Concerns about Periodical Cicada in 2021

For tree fruit growers, the largest concerns are not from the feeding of adults, but from female oviposition (egg-laying) damage as well as nymphal feeding on root systems.

The cicadas (Magicicada septemdecim) will begin to emerge from the ground in large numbers in about the third week of May and continue to emerge until June. They will leave the ground as mature nymphs (an immature life stage), crawl to the nearest vertical surface, and climb up several inches to begin the process of molting. They will then emerge from their exoskeletons as winged, sexually mature adults.

Adults are about 1.5 inches in length, mostly black, with large red eyes and other reddish markings. Males produce a very loud mating call. Females are silent but are attracted to the males’ mating calls. About a week to 10 days after the males begin to sing, they mate, and the females lay eggs in tree branches. For larger trees, this is less of a problem. Females have a preferred branch thickness, and this diameter is relatively small. For large trees, you will see evidence of tip dieback, but on smaller trees, such as high-density orchard systems, where the average branch diameter is much smaller than free-standing trees, as well as in blocks of newly planted trees, this is a serious concern.

The eggs will hatch after about 6 to 7 weeks, and small, white nymphs will fall from the trees to the ground. The nymphs will bury into the ground to feed on root systems (first grass roots, but eventually tree roots) for the next 17 years.

Exclusion netting is an effective control measure for smaller orchards. The mesh size should be no larger than ¼”. If exclusion practices fail, summer pruning and the removal of cuttings from the orchard could potentially remove eggs and nymphs from the orchard, reducing future cicada infestations 17 years later.

If netting is too expensive to be used, pyrethroid insecticides with a long residual action would be useful for young trees. If there continues to be egg-laying pressure, another application may be necessary. Scouting the orchard every 2 to 3 days would provide the necessary insight to determine if any pesticide applications were effective. A pyrethroid application may also cause an increase in mite outbreaks during the season, due to off-target effects on Stethorus species.

Dr. Greg Krawczyk, Extension Tree Fruit Entomologist, contributed to this article.

If you have any orchard questions, please reach out to your local Extension office or tree fruit educator. If you’re an orchardist in southeast PA, Don Seifrit (the author of this article) is available to talk at 610-378-1327 or available by email at dus970@psu.edu