The female cicada lays eggs in twigs. To do this, she uses her ovipositor to cut or saw into the twig. This weakens the twig and may cause the twig to break and die. The dead twig with reddish brown leaves hanging in the tree creates a symptom called 'flagging'. She will oviposit in many species but flagging will be common on oaks, maples, hickory, dogwood, fruit trees, sweetgum, black walnut, ash and other species. The female cicada is present in late May and early June with the 'flagging' symptom present from June to August (Table 1). You will also know they are present by the singing of the male cicada, which is more of a problem to some people than the ‘flagging’ of the trees. The ‘flagging’ to large trees is not a serious setback. It just makes the trees unsightly. However to smaller trees and seedlings in plantations, the ‘flagging’ can be a serious problem to the form of the smaller trees and to the life of seedlings. Hardwood plantations, especially black walnut and oaks, from 1 to 5 years in the field may have the most damage. One or two year old plantings and trees planted this spring may have trees killed by the cicada. These plantings need to be inspected starting in mid May for the cicada's presence. Another way to check for cicada presence is to dig the soil and look for the nymphs. Consulting foresters and landowners may observe the nymphs in the soil when planting trees this spring. The nymphs look like the adult but do not have wings. If you find a large number of nymphs per soil sample, then expect damage. Besides their egg laying, cicadas do not pose any direct threat to humans. They do not bite or sting, nor are they known to contain any toxic chemicals. The chief concern is their noise, and the novelty of the sheer numbers of cicadas.

There are many natural enemies of cicadas. Birds and squirrels will feast on cicadas during a mass emergence. You may also observe more cicada killer wasps. However, the large numbers of cicadas are likely to outstrip the capacity of these natural enemies to control the problem.

Cultural Control

Planting trees in areas or having young plantations where cicadas emerged 17 years ago may put them especially at risk during this outbreak. For young plantations, delay pruning until the cicadas have disappeared. The injured branches can then be removed and corrective pruning done after cicadas have stopped ovipositing. For seedlings, monitor the field during May and June for emergence. If emergence is low, use corrective pruning on the seedlings. If emergence is high consider use of a protective pesticide followed by corrective pruning.  For small ornamental trees and shrubs, covering them with cheesecloth or mosquito netting can protect them while cicadas are present.

Chemical Control

Use the following as a guide to make the decision to spray. If the trees are grafted trees such as black walnut planted within the past 3 to 5 years, spraying is recommended to prevent the loss of the grafted top. For hardwoods planted within the past 3 to 5 years, spraying should be considered if you wish to maintain the terminal and not lose dominance. This is more important for black walnut than other hardwood species. As a general rule, the taller the tree the less need to protect the terminal as the tree will reestablish dominance and perhaps has already formed the first log. For seedlings planted in 2003, the primary damage will be dieback. Seedling mortality will not likely happen, however, seedlings may die back to the root collar and resprout. Seedlings planted in 2004 in or near forested areas could more likely die due to the combination of cicada damage and transplant shock. But be sure to monitor your fields for emergence tubes and your trees for egg laying activity to determine the need to spray. Sprays will need to be applied starting the last week of May in the southernmost counties. Probably, two sprays 5-7 days apart will give adequate protection; but a third spray may be needed. Table 1 will help guide you on spray timing. Don’t wait for dead twigs to start spraying. And, if protective sprays are used, some corrective pruning will also have to be done, as the sprays will not give 100% protection.

Permethrin (Eight or Spectracide Bugstop), or cyfluthrin (Bayer Advanced) are general use pesticides for fruit and ornamentals that could be used by homeowners and commercial producers in accordance with the label. Sevin (Carbaryl) can also be used. Information presented in this article is taken in part from the Purdue University Extension Document E-47-W, Periodical Cicada in Indiana, by Dr. Clifford S. Sadof, Extension Entomologist. You may obtain a copy of this publication by visiting the website - http://www.entm.purdue.edu/Entomology/ext/targets/eseries/Eseries PDF/E-47.pdf.