A spotted lanternfly (Lycorma delicatula) egg mass is collected for research from a section of tree bark. Its gray, mud-like covering blends into the surrounding bark. Lanternflies spend approximately eight months as eggs, providing an extended window in which management treatments could be applied before the next generation hatches. (Photo by Jason Bielski, Ph.D.)

By Jason Bielski, Ph.D.

Jason Bielski, Ph.D.

Before I ever considered graduate school, I remember finding spotted lanternflies in the woods covered in white, fuzzy fungal growth. I didn’t know which fungus I was looking at, but the sight stayed with me. Here was something happening naturally that made me wonder: Could we put insect-killing fungi to work in pest management?

That curiosity sparked my interest in biological control—using living organisms to manage pests. I began following research on spotted lanternfly (Lycorma delicatula) and its natural enemies, and when I started my graduate research at Virginia Tech in 2021, I wanted that interest to be part of my program.

At the time, spotted lanternfly was still expanding its reach, and growers and researchers were asking what other tools we could add to the management toolbox. I kept coming back to one part of its life cycle: the eggs.

Spotted lanternflies spend approximately eight months in the egg stage. While nymphs, the young, wingless lanternflies, and adults move between plants, egg masses stay in one place. That seemed like a window worth investigating. Could we take advantage of those months before the next generation hatched?

Staying Put, But Well Protected

The idea had particular appeal for vineyards, where egg masses often occur near the edges and adjacent wooded areas. Targeted applications with a backpack sprayer might offer a practical way to treat accessible masses before the insects started moving and feeding.

But a stationary target is not necessarily an easy one.

Spotted lanternfly egg masses have a protective outer covering, and each egg presents another barrier. A treatment would need to reach the developing insect or leave behind something that could affect a nymph as it emerged. Products that control nymphs and adults would not necessarily work against eggs.

My colleagues and I wanted to answer three questions: Could we manage lanternflies by treating egg masses? Which products showed promise? And when during that long overwintering period would treatments work best?

Those questions led to two studies examining conventional insecticides and an insect-killing fungus. Our results were published this summer in the Journal of Economic Entomology and Environmental Entomology.

Stopping the Next Generation Before Hatch

In our insecticide study, we tested 13 insecticides in laboratory experiments across three years, applying treatments in winter, early spring, and late spring. We also evaluated malathion in a field trial.

Two organophosphate insecticides, malathion and chlorpyrifos, consistently reduced hatch in the laboratory. The malathion field trial also supported its effectiveness. Other products produced smaller and more variable reductions.

In other words, these treatments stopped some of the next generation before it ever hatched. That egg-killing effect is called ovicidal activity. The results also reinforced why we needed to test the eggs directly: A product that works against a feeding, moving insect might not work against one protected inside an egg.

Organophosphates have toxicity concerns, so turning these findings into a management practice requires careful consideration of the product, application site, and label requirements. Still, the results gave us evidence that the egg stage could be a useful target.

Leaving Spores for Emerging Nymphs

A spotted lanternfly (Lycorma delicatula) nymph, or premature lanternfly, is covered in white fungal growth following infection with Beauveria bassiana. In a recent study, researchers investigated whether fungal spores applied to lanternfly egg masses could infect nymphs as they emerge, targeting the next generation around hatch. (Photo by Jason Bielski, Ph.D.)

Our second study brought me back to the interest that began with those fungal-covered insects in the woods.

We investigated Beauveria bassiana strain GHA, an insect-killing fungus used in commercial biopesticides. Research had already shown promise against spotted lanternfly nymphs and adults. We wanted to know whether treating egg masses could expose newly hatching nymphs to its spores.

The fungus worked differently from the most effective conventional insecticides. It did not reduce egg hatch. Instead, nymphs emerging from treated egg masses became infected and subsequently died. We confirmed fungal infection in the laboratory.

An egg mass could therefore serve as a surface where infectious spores waited for the next generation to emerge. But those spores had to remain alive long enough to meet the insects on their way out.

That was one of our biggest surprises. Some spores survived on the outside of egg masses through winter exposure, and enough remained viable to infect emerging nymphs. I had wondered whether this could work; seeing evidence that it did was exciting.

We also took the question outdoors. Two field trials demonstrated infection in nymphs emerging from treated egg masses, showing that the approach had promise beyond laboratory conditions.

Timing still made a difference. Winter exposure reduced spore viability, and formulation affected persistence. Applications approximately two weeks before hatch offered the most promising timing, although some infection occurred even after applications made 20 weeks earlier.

Those earlier infections were encouraging, but they did not mean we could count on spores surviving all winter. For practical use, matching applications to the expected local hatch would give the fungus a better chance to encounter emerging nymphs while its spores were still viable.

White fungal growth covers portions of the body and legs of an adult spotted lanternfly (Lycorma delicatula) found in the wild. Observations of fungus-covered lanternflies sparked entomologist Jason Bielski, Ph.D., to take an interest in biological control—using living organisms to manage pests. (Photo by Jason Bielski, Ph.D.)

From Groundwork to Vineyard Management

Together, the studies identified two ways to affect the next generation: prevent hatch or infect nymphs as they emerged.

The potential benefit is fewer lanternflies starting the season. What we still need to learn is whether treating accessible egg masses leads to fewer insects feeding on grapevines and less damage later on. Our laboratory experiments and field trials laid groundwork, but they did not answer that larger vineyard-management question.

I still think back to those insects in the woods. What caught my attention then helped shape the questions I asked in graduate school. And one of the most useful questions turned out to concern the stage people might walk right past: an egg mass sitting in place for months, holding the next generation.

Jason Bielski, Ph.D., is a postdoctoral associate in the Department of Entomology at Virginia Tech. Email: jbiel654@vt.edu.