Category Archives: Plant pests and diseases

Wanted Dead or Alive: Spotted Lanternfly

Recently an article appeared in FFXNow.com (Fairfax County local news) with the headline “One of the world’s most wanted insects has landed in Fairfax County.” I immediately contacted Adria Bordas, Fairfax County’s Virginia Cooperative Extension (VCE) agent for horticulture. Spotted lanternfly is one insect I do not want in my garden. If you think a downpour of 17-year cicadas is gross, try looking at a tree dripping with spotted lanternfly. Continue reading

Remove the Bagworms in Your Shrubs and Trees

Bagworms are common pests in the Washington DC metro area. Usually we do not see the actual worms (Thyridoptery x ephemeraeformis), we see their “homes,” which are 2-inch long “bags” they have spun from silk and plant debris. These bags are hung like small, brown ornaments on shrubs and trees. At this time of year, they are prominent and should be removed.

Continue reading

Got Deer? Try These Tactics in the Garden

deerNewcomers to this area will eventually see deer standing on the roadside or venturing out of the woods at dusk. At first, they admire the lovely bucolic sight, gentle deer, twitching their tails, flicking their ears back and forth. But as the newcomers settle down and try their hand at gardening, they learn that the deer are not as cute as they once thought. Continue reading

Gardening Questions? Ask These Experts

cucumberSummer is here and by now your Victory garden is planted. Dreams of fresh red tomatoes and lush green cucumbers are dancing in your head. But wait, what are those green caterpillars? What are those brown spots? Answers to these gardening questions and more are available from your local Master Gardeners and county extension agents. Even during this pandemic, they are standing by to help you with your gardening issues. Best of all, this is a free service for the public. Continue reading

Herbs Attract and Support Beneficial Insects in the Garden

Small thyme flowers

The herbs in my garden live among the annuals, perennials, vegetables, and shrubs. I do not have a separate, formal herb garden.  Every new herb plant gets tucked in any space I can find. I harvest them to use them fresh in the kitchen and for floral arrangements. By summer, many of my herbs are blooming along with everything else but that’s okay, they still serve a purpose. Even if I didn’t get to harvest them, they are helping the rest of the garden by attracting and supporting beneficial insects. Continue reading

Got Deer? Try These Tactics in the Garden

deerNewcomers to this area will eventually see deer standing on the roadside or venturing out of the woods at dusk. At first, they admire the lovely bucolic sight, gentle deer, twitching their tails, flicking their ears back and forth. But as the newcomers settle down and try their hand at gardening, they learn that the deer are not as cute as they once thought. Continue reading

You Got Gardening Questions? Ask These Experts

cucumberSummer is here and by now your Victory garden is planted. Dreams of fresh red tomatoes and lush green cucumbers are dancing in your head. But wait, what are those green caterpillars? What are those brown spots? Answers to these gardening questions and more are available from your local Master Gardeners and county extension agents. Even during this pandemic, they are standing by to help you with your gardening issues. Best of all, this is a free service for the public. Continue reading

Time to Cut Those Bagworms!

Last night, during my evening walk I noticed an unusual number of bagworms on a few evergreens. Bagworms are common pests in the Washington DC metro area. What I saw weren’t the bagworms themselves (Thyridoptery x ephemeraeformis) but their “homes,” 2-inch long “bags” they have created from their spun silk and plant debris. These bags were hung like small, brown ornaments on relatively new plantings in someone’s front yard. Some of the needles were clearly brown and dead.  Interestingly, one bag was hanging from the neighbor’s chain link fence, creating a very visible view of the threads wrapped round the metal.

Bagworms are moths, native to North America. They can attack more than 120 different types of trees but we tend to see them on evergreens such as juniper, arborvitae, cedar, spruce, pine, and Leyland cypress.

