Locust Leafminer

Don’t worry about those brown trees!

By Glenn Palmer –
Every year around this time people start asking about “Those trees that are already turning color”, like fall has come earlier and earlier. Generally they’re referring to roadside stands of Black Locust trees (Robinia pseudoacacia). The discoloration is caused by the offspring of a small beetle called the Locust Leafminer (Odontota orsalis). The female beetle deposits eggs inside Black Locust leaves where the larvae hatch and feed, creating “mines” between the upper and lower surfaces that eventually turn the leaves brown.

This is an annual occurrence, but there seem to be cycles where some areas are particularly hard-hit and entire mountainsides do indeed look like fall has arrived. Although a systemic insecticide applied at the right time might reduce the damage there doesn’t seem to be any long range ill effects on the trees.

Photo by Rebecca Finneran, Michigan State

Photo by Rebecca Finneran, Michigan State Univ

Dirr, in his Manual of Woody Landscape Plants, says “Black Locust is an ‘alley cat’ type of tree which can survive under the toughest conditions like strip-mined areas, highway cuts and fills. Not recommended for the home landscape.”

So, our suggestion is to find something else to worry about. No action needs to be taken regarding those browning trees.

By the way, Locust wood is a survivor, good for ground contact like fence posts or raised garden beds where it generally will last much longer than cedar lumber.

Nature’s Ingenuity

Basic Botany is a useful Tool for any Gardener
by Glenn Palmer

To me one of the important rewards of gardening has been gaining an appreciation for nature’s ingenuity, an understanding of the mechanisms that plants have adopted to carry them through their life cycles.

For example, take peas. The vine needs to fasten itself to the trellis for support as it climbs. But did you ever wonder how tendrils find the trellis? And what makes them twirl around? Or why do they climb in the first place?

Photo by Maria Keays

Photo by Maria Keays

It’s all due to “isms” like phototropism. If the light is overhead when a seed sprouts it will grow toward the light. If the light is off to one side a hormone called auxin causes the cell on the side away from the light to grow faster, bending the stem toward the light source. That’s called positive phototropism. Growing toward the light.

Thigmotropism is growth in response to touch or contact. As the pea climbs, its tip spirals around and then when it contacts something that might serve as a support thigmotropism – a sense of touch – takes over and one-sided growth shifts to make the tendril wrap about that support.

Positive or negative geotropisms cause parts of plants to grow against or toward gravity, away from or toward the earth. Negative geotropism causes White Pines to grow straight up, away from gravity while Sourwoods stick with positive phototropism and wander back and forth seeking the sunlight as the canopy above them changes. That’s why pioneers used naturally bent Sourwood logs as sledge runners.

And then there’s sex. Not an “ism” but something a gardener needs to understand. How do plants reproduce? We cut and plant pieces of a potato – actually they’re pieces of the root – to grow a new plant and more potatoes. But that’s not nature’s way. Given the right conditions – long days and cool nights – potatoes, members of the same genus as tomatoes, will produce small flowers which develop into small green “berries”.

Photo by John Meade

Photo by John Meade

Inside those berries will develop seeds which is the natural way for potatoes to reproduce. Due to our unusual 2015 weather pattern we’re seeing some of these potato berries in our gardens right now. But heads up! Those berries contain a toxin and are not edible!

EMGV Training Class 2016

imageN.C. Cooperative Extension, Buncombe County Center, will not be offering an Extension Master Gardener Certification class in 2016. Positive changes to update and streamline the EMGV training curriculum statewide are underway and more than likely will not be completed in time for the 2016 class deadlines. In addition, NC Cooperative Extension is implementing a strategic plan that affects budget, staffing, resources and programming on the local level, making it difficult to fully manage the many aspects and activities of our current master gardener group.

It is important that we have the program support and curriculum resources needed to provide a great experience for our all of our volunteers. Please be patient as we revamp the program and make sure the class of 2017 has the best EMGV experience possible.

Please call 828-255-5522 to register your name and be notified about the 2017 EMGV Certification application period.

Shedding Bark

By Glenn Palmer – 

imageEvery year around this time we are contacted by homeowners and landscapers who notice bark peeling off crape myrtles and accumulating around trees. This causes great concern because for most tree species shedding bark is very bad. For crape myrtles however, it is completely normal and happens every year. Often the landscape below is strewn with strips of crape myrtle bark.

Some crape myrtle varieties seem to shed more bark and in larger pieces than others. The multi-colored patterned bark is one of the attractive features of these trees and this shedding contributes to those patterns. In any case, just rake it up and figure it is probably a sign of active growth and a healthy tree.

