The newest emerging disease affecting shade trees, Beech Leaf Disease, is spreading across the Northeastern states and it is on campus. This disease affects American beech, European beech, and Oriental beech. It is currently having a devastating effect on the predominant beech/birch/maple forest in New York state and has been present in Massachusetts since 2020.

Symptoms include leaf striping, curling, and leathery texture. These symptoms can be observed from May to October by looking up into the canopy. Microscopic worms, known as nematodes, feed on plant foliage, affecting the leaf tissue and photosynthetic process, which in turn weakens the tree. As the disease progresses, leaf and bud production is impacted along with heavy leaf loss. A single tree can have heavily infected branches and unaffected branches. 

The beech genus, Fagus, lacks any natural defenses to this disease. The two options for treatment are foliar sprays and trunk injections. Foliar sprays are typically for young specimens while mature, large specimens require a trunk injection. Many homeowners are choosing to protect their large, mature specimens with these treatments. 

Here at Scott, we are proactively treating approximately 30 specimen trees in the heart of campus, where we are seeing little to no symptoms at this time. 

Unfortunately, our predominantly maple/beech forest along the Crum Creek is extensively affected. We are letting nature take its course in the woods and are developing plans to replant the beech-dominated areas with native trees. We plan to use a selection of white oaks (Quercus alba), hickories (Carya spp.), and maples (Acer rubrum), and also allow our tulip poplars (Liriodendron tulipifera) to seed in. In the understory, we are planting redbud (Cercis sp.), chokeberry (Aronia sp.), and native dogwood (Cornus florida). 

Learn more about this disease in Pennsylvania here. 

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Garden Supervisor Adam Glas explains best practices on removing plants infected with rose rosette disease.

Learn more about Rose Rosette Disease here.
https://www.scottarboretum.org/rose-rosette-disease/
https://www.scottarboretum.org/update-rose-rosette-disease/

Tune into the Gardener’s Almanac to learn what we are doing in the garden at this moment. Learn from Scott Arboretum staff which plants we are pruning, planting, weeding and which pests we are monitoring and removing right now. This virtual almanac is a great reference guide for gardeners.

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Assistant Garden Supervisor/Plant Health Lars Rasmussen explores the major spring garden pests.

Tune into the Gardener’s Almanac each week to learn what we are doing in the garden at this moment. Learn from Scott Arboretum staff which plants we are pruning, planting, weeding and which pests we are monitoring and removing right now. This virtual almanac is a great week by week reference guide for gardeners.

The post Gardener’s Almanac: April 19 – Major Spring Garden Pests appeared first on Scott Arboretum & Gardens.

Spotted lanternfly adults are red and black with black spots. photo credit: L. Rasmussen

What is a spotted lanternfly?

The spotted lanternfly or Lycorma delicatula is an invasive arthropod species of the planthopper family. These insects undergo four instar stages as nymphs before reaching the adult stage. While the nymphs of Lycorma delicatula have a black exoskeleton with white spots and share the appearance of small spiders or ticks, the adults are red and black with black spots. Despite having wings in the adult stage, Lycorma delicatula are primarily hoppers and crawlers.

Despite having wings in the adult stage, Lycorma delicatula are primarily hoppers and crawlers. photo credit: L. Rasmussen

The spotted lantern fly prefers the “tree of heaven” (Ailanthus altissima), but these insects have been found to feed on a variety of 25 tree species in the state of Pennsylvania alone. The egg masses are laid on smooth bark, stems, and other flat surfaces and resemble grey putty. Each cluster protects as many as 50 eggs. The insects laying ritual occurs in the fall and early winter.

When you find a spotted lanternfly squash the pest. photo credit: R. Robert

Are they dangerous? 

Although these invasive arthropods are not known to be a direct danger to humans and pets, they are certainly a serious pest to some food crops and several tree populations. Rather than outright killing the trees themselves, the Spotted Lanternfly feed on them leaving open lesions from which tree sap will flow and attract other insects. The sugary substance the insects excretes while eating is called honeydew which drips down to branches below and is the cause of sooty mold development, which ultimately weakens the tree. It is disconcerting that these insects may gravely impact tree nurseries as well as crop yields from fruit trees, grapes, soybean, and corn if this infestation continues to spread unchecked.

The Scott Arboretum gardeners are herding the spotted lanternfly to a “trap” tree. photo credit: S. MacQueen

What are we doing about them here at Scott?

Since the Scott Arboretum (along with the rest of Swarthmore and Delaware County) is in the quarantine zone, we support the method of herding the pest population to “trap” trees. This is done through selective destruction of female (and some male) Ailanthus altissima trees and applying a systemic herbicide to inhibit sucker sprouting. The trap trees are then treated with an insecticide for a mass extermination of the local pest population in the area.

