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Plant Insects

Pest Alert: Nantucket Pine Tip Moth

April 17, 2020

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.

Scotch PIne three needle bundle
Three needle bundle pine

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.

Damage caused by Nantucket Pine Tip Moth

Identification:

• 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;

Adult Nantucket Pine Tip Moth

• 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.

Management:

• 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/

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Categories Insect Pests Tags insects, Nantucket Pine Tip Moth, pines

Pest Facts: Hemlock Woolly Adelgid (HWA)

October 28, 2019

Just visit a Western North Carolina forest to see how much destruction this non-native invasive insect pest has caused—and is still causing—on the native Carolina hemlocks (Tsuga caroliniana) and Eastern hemlocks (Tsuga canadensis)! After our recent rains, this is a good time to treat your hemlocks if you see a white cottony substance on your hemlocks.

Hemlock Woolly Adelgid

History

  • HWAs were discovered in Shenandoah National Park in northern Virginia in 1988, likely when crawlers clung to the legs and feathers of migrating birds, such as the black-throated green warbler and solitary vireo that visit or nest in hemlock trees.
  • HWAs were discovered on hemlocks in North and South Carolina in late 2001 and early 2002.

HWA (Adelges tsugae) Life Cycle:

  • HWAs hatch from eggs and then go through a crawler stage—almost invisible to the naked eye. These crawlers cannot fly on their own but can drift in the air from tree to tree, and cling to the legs and feathers of migrating birds.
  • After settling on host trees, the HWAs insert a bundle of mouthparts at the base of a needle and spend the rest of their lives—a few months—sucking nutrients out of the tree.
  • The name “woolly” comes from the fact that adult HWAs are covered with a protective white fluff once they settle.
  • The HWA goes through two generations a year (one in March and one in October in Western North Carolina) and each female—even without being fertilized by a male—can lay between 100 to 300 eggs.
  • This reproductive process is called “parthenogenesis”—the offspring are genetically identical clones of their mother.

Controls

Chemical: Registered pesticides containing imidacloprid or dinotefuran are the most effective chemical treatments for control of HWAs. These are applied as a soil injection or trunk spray. These insecticides are water soluble and move into the tree’s vascular system along with water. Dinotefuran has a faster uptake, but imidacloprid has a longer residual protection. Control of HWAs using imidacloprid can last for 4-5 years. Dinotefuran may require retreatment within 2 years.

Biological:

The species that has so far shown the most promise as a biological control agent is Laricobius nigrinus, a predator beetle native to the Pacific Northwest. L. nigrinus is active from October to March; both adults and larvae will consume all stages of HWAs: eggs, nymphs and adults.

After exhaustive evaluation in quarantine labs, it was cleared by the USDA for use as an HWA biocontrol in the eastern United States in 2000 and has been released in NC since 2003.

Original Article by Glenn Palmer, Extension Master GardenerSM Volunteer, Revised by Bob Wardwell, Extension Master GardenerSM Volunteer

Hemlock Restoration Initiative https://savehemlocksnc.org/

National Park Service Great Smoky Mountains Hemlock Woolly Adelgid

https://www.nps.gov/grsm/learn/nature/hemlock-woolly-adelgid.htm

University of Massachusetts HWA Fact Sheet https://ag.umass.edu/landscape/fact-sheets/hemlock-woolly-adelgid

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Categories Invasive Insects, Pest Management, Trees Tags Biological Control, Hemlock Woolly Adelgid, insects, pest control, trees

The Garden Detective: What Are Those Webs in My Trees?

September 14, 2018

Fall webworms began infesting local trees and shrubs in mid-summer! They create their unsightly webs at the branch ends of hundreds of different woody plant species, including sourwoods, birches, cherries, crabapples, hickories, and walnuts. If you saw web-building pests this past spring, they were likely the Eastern tent caterpillar.

