Southern Pine Beetle infestation. photo credit: W. Costello

This was an immediate indication of some type of bark beetle, but which one?  Having never run across bark beetles on pines at the Arboretum, I turned to the Internet and books for a clue.  The mounds of sawdust and resin on the bark were pretty good indications of Southern Pine Beetle (Dendroctonus frontalis) infestation, as was the blue staining of the wood caused by a fungus transmitted by the beetle.

Blue staining caused by the fungus transmitted by the beetle. photo credit: W. Costello

A call to Bartlett Tree Expert Company confirmed that it was too late for the first two trees, but a couple of applications of an insecticide named Onyx (bifenthrin) would protect the other three trees in the group.  Because of the size and location of the dead trees, it was late summer before they could be taken down. Once on the ground, we discovered the branches in the upper crown riddled with tiny holes.

The upper crown of the tree was riddled with tiny holes, an indication of Ips Beetle. photo credit: W. Costello

This is a good indication of Ips Beetle, sometimes known as Engraver Beetle. After peeling the bark away we could see the intricate patterns formed by the larva as they fed on the inner bark, hence the name Engraver Beetle.

After peeling the bark away we could see the intricate patterns formed by the larva as they fed on the inner bark, hence the name Engraver Beetle. photo credit: W. Costello

We still have not confirmed whether it was the Pine Engraver Beetle (Ips pini) or the Small Southern Pine Engraver Beetle (Ips avulas). While Ips Beetles are less aggressive than Dendroctonus Beetles, they will attack trees under stress.

While we are within the natural range of Ips beetles, most literature says we are north of the Pine Bark beetle range.  Communication with University of Delaware entomologists indicates that activity in southern New Jersey and Delaware are becoming more common due to climate changes. Hopefully scouting and protective sprays will prevent further damage to the other trees.

Here are some tips if you are concerned about pine bark beetles in your garden. First, if your white pines are dropping some yellow needles, don’t panic! White pines do drop old needles this time of year, and as long as it is not the new growth there is no need to worry.

Second, scout around your pine trees in mid-spring and summer. If you notice sawdust lumps mixed with sap on the bark or see a fine sawdust on the ground or on plants around your tree, call in an arborist to check it out.

In mid fall, from early to mid October, large white fruiting bodies of the fungus,  Calvatia gigantiea can be found popping up from the ground. Giant puffballs are in the class of fungi known as Gasteromycetes or “stomach fungi” as all the spores are contained internally. When immature they are pure white inside and out and are edible (see disclaimer below).

As they mature, they will darken and the skin will thicken. The spores will turn dark brown to black and will be dispersed by wind, rain or human/animal activity. Typically puffs of dark spores disperse when kicked , hence the common name. The puffball can typically reach softball to basketball size, but some up to three feet in diameter have been found. Sometimes in the woods, they will form large circles or fairy rings as the micelium spreads.

Calvatia gigantea splitting open. photo credit: J. Coceano

I have found no information to indicate that they are harmful to the garden. They are somewhat of a curiosity, as they will grow in size quickly. When the puffball matures, it will eventually dry out and turn a brownish color. The outer covering will split open and as the spores are dispersed , you will find they are hydrophobic (almost impossible to wet.)  As the puff ball degrades, it will become unsightly and can be removed at any stage as it loses its appeal.

Now as far as eating, they are edible when soft and pure white inside and out.  One recipe, I found says to cut them in ¾ inch strips, dip in a beaten egg and water mix, and dip in bread or cracker crumbs. Fry the strips in olive oil and or butter in a pan until golden brown.  If you find a lot of them and like them, you can precook them, freeze them and heat them up in a skillet later. Several years ago intern and gastropod, John Mannion, prepared some in the kitchen at the Arboretum office. It was interesting to try them.

And now the disclaimer; wild mushrooms and fungi can be very poisonous. Every year people die or become severely ill from eating what they thought was a good mushroom. If you are not sure do not eat it.  There are classes on foraging for wild mushrooms, conducted by experts, that will help you to learn the right ones.

If you have been on campus the last two weeks, you may have noticed a Bartlett Tree Co. spray truck parked around. They have been injecting our American elms, Ulmus americana, with Arbortet fungicide to protect them from Dutch Elm Disease, Ophiostoma ulmi.

Bartlett Tree Co. treating the American elm along railroad tracks by Sharples Drive for Dutch Elm Disease. photo credit: W. Costello

This treatment is done every two years in even numbered years. Small holes are drilled into the root flare of the tree and small nozzles connected to plastic tubing are inserted. The diluted fungicide is then injected under pressure into the sap stream of the tree to be carried throughout the tree.

