Winning at horseshoes not about getting ringer

            Anyone who has spent much time along the Rhode Island coast is familiar with one of the most ancient creatures on Earth, the horseshoe crab. More closely related to spiders and scorpions than to crabs, they evolved more than 300 million years ago, long before the dinosaurs, and they have remained mostly unchanged ever since. With 10 eyes, blue blood, and six pairs of appendages, they can look somewhat frightening. Just don’t believe claims that their tail – called a telson – is poisonous or can sting.  Not true.

            What is true about these remarkable creatures is that horseshoe crabs are far less common at their spawning grounds than they used to be. The days of seeing hundreds or thousands of horseshoe crabs scurrying about in local coves are mostly over. And their decline has implications for a whole host of other marine life. Some sea turtles, for instance, feed on horseshoe crabs, and many shorebirds, including the very rare red knot, consume horseshoe crab eggs to fuel their migration northward. Humans, too, depend on these surprising animals, because their unusual copper-based blood has properties that are used by the biomedical industry to ensure that our medical devices, vaccines and intravenous solutions are free of harmful bacteria.

            The cause of their decline is somewhat uncertain, though large numbers are harvested for use as bait in the eel and conch fisheries. They also get stranded on beaches and accidentally flipped upside down by waves, which gives gulls and other predators easy access to their sensitive parts. And some die during the process of draining a portion of their blood for biomedical testing.

            In Rhode Island, assessments of horseshoe crab populations by state and federal agencies have found them at “low levels of abundance” ever since a management plan was put in place in 1999. Scott Olszewski, a marine fisheries biologist at the Rhode Island Department of Environmental Management, who conducts spawning surveys at several area beaches, said that despite efforts to manage the population, their numbers have not rebounded. About 30 to 40 fishermen obtain permits each year to harvest horseshoe crabs in the state, and they are allowed to take up to 14,500 for use as bait and another 34,000 for the biomedical industry (though those in the latter category are released back where they were captured after some of their blood has been collected).

            “When horseshoe crabs decide it’s time to spawn, they come up on the beach in massive numbers, which makes harvesting them pretty easy,” said Olszewski. That’s why the fishing season often closes just a few days or weeks after spawning begins.

            Other scientists are now paying close attention to horseshoe crabs as well. Researchers at Sacred Heart University are overseeing teams of volunteers who are monitoring them at multiple locations in Long Island Sound, including at Napatree Point in Westerly. And others are doing the same on Cape Cod and in the Mid-Atlantic States.

            At Napatree, volunteers led by the Watch Hill Conservancy go out at high tide on full moon nights from May through July to count and tag the animals. It’s an enjoyable few hours working by moonlight to the sound of the lapping waves, and it helps provide insight into the natural history of an ecological oddity that will likely outlive us all.

            To learn more about becoming a horseshoe crab volunteer at Napatree, contact the Watch Hill Conservancy at napatreenaturalist@gmail.com. And if you see large numbers of spawning horseshoe crabs at other coastal locations, report them to Olszewski at scott.olszewski@dem.ri.gov. 

This article first appeared in The Independent on May 19, 2016.

Winter moth caterpillars prepare to defoliate the region. Again.

            Those annoying white moths that seemed to be everywhere between Thanksgiving and Christmas, and which sometimes formed thick fluttering clouds, are preparing to unleash even greater devastation to the trees in southern New England than they did last year. Winter moth caterpillars defoliated about 27,000 acres of trees in Rhode Island last spring, according to data from the Rhode Island Department of Environmental Management, and one local expert says the insects will do even greater damage this year.

            Heather Faubert, who runs the PlantProtection Clinic at the University of Rhode Island and has been monitoring the approaching onslaught, was hoping that the late cold spell in early April was going to kill off many of the emerging caterpillars. But that doesn’t appear to have happened.

Winter moth caterpillar photo by Milan Zubric

            “I think we’re in trouble this spring,” she said. “Every year since they arrived, it’s been getting worse, and I can’t imagine why it won’t get worse this year, too.”

            Winter moths are a European insect that arrived in North America in the 1950s, beginning in Nova Scotia. They spread to Cape Cod by the 1990s and were first discovered in Rhode Island in 2004.

            “They expand slowly, so there are still some places in Rhode Island where they aren’t found in large numbers yet,” Faubert said. “But they’re coming. The first year they arrive in a new area, you might see the moths in winter but not see many caterpillars the next spring. But once they get going, they grow exponentially.”

The URI entomologist said the adult moths appear in late November and fly around through December looking for a mate. Killing them at that time does little good, since only the males fly. Unseen flightless females lay their eggs on the trunks and branches of trees, and the caterpillars emerge in late March.

            “Hatching typically takes about eight days to complete, but because of the cold weather in April it took about a month this year,” Faubert said.

            The tiny caterpillars then crawl into the buds of the earliest budding trees – mostly maples, but also apple and other fruit trees – and immediately start eating. If the buds of fruit trees are consumed, the fruit crop may be lost for the year. As leaves emerge on trees of all varieties, the caterpillars feed on them until the end of May, when they drop to the ground, burrow into the soil, and pupate before emerging as adult moths in November.

            While one year of defoliation doesn’t typically harm a healthy tree, Faubert said that defoliation three years in a row can kill almost any tree. And this year, Rhode Islanders may have a large population of gypsy moths to contend with as well.

            “Trees that are defoliated by winter moth and then again by gypsy moth later in the season probably won’t recover,” Faubert said.

            Gypsy moths defoliated about 43,000 acres of Rhode Island forest last year, thanks to a dry May that aided their survival. In years when it’s rainy in May, the moisture abets several diseases that get passed back and forth between gypsy moth caterpillars, causing the population to crash. So Faubert has her fingers crossed that Rhode Island will experience a wet May.

            Homeowners seeking to protect their trees from winter moth defoliation should take action immediately. Faubert said that it’s best to spray insecticide on trees while the winter moth caterpillars are still small. “Waiting until the trees are halfway defoliated won’t really do much good,” she said.

            According to a DEM factsheet, the recommended treatment against the caterpillars is a pesticide containing the relatively safe bacterium Bacillus thuringiensis or Bt. Caterpillars die when they consume leaves sprayed with the pesticide, which is most effective before the caterpillars are full grown.

            “That’s the safest thing to do,” Faubert said. “The problem is that the spray only lasts from 3 to 5 days before it breaks down. So if you have a prized tree you’re trying to save and there are untreated trees nearby, caterpillars may get blown onto your tree after the pesticide is no longer effective. So one shot of insecticide may not do the job.”

            Physical barriers like sticky tape or grease applied to the base of trees is not considered effective at stopping winter moths.

            One strategy that Faubert has experimented with is biological control. Researchers have identified a parasitic fly that is known to control the spread of winter moths in their native Europe. The fly lays its tiny eggs on tree leaves, and when the caterpillar consumes the eggs while eating the leaves, the eggs hatch inside the caterpillar and eat the caterpillar from the inside out.

            Faubert released groups of the parasitic flies in seven locations in Rhode Island between 2011 and 2014. But, she said, “if it’s going to work, it takes years.”

            In the meantime, she advises residents concerned about their trees to contact a local landscaper or arborist who can assess and treat their trees. The website of the Rhode Island Nursery and Landscape Association has a list of those who can do the job.

This article first appeared on EcoRI on April 28, 2016.