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Periodic Cicada Information

We’ve been getting A LOT of questions about the upcoming Cicada emergence that will be happening this spring / early summer. There’s been a lot of talk in the news and online about it, much of which is nothing more than sensationalism. Here are the facts.

 

Here in Northern Illinois Brood XIII of the 17 year cicada will emerge. South of Springfield, Brood XIX of the 13 periodic cicada will emerge. Both will emerge for the first time in 221 years…however in Northern Illinois we will not see a co-emergence as we are too far north. Cicadas spend most of their life in the soil as a larva feeding on small roots and then emerge as adults. They will then mate and lay eggs (on small twigs and branches) and return to the soil to start the 17 year process over again. It is important to keep in mind that this is a natural occurrence and has been happening for hundreds, if not thousands, of years. Despite what some of the headlines read, all of our trees are not going to die and we are not going to be living in a barren wasteland when the emergence is over. If you have or will be planting tiny little seedling trees (like those given away on Arbor Day or those purchased from Soil and Water Conservation), you may have reason for concern. Consider planting larger trees (like those that we grow / sell) that won’t be damaged or consider planting the trees in the fall after the egg laying is through. If you already have very young seedling trees, consider netting them with a fine bird netting. Use insecticides sparingly and consider the broader ramification of their use. While most of Illinois will see cicadas emerge this spring, the emergence will be particularly heavy in areas with older stands of trees. Heavier wooded areas or areas with very mature tree cover will see more cicadas than areas with lower tree cover (farm land, prairie land, newer subdivisions / communities. In the Tri-city area in 2007, the last emergence of this particular brood of periodic cicadas, we did NOT see heavy infestations or any resulting damage from egg laying.

Does egg laying (oviposition) harm trees?

While adult ovipositional damage on mature trees and shrubs is usually no more than natural pruning, very young woody plants and whips can be more seriously damaged. The female cicadas’ ovipositing on the young stems can cause wounds that may lead to breakage of the stem or top kill, and also may provide entry for canker-causing fungi and wood-boring insect pests. A number of studies have found that there appears to be a minimum and a maximum twig/branch diameter that is preferred for oviposition, ranging from 1/8 to 7/16 inch. {Miller}

Does nymph feeding on the roots cause damage?

 In a 2010 study, no effect was found from root feeding by cicada nymphs prior to emergence on five Midwestern forest trees: sugar maple (Acer saccharum), white ash (Fraxinus americana),pin oak (Quercus palustris), black oak (Q. velutina), and sassafras (Sassafras albidum). However, three of the species’ chronologies showed a significant reduction in growth the year of or the year after the emergence year, and three chronologies showed an increase in growth five years following the cicada emergence event.

Does the wound left from egg-laying (oviposition) heal? 

Once ovipositional damage has occurred, how long is it before the plants “heal up” or callus over the wounds? In two studies in 1997 and 1998 examining 140 exotic and native woody plant genera and 14 different urban forest parkway tree taxa, they found that most plants callused over the wounds within one to two years after a cicada emergence. Exceptions were alder (Alnus spp.), black walnut (Juglans sp.), redbud (Cercis sp.), lilac (Syringa spp), linden (Tilia spp.), honey-locust (Gleditsia triacanthos), northern red oak (Q. rubra), hackberry (Celtis occidentalis), Redmond linden (Tilia americana ‘Redmond’), and littleleaf linden (T. cordata), which took at least three years to heal. {Miller}

Should I / can I spray insecticides?

Nonsystemic (aka contact insecticides) insecticides were not effective and did not deter adult females from landing on host plants or deter them from laying eggs on host plants. Young trees treated with systemic insecticides (such as imidacloprid – soil drench) have been observed to have less egg nests and scars than untreated trees. Netted trees however, showed little or no damage from egg laying.
References Cited:
Dr. Fred Miller, PhD, Morton Arboretum Senior Entomologist
Photo of a Cicada: