and Minute Cypress Scale : A Pest of Nursery and Landscape and (DRAFT COPY)

Introduction The juniper scale, juniper, and its closely related look-a-like, minute cypress scale, , have been found with increasing frequency on leyland cypress, cyrptomeria and arborvitae in landscapes and nurseries. We are covering both of these armored scales in this fact sheet since they have very similar life stages and are found similar material. Researchers in Pennsylvania (Stimmel, 1979) found that juniper scale and minute cypress scale life stages are in synchrony. Minute cypress scale appears identical to juniper scale and the two can only be distinguished after microscopic examination.

Both of these two armored scales are difficult to control after are moved into a landscape. Many of the species they infest such as Leyland cypress, arborvitae, and Cryptomeria grow very large. Getting enough coverage with pesticides is very difficult when plants are greater than 20 ft tall.

Both Juniper and minute cypress scale are very small in size. Both are creamy white in color. They are difficult to detect easily at low populations. Often cuttings taken of Leyland cypress, Arborvitae, and Chamaecyparis to propagate the plant asexually contain small infestations of juniper or minute cypress scale that may go undetected. The scale population continues to grow as the plant is moved in the nursery growing area.

Unless monitored carefully and controlled early, populations of these two armored scale can become well established in a throughout a nursery and spread to several species of . In the landscape many species of conifers can become infested and build up to levels that cause dieback and even death of infested plants. Symptoms of scale feeding include loss of vigor and normal color, reduced or no new growth, and dieback and death of branches. Severe infestations may kill entire plants.

PLANTS ATTACKED Both juniper and minute cypress scale attack similar plant species. The juniper scale, native to Europe, is now distributed throughout the United States, is known to attack (Juniperus spp.); all members of the cypress (}, particularly Cuppressocyparis spp., including Leyland cypress and spp., including Lawson Cypress); Falsecypress (Chamaecyparis); Western redcedar (Thuja plicata) and Incense cedar (Calocedrus decurrens). It has also been found on cryptomeria and cedar (eastern redcedar and northern white cedar). The most commonly infested ornamental junipers include eastern redcedar (J. Virginiana); Common or Irish juniper (J. communis ‘Hibernica’); Savin juniper (J. Sabina); and Chinese juniper (J. chinensis ‘Pfitzeriana’). Minute Cypress Scale also similiarly attacks only conifers, including Falsecypress (Chamaecyparis); Cuppressocyparis spp., including Leyland cypress); Cryptomeria; Cedars (including eastern redcedar and northern white cedar); Cupressus spp. (including Lawson Cypress); and Junipers, as well as Spruce (Picea), arborvitae (Thuja), Cypress Pine (Callistris), and Sequoia.

Identification in the Field Juniper and minute cypress scales are member of the armored scale family . In the field, the adult male and female covers looks very similar for both juniper and minute cypress scale. Minute cypress scale tends to be slightly smaller. The female cover is arched to convex, somewhat circular and approximately 1.5mm in diameter. The cover is bright white but there are yellow-brown cast skins at the tip of the cover in the center of the cover. The male cover is more elongated and oval-shaped but is also bright white with yellowish cast skins at the tip. The male cover can have 1 – 3 faint ridges running parallel along the cover length. If the covers are removed exposing the body of either the minute cypress scale or juniper scale then adults of both male and females are faint yellow to slightly greenish color. Females that are filled with eggs have a pink to red coloration. The eggs are reddish to yellow in color. Adult males when they emerge from the pupal casing are yellow to orange and have one set of wings and one tarsal claw on each leg.

