And Other Predators of Beech Scale in Central New York
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mhon Beech Bak Disease: Bidogical Contrd Relationships ~1U)CORUS (COLE0ETEPA:COCCINELLIDAB) AND OTHER PREDATORS OF BEECB SCALE IN CENTRAL NEW YORK~ Mark Mayer2 and Douglas C. ~llen~ Abstract.--The twice-stabbed lady beetle Chilocorus seigma (Say), was studied in two infestations of beech scale, CrYptoarcus fagisuga Lind., to elucidate predator biology and to determine the predator's effect on scale ppulations. -C. is univoltine in north-central regions of New York and its seasonal occurrence is well synchronized with that of C. faqisuqa. The predator was most abundant in dense scale populations. and ewhihited a numerical reswnse- at hiqh scale densities. The effectiveness of C. stigma was limited by the Propensity of adults to disperse following eclosion, its apparent fai1;re to feed on all-life stages of the scale, mortality during the beetle's pupal stage and high rate of host reproduction. Four species of mites were also noted as predators of C, fagisuga. Beecn bark disease first appeared in and makes excellent fuelwood. Spread of the North America during the 1890's when the beech disease south and west from its initial point Scale, Cr~~tococcusfaqisu~ Lind., was of entry in Nova Scotia has encouraged introduced from Europe on a species of research on the ecology (Houston 1975; ornamental beech, sylvatica L. The Bouston et al. 1979) and management of disease results when C, faqisuga initially infested stands (Filip 1978). However, infests the stems of American beech, relatively little information about the grandifolia Ehrh. and a fungus, twice-stabbed lady beetle, Chilocorus stigma coccinea var. faginata Lohman, Watson and (Say), a native coccinellid predator of the Ayers then penetrates the bark through feeding beech scale, is available, and other natural Wounds. kale populations alone widently enemies of & faqisuga have received only have little impact on the health of the tree, Cursory attention. but in conjunction with m,Roderate to heavy scale populations may kill trees within C. stigma was first associated with 3-5 years. Presently, extensive areas of dead popul~ionsof & faqisuqa by Ehrlich (1934) beech pervade northern hardwood forests in the who noted the presence of r, atiqma northeastern United States. (identified as C, bivulnerus Muls.) in beech scale-infested sample rrlots in Nova Scotia.~~ ~ This disease has generated more concern Ehrlich reviewed the ~iropeanliterature and in recent years because modern kiln drying reported several vague references to other methods have enhanced the value of beech, insects and arachnids that were thought to be predators of beech scale. Brown (1934) whose wood is used for floorinq,-. -plvwood, - dowels, Shuttles, containers and furnitu;e. suggested that C. stigma was the only Beech is also an important pulproad species predator in New England that had potential to control populations of beech scale. 'paper presented at the IUFRO Beech Bark The general biology of C. stigma was Disease Working Party Conference, Hamden, CT. first investigated by Girault (1907). who USA, 27 Sep to 7 Oct 1982. determined that the beetle wiposited in bark cracks, crevices, and under loosened bark on -est Entonologist, New Jersey Dept. of scale-infested apple trees. Marlatt (1902) Agriculture. and Deband Weidhaas (1976), on the other hand. reported that the beetle oviposited 3Professor of Forest Entamlogy, State beneath scale secretions and predominantly fed University of New York, College of Environmental Science and Forestry, Syracuse, NY. on immature scales. M uma (1955) indicated height. Two strings, one meter long and that oviposition occurred on the leaves, subdivided into 10 em units, were vertically trunk, fruit and t wigs of Flor ida citrus attached to the 10 em marks around the trees. Be found that adults and all four circumference of the tree. A ladder and tree instars voraciously fed on adult scales. ~ trimmer's apparatus were used to climb each stiqaaa has been re<:orded as a predator of 18 tree and sample 3600 around the bole. species of scales, 7 species of aphids, and one species of coccinellid (Thompson and The number and posit ion of Chilocorus Si1111110nds 1965) • were determined within each 10 em sq. Populations of ~ faqisuqa in each sq were DeBoo and Weidhaas (1976) examined ~ arbitrarily classified as light, medium , and stigma in central New Yor k as a predat or of heavy (DeBoo and Weidhaas 1976) , based on five pine needle scal e, Phenacaspis pinifoliae subsamples that were obtained by placing the (Fitch). The coccinell id colonized moderately mouth of a vial (2 em dia . ) o n an ink pad and and severely infested Scotch pine (Pinus then prossing tho ink-coated rim onto the sylvestris L.) in nat urally regenerated tree. Counts were made of the number of adult stands, but was absent on sparsely infested scales within the circle. The sample unit was trees. Lady beetles aggregated on trees that 3. 