If you’re spending more time outside as the weather warms, you might notice problems in your landscape. One homeowner called the Garden Helpline about white webbing on the ends of some of the branches of a tree purchased as a live Christmas tree. She planted the tree in a special place in her yard as a reminder of that happy occasion. Although she knew it was a pine, diagnosing the problem required determining what pine species it was. The number of needles in each needle bundle can identify pine species. She reported that there were 3 needles in each bundle, helping identify the tree as a Scotch pine (Pinus sylvestris), a very popular Christmas tree species.
Damage: The description of the webbing she saw helped determine that her tree was infested with the Nantucket pine tip moth, (Rhyacionia frustrana). Other signs include:
• Deformed growth (stem crooking) or a reduction in growth (bushy or stunted growth);
• Fecal deposits may be present in the webbing on the outside of infested shoots;
• Trees can be killed when exposed to repeated Nantucket pine tip moth larval infestations.
• In North Carolina, this pest overwinters as pupae in hollowed out pine shoots;
• On warm days as early as January and February, new moths emerge to mate;
• Adult moths are 1/4 inches (6.3 mm) long with the head and body covered with gray scales. The forewings are covered with brick-red to copper-colored patches that are separated by irregular bands of gray and white scales;
• Adult females lay white to opaque eggs on shoots, needles, or terminal growth in spring;
• From 5 to 30 days later, young larvae (caterpillars) hatch from eggs and feed on the surface of new growth. These are 1/16 inches (1.6 mm) long, and cream-colored with a black head. They then move to the shoot tips, construct protective webs at the base of buds, and begin to bore into the bud or stem.
• Feeding continues inside the bud or stem until the caterpillars are fully grown in 3 to 4 weeks. The caterpillars then pupate inside the damaged stem.
• Proper watering, fertilization, and mulching practices to keep pine trees healthy;
• For minor infestations, you can hand prune infested shoots if branches are reachable.
Susceptible pine species:
• Other three needle bundle pines, which include pitch pine (P. rigida) and loblolly pine (P. taeda).
• Two needle bundle pines are highly susceptible to infestation. These include Japanese red pine (P. densifolia), mountain pine (P. mugo) and Japanese black ine (P. thunbergii).
Resistant pine species:
- Eastern white pine (P. strobus) and Virginia pine (P. virginiana), which have five needle bundles.
Article by Bob Wardwell, Extension Master Gardener Volunteer
For more Information:
Nantucket Pine Tip Moth: https://content.ces.ncsu.edu/nantucket-pine-tip-mo
How to Identify Pines: https://smallfarms.cornell.edu/2019/02/arent-they-all-just-pines-how-to-id-conifer-trees/