In September 2014, the Pennsylvania Department of Agriculture (PDA) received a call from a company near Reading, Pa. Employees had found a strange bug at the back of their property in a tree of heaven (Ailanthus altissima) grove.
When the PDA inspectors arrived at the company, they saw gray-winged bugs about an inch long, covering the trunks of the Ailanthus trees. A rain of ”honey dew” dropped down onto the inspectors from the overhead branches. It was later discovered to be the excrement from the thousands of bugs in the tree canopy.
Back at their lab, the PDA inspectors discovered that the specimens they had collected were spotted lanternfly (Lycorma delicatula), an invasive pest not found in this country before. A native of China, Vietnam and India, the pest has spread to Japan and South Korea and, now, to North America.
Alarmed, the PDA immediately began a program to eradicate the pest. Thought to be in a relatively small area, eradication seemed very feasible with an intensive effort using the combined resources of the PDA, U.S. Department of Agriculture (USDA), local governments and the public in the affected area.
Initially found in only a few townships in one county (Berks), each year the affected area grew due to this bug’s ability to “hitchhike” and lay eggs on cars and other vehicles. The bug has been found now in six counties, an area that includes most of southeastern Pennsylvania. Head over to the Pennsylvania Department of Agriculture website for a list of the quarantined municipalities where SLF has been found.
Both PDA and USDA continue to believe that eradication of the pest is still within reach, but it will take a massive effort.
Why the concern?
While the spotted lanternfly (SLF) prefers the tree of heaven for part of its life cycle, the bug causes damage to fruit and vegetable crops, especially grapes, agronomic crops and native species of trees, including maple, willow, poplar and others. The bug creates crop and tree damage with its piercing mouth parts, sucking the phloem from new growth. Tree branch flagging can be observed shortly after an infestation.
The bug is also prolific. In climates with a cold winter like Pennsylvania, the SLF has one life cycle per year, but can mate and lay egg masses several times, laying 30 to 50 eggs each time. The egg masses will be attached to any hard surface. Egg masses have been found on the bark of many tree species, rocks, motor vehicles, outdoor furniture, the sides of houses and more.
In infested areas, the adult bugs gather in masses, covering tree trunks, patios and the sides of houses. While they don’t bite, the SLF are attracted to and land people moving among them, making simply being outside very unpleasant.
As the SLF sucks the phloem from trees and shrubs, they excrete honey dew, a sticky sweet substance. When walking under an infested tree canopy, the honey dew falls like rain. This honey dew also attracts wasps, ants, bees and other insects drawn to the sweet substance.
To make matters worse, the honey dew is host to sooty mold, which quickly colonizes a surface onto which honey dew has been excreted. These surfaces turn black as the mold colonies grow. A patio would be very uninviting if covered by a tree canopy infested with SLF.
The danger for SLF to spread is most acute in states south of the Mason-Dixon line where milder winters could give the bug year-round reproduction capability and reduce winter kill of egg masses.
What to do?
If you’re in an area not currently infested with SLF, SLF can reach you in two ways. First, eggs may be laid on vehicles, pallets, stone, pavers, nursery stock or any hard surface. Second, the live nymphs or adults can hitch a ride. Adult spotted lanternflies were recently found in a crate of apples shipped from within the infested area. If you have vehicles moving through or are purchasing any materials from within the infested area, be sure to inspect vehicles and materials for live nymphs, adults or egg masses and destroy any you find.
The tree of heaven is an invasive species imported to this country from China. In many states it’s considered a noxious weed. States spend millions each year attempting to control the invasive species on highway rights of way. It thrives in poor, disturbed soils like those found along roadsides, old construction sites and the rear of warehouses, factories and parking lots.
Although scientists are not sure exactly what role tree of heaven plays in the life cycle of the spotted lanternfly, they suspect the SLF must have contact with the tree to complete its life cycle.
The Pennsylvania Department of Agriculture is now recommending that tree of heaven be removed as one of several control methods for spotted lanternfly. The tree is dioecious, meaning it has both male and female forms. PDA suggests that all trees be cut down and treated with herbicide, except for one or two non-seed producing males to act a trap trees. The trap trees should be treated with a systemic pesticide such as Dinotefuran so that the SLF nymphs and adults come to the tree to feed and are killed by the pesticide.
More information on the spotted lanternfly, its identification and treatment, is available at the Pennsylvania Department of Agriculture website. Halting its spread will take a coordinated effort by government, our industry and the public.
