138 Hubbard and Potter: Managing Calico Scale Infestations Managing Calico Scale (Hemiptera: Coccidae) Infestations on Landscape Trees Jamee L. Hubbard and Daniel A. Potter Abstract. Calico scale, Eulecanium cerasorum (Cockerell), an invasive pest of shade trees, has reached outbreak levels in landscapes and on horse farms in Kentucky, U.S. We evaluated efficacy and timing of conventional and reduced-risk foliar insecticides as well as trunk-injected or soil-applied systemics for managing E. cerasorum. Acephate, bifenthrin, carbaryl, cyfluthrin, and pyriproxyfen killed young settled crawlers on individually sprayed shoots. Whole-canopy pyrethroid sprays, however, gave <66% control, underscoring the difficulty of reaching settled crawlers within large shade trees. Horticultural oil and insecticidal soap were relatively ineffective even with full spray coverage. Preventive sprays with bifenthrin or pyriproxyfen in mid-May, at first egg hatch, intercepted crawlers before they settled on leaves. Dormant oil failed to control overwintered nymphs or reduce subsequent numbers of adults or crawlers. A plant antitranspirant applied in late March provided 33% suppression. Trunk-injected imidacloprid was ineffective, whereas dicrotophos (bidrin) gave at best <50% control. Soil injection with imidacloprid in November, December, or March failed to reduce subsequent densities of adults on branches or crawlers on leaves. Reasons why it is difficult to eliminate calico scale in mature landscape trees are discussed in the context of the pest’s feeding sites and behavior. Key Words. Calico scale; Eulecanium cerasorum; integrated pest management; microinjection; plant health care; scale insects; systemic insecticide. Calico scale, Eulecanium cerasorum (Cockerell), an invasive coccoid pest of shade and ornamental trees, has reached out- break levels in Kentucky and elsewhere in the eastern United States (Hubbard and Potter 2005). Heavily infested hosts suf- fer twig and branch dieback and may be severely stressed or killed (Hubbard and Potter 2005). In spring, maturing females excrete copious honeydew that attracts wasps and other nui- sance insects and promotes growth of unsightly sooty mold on bark and leaves. Honeydew falling on parked vehicles, decks, or other objects may require removal of infested trees. Highly susceptible hosts include maples (Acer spp.), sweet- gum (Liquidambar styraciflua L.), honey locust (Gleditsia triacanthos L.), Japanese zelkova (Zelkova serrata [Thunb.] Makino) crabapples (Malus spp.), and other cultivated trees, as well as wild hackberry (Celtis occidentalis L.). Calico scale is univoltine, overwintering as second instars on twigs, branches, and trunks and molting to the adult stage in late March to mid-April in Kentucky (Hubbard and Potter 2005; Figure 1). Females each produce several thousand eggs (mean, 3,700 to 4,700) beginning in late April. First egg hatch ranged from 21−26 May in 2001 to 2003 after mean accu- mulation of 818 ± 2°C degree days (1473 ± 4°F degree days) from 1 January at 4.4°C (40°F) base temperature (Hubbard and Potter 2005). Female coloration fades from bright black with white spots to dull black with light to dark brown spots approximately 1 week before the first crawlers appear. Crawler dispersal lasts approximately 2 to 3 weeks, nearly all ©2006 International Society of Arboriculture of them having settled on leaves by mid-June (Hubbard and Potter 2005). Crawlers may be windborne or remain on their tree of origin. Approximately mid-July, settled crawlers molt to second instars, which continue feeding on the leaves until just before leaf abscission in autumn, when they move to wintering sites on bark. In central Kentucky, calico scale is a particular problem on thoroughbred horse farms where rows of single tree species are planted in narrow grassy strips between paved lanes and fenced pastures or paddocks. Labeled grazing restrictions, spray drift, concern about equine exposures, and associated liability preclude spraying broadly toxic pesticides on such sites (Potter et al. 2005). Similar issues occur when managing infestations in urban landscapes. This study evaluated re- duced-risk chemical control of calico scale on horse farms and in urban landscapes. MATERIALS AND METHODS Thirteen trials evaluating strategies for controlling calico scale were conducted from June 2001 to May 2005. Eleven were conducted on horse farms in Fayette County or Wood- ford County, Kentucky, using rows of naturally infested, cul- tivated trees. A few trials were done on wild hackberry trees bordering pastures; two others used rows of cultivated sweet- gums or Japanese zelkova along municipal roads. Trunk di- ameters, unless specified otherwise, ranged from 15 to 25 cm (6 to 10 in) at 1.2 m (4 ft) above ground. All treatments
July 2006
| Title Name |
Pages |
Delete |
Url |
| Empty |
Search Text Block
Page #page_num
#doc_title
Hi $receivername|$receiveremail,
$sendername|$senderemail wrote these comments for you:
$message
$sendername|$senderemail would like for you to view the following digital edition.
Please click on the page below to be directed to the digital edition:
$thumbnail$pagenum
$link$pagenum
Your form submission was a success. You will be contacted by Washington Gas with follow-up information regarding your request.
This process might take longer please wait
