Mealy Bugs and Scales
Mealy Bugs and Scales are very similar insects. They are all considered to be pests that can cause severe damage to plants and agriculture. Below are description of
mealy bugs and scales, including their life cycle, feeding habits and interesting facts.
Mealy Bugs Scales
Differences between Mealy Bugs, Scales and White flies:
Mealy Bugs, Scales and White flies are similar insects but have distinctive differences.
Mealybugs appear in cottony blobs found in the nooks and crevices of plants.
Scales and White flies will fly around a persons nose and eyes; they both live in soils that are kept moist and soggy.
Adult mealy bugs vary in appearance between males and females. Females are wingless, oval, flattened and are covered in white wax hairs. Males are tiny gnat like insects that change to a “wasp like” appearance as adults. Males are short lived,
do not feed as adults and their only purpose as an adult is to fertilize the female eggs.
Female mealy bugs produce between 50 to 100 eggs. They are covered in a waxy layer for protection. Some female species
do not lay eggs, but give birth to nymphs that can already crawl. Nymphs have body parts out of proportion with each other, and
do not have fully developed wings. Upon hatching from their eggs, “crawlers” move to search for feeding sites in sheltered areas. Both nymphs and crawlers go through five molts before becoming an adult. Males in the last molting stage, pupate in a silk cocoon, emerge as a winged adult and fly in search of a female
to whom they can mate.
Mealy bugs have straw-like mouthparts called stylets that they insert into the plant to remove fluids. They feed on the plant juices of greenhouse plants, house plants and subtropical trees.
Plants that are the most susceptible to mealy bugs are citrus trees, sugar cane, grapes, pineapple, coffee trees, fern and orchids.
Sucking the juices from the plant weakens the plant and causes the leaves drop. Severe infestations look like patches of cotton on the plant. During the feeding process, they excrete lots of wax (known as honeydew) and if left on the plant can lead to the growth of sooty mold.
Ants are attracted to the wax that is secreted and in the process of consuming the
wax, they protect the mealy bug from predators and parasites. The mealy bugs main predator are
ladybugs. Mealy bugs can be transported by people and pets. They can also crawl from an infected plant to a non-infected plant.
Mealy Bugs were discovered in the Caribbean in 1994 while the scale was discovered in south America in 1998.
Both species have spread throughout the United States.
The USDA found 3 wasps to help control mealy bugs and scales.
One is 1/32 inches long yellow wasp. Genus: Acerophagus. They attack young mealy bug nymphs and lay an egg in each.
The second is part of the Genus of aangyrus and is 1/8th inch long yellow and brownish black markings on its antenna. They attack larger nymphs and adult mealy bugs and lay an egg in each.
The third is 1/16th inch long black wasp and part of Genus: Apoanagyrus. They attack larger nymphs after 3-5 days. The eggs that are implanted cause the mealy bug to mummify and blow up like a cigar, killing
Slow moving, Scales are hard shelled pests that look like a small raised bump or a small flat brown disc on a plant stem. Its shell often protects the babies underneath. They are small insects with sucking mouthparts that are brown, white and black. There are several different species of scales.
Types of Scales
Pine Needle Scale Pine Tortoise Scale
Spruce Bud Scale Oystershell Scale
Scurfy Scale Cottony
Maple Scale European Elm Scale
Pine Needle Scale
The pine needle scale is white, oyster shaped and covered in wax. Males are often smaller than females but both have a yellowish spot on one end. Female adults are wingless while males grow wings and mates with the female before dying. Eggs and newly hatched crawlers are bright red changing to pale yellow then tan as they molt. There are often forty eggs beneath scales hard covering. Nymphs insert their mouth parts into the needles of the pine to feed.
The pine needle scale attacks the Mugo pine, the Scotch pine, the Austrian pine, the Red pine, the Eastern white pine, spruce trees, the Douglas fir tree and cedars. Damage they cause turns pine needles a yellowish brown color and often heavy infestations can cause a frosted appearance and twigs and branches to die. These types of scales are spread by the wind and by birds and mammals when they touch the infested tree branches.
Pine Tortoise Scale
The pine tortoise scales gets its name from the appearance of the adult females who look like tiny tortoises.
They are found on one and two year old shoots of the Scots pine, the Jack pine and the Austrian pine. Females lay about 500 eggs beneath her body and nymphs emerge from late June to July. Adult males often die after mating. Like scales, they secrete waxy honeydew.
Spruce Bud Scale
The Spruce Bud Scale attacks mainly the Norway spruce, but will attack other spruces. The scales are found at the base of new shoots in groups of eight. Because of their size and color, they are often mistaken for buds. Adults are round and reddish brown and produce one generation per year. They over winter on the underside of needles and in the spring they move to twigs to feed.
The Oystershell Scale attacks many woody plants including ash trees, cotoneasters, dogwoods, lilacs, poplars and willows. Adults over winter on bark of the trees. They are 1/8 inch long and brown or gray and in the general shape of an oyster shell. Old scales stay attached to the trees for several years before falling off. Adults produce two generations per year. Crawlers and nymphs are smaller than a pinhead and once attached to tree and feeding they are covered with a waxy film that protects them from most insecticides.
The Scurfy Scale is pear shaped flat and whitish gray color. They attack apple trees, Mountain Ash trees and crabapple trees. Young over winter beneath the dead mother scale and begin appearing in June when they feed on leaves, branches and tree trunks. Nymphs mature in August, mate and begin laying their eggs to prepare for winter.
Cottony Maple Scale
The Cottony Maple Scale is recognized by the large cotton looking egg sack that protrudes from the adult females rear body. Adults have a pale to dark brown body that is soft. Heavy infestations produce sooty black mold, foliage drop and cause twigs and branches to dieback. The young over winters on twigs until spring, when the egg sack appears. Crawlers emerge from June to July and feed under leaves. Adults mate and the females move back to twigs to prepare for winter.
The cottony maple scale attacks maples, honey locust trees, linden and other hardwoods.
European Elm Scale
The European Elm Scale has an oval body with a reddish color surrounded by a waxy fringe. When crushed, a blood like red liquid appears.
They attack elm trees, hence its name. Infestations cause stunted growth, foliage drop and branch dieback.
Sooty mold growth on the tops of branches gives the tree a black appearance. Adults over winter on bark of elm trees in cracks and crevices. They mate in May and crawlers emerge in June to feed on leaves through the summer when they migrate to branches before the trees leaves drop in the fall.
Our thanks to Lani Powell for research and writing which made this mealy bug information page possible.
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