Parthenocissus henryana is a favorite of the spotted lanternfly. photo credit: J. Coceano

Trends in the Delaware Valley

We have observed that the pest likes Parthenocissus and all plants in the grape family, Vitaceae, in general. We have been herding the lanternflies to our native Virginia creeper (Parthenocissus)  to use as a “trap” tree.

Egg masses should be scrapped off surfaces. photo credit: L. Rasmussen

 What do I do when I see one or many?

If you find a bug, simple squish the pest. They are hopping insects and thus easy to catch. During this time of year, you will find egg masses, which should be scraped off and disposed of. Please do not broadly apply pesticides to control this pest. Consider using sticky pads on targeted plants to trap this pest.

Get answers to all your question at our info session “Tips for Dealing with Spotted Lanternflies” on Tuesday, December 10, 2019 from 7 to 8:30 pm.

For more reference please see

https://www.agriculture.pa.gov/Plants_Land_Water/PlantIndustry/Entomology/spotted_lanternfly/SpottedLanternflyAlert/Pages/default.aspx

https://extension.psu.edu/spotted-lanternfly

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Today we removed another 13 rose plants from the Dean Bond Rose Garden because of Rose Rosette Disease. This virus affects many rose cultivars. Read more in our 2009 Garden Seeds post.

Distorted leaves are a symptom of Rose Rosette Disease. photo credit: A. Glas

We have been removing all roses when they show signs of illness since 2009. This part of the garden will not be replanted for a year to avoid Rose Replant Disease, which occurs when a new rose is planted in the same soil as the one removed. The source is believed to be a soil imbalance caused by the removal of trace elements, a natural build-up of fungal soil disease and soil micro-pests caused by the old rose.

Rapid elongation of new shoots is a symptom of Rose Rosette Disease. photo credit: A. Glas

Rose Rosette Disease symptoms include rapid elongation of new shoots; 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 maturing to green. If you observe these symptoms remove the plant. Do not replant with roses for at least a year.

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Strolling in the garden at this time of year, you might be surprised to find your Asclepias spp. (milkweed) infested with orange- and black-spotted bugs. Often seen in groups of a dozen or more, they can be a shocking sight to gardeners. No need to worry: Oncopeltus fasciatus, the milkweed bug, causes minimal damage to plants.

This time of year, all stages of these insects’ lifecycles can be found on Asclepias seed pods.  Adults typically live a month during the summer, with females laying over 2,000 eggs in a lifetime. These eggs are placed in the milkweed seedpods or in crevices between pods.  Nymphs lack the full wings of adults, and are mostly red with black antennae and a few black spots.  Throughout growth, these black spots develop as do wing pads.

This true bug (order: Hemiptera) is more of a nuisance than a threat, feeding on the seed, leaves, and stems of milkweed. Most gardeners live with the minimal damage caused by these orange beauties because it lasts for such a short time.

This time of year, all stages of these insects’ lifecycles can be found on Asclepias seed pods. photo credit: R. Robert

They can be controlled by removing leaf litter and spent stalks in the fall as this is where the adults overwinter. While one could use insecticidal soaps to eliminate milkweeds bugs, this is a poor method because any soap used will also prevent butterflies from living on the plant. Monarchs butterflies cannot survive without milkweed; their caterpillars eat only milkweed (Asclepias spp.), and adults need milkweed to lay their eggs.

Enjoy the colorful bug display for the month!

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This gall is produced by the harmless Cynipid gall wasp (Callirhytis seminator). photo credit: R. Robert

This gall is produced by the harmless Cynipid gall wasp (Callirhytis seminator). These wasps lay their eggs on a specific plant and the eggs produce the grubs whose secretions cause the gall formation. The gall provides protection and nutrition. Their favorite host plants are oaks.

The galls do not harm the tree, so the best integrated pest management practice is to co-exist. One-to three-weeks later a wasp will emerge. It is another amazing insect-plant relationship.

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During damp springs, cedar quince rust (Gymnosporangium clavipes) produces cushion-shaped, orange, gelatinous blisters through the bark where the branches are swollen on cedars and junipers. photo credit: R. Robert

This fungus has a two-host lifecycle.  A few hours of wet, cool (74 to 78 degrees F) spring weather are sufficient for telial swelling on the juniper and the release of basidiospores.

Chaenomeles speciosa ‘Appleblossom’ can be a second host for cedar quince rust. photo credit: J. Jin

These basidiospores travel to the second host, members of the rose family including quince, apple, crabapple, and hawthorn. There they infect stems and fruit, producing tiny black dots within a few days. Four to seven weeks later, in late summer/early fall, aeciospores become airborne and infect cedar or junipers again.

