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Experts Sound the Alarm on New Invasion Threatening Christmas Tree Farms

Invasive insects that resemble tiny wasps are quietly spreading across the United States, threatening pine trees, and experts say Christmas tree farms could be next. The Cool Down reported that European pine sawflies (Neodiprion sertifer) have been actively feeding on pine needles in Washington's Pierce County, and their slow but steady spread could pose a real risk to ornamental and plantation pines this summer. Sawfly larvae, which hatch from eggs laid in pine needles in the spring, can feed together in groups of dozens, stripping older needles clean, even if younger foliage remains safe. While they don't typically kill large trees, repeated feeding can stunt growth and create unsightly bald patches, which is a significant concern for growers and homeowners alike. These insects were first spotted in Washington in 2008, but their spread has been gradual since adult sawflies are poor fliers. Instead, they hitch rides on infested nursery stock, mulch, or soil, making nurseries and Christmas tree farms particularly vulnerable. The aesthetic damage is more than just cosmetic. 'It's the most common sawfly found infesting landscapes and Christmas tree plantations,' according to the University of Wisconsin, which notes these sawflies thrive in pines like Scots, red, Jack, and Mugo—common species in holiday tree lots. If you spot pine needles stripped bare like a bottle brush, you may have a sawfly infestation. These larvae can consume huge patches of older needles before moving on. While trees usually survive, the lasting effects can take a toll on growth and appearance. Experts recommend regular monitoring from spring through early summer. For light infestations, simply knocking larvae off or pruning affected branches may do the trick. Horticultural oils and insecticidal soaps can help against young larvae, while more persistent outbreaks may require targeted insecticides like acephate or spinosad. Natural predators, including certain birds, wasps, and small mammals, also feed on sawflies and their cocoons, offering a built-in defense mechanism. For Christmas tree farmers and homeowners who value healthy pines, early detection and control are key. Combined with native plantings that support wildlife, these steps can help prevent sawfly damage and protect future holiday trees. So, before you hang that ornament or wreath, take a close look at your pine branches. A handful of hungry sawflies now could mean a thinner, weaker tree come Sound the Alarm on New Invasion Threatening Christmas Tree Farms first appeared on Men's Journal on Jul 3, 2025