Description and life cycle
Beginning about the third week in May, in areas where cicada are due to emerge and continuing into June, mature nymphs (young) dig themselves out of the ground in great numbers, crawl to the nearest tree trunk, shrub, or other vertical surface, and climb several inches up. The nymph’s skin then splits down the back, and the winged, sexually mature adult emerges. The adult is about 1.5 inches long, mostly black, with red eyes and other reddish markings. The wings are large and clear except for orange-red veins. Males are capable of producing an ear-splitting, high-pitched whine. Females, which produce no sound, are attracted to the males to mate.
A week to 10 days after the males begin “singing,” the females begin to lay eggs. Each female lays up to 400 eggs in 40 to 50 pockets in the wood of several small branches of many types of trees. More than 75 species of trees are known to be attacked. The type of branch preferred by the females is about the width of a pencil up to ½ inch in diameter or a little larger. To lay eggs a female slices into the wood of the branch with her egg-laying apparatus and places the egg into the wood. She usually lays one to several dozen eggs in a single branch before moving to another branch or tree. This egg-laying activity lasts approximately 30 days, and about 6 to 7 weeks later the eggs hatch into tiny white nymphs. The nymphs fall to the ground and burrow into the soil to feed on grass roots and, eventually, tree roots for the next 17 years. A numbering system established in 1893 to keep track of these broods is still used today.
||Adams, Cumberland, Franklin
||Berks, Bucks, Carbon, Chester, Dauphin, Delaware, Lancaster, Lebanon, Lehigh, Luzerne, Monroe, Montgomery, Northampton, Philadelphia, Pike, Schuylkill, Wyoming
||Fayette, Greene, Somerset, Washington, Westmoreland
||Bucks, Dauphin, Lancaster, Lehigh, Montgomery, Northampton, Philadelphia, Westmoreland
||Allegheny, Butler, Washington, Westmoreland
||Allegheny, Armstrong, Beaver, Butler, Cambria, Clarion, Crawford, Fayette, Forest, Huntingdon, Indiana, Lawrence, Mercer, Venango, Washington, Westmoreland
||Adams, Bedford, Berks, Blair, Bucks, Carbon, Chester, Clinton, Columbia, Cumberland, Dauphin, Delaware, Franklin, Fulton, Huntingdon, Juniata, Lackawanna, Lancaster, Lebanon, Lehigh, Luzerne, Lycoming, Mercer, Mifflin, Monroe, Montgomery, Montour, Northampton, Perry, Philadelphia, Schuylkill, Snyder, Somerset, Union, York
Cicadas damage fruit trees in two ways. The most obvious damage is done during the egg-laying process. The slits made by the female in small branches severely weaken them; often the weakened branches snap off in the wind. Under a heavy attack a majority of the branch tips may be killed. In larger trees, where most of the branches are larger than the preferred thickness for egg laying, the loss of even most of the branch tips may not severely damage the tree. However, in small trees 4 years old or less, most of the branches are of the preferred size. Under a heavy attack such a tree can be severely damaged and sometimes killed. Therefore, control measures should be concentrated on these small trees. Moreover, with the emphasis placed on early training and pruning of fruit trees, the loss of incipient scaffold limbs can affect the productivity of a tree for the rest of its life.
The second type of damage is less obvious. After entering the ground the nymphs eventually attach themselves to the roots of the fruit tree, insert their needlelike mouthparts into the roots, and feed on nutrients that would otherwise help the tree grow and produce fruit. Feeding by hundreds or even thousands of these insects on a tree root system for 17 years probably affects the tree productivity, although this has never been fully documented.
It is difficult to predict whether or not a particular orchard will be severely affected. The best strategy is to be alert for the first signs of male “singing” and to scout the orchards intensively a week later to look for egg-laying females. Considering the potential damage this insect can cause, a fruit grower can take several actions to minimize any detrimental effects.
Such actions include delaying planting to avoid cicada emergence and postponing until summer the winter pruning of trees less than 4 years old. Delayed pruning would decrease the probability of damage to incipient scaffold limbs and give the grower a chance to remove damaged wood after cicadas have finished laying eggs. Summer pruning and the removal of trimmings from the orchard, if done within the 4- to 6-week period after eggs are laid but before nymphs fall to the ground, would allow the grower to prevent many cicadas from feeding on tree roots for the next 17 years.
During the emergence period the most immediate problem is to protect trees (especially young trees) from damage caused by egg laying. There are two strategies to accomplish this objective, depending primarily on the size of the orchard. Trees in small orchards or backyards can be protected mechanically by enclosing them in netting or some other kind of cloth for the duration of the egg-laying period. This cloth should have a mesh size no larger than about ¼ inch. The netting should be placed on trees when the first male singing is heard and removed after adult activity has stopped. All branches less than ½ inch in diameter should be protected.
If netting is too expensive or too time-consuming, pesticide sprays may be used. There are several pesticide options. Pyrethroid insecticides, with quick knockdown, a fairly long residual action, and repellant properties, are recommended for young fruit trees. The frequency of applications will depend on egg-laying pressure. We recommend scouting the orchard every 2 or 3 days during the egg-laying period to check on the effectiveness of any insecticide applications that have been applied. If much egg-laying activity is apparent, another repeat application should be considered. Neonicotinoid insecticides should also provide adequate control of adult cicadas.
Remember that a constant vigil must be kept during an outbreak because cicadas can reinvade an orchard from adjacent woodlots. Be aware that pyrethroids can be disruptive to the Stethorus-mite balance in the orchard and will probably cause mite outbreaks later in the season. With small trees, however, this is usually manageable. In orchards with older trees pyrethroid use is not recommended because subsequent mite problems may be more costly than the cicada injury. We do not recommend using carbaryl because of its possible impact on thinning and mites. Specific chemical recommendations for home gardeners are in Fruit Production for the Home Gardener, and recommendations for commercial growers are in the Penn State Tree Fruit Production Guide.