Brood X cicadas will soon be emerging from the ground in Indiana, a hotspot for these periodic insects, and experts are warning that some young trees may need protection to survive.
“The17-year cicadas are coming, and that’s especially important to people with new trees. New fruit trees are particularly susceptible to cicadas,” Rebecca Koetz, Lake County Purdue University Extension urban agriculture educator, explained. “Cicadas are harmless to humans and provide food for wildlife but lay their eggs in new growth, and this can cause branches to die out.”
The best advice is to delay planting any new trees until after the cicadas leave and to cover young trees with insect netting while they are here, she added, noting that more mature trees can handle the damage.
“Larger trees do not need to be protected from cicadas. They may experience minor dieback at the tips of branches, but this will not harm the overall health of the tree,” Koetz said.
The goal is to prevent the cicadas from having access to the branches of young trees so that they will lay their eggs elsewhere.
The 17-year cicadas, also known as Brood X, will emerge throughout Indiana, but the biggest populations will be in southern Indiana. Expect up to 1.5 million cicadas throughout the state during the upcoming emergence.
Their last emergence in 2004 saw these insects appear in large numbers in Bloomington, Brookville, Clinton Falls, Dillsboro, Fishers, French Lick, Indianapolis, Lawrenceburg, Lexington, Martinsville, McCormick’s Creek State Park, Nashville, North Vernon, Skiles Test Park and Spencer.
“Timing of the emergence depends on temperature. We can expect them to emerge from the southern part of the state several weeks before they emerge in the north. The weather can also have an impact on emergence,” Koetz said.
A warm spring might make the cicadas emerge sooner, while a cold spring will delay the emergence. However, in most places the major emergences are expected to start in mid-April and continue through mid-May.
A good rule of thumb is to expect the cicadas to emerge around the same time as irises start to bloom.
Cicadas need to feed on trees nearly constantly for most of their lives, drinking sap from tree roots. They are therefore typically found only in areas that had trees 17 years ago and have continued to have trees since then.
Once every 17 years they emerge, climb up trees, sing, mate and lay their eggs on the tips of tree branches.