Landscape - Fall Needle Drop in Pines

Inner needle drop is a natural occurance in pines and other evergreens in the fall. The following is more information.

White pines with inner needles turning yellow are not dying, they are just experiencing normal fall yellowing and leaf drop. While evergreens do not loose all their leaves in the fall, individual leaves/needles do not last on the tree forever. If trees are small, you can shake them and loosen the needles. You will end up with a nice pine straw mulch below the trees.

In some years, the natural needle drop will occur in a relatively short period of time, with rapid and noticeable browning of the older needles, which leads to fears the tree is dying. In other years, people don't even notice it happening, because the browning is spread over a long period of time.

The symptoms are normal for the fall. Pines and arborvitaes normally shed their oldest needles in the Fall. White pines usually retain their needles for one to two years. The older needles, those towards the center of the tree, turn yellow before dropping. Older arborvitae leaves turn a reddish brown. Natural needle discoloration may be more noticeable on trees that have experienced root stress due to less than optimal growing conditions. Extended dry periods during the summer months, as well as sites with poorly drained, heavy clay soils may accentuate root stress to pines. Since the newest growth (this year's needles) are still green and healthy in appearance, you can be assured that this yellowing phenomenon is a natural one.

Fall needle drop in pine. Photo from the Plant & Pest Digital Library at Purdue University.

Information from the Ornamentals Hotline Newsletter from UD Cooperative Extension and Gail Ruhl and Jeff Burbrink, Purdue University.

Landscape - Pine Needle Scale

I recently identified pine needle scale on white pine. The following is information about the life cycle of this common pest.

The pine needle scale, Chionaspis pinifoliae (Fitch), is probably the most common armored scale found on conifers in the United States and Canada. The white, oystershell shaped scales can completely cover needles, causing plant discoloration to needle and branch death.

This scale settles on the needles of its host and forms white, oyster shell-shaped wax covers. These covers or armor are about 1/16 to 1/8- inch long when the scales are fully grown and there is a yellowish spot, the exuvim, on the small end. The male scales are usually smaller and more slender. This scale overwinters as deep reddish colored eggs protected under the female's old armor. The eggs hatch in mid-May into tiny, flat nymphs called crawlers. These crawlers creep to new places on the tree in order to find suitable needles on which to feed. These clumsy crawlers often fall from the trees and may be blown onto nearby trees. Once settled on a suitable needle, the crawler inserts its hair-like mouthparts, and begins to form the new armor. After a couple of weeks, the nymph molts under the armor and continues to increase in size for about three weeks. By this time male scales are smaller and more slender than the females. The males molt into a pre-pupa for a week before emerging as winged adults. The females, however, molt into wingless nymph-like adults. After mating, the females continue to grow for a couple of weeks before laying eggs under the armor. Females produce an average of 40 eggs.
Two generations of this scale occur. The overwintering eggs hatch in mid-May and the summer produced eggs hatch in late July. Unfortunately, the eggs may hatch over a period of two to three weeks.

Information from the Ohio State University http://ohioline.osu.edu/hyg-fact/2000/2553.html

Landscape and Nursery - Pine Needle Scale

The following is information on pine needle scale. Crawlers are now active in Delaware

Pine needle scale, Chionaspis pinifoliae, crawlers are actively searching for places to settle and feed. Crawler activity often begins when Forsythia intermedia is in full bloom, however peak crawler activity is 498 (range 63-1046) GDD base 50 . Crawlers are light purple in color until they settle and turn light yellow with a dark longitudinal line down the center. Crawlers, found on needles, may spread by crawling, wind or birds. This scale prefers pines, especially Scotch and mugho, but may also be found on firs, Douglas-firs and spruces. Adults appear as white oyster-shaped scales and when populations are large, give plants a frosted appearance. Untreated heavily infested plants may cause needles to turn yellow to brown and may cause twigs or branches to die. Females lay about 40 reddish colored eggs during the summer around 1622-2745 [2053 peak] GDD base 50 . The second generation of crawlers usually begins at 1791 GDD base 50 . Another closely related scale, Chionaspis heterophyllae (commonly called PINE SCALE or PINELEAF SCALE), is known to feed on pines predominately, but has been reported on fir and spruces. The differences between the two are only noticeable under a microscope.

Natural enemies such as the twice-stabbed lady beetle and parasitoids attack this scale species. Treatment options include: horticultural oil, insecticidal soap, dinotefuran, acetamiprid, pyriproxyfen, acephate, and synthetic pyrethroids such as deltamethrin. In some cases, such as on Christmas tree farms, removal of heavily infested trees reduces the likelihood of other nearby trees becoming infested.

Pine needle scale giving a frosted appearance. Photo by Whitney Cranshaw, Colorado State University, Bugwood.org.

Information from Brian Kunkel, Ornamental IPM Specialist, UD.

Landscape - European Pine Sawfly

The following is information on the European Pin Sawfly.

