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Home , Coccidae, Coccus (insect), Coccus hesperidum, Diaspididae, Kermesidae, Kermes (insect)

Scale & Their Relatives

O & T Guide [O-#07]

Carol A. Sutherland Extension and State Entomologist

Cooperative Extension Service z College of Agriculture and Home Economics z October 2006

For most of their lives, scale insects look like Legs are usually present and the antennae may anything other than insects. Some are fairly either be missing or much reduced. Males may flat while others are raised and wart-like; some be winged or wingless. Brown soft scale, are well camouflaged on their hosts while hesperidium, is usually the most others are extremely obvious. are common soft scale of greenhouse and covered with dusty or mealy filaments of wax interior landscape plants in New Mexico. secreted by glands in their integument. The corni, the European fruit life cycles of some scales and their relatives lecanium, and its relatives are reddish-brown are complex, others are fairly simple and a few to black, crusty and hemispherical with a are still poorly known. Damage potential diameter about the size of a pencil eraser; it varies considerably by . attacks twigs on a variety of fruit, nut and shade trees. Cottony maple scale, Scientifically: According to a recent innumerabilis, is a fairly large (about ¼ inch taxonomic reorganization, these insects belong long) reddish-brown scale whose eggs are laid to the Order , Superfamily on maple twigs in a large, cottony mass that Coccoidea. protrudes from the end of the scale.

Metamorphosis: Simple With over 300 species known in the U.S., the Mouth Parts: Piercing-sucking family of armored scales () is the Pest Stages: Crawlers, nymphs, female adults largest family of scales, containing some very of some species important pest species. Females are very small and soft-bodied and are concealed under a Life Cycle: Egg (may be retained in some scale covering that is usually free from the species that give live birth)Æseries of Nymphs body of the underneath. The scale of which only the first may be mobile (the covering is formed by a combination of wax “crawler”)ÆAdult. Females are immobile in secreted by the insect plus old cast skins and some species but mobile in others; males, if excretions. Female armored scales lack eyes known, usually have one pair of wings. Most and legs and the antennae are absent or much are very small and very weak fliers, remaining reduced. Depending upon species, these scales close to their host plant. may be circular or elongate, smooth or rough, and colored variously. Male scales usually Soft scales (Family ) include the wax have covers that are smaller and more and tortoise scales among others. Females in elongated than those of females. Adult male this group are elongate-oval and generally armored scales are winged (only one pair of about 1/8 inch long, occasionally more, wings) and have well-developed legs and depending upon species. They are usually antennae. Reproduction may be with two convex but sometimes flattened with a hard, sexes or parthenogenetic (i.e. females lay their smooth integument or a covering of soft wax. eggs without fertilization from males). Some O & T Guide [O-#07] – page 2 species lay eggs under their scales. Others hard or tough scale covers and resemble small give birth to live young. The first instar young, galls. or crawlers, are active insects that may crawl some distance before they find a suitable site Dactylopid Scales or Insects to settle and begin feeding. Crawlers may also (Dactylopidae) are pests of Opuntia cacti, be dispersed on the wind or even the feet of especially the pad types. Scale colonies are birds landing on infested plants. Once the covered by a dense mat of sticky white wax. crawlers have settled and inserted their long The actual scales are minute, dark purplish red stylets into the host, they start to lose many of insects that are broadly oval in form and their insect attributes with succeeding molts. distinctly segmented. Females remain in one spot for the rest of their lives; males emerge, fly around their host Pinyon Needle Scales () are looking for females and die soon after mating. common pests of New Mexico pinyon, both in forests and cultivated settings. Affected plants • , may have rather thin foliage clumped near the perniciosus, probably an import from ends of twigs. Closer examination of the tree, Asia in the late 1800s, is an important especially in the fall, reveals numerous tiny pest of orchard and shade trees, as black “beans” adhering loosely to the needles. well as numerous shrubs. It is minute In late winter, yellowish, mobile females and volcano-shaped; females give live emerge from these “beans” and begin crawling birth to crawlers. down the branches and trunk towards the bases of their host plants. They are soon joined • Oystershell scale, ulmi, by gnat-like winged males of the species that is brown and shaped and textured like have emerged from some of the other “beans.” its namesake. Infesting many varieties After mating, the females lay their eggs into of orchard and shade trees, it can be masses of filamentous waxy material that they lethal to aspens in New Mexico. also produce around the bases of host trees. Females lay their overwintering eggs The crawlers soon hatch and begin the return under their scales. trip up the host tree where they settle to feed for the rest of their nymphal lives on the new • Euonymus scale, euonymi, growth needles. One generation occurs attacks and often kills its host in New annually. Mexico. These scales are easily overlooked initially; the actual scales Mealybugs () are so named from are tan and minute but the fluted waxy the mealy or waxy white secretions that cover extensions produced by the females the bodies of these insects both as immatures eventually give them away. and adults. Females of most species have elongate-oval, segmented bodies with • Pine needle scale, functional legs. Some species lay eggs while pinifoliae, is an elongated, waxy white others give birth to live young. The egg- scale often found on pine foliage and producers cover their clutches in loose sometimes other conifers. Although filaments of sticky white wax. Various life common on some pines in some areas, stages of mealybugs may be found on virtually these usually are heavily parasitized any part of their host plants. Several important and are minor pests of pine needles. pest species are common in New Mexico including: Kermid or Gall-like Scales () are most commonly seen on twigs or leaves of • , citri, in New Mexico. Females in this small and and long-tailed mealybug, poorly known family are rounded, often with longispinus, are both O & T Guide [O-#07] – page 3

