Maryland Grows

Why are Oaks Declining? Dr. Dave Describes 3 Oak Diseases

oak wilt symptoms

Leaves showing oak wilt symptoms, Pittsburgh, PA (Photo: Dave Clement)

We’ve recently received inquiries about oak trees declining and dying. People usually want to know if this is caused by oak wilt. Importantly, oak wilt is not known to occur widely in Maryland. Two common leaf diseases of oaks in Maryland are oak anthracnose and bacterial leaf scorch of oak.

oak anthracnose

Oak anthracnose

Oak anthracnose is caused by a fungal pathogen, Apiognomonia quercina, and it typically is a cool, wet weather, springtime disease. In wet cool summers like the one we’re experiencing this year however, the symptoms can continue through the season. Most oak species will show a range of symptoms scattered through the leaf canopy. Symptoms range from small brown spots and irregular dead areas on distorted leaves to severe blight that kills twigs and causes leaf shriveling. This disease in oaks typically doesn’t cause much leaf drop.
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Lawn and Garden Tips and Tricks for September

Every month, we will highlight a few timely, key tips for Maryland homeowners’ lawns and gardens.

Lawn:

  • If needed, this is the ideal time to begin a total lawn renovation project. Total renovation is best if your lawn is always failing due to poor soil, has over 50% weeds or is mostly dead. For the best results, work in ample amounts of organic matter. Use leaf gro, thoroughly composted horse or cow manure or peat moss. See our lawn renovation publication,  (PDF) HG 102 Lawn Establishment, Renovation, and Overseeding.  In addition, take a look at our recent blog post on the subject.
  • The dormancy (browning) of cool season grasses is a natural response that helps turfgrass survive drought and heat. Grasses that go dormant will usually green-up and grow vigorously again in the fall. If you have areas in your lawn that haven’t greened up yet you should consider reseeding them now.

Insects and Pests:

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The Three Sisters Garden

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Our planting in July

This year at the Derwood Demo Garden we acquired some new planting space, which I decided to use for a growing technique we just haven’t had the square footage for in many years: a Three Sisters garden. Growing corn, beans, and squash together in this symbiotic way is an innovation of several Native American peoples, particularly the Haudenosaunee or Iroquois. Each of the sisters has a role: the corn, grown in small groups in separate hills, creates a tall structure; the beans twine up the corn and stay high up for picking; the squash spreads out to suppress weeds and deter animals. Read More

Get Your Lawn Back in Shape This September

With summer winding down — nights are getting longer and days getting cooler — September is a perfect time to rejuvenate tall fescue lawns. Aerating and overseeding now in the fall will make your lawn stronger and better able to resist pests and weed encroachment for next season.

Here are a few points to remember when aerating and overseeding for a lawn rejuvenation this fall:

  • The aerator you use makes a difference. A heavier, more powerful (> 5 HP) aerator will be more forceful and more effective in creating deeper cores. Ideally, you should be able to aerify to a soil depth of at least 3-4”.  Equipment rental stores often have suitable aerating machines available. Remember not to go over the lawn too fast and allow the machine to just “bump” along. Travelling slowly and ensuring the area isn’t too dry will help encourage quality cores to be pulled from the soil.

    Lawn aerator

    Aerifying in fall provides more oxygen to the roots and protected holes for new seed to germinate.

  • If you have substantial areas of dead grass or crabgrass weeds, it is probably more effective to remove the dead grass leaves with a hard rake, a “power rake”, or a de-thatcher. The turf seed will need to have good soil contact in order to germinate and grow to provide better coverage. By seeding into an area with a lot of dead debris, the seed may germinate and then dry out – or not “take” at all.

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What causes holes in my cherry tree leaves?

Q: I have a cherry tree that has been in the ground for three years and has grown well. This year, the leaves have holes and they are falling to the ground already. The tree was sprayed twice with an insecticide and a fungicide. All sprays have been at the recommended dilutions. The leaves continue to fall. What is the problem?

A: The foliage of your tree looks like it was subject to cherry shot hole disease. Infected leaves will turn yellow and drop from the trees in mid-summer, if the infection is severe. This disease can be common when we have wet spring weather. The pathogen may continue to infect leaves throughout the growing season if rainy weather persists. In most cases, trees recover from this disease and no treatment is necessary. Rake and dispose of fallen leaves in the fall to reduce overwintering pathogens.

In addition, be sure to identify a pest or disease before you decide to spray. Some insecticides are “broad-spectrum” products which will also harm many beneficial insects. Also, an insecticide will not do anything to treat a fungal or bacterial disease.

Learn more about cherry shot hole on flowering cherries and how to manage it.

Have a plant or pest question? University of Maryland Extension’s experts have answers! Send your questions and photos to Ask an Expert.

Q&A: Do bagworms kill trees?

Bagwoom cocoon

Bagworm cases are made with evergreen needles and leaf material

Q: Do bagworms kill trees?

A: If there is a large infestation of bagworms on an evergreen tree, it is indeed possible for them to kill the tree if the defoliation is severe. Bagworms can be a problem on deciduous trees as well, but they typically do not kill them.

Bagworms are a common pest in Maryland and we receive a lot of questions about how to deal with them. Fall and winter are the best time to remove and destroy the bags that contain the eggs.

Here are a few tips about the lifecycle of bagworms and how to control them. Read More

Tomato problems? You’re not alone!

Concentric cracking of tomatoes

Concentric cracking of tomatoes

We are at the peak of tomato harvesting and enjoyment time in Maryland. But many gardeners are unhappy, to varying degrees, with the quantity and quality of the fruits of their labor. Those tomatoes we waited so patiently for may have disappointing spots, rots, cracks, and holes.

Before we get into the specific problems, let’s agree that we cannot expect all of our fruits to be perfect, no matter how much time, money, and effort we invest. It’s a garden, not a climate controlled factory. Weather and climate change, soil and sunlight, cultivars and spacing are just some of the many factors affecting plant growth — and they change every year.

This is a good time to think about what we can do next spring to get more out of our tomato plants next year. Picking fruits when they begin to change color from green will increase the number of usable fruits. It allows you to get your fruits off the vine before problems strike. Ripen them indoors on a counter or in a box, basket, or bag. I think you’ll find they taste just as good as their “sun-ripened” sisters.
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