European pine sawfly should be active at this time. The European pine sawfly is a pest of mugo Japanese black, red, and scotch pines. Larvae are dark green with a black head and closely align themselves along the needles so are very difficult to detect. European pine sawfly feed on last year's growth. They can defoliate needles rapidly as they mature. Hosts look sickly, growth is reduced and they have a "bottle brush" or "poodle tail" appearance due to removal of needles behind the new season's growth especially in the early instars. Small larvae feed on the surface of needles, causing them to turn brown and wilt. Larger larvae eat entire needles but do not feed on new growth. They usually occur in small clusters, if enough are present, they can consume most of the needles on the plant. Mature larvae will drop to the ground and pupate in brown paper-like cocoons that are blunt at each end. There is one generation each year. Plan to scout now--it is hard to see the 1st and 2nd instar larvae but they are easier to control and early control can reduce host damage. Control options include a host of materials such as sevin and the pyrethroid insecticides. Spot spraying works if you only have a few trees, but scout carefully to detect each colony. Remember sawflies are not caterpillars (although they resemble them) so B.t. will not provide control. Unfortunately, infestations often are not noticed until most of the larval feeding is finished.

European Pine Sawfly. Photo by Steven Katovich, USDA Forest Service, Bugwood.org.

Information from the University of Delaware and University of Kentucky.

Landscape - White Pine Weevil Pictures

The following are pictures of the white pine weevil and its damage.

Terminal demonstrating characteristic "shepherd's crook" on pine from white pine weevil. Photo by USDA Forest Service Archive, USDA Forest Service, Bugwood.org.

Close-up of two white pine weevil adults. Photo by Dave Powell, USDA Forest Service, Bugwood.org.

White pine weevil larvae. Photo by Joseph O'Brien, USDA Forest Service, Bugwood.org

Newly emerged adult white pine weevil and exit holes on a pine terminal. Photo by Steven Katovich, USDA Forest Service, Bugwood.org.

Drooping leaders which eventually die on white pine or Norway spruce are the familiar symptoms of white pine weevil attack. Photo by John A. Weidhass, Virginia Polytechnic Institute and State University, Bugwood.org.

Landscape - Sawflies on Pines

Sawflies can cause significant damage to pines in the late summer. The following is more information.

Sawflies are members of the same insect order (Hymenoptera) that includes ants, bees, and wasps. The larval stage has a caterpillar-like body that may be brightly marked with stripes or spots. Some species change significantly in appearance as they grow, making identification confusing. Large numbers of sawflies can strip the needles from a tree in a short period. Several species can be found on pines in Delaware.

Feeding is most severe in the crown to upper half of the tree but heavily infested trees can be completely defoliated. If this occurs after the winter buds have formed, many branches or even the entire tree can be killed. There are two generations each year in some sawflies. The second generation feeds on both old and new needles during August and September.

Sawfly populations are usually controlled by combinations of natural enemies, predators, starvation, disease, or unfavorable weather. Outbreaks can occur when natural control does not produce high mortality. Regular inspection of pines will help to detect sawfly infestations before the larvae reach a size that can cause significant defoliation. Since eggs are laid in clusters, feeding by groups of larvae can cause unsightly damage to ornamental or landscape plantings, as well as nursery trees.

If only a small number of colonies are present and accessible, they can be handpicked, shaken off, or pruned from the tree and destroyed. Some of the insecticides that can be used for sawfly are acephate, bifenthrin, carbaryl, esfenvalerate, and permethrin. Although sawflies look like caterpillars, they are not susceptible to Bt sprays.

Adapted from "SAWFLIES - LATE SEASON PINE DEFOLIATORS" By Lee Townsend in the August 18, 2008 edition of the Kentucky Pest news from the University of Kentucky, College of Agriculture.

Landscape and Nursery - Fusiform Rust of Pine

The following is information on a rust disease we are currently seeing in pines.

Fusiform rust of pine is caused by the fungus Cronartium fusiforme, and is widely distributed in southern states up to Maryland and Delaware. Infections result in swollen, spindle-shaped (or oval) galls on branches of the pines with orange spore production in the spring. Loblolly and slash pine are both very susceptible. The disease may kill trees less than ten years of age, and cause deformed branches on older trees. This fungus requires an alternate host, oak, and there are usually oaks in the vicinity of infected pines. Black and red oaks are the most susceptible and symptoms occur only on the leaves. The best control is the use of resistant varieties. Pruning of infected branches or rouging out of infected pines will reduce infection. Some years may be worse than others for infection and sporulation. Do not fertilize infected trees and stimulate excess growth.



Nancy Gregory, Extension Plant Diagnostician, Department of Plant & Soil Sciences, University of Delaware

Ornamentals Hotline Disease Pictures for Issue 18, July 27, 2007

Nectria Canker on Honeylocust

Photo: Robert Blanchette, University of Minnesota Extension

Diplodia Tip Blight on Pine
Photo by Minnesota Department of Natural Resources Archives

forestryimages.org

Diplodia Tip Blight on Pine
Photo by Susan K. Hagle, forestryimages.org