Equipment used to inject fungicide into the trees. photo credit: W. Costello

Dutch Elm Disease first arrived in America in the 1920’s creating devastation through the American Elm population. This fungus attacks the vascular system of the tree and causes it to plug up the xylem and phloem. The clogged vessels cut off the flow of water and nutrients to the branches and cause the tree to wilt and die. This can happen within months or even days. Elm bark beetle is the main carrier of this fungus, although natural root grafts of closely planted trees will also spread it.

We have some very massive American elms on campus between the Scott office and McCabe Library, and along the railroad tracks by Sharples Drive. So far the treatments have been working for us.

The saddleback caterpillar is stunningly beautiful, but it is most likely to impress its presence upon you with a devilish sting. If you innocently brush against one where it hangs on the underside of a leaf, you will be punished with an intensely burning welt for several minutes at least. Perhaps you can forgive its cruelty as you marvel at its vivid color and otherworldly form.

The caterpillar’s common name refers to the brown, saddle-like blotch in the center of its rich kelly green back. Each end is capped with reddish-brown and bears a pair of imposing bristly “horns.” The head is moustachioed with additional spines and the tail end bears large white eye spots reminiscent of spiderman’s. Both sides of the abdomen are lined with yet more spines.

Saddleback capterpillar photo credit: N. Lewis

The saddleback caterpillar is the larva of a fairly inconspicuous brown moth. The species, Acharia stimulea (formerly Sibine stimulea), is native to the eastern United States. You are most likely to encounter the caterpillar in August and September. I have found them on roses, Itea, shrub dogwoods, and Carex, but they are documented to feed on dozens of common garden plants.

Dogwood sawfly, Macremphytus tarsatus, has been found on shrubby dogwood species on campus. While this pest looks like a caterpillar, it is actually the larval stage of a wasp-like Hymenoptera species.

Adult sawflies emerge in late spring and lay their eggs on the undersides of leaves. When the eggs hatch in mid-summer, the first stage larvae are tiny, yellow, and translucent. As they grow and molt, they become covered with a white waxy coating. They usually spend the daylight hours curled up and clinging to the underside of leaves. They can be quite gregarious, with a dozen or more congregating on one leaf. In large numbers, they can cause considerable defoliation and while unsightly, it usually will not harm the plant because it is late in the season. After the last molt, they usually stop feeding and seek a protected spot to overwinter. In early spring, they will pupate and later emerge as adults.

Leaf damage on shrubby dogwood. photo credit: W. Costello

The best control method is to handpick and drop them into a container of soapy water. You can also squash them under foot if you are so inclined (messy but effective.)

Occasionally, wasps or hornets will attack the larvae, which is fascinating to watch. They usually chew the sawfly in half and fly them back to their nest.

Dogwood sawfly on the underside of the leaf. photo credit: W. Costello

When the sawfly is detected early, insecticidal soap or horticultural oil is an effective control. In large plantings, chemical controls may be required. When the sawflies are larger, one of the contact or systemic insecticides registered for control may be needed.

We are excited about weevils at the Scott Arboretum. The stem-boring weevil, Rhinoncomimus latipes, has been found throughout the Arboretum nibbling on the invasive mile-a-minute weed, Polygonum perfoliatum.

Mile-a-minute weed is an annual Asian vine that has invaded habitats in the northeastern US: forested floodplains, streamside herbaceous wetlands, and upland forests. It can be found growing along the Crum Creek, in the Crum Woods, and on banks throughout the campus.

This prickly, branching vine germinates in April in the Mid-Atlantic region and proceeds to rapidly climb over other plants. It produces iridescent blue berry-like achenes in the beginning of mid-summer, completing its cycle with the killing frost in the fall. The next generation of this annual vine is spread by birds, mammals, and water. The seed which germinates underneath established plants requires a cold period for germination and can last for 3 years in the seed bank.

In an effort to control this invasive, the Forest Service initiated a biological control program in 1996 with host specificity tests conducted in China and in quarantine conditions in Delaware. This small, black stem-boring weevil eats small holes in the leaves of mile-a-minute vine. In the field, the adults are often found at terminals of the plant. Eggs laid in leaves and stems hatch larvae that bore into the stem. After completing development, they exit the stem and drop to the soil to pupate.

Damage to mile-a-minute vine by weevils. photo credit: R. Robert

The Forest Service trials identified the stem-boring weevil, Rhinoncomimus latipes, as host-specific to mile-a-minute vine. This is exciting because unlike the virus released to control the invasive Rosa multiflora, it will not to spread to other plants, particularly cultivated plants. While the weevils do not outright kill the invasive vine, they severely set the plant back.