significant pests of greenhouse and only populations. Where males are known, interiorscape plants. they often lack mouthparts and have only one • obscure mealybug, Pseudococcus pair of wings; males are minute and very poor affinis, is a widespread pest of both fliers. woody and herbaceous plants. Habitat and Hosts: Scale insects and their relatives are well adapted to parasitize their Descriptions of Life Stages: host plants. Most are very well camouflaged; their small size, particularly as crawlers, Eggs: Eggs are usually minute, white, yellow, permits them to squeeze into a variety of pink or pale orange for most species. Eggs are places on their hosts, many of which would found under the female scale in armored scales not be readily visible, let alone accessible to or in waxy coverings exuded by females of topical treatments. Some, especially other members of this diverse group of insects. the mealybugs, can occur almost anywhere on Other species retain their eggs and give live the exterior of their hosts, including below- birth to crawlers. ground plant parts. The kermid scales are the least known biologically and taxonomically of Nymphs: The first instar is called a “crawler” all of the scale insects and relatives for most insects in this diverse group. Most mentioned. Many species of soft and armored crawlers are barely visible to the naked eye, scales as well as mealybugs have extremely segmented, with short antennae, small eyes broad host ranges, despite their common and three pairs of legs. Their mouthparts are names. visible but are not used in the crawler stage. Upon settling down on an acceptable site on Damage: Many species of soft and armored the host, the crawler inserts its filamentous scales produce large amounts of honeydew. feeding stylets into host leaves or stems and , bees, and flies can be attracted to begins to feed on sap. Shortly afterward, it honeydew deposits. In humid conditions, molts and begins to lose its insect attributes honeydew becomes a substrate for growth of with successive molts. Immature mealybugs black, sooty mold on foliage. In addition to remain mobile for the duration of their lives; being unsightly, foliage covered by sooty they also produce powdery or waxy filaments mold often falls from the plant, diminishing from glands in their integument. Male armored food production by the plant and stressing it to scales usually have smaller, narrower scale produce regrowth. Usually feeding on the coverings than females of their species undersides of leaves, small twigs or branches, scale insects can cause yellowing of foliage, Adult: Adult mealybugs look like larger leaf drop and twig die-back. Sap loss causes versions of their nymphs, only they are able to some of these problems while salivary reproduce. Any “tails” on the end of the enzymes produced by these feeding pests abdomen or filaments on the sides of the body contribute to tissue damage and growth are likely to consist only of wax that is easily irregularities. Some, such as San Jose scale, damaged; also, this wax will dissolve in can infest developing fruit, causing irregular alcohol if the insect is collected for ripening and hardening the flesh under the identification, leaving the bare bodies of the skin. Armored scales feed mainly on perennial insects. Similarly, the wax of cochineal insects shrubs and trees. Large populations can will dissolve in alcohol, leaving only the dark encrust twigs or branches, severely weakening red bodies of the females and nymphs. Of the or killing their host plants. Many species of scale insects, soft scales have their bodies scale insects and their relatives are firmly attached to their scales while armored economically important pests of greenhouse scales have a generally loose attachment and nursery crops, interiorscape plants, shrubs between the soft body and scale covering. and a variety of native and imported tree Some of these insects are known from female- species. O & T Guide [O-#07] – page 4