Webworm Web_Tim Lenz_CC BY 2.0_Flickr
Fall webworm web in tree

What are fall webworms?
Fall webworms really aren’t worms at all, but the caterpillar stage of a white moth, Hyphantria cunea Drury. What you see is the larval stage of this pest consuming leaves inside the protection of an unsightly tent-like web. The damage they inflict may occasionally defoliate a tree but rarely kills it because the damage occurs shortly before normal leaf-drop. A relatively benign native of North America, these fall webworms are invasive pests throughout Europe and Asia.

Fall webworm lifecycle
The caterpillars currently feeding on your trees hatched from eggs laid by adult fall webworm moths. The small moth is fluffy white, sometimes with black spots, about 1½-inches long. After hatching, caterpillars feed for 4 to 6 weeks, creating a tent-like web as they eat tree leaves. They emerge from the web only when they are ready to pupate, seeking shelter in tree bark or other crevices on or in the ground. There they spin cocoons in which they spend the winter. Next spring, adult moths will emerge from these cocoons and mate—then the females will lay eggs, beginning the cycle all over again! Many of the webs you see now are empty because the caterpillars have already moved on to shelter for the winter.

Fall Webworm Caterpillar (Hyphantria cunea)_Katja Schulz_CC BY 2.0_Flickr
Fall webworm caterpillar
Fall Webworm (Hyphantria cunea)_James Emery_CC BY 2.0_Flickr
Fall webworms
Fall Webworm Moth (Hyphantria cunea)_Katja Schulz_CC BY 2.0_Flickr
Fall webworm moth

What to do?
The webworms will devour the leaves within the web, but not the branches, so it is fine to do nothing! Birds, predator insects, and parasitoids help by eating moth eggs and attacking the developing larvae. The webs will deteriorate over the winter and the tree will refoliate in the spring.

If you prefer, when you first see the webs, prune away the branch tips holding them and destroy any active caterpillars, or pull the webs down with a stick—burning webs is not recommended! If you are concerned about the health of a young tree with a heavy infestation of fall webworms, contact the local Extension office for an approved insecticide recommendation for webs containing active caterpillars. Chemical control is most effective when the webs and larvae are still small.

What if I see webs in the spring?
Eastern tent caterpillars build the webs located in tree-branch crotches—rather than branch tips—in the spring. Found throughout the Eastern United States, they mostly affect apple, cherry, and crabapple trees, although they can attack other woody plants. Like fall webworms, tent caterpillars are the larval stage of a moth (Malacosoma americanum) and spin a web for protection.

Tent caterpillar life cycle
Unlike webworms, Eastern tent caterpillars overwinter as egg masses on trees. As the larvae hatch, they form tents in branch crotches. They leave their nests during the day to feed and return at night. They pupate in cocoons on trees or other nearby structures. The reddish-brown moths that hatch out in early to mid-summer have two white stripes on their wings. After the moths mate, females’ egg-laying begins a new cycle.

Eastern tent caterpillar web_Chesapeake Bay Program_CC BY-NC 2.0_Flickr
Eastern tent caterpillar web
Eastern Tent Caterpillar (Malacosoma americana)_Katja Schulz_CC BY 2.0_Flickr
Eastern tent caterpillar
Eastern Tent Caterpillar Moth_Malacosoma americanum_Seabrooke Leckie_CC BY-NC-ND 2.0_Flickr
Eastern tent caterpillar moth

Eastern tent caterpillar control
While the tents are unsightly, tent caterpillars seldom permanently damage trees, unless the new leaves are stripped year after year, or if a young tree is completely defoliated. Typically, trees refoliate within weeks of this spring damage. If you spot the egg masses, prune and destroy them. You can remove the nests with a stick and crush any live caterpillars—this is best done in the evening when the larvae return to the nest. As with webworms, controls work best when you first spot those tents! 

Article written by Barbara Hayes, Extension Master GardenerSM Volunteer.

More information
See a photo of an Eastern ten caterpillar egg mass.
Tent Caterpillars
by Joe Collins, University of Kentucky College of Agriculture

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Categories Plant Insects, Seasonal Chores Tags Eastern tent caterpillar, fall webworms, webs in trees

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