By Anne L Nielsen, PhD, Extension Specialist in Entomology
Spotted lanternfly (SLF), the jumpy plant hoppers that resemble brightly colored moths when in flight, are being spotted throughout New Jersey. While some New Jersey residents are already familiar with these invasive bugs, others are getting their first glimpses of the 1″ long adults.
There is no need to panic! SLF is certainly a bad bug, but it will not cause harm to people or pets, it is strictly a plant feeder. In gardens – cucumbers, roses, and grapes appear to be favored by the nymphs. While large feeding populations can damage plants, sturdy hardwood trees can withstand a fair amount of feeding and it takes large, sustained populations over multiple years before trees show signs of decline. Concern lies with the threat primarily posed to the New Jersey wine grape industry, as well as the nuisance factor of thousands of large jumping insects in green spaces and backyards.
As Fall approaches, SLF throughout New Jersey will have molted to the adult, winged stage. Egg laying will occur in October and the eggs will be present until the nymphs hatch in the Spring. Adults congregate on host plants, primarily hardwood trees, to feed on the plant phloem or sugar water. It can be impressive seeing adults completely cover the trunk. In the Fall, adults prefer black walnut, sycamore, river birch, red maple, willow, and of course the invasive tree of heaven. As they feed, they excrete the extra plant sugar in the form of honeydew. Honeydew may attract bees, wasps, and even ants which dine on this sugar-rich “manna from heaven.” However, fungal mats or sooty mold can quickly form on the base of the tree or understory plants, creating a nuisance.
Adults will be around until the first hard frost but the best time for management is in early Fall before they start laying eggs in October. If adults can be killed before they lay eggs it will contribute to population control. You may have heard of home remedies such as grits or pine sol mixed with sugar – these aren’t effective! SLF are brightly colored as a warning to bird predators that they are distasteful. Despite this, it is not uncommon to see predators such as spiders or preying mantids feasting on lanternflies, but they will not be able to control SLF. Two primary modes of control are available: 1) physical removal and 2) insecticide. If there are only a few adults, physical removal may be possible with a shop vacuum. A sock or nylon stocking can be fitted inside the hose to capture collected bugs which can then be frozen and discarded. However, given their jumping ability, simply vacuuming up these bugs may not be as easy as it sounds! If there are thousands of lanternflies in the garden and yard, the most effective way to kill adult SLF is with insecticide treatment. Many insecticides are available for purchase at garden stores that are effective, such as those containing the active ingredients carbaryl, or dinotefuran. Check all insecticide labels to make sure they are approved for application on the host tree before applying and wear protective equipment. Alternatively, landscape professionals and even some pest management companies can provide treatment.
Physical removal extends to the nymphs too. While egg removal may be a useful tool, many of the eggs are not safely accessible. However, nymphs hatch in May and are easier to target. Nymphs move up and down trees daily, and this provides a way to physically remove them with trapping. The original method was to use sticky bands, but this captures other organisms like bees, tree frogs, and birds. Covering the sticky band with loose chicken wire can reduce capture of non-targets but another option is a circle trap. Originally designed by the USDA, there are DIY instructions here: extension.psu.edu/how-to-build-a-new-style-spotted-lanternfly-circle-trap or simply search “circle trap SLF” on your internet browser for pre-made ones. Pick the host tree based on observations of this year’s high adult populations. In 35 traps, Rutgers has removed over 8,000 nymphs this year. That is 8,000 fewer future adults and thousands fewer eggs!!
All these strategies are not one-shot deals. Management of SLF will take multiple years and we are likely to be dealing with this bug for a long time. What the community can do is reduce the impact to their landscapes and green spaces. Removal of SLF’s primary host, tree of heaven, may help but SLF can complete their lifecycle without it, it just takes a bit longer. Removal is not an easy process, please visit extension.psu.edu/controlling-tree-of-heaven-why-it-matters. We hope this will help protect our farmers in the long term as well as any backyard gardens. For more resources visit njaes.rutgers.edu/spotted-lanternfly or www.nj.gov/agriculture/divisions/pi/prog/pests-diseases/spotted-lanternfly .
This article originally appeared in the September 2021 issue of Gardener News.