Late Tomato Blight is Here

Late tomato blight was discovered in Buncombe County last week. This is a reprint of a post written by Debbie Green, originally published two years ago.

Tomatoes should be reaching their prime, and if you have lush green plants with ripening fruit, enjoy your harvest. If your plants aren’t looking so good however, they may have one of the many tomato diseases that sometimes thwart even the most experienced vegetable gardeners. One of the most serious of these is late tomato blight, which typically affects plants later in the growing season, but has been confirmed on plants in West Asheville as of early July this year. This disease can spread spores as far as 20 miles, so identifying the disease and destroying the affected plants may spare others’ tomatoes from developing the symptoms.

 The first symptoms of late blight on tomato leaves are irregularly shaped, water-soaked lesions.

The first symptoms of late blight on tomato leaves are irregularly shaped, water-soaked lesions.

Rain and high humidity are both favorable conditions for the spread of late blight. Once your plants are infected they can’t be cured; fungicides containing copper or chlorothalonil are currently the only treatments proven effective to prevent late blight. If you spray your plants, follow label directions. Take care to cover all leaf surfaces; use eye protection and other precautions to prevent contact with the spray.

The good news is there are less devastating diseases that are not late blight, so getting a positive diagnosis is important. The first signs are irregular dark spots that look water-soaked on the newer leaves at the top of the plant, often with a lighter-colored “halo” around them. As the spots enlarge, the leaves shrivel and die. You may also see white cottony growth on the underside of the leaves. Both ripening and green fruits are also affected, with greasy looking spots that turn brown and leathery.

During humid conditions, white cottony growth of P. infestans may be visible on the underside of affected leaves.

During humid conditions, white cottony growth of P. infestans may be visible on the underside of affected leaves.

There are many images available online to help you determine if you have late blight; one of the most comprehensive series of photos is this one prepared by Dr. Meg McGrath of the Long Island Horticultural Research and Extension Center: If you are unsure about the diagnosis, you can bring photos and samples of your plants to the Master Gardener Clinic at the Buncombe County Extension Office.

If you do have late blight, bag up your plant as soon as you can, but do it on a sunny day to reduce further spread of the disease. You can salvage already ripened fruit or green tomatoes that don’t show symptoms; these are safe to eat. Take care to look for affected plants other than tomatoes, especially potatoes and petunias. Weeds in the nightshade family may also show symptoms and should be removed and bagged.

 Infected fruit are typically firm with spots that eventually become leathery and chocolate brown in color.

Infected fruit are typically firm with spots that eventually become leathery and chocolate brown in color.

If you lose your plants, there is always next year. There is ongoing research on less susceptible varieties and some evidence that ‘Defiant,’ ‘Mountain Merit,’ ‘Mountain Magic,’ and ‘Plum Regal’ tomato varieties are resistant to late blight. Consider planting these varieties next season if you want to increase your chances of a blight-free crop.

For more information see

What is Bugging Your Garden

By Debbie Green

The garden isn’t looking good and you see bugs on some of the plants—what should you do? Identify both the plants and the critters you see; those bugs may be the solution rather than the problem!

The Facts

Environmental issues—soil, nutrient and weather extremes or damage by people or wildlife cause more sad-looking plants than insects or diseases. And 90% of insects are either beneficial or “innocent bystanders,” not pests! The bug you see on a chewed leaf may be on its way somewhere else or getting ready to consume the eggs, larvae or adults of the bad guys responsible for the damage.

Plant and Bug ID

Mistaken identity takes many forms. Plant pests are often specific to one or a few closely related plants, so it’s important know what plant is affected. Both plants and bugs have look-alikes that might fool you. For fruits, vegetables and ornamental plants, shrubs and trees you’ve planted, checking the seed packets or plant tags is easy. For things already in your landscape, do some detective work—our Extension Master Gardener Volunteers can help! We can help with the bugs, too, but check the resources listed to know your insect companions.

Next Steps

If you find a pest on a plant, doing nothing may be best. Most pesticides will kill any beneficial insects working to clear out the offenders, so handpicking large pests or using water to hose off smaller ones may be all you need to limit the damage. If the plant is severely damaged, decide if keeping the plant is worth the cost of using a pesticide. If you want to proceed, verify the product will kill the insect you’ve identified and is safe for the plant so you don’t grow perfect tomatoes you can’t eat.