Weevil eating mile-a-minute vine. photo credit: E. Lake

In 2008, Ellen Lake, a Ph.D. student at University of Delaware, visited the Scott Arboretum to release these beneficial weevils in the Crum Woods. Upon arrival she identified that they have already arrived and were chewing away on our mile-a-minute vine infestation. Since then these helpful weevils can found throughout campus gnawing on this pesky vine.

If you are battling this invasive vine on your property, look for this beneficial weevil to be feeding on your vines.

If you have visited the Dean Bond Rose Garden this growing season, you may have noticed a large section of the climbing and hybrid tea beds now contains marigolds, Tagetes patula cultivars, instead of roses. This April we removed about 17 rose shrubs because they were infected with Rose Rosette Disease (RRD).

RRD was first observed by a local gardener and Scott Associate, Judy Penney, on her climbing rose in Swarthmore. The disease has since devastated her once prolific rose and symptoms have begun to appear in the Dean Bond Rose Garden.

On the left a healthy branch of a rose bush and on the right a branch affected by Rose Rosette Disease. photo credit: R. Robert

Symptoms

Symptoms of RRD are highly variable depending on the species and cultivar of rose. These symptoms include: rapid elongation of new shoot; witches’ brooms with small, distorted leaves; excessive growth of unusually soft and pliable red or green thorns; canes that appear thicker than parent canes; and new growth’s traditional red pigmentation never matures to a green tone. To see a complete list of symptoms read the Plant Disease Fact Sheet from Virginia Cooperative Extension. In the Rose Garden, we have observed witches’ brooms with small, distorted leaves and conspicuous red pigmentation as well as rapid elongation of shoots with excessive thorniness.

Caused

RRD is believed to be caused by a virus originally introduced to control the invasive Rosa multiflora. While this virus is effective at overwhelming R. multiflora, cultivated roses are also highly susceptible to it. The disease is transmitted by a microscopic wingless mite, Phyllocoptes fructiphylus, or by grafting. These mites are known to travel on wind currents from infected to healthy plants.

Truck full of rose bushes removed because of RRD. photo credit: R. Robert

Control

At this time there is no effective control available for infected plants. It is recommended to remove all infected plants to prevent transmission to healthy specimens. The pathogen can survive on old root pieces in the soil, thus be sure to thoroughly remove all parts of the infected plants. Where permitted, burning can be used as removal technique. Once uprooted be sure to remove infected plants from the vicinity of remaining healthy roses. At this time no resistant species or cultivars have been identified.

Digging out every last piece of the diseased roses. photo credit: R. Robert

Because there is no direct treatment for the virus, we are attempting to control the carrier of the disease, the microscopic wingless mite. We are applying a miticide, Avid, along with other treatments on the garden.

Historically, marigolds have been used in vegetable gardens to help mitigate the effects of many problematic pests. In England, marigolds have also been planted in rose beds where roses have been removed to help reduce the effects of Rose Replant Disease, which is another problem in the Dean Bond Rose Garden. It is our hope that the marigolds will ward off the mites. Thus we have planted Tagetes ‘First Lady’, ‘Inca Orange’, and ‘Sweet Cream’ in an attempt control RRD.

Tagetes cultivars planted to control the disease. photo credit: R. Robert

Other efforts include sterilizing pruners between pruning and deadheading as well as monitoring and removing any newly infected plants.

This fall the marigolds will be removed and the bed will be replanted with roses. Check back with GardenSeeds to see which species and cultivars we will reintroduce to this location of the Rose Garden.

This month you may have noticed shriveling of some stems on your clematis, while others of us have been so unlucky as to experience a dramatic demise of the entire plant shriveling and turning black in a week. These symptoms are typical of a disease called clematis wilt.

Cause

These dramatic symptoms most often manifest just as the plant is about to flower, typically striking the flower buds and new growth first. In my research, I have found 2 fungi credited with causing this theatrical demise, Phoma clematidina and Ascochyta clematidina. These pathogens enter the vine’s vascular system and clog the fluid-carrying tubes causing all parts of the plant above the clog to wilt as if it needs water.

The new growth of Clematis 'Piccadilly' shriveled from clematis wilt. photo credit: R. Robert

Treatment

Luckily, this disease does not attack the roots. Simply prune out the affected stems or trim the plant to the ground. New shoots will emerge and some cultivars will bloom again in the same season. Be sure to disinfect your tools after pruning the infected plants to avoid transmitting the disease to other plants.

