Brood X is on its way. This is one of the largest broods of periodical cicadas, and the insects will soon be seen in a number of states including Delaware, Georgia, Illinois, Indiana, Kentucky, Maryland, Michigan, North Carolina, New Jersey, New York (nearly extinct), Ohio, Pennsylvania, Tennessee, Virginia, West Virginia, and Washington D.C. If you lived in these areas in 2004, you may remember seeing (and hearing) the noisy, prolific insects in your landscape. They emerged, molted, mated, layed eggs, and died within just 4-5 weeks and then seemed to disappear. But quietly those eggs hatched and the nymphs burrowed underground, feeding, growing, and biding their time, until now.
Every seventeen years, this hoard emerges. In 2021 there will once again be a cacophonous swarm, filling the bellies of squirrels and birds, forcing windows closed at night, and potentially damaging valuable plant material in landscapes.
When will Brood X arrive?
Brood X nymphs will begin to surface when soil temperatures reach 64 degrees (from late April to early June depending on the location). They will attach to any surface available, emerge as winged adults from their nymphal exoskeletons and then take flight.
How will Brood X impact shrubs and trees?
For nourishment, cicadas suck sap and nutrients from trees and shrubs. This feeding activity usually only causes major damage when it occurs over several years, or if the plant is already under stress. Egg-laying activity is more likely to pose a potential issue. Females use a saw-like ovipositor (egg laying appendage) to cut slits into the twigs of trees and shrubs where they will lay their eggs. Just one single female may produce as many as thirty-five bark punctures. Twig death can occur beyond the oviposition scars. Most of this damage is aesthetic, but it can cause harm in rare cases.
To prevent damage to smaller and vulnerable high-value trees and shrubs, nets can be cast over the crowns. This netting should not be placed directly on branches. New shoots will either grow through the netting or be forced to curl beneath it, deforming that growth. The damage that ensues is often as bad or worse aesthetically than the damage that would have been inflicted by the insects. Alternatively, netting should be supported on a framework to protect growth and deter insect egg-laying activity. These netting structures must be in place before new growth begins and before cicadas mate and lay eggs. Proper installation of netting can be expensive so this should be reserved for the most valuable and vulnerable trees and plants.
After the cicadas have once again gone underground, a Certified Arborist can review any trees or shrubs that have been damaged. Fertilization and soil care can reduce stress and aid in recovery. Pruning to remove dead or dying branches may also be recommended. Other treatments can help suppress insects, like borers, that typically target and attack damaged plants.