Come to our “Good Bug, Bad Bug” presentation 7/16/15 
10:00 – 11:30 am

Buncombe County Extension Office Classroom
94 Coxe Avenue, Asheville


Debbie Green and

Bob Wardwell

Another Heads up!

Tulip Poplar Weevil DamageWe have an uncommon insect appearing in our Tulip Poplar trees. Magnolias and sassafras trees are also at risk. The poplars will have leaves with brown dried edges and small brown spots. From a distance, the trees appear to suffer from leaf scorch or some other disease, but this is the work of small dark insects called the Yellow Poplar Weevils, Odontopus calceatus. Generally, these are most common further north in central Appalachia.

If you do have weevils, more than likely you’ll find the damaged leaves on the ground. While the appearance may be unsightly, the injury to large, established trees in landscapes or wooded areas is probably inconsequential. Chemical control is not needed

Poplar WeevilsBy mid-summer the adult weevils will have retreated into the leaf litter, where they’ll remain inactive until the following spring. It’s really too late to do anything now except clean up and dispose of the damaged leaves. Burn or bury. Do not compost.

U.S. Drought Monitor: Asheville Now in Moderate Drought*

But first, recognize that in our mountains all weather is local! Native Americans referred to the Weaverville area as the “Dry Ridge” and it is indeed one of the driest points in the eastern US. Yet only some 30 miles away but several thousand feet higher in altitude, Alta Pass is among the wettest, continually dampened as rising air from the west is forced to drop its load of moisture.

Then you have anomalies like the fact that Asheville’s “official” rainfall is not actually measured at Asheville. The official weather station for Asheville, North Carolina is located at the Asheville-Hendersonville Airport, ten miles south of, and not even in the same county as Asheville.

imageSo that’s why your own journal notes and observations are important. Gathering data from your own rain gauge and thermometer readings can be helpful in comparing one year to the next and identifying needs or trends in your garden. Even better than judging rainfall by the condition of your neighbor’s lawn!

Back to the Drought Monitor. By their definition in a “moderate drought” we can expect “Some damage to crops, pastures; streams, reservoirs, or low wells; some water shortages developing or imminent; voluntary water-use restrictions requested.”

So, fellow gardeners, it’s time to start setting priorities on which plants get first dibs for irrigation. Get outside before breakfast and water early in the morning. Mulch to help conserve what soil moisture you do have. Maybe change some priorities for your plantings in the fall garden. Perhaps let some space stand fallow or with a cover crop.

imageAnd a self-serving reminder: Buncombe County Cooperative Extension has rain barrels for sale! Even occasional brief rain can fill a rain barrel.

*U.S. Drought Monitor of North Carolina, June 23, 2015

For more information about coping with drought:

Heads up! Watch for Oak Leaf Blister this summer



As a result of our damp spring, this fungal disease has been appearing on our landscapes more frequently than normal this summer. Members of the red oak group, the ones with the sharp points on their leaves, are particularly susceptible. Less so are the white oaks, identifiable by their leaves with rounded lobes.

Oak Leaf Blister

Oak Leaf Blister

Oak Leaf Blister

The only tree damage from this disease is to the leaves. Symptoms are yellow, blister-like, raised areas, 1/16 to ½ inch in diameter, scattered over the upper leaf surface, with corresponding grey depressions on the lower surface. They will turn from yellow to reddish brown with age. Several blister areas may merge and cause the entire leaf to curl.

The fungus reproduces from spores that lodge in and overwinter in the buds.

If the tree is in good health, little harm is done. No control is really needed. However, in a landscape situation where “near perfection” is the standard, a dormant application of a fungicide containing chlorothalonil just before new growth begins in the spring, can be helpful. One application should suffice. To be effective, fungicide must cover all the buds and twigs on the tree. Generally, this is a job for the tree professional.

Good Bug, Bad Bug Class July 16

Gardening in the Mountains presents:
Good Bug, Bad Bug
July 16, 2015
10:00-11:30 am

Buncombe County Extension Office Classroom
94 Coxe Avenue, Asheville

Presenters: Debbie Green and Bob Wardwell

imageDo you assume that any insect you see in your garden is a “bad bug”? Or do you recognize that some insects are “good bugs”? If you want to learn how to decide which insects are harmful or beneficial and what you should – or shouldn’t – do, come learn the basics of insect identification and Integrated Pest Management. Bring insects (in a bug-proof container, please!), insect-damaged plant samples or photos if you have specific bugs you would like to identify.

The talk is free but pre-registration is requested by calling 828-255-5522
Free parking is available in the lot across the street on the corner of Coxe and Hilliard Avenues.