Once the plant has established heavy, tough stems the problem appears to lessen. In other words, the plant can outgrow the disease. These symptoms have lead some gardeners to call the disease “juvenile wilt disease”.

Clematis addisonii, a small-flowered species. photo credit: R. Maurer

These fungi appear to primarily attack early-season, large-flowering hybrids. If you would like to avoid the trauma of seeing your entire clematis shrivel up and die, plant small-flowered species like Clematis montana, C. macropetala, C. alpine, and C. viticella.

Now is a good time of year to scout your trees and shrubs for insects because there is no foliage present to hide insects living on the stems or branches. An insect not known to survive Pennsylvania winters, except for the Philadelphia region, is Indian wax scale, Ceroplastes ceriferus. Bill Costello, IPM coordinator, has been seeing these insects on Callicapra and cherry laurel in the John W. Nason Garden for the past three years. For the first time this year, he found them on Japanese maples outside of the Harry Wood Garden.

Indian Wax Scale on the stem of cherry laurel. photo credit: R. Robert

Found mostly on shrubs in the North as opposed to tree infestations in the South, Indian wax scale looks like someone stuck their white chewing gum in the crouch of the plant’s stems. If you remove the “gum” the underside of the scale is pink or red. The white substance is the wax the insect secretes to protect its body. The pink or red underside is the actual scale. Scale most often chooses hollies, euonymus, boxwood, pyracantha, and Viburnum as its hosts in Pennsylvania.

Indian Wax Scale on the stem of Callicarpa. photo credit: R. Robert

Indian wax scale feeds by extracting sap from the vascular system. A heavy infestation can cause premature leaf drop and branch dieback as well as producing large quantities of honeydew. These quantities of honeydew encourage black sooty mold which renders the plant and surrounding area unsightly.

During this time of year the best control is mechanical. Simply remove the scale from your plants with your hands. The females overwinter to produce eggs in May. Bill has identified several plants to leave the population in place to monitor their development. Once the monitored population begins its emergence period, he will apply horticultural oils to attack the newly hatched crawlers. This is when the insect is most vulnerable. Because of an extended emergence period (2 to 3 weeks), it is important to apply oils throughout this time period.

Good IPM practices require monitoring of your plants. Be sure to take a moment the next time you are working in the garden to inspect your plants for insects and diseases.

You probably haven’t seen the Emerald Ash Borer, Agrilus planipennis. Yet. This beetle from Asia was first discovered in this country in 2002 in a suburb of Detroit, Michigan and currently populates about 5,000 square miles in various states. The closest to us is Virginia, Maryland, and two counties in Western Pennsylvania: Allegheny and Butler. Yesterday, some of us at the Scott Arboretum were shown a presentation by Ron Kushner of Albrecht’s Nursery about the destruction that this insect has caused thus far. It’s pretty incredible.

Fraxinus americana 'Greenspire' at the Scott Arboretum

The Emerald Ash Borer lives and completes its life cycle only on the genus Fraxinus. The beetle mates in early summer and has a life span of only about three weeks. The females lay their eggs in the bark of the tree. The juveniles emerge and tunnel in the cambium layer in an “S” shape throughout the summer and fall. This is where the real destruction takes place. The boring of this “S” shape strangles the tree and stops the flow of water and nutrients. The adults emerge from April through June through a “D” shaped hole in the bark and will eat around the perimeter of the leaves. They can kill the host ash tree within 2 years.

Street trees all over Michigan and elsewhere are dying and being taken down every day. Streets once lined with beautiful ash trees that provided shade for people and habitat for animals are now gone, leaving barren, sun-bleached landscapes. Because this insect reproduces so profusely and has moved around on firewood and nursery stock, all ash trees in this country are at a certain level of risk.

Control and management of this insect has been extremely difficult. According to Doug Tallamy’s research, up to 1,500 different kinds of insects can live in one oak tree, so people are hesitant to begin spraying ash trees because many other kinds of insects would die in addition to the Emerald Ash Borer.

What can you do as a gardener in southeastern Pennsylvania? Be on the lookout for this insect. Know your ash trees and monitor them by looking for leave damage and “D” shaped holes in the bark. Report a sighting immediately to badbug@state.pa.us. Do not transport firewood or buy ash trees from nurseries in infected areas. For more information, visit http://www.emeraldashborer.info/.

If you are you interested in learning more about insects and their relationships to plants and animals, join Doug Tallamy for his lecture Gardening For Life on February 12th here at the Scott Arboretum.