Did you Know? Some Nematodes Offer Natural Defense for Cranberries
October 22, 2021 Nematodes with a taste for “insect innards” may offer cranberry growers a natural alternative to fighting hungry crop pests with chemical insecticides.
Scientists with USDA-ARS and University of Wisconsin (UW) are now exploring the possibility in field trials.
They’ve set their sights on redheaded flea beetles, Sparganothis fruitworms and other cranberry pests that attack the cranberry plant itself or its tart-tasting fruit. Severe infestations can force growers to apply insecticides, ratcheting up their production costs. Developing alternative controls as part of an integrated pest management approach can reduce or replace the need for insecticides, says Shawn Steffan, an entomologist with the ARS Vegetable Crops Research Unit in Madison, WI.
For his part, he and UW collaborator Shane Foye are working to formulate a bio-insecticide that’s made of entomopathogenic (“insect-killing”) nematodes. One species they’re particularly excited about came from the self-same environment that cranberries thrive in — the marshland and bogs of central Wisconsin. Cranberry also happens to be the official fruit of the state, which produces 60% of the nation’s total crop. However, the path from bog to juice bottle (or table) can be a perilous one. Nature, though, has seen fit to make these pests a favorite food of the nematodes Heterorhabditis georgiana and Oscheius onirici. Both species were found in the acidic, wet bogs of central Wisconsin. Interestingly, H. georgiana was originally discovered by David Shapiro-Ilan (another ARS scientist) in Georgia.
“O. onirici was originally found within caves in Italy, but clearly there are populations making a living in the marshlands of Wisconsin,” Steffan says.
The researchers hope both nematode species will prove to be an especially useful ally to both conventional and organic cranberry growers. Neither species is a threat to people, pets, or other vertebrate animals. But what they do to their preferred prey isn’t pretty. After entering a natural body cavity, the nematodes release symbiotic bacteria that liquefy their prey’s internal organs and tissues. This creates a nutritious soup that the nematodes eat. Afterwards, they mate and deposit eggs inside their host’s remains. Eventually, juvenile nematodes wriggle free in search of new hosts to infect, a cycle that lasts as long as their prey does.
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