In the beginning of the summer, the eggs hatch and the larvae move out of the bags. The tiny caterpillars, 2 millimeters long, eat foliage and/or move to other trees via their silk threads. When they settle on their host tree, they spin a small bag of silk and plant debris. As they grow, their bags become bigger with more material collected from the host plant. By August, they have matured and the bags are very visible. During August and September the male adult bagworms, i.e., moths, emerge and fly to find a female to mate. The females cannot fly, they are grub-like and never leave the bag. Mating occurs through the bag and after mating, the female lays 500 to 1,000 eggs within her pupal cast skin and dies. The eggs overwinter and hatch next year in May or June.

Bagworms can defoliate and kill trees, especially evergreens. Although they can attack deciduous trees, most are not defoliated enough to be killed. Bagworms can also kill twigs by winding their silk around the twigs too tightly.

note white silk thread wrapped tightly around chain link fence

Now is the time to look for the bags and remove them by cutting them off–not pulling–bagging and disposing. Do not put them in your compost bin. If they are on the perimeter they will be easy to find but don’t forget to move branches aside and look within the tree. It goes without saying that a tree that has a bag will be damaged repeatedly each year, weakening the tree and possibly killing it.

Another option is to spray the tree with Bacillus thuringiensis (Bt) in May or June when the caterpillars have hatched and are on the foliage. This is a type of bacteria that kills the worms but does not harm the tree. If the tree is too tall, call an arborist. Spraying them later in the season after they have created their bags will not work since the bags will protect them. Or replace the evergreens with more resistant plants. But go out there now and inspect your plants, you need to remove them before the males emerge!

Pegplant’s Post Giveaway: Bobbex Deer Repellent Spray

I am very excited about the giveaway for the January 2019 issue of Pegplant’s Post. Bobbex, a company known for effective deer repellent, has generously offered to ship one 48 oz. E-Z ready to use sprayer and one quart bottle of concentrated spray of their deer repellent, a $55 value. Their deer repellent was rated number 1 by an independent study conducted by the Connecticut Department of Forestry and Horticulture. Environmentally friendly, the Bobbex deer repellent is a foliar spray that protects ornamental plantings, shrubs, and forest trees from browsing and feeding by deer, moose, and elk (we don’t have moose and elk in the DC metro area but we have plenty of deer). The spray is a blend of ingredients that are offensive to deer but harmless to humans and safe for wildlife. The Bobbex website has very useful information on how to recognize and deter deer, goose, rabbits, and small animal damage and offers a variety of repellent products.

This giveaway opportunity is for subscribers of Pegplant’s Post, an online, free newsletter for people interested in gardening in the Washington DC metro area. Each issue provides at least 50 but up to 100 gardening events; newly published gardening books; local tips, advice, and articles; and a monthly giveaway contest.

To subscribe, click here or visit pegplant.com and enter your e-mail address in the box above “subscribe!” on the right column. Pegplant’s Post will be issued on the last weekend of the month.

What’s That in the Tree? Fall Webworm

August turns up all kinds of pests and disease in the garden. You may be noticing large webs across the terminal branches of your trees now, similar to stretched pantyhose. Look closely and you will see small caterpillars inside, each marked with parallel rows of black spots on the back. The fall webworm (Hyphantria cunea) is very noticeable now but at this stage, the caterpillars stay in the web and feed inside on the leaves. The web is unsightly but their feeding will not kill the tree. However, this would be a good time to cut the branches and bag the webs, caterpillars and all. Close up the bags tightly and dispose of in the trash. Later, after the last molt, they leave the web and crawl all over the tree. Then they spin cocoons, pupate, and emerge as white moths. If you are not able to bag the web don’t despair, there are many natural enemies of the fall webworm. Another tactic is to spray the first generation in the spring with horticultural oil, Bt (Bacillus thuringiensis), or insecticidal soap before they create the web. Don’t try to burn them out though, it is too dangerous to the tree. For more information on plant pests and diseases, check out the Plant Pests and Diseases tab on pegplant.com.