used as landscape ornamentals. Kermid scales Kermid scales produce the often noticeable and likewise are native to the Southwest. and objectionable pea-sized, woody galls on Although they rarely kill their hosts, kermid oak twigs. Progressive twig die-back is scales can damage the appearance of specimen common with these infestations. Most species landscape oak trees. and details of their life cycles are poorly known. Environmental stresses and some growing practices may favor infestations and outbreaks Cochineal insects produce very obvious white, of scale insects and their relatives. Scales can cottony colonies that detract from the infest cuttings or recently received plant stock. appearance of their “prickly-pear cacti” host Crawlers may move to uninfested hosts plants. Left alone, these pests weaken the directly, particularly when plants are crowded. pads, progressively killing the plant. Alternatively, natural wind currents or greenhouse blowers can disperse crawlers Pinyon needle scales also can progressively from one growing area to another. Constant weaken their pinyon hosts to the point that the scouting of new and older plants is required, only needles on the branches are at the very as is fast action to minimize damage. ends and these are densely covered with the black “beans” of the developing pests. The Many species of damaging scale insects are late winter-early spring congregation of adult not native to New Mexico or the U.S. and pinyon needle scales at the base of the plant or have arrived here without their natural in crotches of limbs is unsightly. Large enemies. Whether or not effective natural populations of these pests can kill pinyon trees enemies could be identified in the homelands unless treated; they also can stress their hosts, of these pests, safely imported by regulatory making them more susceptible to infestation authorities and adequately established in this by other pests, particularly bark . area to control these exotic pests is beyond the scope of this handout; in many cases, these Mealybugs are extremely difficult pests to projects are probably too costly to investigate control. Easily transmitted to other hosts by or implement. physical contact and overcrowded growing conditions, the pests can be very difficult to Where some biological control agents do help find because of their invasive nature, secretive curb populations of various scale insects, habits and camouflage. They can feed on certain or treatment frequencies almost any live part of the plant where the may foster scale pest outbreaks because they bark or external covering is thin enough to eliminate the effective natural enemies better allow penetration of the mouthparts. Eggs may than they do the pests. Producers and plant be hidden in the axils of leaves, crevices of managers should be aware of these risks and branches, rough bark, surface roots or choose appropriate treatments wisely. concealing plant parts. In addition they are covered with thick coats of protective wax For many infestations of scale insects and their which resists wetting. relatives, insecticides may work poorly because of poor timing or because the non- IPM Notes: The insects presented in this fact living coverings on the pests protect them sheet often are serious pests of various from applied toxins. The timing issue is best ornamental plants for different reasons. addressed by scouting for crawlers, a susceptible and unprotected life stage. Use a Cochineal insects and their Opuntia sheet of white typing or copy paper and a hosts are both native to New Mexico and the small hand tool like a trowel, short tool Southwest; despite their long relationship with handle, tree branch or similar object. Holding each other, the insects can disfigure and kill the paper under a potentially infested host their hosts, situations not acceptable for cacti branch, hit the branch sharply several times; O & T Guide [O-#07] – page 5 watch for small particles landing on the paper to start moving. These are likely to be the crawlers. applications made when crawlers are active can significantly reduce pest populations and improve plant health; they can break the cycle of damage before a new generation infests host plants. Even better results may come from treatments with labeled systemic insecticides. These products can kill crawlers and young nymphs by ingestion, regardless of where the pests may be hiding and regardless of application methods that Cottony maple scale, Pulvinaria may result in less than complete and thorough innumerabilis, on maple twig. Photo: Southern coverage. Forest Insect Work Conference Archives, Southern Forest Insect Work Conference, www.forestryimages.org

Brown soft scale, , adults and nymphs. Photo: Whitney Cranshaw, Colorado Close-up of San Jose scale, Quadraspidiotus State University, www.forestryimages.org perniciosus, on an apple. Photo: Biologische Bundesanstalt Archives, Germany, www.forestryimages.org

European fruit lecanium, Parthenolecanium Close-up of oystershell scale, Lepidosaphes corni, on oak. Photo: Haruta Ovidiu, University ulmi. Photo: USDA Forest Service - Rocky of Oradea, www.forestryimages.org Mountain Region Archives, USDA Forest Service, www.forestryimages.org

O & T Guide [O-#07] – page 6

Close-up of euonymus scale, Unaspis scale, Kermes sp., on white oak. euonymi, on euonymus. Photo: Lisa Ames, Photo: James Solomon, USDA Forest Service, UGA, www.forestryimages.org www.forestryimages.org.

Close-up of the overwintering stage (“black Cochineal scale or Dactylopid scale, bean”) of pinyon needle scale, Matsucoccus Dactylopus confusus, on a pricklypear cactus acalyptus. pad. Photo: USDA Forest Service - Ogden Archives, USDA Forest Service, www.forestryimages.org

Pinyon needle scale, Matsucoccus acalyptus, on pinyon. Note the “black bean” stages on the older, brown foliage. Photo: Whitney Cranshaw, Colorado State University, Close-up of a long-tailed mealybug, www.forestryimages.org . Photo: David Cappaert, , www.forestryimages.org New Mexico State University is an equal opportunity/affirmative action employer and educator. NMSU and the U.S. Department of Agriculture cooperating.

October 2006 Las Cruces, NM O & T Guide [O-#07] – page 7