Scale Insects

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22. Scale insects constitute a very large group of unusual plant feeding insects. This group is commonly divided into soft scales and armored scales.

23. Wingless and legless adult scales spend their lives pressed against their hosts under tiny, protective shells. Soft scale insects have a waxy film secreted over their body wall, while armored scales are well protected beneath a separate cover secreted over their bodies.

24. Female scale insects lay their eggs under their bodies or scale covers. When they first hatch, young scales have legs and are quite active. At this stage, they are called crawlers. Crawlers disperse, locate new feeding sites, and then transform into immobile adults.

25. Because of their waxy coating or cover, adult scales are will protected from most insecticides. Control measures should be timed to coincide with the hatching of unprotected mobile crawlers. This is oak lecanium scale, showing dead females on the twig and settled crawlers on the leaf. It has only one generation per year, and crawlers are active during late spring or early summer.

26. Magnolia scale, the largest scale insect in the United States, is up to 1/2 inch across. Crawlers of this species are active in September. Dormant oil sprays which are applied in late spring before leaves begin to open are effective against the overwintering immature females, as well as other species of scales.

27. Many kinds of houseplants are susceptible to scale insect pests. This is hemispherical scale. Because of the constant indoor environment, generations overlap and all stages may be present simultaneously. An adult female and several settled crawlers are visible in this picture.

28. This cycad is heavily infested with hemispherical scale. Like aphids, scales produce honeydew. A clear, sticky coating on the leaves is sometimes more noticeable than the scales themselves.

29. Wax scale is an easily recognized pest of azalea, camellia, Chinese holly, and many other ornamental plants. In Virginia, wax scale has been reported only from the Piedmont and Coastal regions of the state.

30. Arborvitae and yew can be seriously weakened by outbreaks of Fletcher scale. Due to premature needle drop, infested plants become thin and a crust of sooty mold covers twigs and remaining needles.

31. One group of soft scales lays its eggs under a covering of white cotton-like material. These are the cottony scales. While the young scales are small, brown, and difficult to see, their egg sacs are large, white, and conspicuous. Appearance of these cottony egg sacs in late spring indicates that the crawlers will be hatching soon, and control measures, should they be necessary, need to be undertaken in the next few weeks. Cottony maple scale can be found most frequently on the twigs and small branches of maple, box elder, dogwood, oak, and occasionally on a few other common shade trees. A similar species, the cottony maple leaf scale, can be found on the leaves of some of the same hosts.

32. Cottony camellia scale is also known as cottony taxus scale because it is a serious pest on taxus as well as camellia and holly. Rhododendron, hydrangea, and English ivy are less frequently attacked.

33. Armored scales are generally smaller than soft scales, but they sometimes occur in tremendous numbers, and they can seriously weaken or even kill their host plants. Enonymus scale has two to three generations per year and can build up until whole plants are covered by scales. Control of heavy infestations requires repeated insecticidal sprays timed to coincide with the crawler stage of each generation.

34. Male and female enonymus scales are so different in appearance that they are often mistaken for different species. The pear shaped, dark grey scales in the previous picture were females; the males are small, narrow, and white and occur primarily on the leaves.

35. Juniper plants which have lost their normal healthy green color are often infested with juniper scale. Upon close inspection, numerous white scale covers with yellow-brown centers can be seen on the foliage. Heavily infested branches yellow and eventually die.

36. Few scales are as insidious or as destructive as the obscure scale. Primarily found on oaks, this pest causes dieback of branches, limbs, and sometimes entire trees. Inexperienced observers often mistake these scales for flakes of bark even at close range. The name obscure scale fits perfectly since the insects blend in so well with the background on which they settle.

37. Not all scales are as difficult to detect. Ornamental pines, especially mugho and Scots pine, are attacked by a white scale which may nearly cover the needles. Feeding by pine needle scale causes needles to yellow and drop prematurely. Infested trees become sparse and sickly looking.

38. Pine needle scale overwinters as eggs beneath the female s shell and has two generations per year in Virginia. Once again, control measures must be properly timed to coincide with hatch of the crawlers.

39. White peach scale is another serious pest of ornamental trees and shrubs. This insect has three generations a year. Trunks and branches of flowering cherry, privet, lilac, dogwood, and many other hosts can become thoroughly encrusted with this scale.

40. Female white peach scales resemble miniature fried eggs. . .

41. . . . while males are elongate and snowy white.

42. It is easy to see why this insect is called the oystershell scale. Lilac, willow, apple, and dogwood are among over 100 plants known to be hosts of this pest. Should you discover a problem with this or any other scale insect, your county agent can help with proper identification and control recommendations.

