Order: Diptera
Family: Agromyzidae
Scientific Name: Phytomyza ilicicola
Description.. Leafminers are small, usually dark, flies. These flies are fairly similar and are more easily recognized by their host plant and the damage to the host plant than by the insect itself.
Biology. Holly leafminers make serpentine mines in the leaves of hollies. The maggots pupate at the large end of the tunnel and the adult fly emerges from a hole in the pupal skin and the upper leaf surface. Each species of holly has its own leafminer species. Deciduous holly leafminers have several generations per year, whereas the leafminers of evergreen hollies have only one generation per year. Leafminer maggots have parasites that often decimate the leafminer population.
Control. Because leafminers are plagued by parasites, it may be better to rely on parasites to suppress leafminers than to apply pesticides that might eliminate the parasites and necessitate an ongoing spray program.
If the leafminers appear to be getting out of hand--realizing that the adults emerge in the spring to lay eggs in new leaves in early April--some infested leaves can be placed in a dry plastic bag and placed in the shade. When the small, dark flies are found in the bag, that is the perfect time to spray. If a pesticide application is deemed necessary, timing of pesticide application is important for optimum suppression.
Because leafminers are usually protected by both the top and bottom leaf surfaces, systemic pesticides (pesticides absorbed and translocated by the plant) should be given consideration for control. The foliage of susceptible plants should be observed for early signs of an infestation (tunnelling present). The North Carolina Agricultural Chemicals Manual should be consulted for the most current labeled chemicals.
INDIAN WAX
SCALE
Photo courtesy of Dr. Jim Baker, North Carolina State
University
Description. Indian wax scale insects are brownish-purple females with microscopic legs and a thick covering of sticky, white wax. There are no males.
Ovoid and pale purple, the eggs resemble pollen when shaken onto a white surface. The eggs are found under adult scales. Crawlers are flat and tiny. In a mass, newly hatched crawlers appear rusty red. After molting, each scale secretes wax tufts, forming a star. This is called the star stage. Larger nymphs secrete wax tufts that merge to resemble a cameo pin. This is the cameo stage.
Biology. The Indian wax scale is found from Florida to Virginia and Maryland. Indian wax scales have been reported on azalea, blueberry, camellia, Chinese elm, citrus, fig, eugenia, gumbo-limbo, Chinese holly, yaupon, jasmine, mulberry, pear, persimmon, plum, quince, sabodilla, turkscap, and other plants.
A severe infestation of Indian wax scale detracts from the host plant's appearance because of the many white scales and the copious honey-dew that they secrete. A black fungus called sooty mold which grows in the honeydew further disfigures the host plant.
Indian wax scales begin to lay eggs in March, each scale laying from 1,200 to 2,000 eggs. By late May, tiny crawlers hatch and move about, searching for a place to feed. Feeding occurs mostly along the twigs. Occasionally wax scales settle along the leaf midribs. Once the crawlers insert their sucking mouthparts into the host plant, they do not change locations again. The crawlers then secrete the waxy covering from which the name is derived. The young Indian wax scales mature throughout the summer, producing a thicker waxy covering and becoming increasingly tolerant to pesticides. They overwinter as adults.
Control. Handpicking scales in winter (if practical) is an effective control measure. Since they may lay their eggs apart from their host plant, the scales should be destroyed after removal. The Indian wax scales seems to be one of the most difficult ornamental plant pests to control during much of the year. However, the crawlers are extremely susceptible to pesticides. Because there is only one generation per year, applying an appropriate pesticide to the crawler stage in early June will give virtually complete control.
SOUTHERN RED
MITE
Photo courtesy of Dr. Jim Baker, North Carolina State
University
Order: Prostigmata
Family: Tetranychidae
Scientific Name: Oligonychus illicis
Description. Southern Red Mites are cool-weather mites. They are dark red in color and when their legs are extended, are no larger than the period at the end of this sentence. Mite eggs are red or brown, round and a little flattened. They have a tiny hairlike "stripe" that sticks up in the center. Larvae are slightly larger than the eggs and have eight legs. Nymphs are similar to adults although some nymphs are smaller.
Biology. Southern red mites feed on the lower leaf surface, causing mesophyll collapse. Infested leaves turn gray or brown and may fall prematurely. Heavily infested shrubs may die.
Spider mites hatch from eggs and develop through a larval stage and nymphal stages before maturing into adults. Males mate with females as soon as the females molt into the adult stage and females soon begin laying eggs. Southern red mites overwinter as eggs glued to the lower leaf surface. If the winter is mild, all stages of this mite may survive. As the weather moderates in late winter, southern red mites increase. Most of the feeding damage occurs in early spring.
When populations of predaceous insects and mites are active in summer, southern red mites populations are greatly reduced and only the eggs survive in hot weather. If the summer is mild, all stages of this mite may survive. As temperatures cool in autumn, mite populations build up again.
Control. Because these mites are active in cool weather, infestations should be treated at the end of winter or summer. The North Carolina Agricultural Chemicals Manual should be consulted for current chemical recommendations.
TEA SCALE
Photo courtesy of Dr. Jim Baker, North Carolina State
University
Order: Homoptera
Family: Diaspididae
Scientific Name: Fiorinia theaeGreen
Description. The armor (test) of female tea scale insects is first flat and light yellow and later becomes hard and brown. The armor is shaped like an elongated oval or boat, and it is about 1/16 inch long, with the residue from the first molt attached at one end. Male armor is soft, white, and narrow with a ridge down the middle of the top.
Eggs are yellow and lemon shaped. Eggs are always found within the armor of the female scales.
The nymph is a flat, yellow "crawler" that has six tiny legs, and a pair of antennae.
Biology. In the Southeast, tea scale is a serious pest of camellias as well as Chinese and Japanese hollies. It has also been reported on bottlebrush, dogwood, ferns, euonymus, mango, Satsuma orange, tea plant, orchids, and yaupon.
Tea scales occur primarily on the undersides of leaves. The most conspicuous characteristic of an infested plant is yellow splotching on the upper leaf surfaces, the effect of feeding insects underneath. The whole plant may appear unhealthy, and the leaves may drop prematurely. The number of blooms decreases or cuttings may die before roots develop.
Each female deposits from 10 to 15 eggs under her armor. They hatch in 7 to 21 days, depending on the weather. The flat, yellow crawlers migrate to the newer growth on the plant and soon attach themselves. At first they secrete thin, pale tests. Males sometimes produce great quantities of white strands. When the population of nymphs is dense, the undersides of the leaves may be covered with this cottony secretion.
The nymphs molt 18 to 36 days after hatching, and a second molting occurs about a week later. From 41 to 65 days after hatching, female scales begin to lay eggs. The life cycle is usually completed in 60 to 70 days. Tea scale nymphs hatch throughout the year, although it is less frequent in cold than in warm weather. Because there are many overlapping broods, crawlers hatch continuously from February to November.
Control. Several spray mixtures are recommended for the control of tea scale. Sprays should be applied thoroughly to the undersides of leaves. The best time to spray is in the spring, after the plants have finished blooming and the danger of cold weather has passed. The North Carolina Agricultural Chemicals Manual should be consulted for current recommendations.
Return to Holly
Send comments, questions to WebManager at
webmail@ncsipm1.cropsci.ncsu.edu