14 sq. em of bark, and an average of 1-10 harbored the greatest number of scales, but scales, 11-25 scales and 25+ scales per sample only in stands that had a large number of were regarded as light, medium and heavy infested trees. In areas with small isolated populations, respectively. infestations, the beetles did not remain (or reproduce) on scale- infested trees and did not Adults and pupae of ~ ~ were easy significantly reduce scale density. DeBoo and to recognize. The last three instars were Weidhaas hypothesized that alternate prey on distinguished by size; color was used to nearby plants prevent ed ~ stigma from identify first instars. The dorsal midline of congregating on trees i nfested with pine t he thoracic and abdominal regions and much of needle scale. MOnocul t ures (plantations) of the dorsum of the first abdomi nal segment of Scotch pine resulted i n high numbers of pine instars II-IV are light cream to white (Muma needle scale, which subsequently supported 1955). First instars are unif ormly dark gray abundant natural enemies that eventually and approximately 1 mm long. Second instars controlled this host. are 2.5 to 3.5 mm long, the third instar is 4.0 to 5 . 0 mm long, and fourth instars are 6.0 The objectives of the present study were mm or longer. Whenever identification of to (1) determine the biology of ~ ~. instars was questionable, setaceous dorsal and (2) to evaluate the effe<:t of ~ ~ on lateral processes, the senti (sic Gage 1920), populations of ~ faqisuga, and (3) to were examined. identify other predators of ~ faqisuqa. RESULTS AND DISCUSSION MATERIALS AND METHODS Periodic examination of beech boles made The study sites at Wanakena, New York it possible to (1) determine t emporal changes (St. Lawrence County) and Tully, New Yor k in populations of ~ ~ ; (2) estimate (Cor tland County) consisted of mature beech, population density by mapping the scale eastern hemlock, Tsuqa canadensis (L.) Carr, infestation; (3) examine the relationship sugar maple, ~ saccharum Mar sh, red maple, between changes in the scale and predator Acer rubrum L., and yellow birch, Betula populations and; (4) observe the effect of il'i'le9~sis Britton. To deter11ine the physical variables on the scale and beetle response of ~ ~ to different densities populations. Also, this approach enhanced the of ~ fagisuqa at Wanakena, as well as to probability of finding other predators and/or facilitate observations, 12 beech trees 10-20 parasites of ~ faqisuqa, because a large m tall that represented a range of ~ total area of tree bOle was systematically faqisuqa densities were selected for examined throughout several 24 hr periods. population measurements. The four most heavily infested trees were sampled weekly from June through October, 1979 (n • 17-19 Effect of C. fagisuqa density ~ populations obs./tree) and the remainder were examined of c. stigma biweekly (n = 8-9 obs. /tree). There was a significant positive Sample trees were divided into 1 11 correlation between the density of ~ stigma vertical segments and each meter was and that of its prey. While the correlation subsectioned into 10 em x 10 em squares. This (r = 0.75, p • .05) between scale density and was accomplished by marking every 10 em around predator density is encouraging from a natural the circumference of the tree at each meter control standpoint, it is important to examine 90 the within-tree distribution of the predator a higher predator density than the medium population at different host densities. In infestations (M) , which in turn supported more other words, predator abundance should be predators than did the liqht infestation (I). viewed in terms of the proportion of total This relationship is typical of a predator bark surface area occupied by an infestation with well developed searching behavior and level (i.e., light, medium or heavy) (Fig. host finding capabilities. & stigma was 1 Initially, as the proportion of bole area able to locate prey colonies even when a small occupied by each infestation level increased, proportion of the bole was infeated. The data the proportion of predators found in that area indicate that the density and distribution of also increased. However, the data indicate -C. on beech boles was influenced by that beetles do not readily establish the density and distribution of C, fagisuqa. themselves on trees that are lightly infested. Bven though a light infestation occupied a This may account, in part, for the fact that relatively large total bark area, the beetle sparse scale colonies are capable of rapid density in that category was usually lower numerical increases over a relatively short than that in the next highest infestation Period. Apparently, the predator concentrates category. on trees, or portions of trees, where the host is easily found (i.e., dense populations). The decrease in predator densitv when 15%of -Life history of C. stigma the infested area contained a medium scale density, and the increase in predator density C.