Return to Insects that Feed by Sucking Plant Juices

	22. Scale insects constitute a very large group of unusual plant feeding insects. This group is commonly divided into soft scales and armored scales.
	23. Wingless and legless adult scales spend their lives pressed against their hosts under tiny, protective shells. Soft scale insects have a waxy film secreted over their body wall, while armored scales are well protected beneath a separate cover secreted over their bodies.
	24. Female scale insects lay their eggs under their bodies or scale covers. When they first hatch, young scales have legs and are quite active. At this stage, they are called crawlers. Crawlers disperse, locate new feeding sites, and then transform into immobile adults.
	25. Because of their waxy coating or cover, adult scales are will protected from most insecticides. Control measures should be timed to coincide with the hatching of unprotected mobile crawlers. This is oak lecanium scale, showing dead females on the twig and settled crawlers on the leaf. It has only one generation per year, and crawlers are active during late spring or early summer.
	26. Magnolia scale, the largest scale insect in the United States, is up to 1/2 inch across. Crawlers of this species are active in September. Dormant oil sprays which are applied in late spring before leaves begin to open are effective against the overwintering immature females, as well as other species of scales.
	27. Many kinds of houseplants are susceptible to scale insect pests. This is hemispherical scale. Because of the constant indoor environment, generations overlap and all stages may be present simultaneously. An adult female and several settled crawlers are visible in this picture.
	28. This cycad is heavily infested with hemispherical scale. Like aphids, scales produce honeydew. A clear, sticky coating on the leaves is sometimes more noticeable than the scales themselves.
	29. Wax scale is an easily recognized pest of azalea, camellia, Chinese holly, and many other ornamental plants. In Virginia, wax scale has been reported only from the Piedmont and Coastal regions of the state.
	30. Arborvitae and yew can be seriously weakened by outbreaks of Fletcher scale. Due to premature needle drop, infested plants become thin and a crust of sooty mold covers twigs and remaining needles.
	31. One group of soft scales lays its eggs under a covering of white cotton-like material. These are the cottony scales. While the young scales are small, brown, and difficult to see, their egg sacs are large, white, and conspicuous. Appearance of these cottony egg sacs in late spring indicates that the crawlers will be hatching soon, and control measures, should they be necessary, need to be undertaken in the next few weeks. Cottony maple scale can be found most frequently on the twigs and small branches of maple, box elder, dogwood, oak, and occasionally on a few other common shade trees. A similar species, the cottony maple leaf scale, can be found on the leaves of some of the same hosts.
	32. Cottony camellia scale is also known as cottony taxus scale because it is a serious pest on taxus as well as camellia and holly. Rhododendron, hydrangea, and English ivy are less frequently attacked.
	33. Armored scales are generally smaller than soft scales, but they sometimes occur in tremendous numbers, and they can seriously weaken or even kill their host plants. Enonymus scale has two to three generations per year and can build up until whole plants are covered by scales. Control of heavy infestations requires repeated insecticidal sprays timed to coincide with the crawler stage of each generation.
	34. Male and female enonymus scales are so different in appearance that they are often mistaken for different species. The pear shaped, dark grey scales in the previous picture were females; the males are small, narrow, and white and occur primarily on the leaves.
	35. Juniper plants which have lost their normal healthy green color are often infested with juniper scale. Upon close inspection, numerous white scale covers with yellow-brown centers can be seen on the foliage. Heavily infested branches yellow and eventually die.
	36. Few scales are as insidious or as destructive as the obscure scale. Primarily found on oaks, this pest causes dieback of branches, limbs, and sometimes entire trees. Inexperienced observers often mistake these scales for flakes of bark even at close range. The name obscure scale fits perfectly since the insects blend in so well with the background on which they settle.
	37. Not all scales are as difficult to detect. Ornamental pines, especially mugho and Scots pine, are attacked by a white scale which may nearly cover the needles. Feeding by pine needle scale causes needles to yellow and drop prematurely. Infested trees become sparse and sickly looking.
	38. Pine needle scale overwinters as eggs beneath the female s shell and has two generations per year in Virginia. Once again, control measures must be properly timed to coincide with hatch of the crawlers.
	39. White peach scale is another serious pest of ornamental trees and shrubs. This insect has three generations a year. Trunks and branches of flowering cherry, privet, lilac, dogwood, and many other hosts can become thoroughly encrusted with this scale.
	40. Female white peach scales resemble miniature fried eggs. . .
	41. . . . while males are elongate and snowy white.
	42. It is easy to see why this insect is called the oystershell scale. Lilac, willow, apple, and dogwood are among over 100 plants known to be hosts of this pest. Should you discover a problem with this or any other scale insect, your county agent can help with proper identification and control recommendations.