Aesthetically this rust can cause some dieback on the junipers and cedars.

A few hours of wet, cool (74 to 78 degrees F) spring weather are sufficient for telial swelling on the juniper and the release of basidiospores. photo credit: R. Robert

Good integrated pest management practices include:

1. Pruning out the crankers.
2. Co-exist with the disease. We typical live with the plant and some orange goop in the spring if the infection is minor.
3. Avoid planting susceptible plants together. Unfortunately in the BioStream, we have Juniperus virginiana (particular susceptible species) and a hawthorn with the quince collection all planted within wind distance.
4. Select resistant varieties. If you are not comfortable with the damage being caused, remove the diseased plants and select cultivars for rust resistance.

The cedar-quince rust galls may remain infectious for 4–6 years or more (up to 20). The infection cycle only appears when wet conditions are just right. Some years the symptoms do not appear at all.

Juniperus virginiana ‘Burkii’ look great in winter display for the BioStream and show no symptoms of cedar quince rust. photo credit: J. Coceano

Thus, we just live with a little bit of orange goop in the spring. As we progress into the hot temperatures of summer, the goop will dry up.

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Most of the Prunus ‘Okame’ blooms were destroyed by frost. photo credit: R. Robert

No need to panic. Your tree is not dead. It is just a victim of unseasonably warm temperatures in February and then a return to cold temperatures in March. The warm temperatures caused early blooming cultivars like Prunus ‘Okame’ and Magnolia  x loebneri ‘Leonard Messel’ to bloom or almost come into full bloom.

The middle flower of Magnolia x loebneri ‘Leonard Messel’ was burnt by frost. The other two buds were not open during the cold snap and thus have bloomed beautifully. photo credit: R. Robert

Closed buds can handle the freezing temperatures but open flowers are susceptible. Unlike some plants such as witchhazels and crocus whose blooms can withstand a cold snap and dip below freezing, the open flowers of most cherries and magnolias are not as resilient. The frost has destroyed their seasonal display.

Later blooming cherries are looking wonderful in the garden right now. photo credit: R. Robert

The good news is your tree is fine and will leaf out in another week or two. Barring another late winter/early spring major temperature swing, you will enjoy another “pink” spring with your cherry tree next year.

Prunus x yedoensis typically opens mid-season thus was not affected by the cold snap. photo credit: R. R.obert

If you have planted early and late bloomers in your garden, you can enjoy a show no matter the volatility in temperature.  While the Arboretum will not experience a show from Prunus ‘Okame’ this year, other varieties like Prunus x yedoensis are looking stunning right now in the Cherry Border. The season typically ends with the wonderful double-pink flower from Prunus ‘Royal Burgundy’. To explore all the flowering times of cherries, download the Cherry Collection brochure.

These magnolias flowers were in full bloom before the frost. Now they are just brown. photo credit: R. Robert

If you are looking for later blooming magnolias, consider yellow selections like: Magnolia ‘Elizabeth’, M. ‘Butterflies’, and M. ‘Golden Endeavor’.

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Have you ever notice a “fishy” smell coming from the Dean Bond Rose Garden? This is part of our organic rose garden procedure. Applied roughly every two weeks depending on conditions, a mixture of fish hydrolysate and water (1.5 ounces per gallon) is sprayed liberally on the plants of the Dean Bond Rose Garden.

Black spot on leaves in the Dean Bond Rose Garden. photo credit: R. Robert

In addition to working as a fertilizer, fish hydrolysate applications function as a fungicide. Similar to a chemical fungicide, fish emulsion is applied while wearing protective gear; the entire plant is coated. This prevents the spread of funguses like black spot.

Fungal spores can splash onto healthy leaves from fallen infected leaves on the ground. photo credit: R. Robert

Besides fertilizing the roots and building microbial activity in the soil, a drenching of fish emulsion suppresses the fungus spores from splashing on other plants to spread disease. We are currently working on identifying and removing cultivars of roses highly susceptible to black spot. The remaining resistant cultivars will enjoy the benefit of a restored healthy balance in the soil structure created by these applications which will increase in their resistance to disease.

If you see a gardener in a spray suit applying a smelly substance in the Dean Bond Rose Garden, it is not chemical based even though these treatments are applied with equipment similar to traditional treatments. photo credit: R. Robert

So if you see a gardener in a spray suit applying a smelly substance in the Dean Bond Rose Garden, it is not chemical based even though these treatments are applied with equipment similar to traditional treatments.

Similar equipment is used to apply fish hydrolysate. photo credit: R. Robert

Consider these organic alternatives for your garden. The fishy smell lasts only until the liquid dries, allowing everyone to smell the roses. For more information on the Dean Bond Rose Garden efforts, check out the 2015 Winter issue of the Hybrid.

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