrate twice, which may increase the chance of wind dispersal within an area. At high densities, more than one female may feed at the base of a petiole (Hamon et al. 1976) or along a branch, which increases the risk of branch dieback. However, exact damage thresholds have not been defined. We were unable to achieve consistent, satisfactory control from the insecticide test using horticultural oil, acephate, bifenthrin, or imidacloprid, although the acephate and oil combination appeared the most promising of those treat- ments. Repeat applications may be needed, given the ex- tended nymphal activity period. The systemic treatment of imidacloprid should have provided greater control of A. kingii if it feeds in the phloem (Salvatore 1997), but the exact placement of the stylet in the plant tissue is unclear. It is also possible that soil or trunk injections with imidacloprid could provide greater control, or that more time was needed for imidacloprid to reach its maximum efficacy (Sclar and Cranshaw 1996). Acephate may have been more effective because it is more soluble than imidacloprid, allowing more insecticide to move into nonvascular plant tissue (Rebek and Sadof 2003). Pyrethroid insecticides may not be viable scale control products because of their negative impacts on natural enemies and tendency to cause secondary pest outbreaks (Clarke et al. 1992). F = 6.03 df = 5, 24 P = 0.001 F = 0.91 df = 5, 24 P = 0.49 *Means within a column followed by an asterisk are significantly different from the control (Dunnett’s test) at P < 0.05. LITERATURE CITED Clarke, S.R., J.F. Negron, and G.L. Debarr. 1992. Effects of four pyrethroids on scale insect (Homoptera) populations and their natural enemies in loblolly and shortleaf pine seed orchards. J. Econ. Entomol. 85(4):1246–1252. Hamon, A.B., P.L. Lambdin, and M. Kosztarab. 1976. Life history and morphology of Kermes kingii in Virginia (Homoptera: Coccoidea: Kermesidae). Virginia Polytech. Inst. & State Univ. Res. Div. Bull. 111:1–31. Harms, W.R. 1990. Live oak, pp. 751–754. In Burns, R.M., and B.H. Honkala (Eds.). Silvics of North America, Vol. 2. Agric. Handbook 654. USDA Forest Service, Washington DC. Kosztarab, M. 1996. Scale Insects of Northeastern North America: Identification, Biology, and Distribution. Virginia Museum of Natural History, Martinsburg, VA. 650 pp. Raven, J.A. 1983. Phytophages of xylem and phloem: A comparison of animal and plant sap-feeders. Adv. Ecol. Res. 13:135–234. Rebek, E.J., and C.S. Sadof. 2003. Effects of pesticide appli- cations on the euonymus scale (Homoptera: Diaspididae) and its parasitoid, Encarsia citrina (Hymenoptera: Aphelinidae). J. Econ. Entomol. 96(2):446–452. Salvatore, M. 1997. General life history, pp. 251–256. In Ben-Dov, Y., and C.J. Hodgson (Eds.). Soft Scale Insects: Their Biology, Natural Enemies and Control, Vol. 7A. Elsevier, Amsterdam, The Netherlands. F = 4.90 df = 5, 24 P = 0.003 5.2 ± 2.8 7.8 ± 3.0* 2.6 ± 1.5 14.2 ± 12.7 94.0 ± 25.9 117.8 ± 49.6 12.6 ± 4.3 71.6 ± 22.5 13.0 ± 4.9 56.0 ± 14.2 25.6 ± 8.5 52.4 ± 37.1 23.6 ± 6.1 57.6 ± 27.3 9 May (pretreatment) (1 WAT) 69.0 ± 32.1 100.0 ± 54.8 85.0 ± 24.0 66.6 ± 24.0 26.2 ± 8.3 44.4 ± 22.2 22 May (3 WAT) 41.2 ± 8.4 13.4 ± 2.4 16.8 ± 7.7 5 June (5 WAT) 43.2 ± 13.3 40.6 ± 17.3 70.8 ± 40.9 19 June (7 WAT) 33.2 ± 10.9 41.2 ± 21.4 308.2 ± 118.7* ©2005 International Society of Arboriculture
July 2005
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