Life Cycle The limited published literature on juniper and minute cypress scale indicates that for both species there is one generation per year in climates such as those found in Northern Japan, Pennsylvania and Maryland, where fertilized 3rd instar females overwinter. Davidson and Miller (2005) note that in Italy the minute cypress scale life cycle is two weeks ahead of the juniper scale life cycle, while in England juniper scale life cycle is 2 weeks ahead of the minute cypress scale life cycle. In Pennsylvania (Stimmel 1979) records that these two scales are in synchrony. In 2013 we recorded life cycle of the juniper scale in Maryland on Leyland cypress. In Maryland, in 2013, we had egg laying beginning in mid-May at 321 degree days, peaking in late May at 544 GDD. Crawlers started to emerge at 430 degree days (May 20th in 2013) and peaked at 546 GDD, continuing to emerge for six weeks, with the ending crawler period at 829 GDD degree (June 10). Peak crawler activity was at 546 degree days. Second instars appeared at 977.5 degree days. Third instar females were present by 1132.5 degree days. Stimmel (1979) in Pennsylvania noted similar life cycle of minute cypress scale to juniper scale.

Cotinus coggygrias (Smokebush) and Syringa chinensis (Chinese lilac) were in full bloom at the time of first generation crawler activity and can be used as phenological indicators. Aralia spinosa (devil’s walkingstick) was in bud at the time of second generation activity.

Damage and Monitoring Scales are sucking insects that remove plant sap. High populations can cause premature drop, branch dieback, and ultimately tree death. In addition, white scale covers that accumulate on the needles and of plants often remain for a period of time following control measures, are unsightly, and have led to rejection of plant shipments. When nearing the appropriate DD for crawler activity closely monitor for signs of crawlers. Look for discrete circular holes in scale covers that indicate parasitoids are attacking the JMS population.

Management

Biological: Dustywing larvae and adults, (beneficial predators in the insect family Coniopterygidae), feed on eggs and other life stages of these scale insects. Four species of tiny wasp parasitoids are known to attack this pest. Lady beetle larvae and adults are also often associated with infestations. Look closely at scale covers to determine if they have been attacked by beneficial predators or parasitoids. Covers with ragged, chewed holes were likely attacked by predators. Covers with smooth round holes were likely attacked by parasitoids as they exit.

Mechanical: Use a high pressure water spray or gentle scrub brush with water to remove scale covers from trunks of trees to improve aesthetic appearance and/or reduce populations. Prune out dead branches with scales. Chemical: Dormant applications of horticultural oil should be applied at 2-3% rates in the fall after leaves drop or in spring before bud break. If applying in fall or spring, apply when temperatures are above 50-60 °F for 4 to 5 days. During the growing season target the crawler stage for optimal control. See the degree day crawler activity table above. Horticultural oil at a summer rate of 2.0 % can be applied when crawlers and early instars are present. Do not apply horticultural oils to drought stressed plants. When crawlers and early instars are present and at peak activity, one of the two insect growth regulators (IGRs), pyriproxyfen (Distance) or buprofezin (Talus) can be applied. The addition of 0.5 or 1% horticultural oil has been shown to improve coverage. The IGRs will prevent the crawlers or early instar stage from developing into the next instar stage, resulting in death of the insect. IGRs are slow acting so be patient. Two to three applications may be necessary. Read and follow the label directions of pesticides carefully.

References Johnson, Warren J., and H.H. Lyon. 1991. Insects that Feed on Trees and Shrubs – Second Edition, Cornell University Press Miller, Douglass R., and J.A. Davidson. 2005. Armored Pests of Trees and Shrubs. Cornell University Press Miller, Douglass R., G.L. Miller, G.S. Hodges, and J.A. Davidson. 2005. Introduced Scale Insects (: Coccoidea) of the U.S. and their Impact on U.S. Agriculture. Proc. Entomol. Soc. Wash. 107 (1): 123-158. Stimmel. J. F. Seasonal distribution of Carulaspis minima (Targ-Toss) in Pennsylvania. Proceedings of Entomological Society of America, Washington, 81:222-229

Authors: Stanton Gill ([email protected]) and Paula Shrewsbury ([email protected]) University of Maryland Extension, and Debby Smith-Fiola, Landscape Enterprises, LLC

The information given herein is supplied with the understanding that no discrimination is intended and no endorsement by University of Maryland Extension is implied. Read labels carefully.