198 Turner and Buss: Biology and Management of Allokermes kingii on Oak BIOLOGY AND MANAGEMENT OF ALLOKERMES KINGII (HEMIPTERA: KERMESIDAE) ON OAK TREES (QUERCUS SPP.) By Jay Cee L. Turner1 and Eileen A. Buss2 Abstract. The northern red-oak kermes scale, Allokermes kingii (Cockerell), is a native, gall-like scale insect found on oak trees (Quercus spp.) in the United States. Its feeding causes branch dieback, flagging, reduced growth rates, and occasionally tree death. Allokermes kingii has one generation a year throughout most of the United States, but we found two generations a year in Florida. It also infests Q. geminata Small and Q. virginiana Miller, which represent new host records. The insecticides tested (acephate, bifenthrin, imidacloprid, horticultural oil, and combined acephate and oil) appeared to suppress the nymphal population, but none caused >42% mortality. Very few natural enemies occurred on the study trees, and were thus considered ineffective at reducing the scale population at this site. Key Words. Allokermes kingii; insecticide trial; Kermesidae; northern red-oak kermes; Quercus geminata; Quercus virginiana. univoltine species, and management based on the life cycle determined in Virginia was ineffective. Thus, we examined the life cycle and insecticidal control of A. kingii on street trees in central Florida. MATERIALS AND METHODS Study Site Eight oak trees (two sand live oaks [Q. geminata Small] and six live oaks [Q. virginiana Miller]) with natural infestations of A. kingii in Clearwater, Florida (Pinellas County), U.S., were examined from May 2002 to August 2003. The trees were located in a parking lot about 300 m (328 yd) from the Gulf Coast. On 10 May 2002 and 29 August 2003, tree height was measured using a clinometer, and diameter at breast height (dbh, 1.4 m [55.1 in.]) and crown diameter were measured with a centimeter cloth measuring tape. Kermes scales (Hemiptera: Kermesidae) are native, gall-like insects that primarily infest oak trees (Fagaceae: Quercus spp.) in the eastern and midwestern United States (Kosztarab 1996; Scalenet 2004). Their feeding often results in branch dieback or reduced tree growth rates (Raven 1983; Vranjic 1997), and their honeydew secretions result in sooty mold growth on branches. Severely infested trees may die if populations are not suppressed (pers. obs.). The most economically damaging kermes scales are Allokermes cueroensis (Cockerell), A. galliformis (Riley), and A. kingii (Cockerell) (Kosztarab 1996). Of these species, however, only the life cycle of A. kingii has been studied (Hamon et al. 1976), and little is known about the biology of other scales in the family Kermesidae (Kosztarab 1996). Large (4 to 5 mm [0.16 to 0.2 in.]), round, mottled-brown females feed along branches, in tree wounds, at the base of buds, and at the base of leaf petioles (Hamon et al. 1976). Tiny (1 mm [0.04 in.] long), white, oval males occur in bark crevices along tree stems. In Virginia, A. kingii has one generation each year (univoltine). Oaks are commonly planted street trees in the United States, and live oak (Q. virginiana Miller) is a particularly popular species in Florida (Harms 1990). Infestations of A. kingii appeared to be developing faster on live oaks in Florida nurseries and urban landscapes than expected for a ©2005 International Society of Arboriculture Life Cycle To determine the life cycle of A. kingii, five branches (20 to 26 cm [8 to 10 in.] long), approximately 1.8 to 3.7 m (5.9 to 12.2 ft) off the ground, were cut from each tree every 2 to 3 weeks from 6 June 2002 to 29 August 2003. Branches were transported to the laboratory in a cooler, frozen, and later examined with a dissecting binocular microscope (10× to 20× ). The number of live first and second instars and live female adults on each branch was counted and totaled by life stage for each tree. The total number of live A. kingii (all life stages combined) per main branch and lateral branches, the total length of each main branch, and the total number and length of lateral branches per main branch were recorded. Male A. kingii were primarily located on tree trunks, rather than branches, and were thus not examined in this study. Insecticide Test Insecticide applications were targeted against the first and early second instars of the first generation A. kingii. Six treatments were assigned to trees using a randomized complete block design, with five replicates (trees). Thirty oak trees naturally infested with A. kingii in Clearwater, Florida, were selected (height: 5.5 ± 1.0 m [18.2 ± 3.3 ft]; dbh: 22.8 ± 3.3 cm [9.0 ± 1.3 in.]). Trees were separated by
July 2005
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