The short answer: We do not anticipate that spotted lanternfly will be an issue for field crops
The long answer: Detection of an established spotted lanternfly (Lycorma delicatula) population in Forsyth County has generated concern among farmers and backyard gardeners from the mountains to the coast. This is the southernmost detection of this invasive pest since its introduction into Pennsylvania around 2014 (current distribution). We also have nine counties across the state where this insect has been reported but populations were not detected (Currituck, Brunswick, Granville, Wake, Chatham, Cabarrus, Union, Mecklenburg, and Henderson). We anticipate that populations will become more widespread in NC and the southeast over the next several decades.
Which crops could be impacted? This pest can persist on hundreds of plants, but is most commonly associated with tree of heaven. Because tree of heaven and other non-crop hosts are common in NC, limiting the spread of this invasive insect will be challenging.
We do know that that this insect can cause significant damage to grapes, including common grapes and probably muscadine varieties. This information has triggered monitoring for spotted lanternfly in vineyards across the state. Over time, more detections will not be surprising. Researchers in the NC State’s Center for Geospatial Analytics predict that spotted lanternfly populations will establish throughout much of the eastern United States over the next two decades and may become a serious pest of grapes, hops, fruit trees (including apples), and several tree nut crops (the study can be found here: Jones et al., 2022).
What about field crops? As for field crops, we do not think spotted lanternfly will be a major issue. This insect overwinters in the egg stage and nymphs develop on the hosts near to the place where eggs hatch. Later in the summer nymphs develop into winged adults, enabling longer distance movement from development hosts and development of mating swarms.
We think that the biology of this insect is important to consider when estimating their potential impact on field crops. The keys to our damage interpretation are three-fold:
1) Field crops have not been reported as hosts in its native range (host list here: Barringer and Ciafré 2020).
2) Field crops are a transient component in the landscape. If spotted lanternfly lays eggs in a crop during the late summer that crop will be harvested and will not be there in the spring. As a result, it is unlikely that flightless nymphs will survive to colonize subsequent field crops in the spring.
3) Common insecticides used in field crops are very effective against spotted lanternfly. Researchers have documented that bifenthrin and thiamethoxam have a long period of residual activity (insecticide screening here: Leach et al., 2019). Moreover, several other modes of action also have knockdown activity.
We use many of these insecticides for NC pests throughout the cropping season. We anticipate that the timing of spotted lanternfly dispersal to hosts in the late summer will also coincide with some of the most intensive management of our field crops (e.g., stink bug/bollworm control in cotton during August). It is likely that these applications will also suppress colonization of spotted lanternfly.
