Archive | July 2015

Christmas in July? It must be bagworms

bagworm bags

Inside each spindle-shaped bag is the larva of the leaf- and ~needle-eating bagworm ( )..

Sometimes I need to heed my own advice and spend more time scouting my garden and landscape for problems. As we all know, small problems tend to be easier to solve than big ones. This past weekend, I ran into a big problem with my Atlantic white cedar (Chamaecyparis thyoides), which was adorned with a variety of nearly identical “Christmas ornaments”. Unfortunately, I quickly realized that Christmas was more than 5 months away, and that these nature-based “ornaments” hanging from the scantily clad limbs were the handiwork of bagworms (Thyridopteryx ephemeraeformis).

Bagworms, the larval or caterpillar stage of a moth that is rarely seen, defoliate many other conifers, including juniper, arborvitae, cypress, spruce, and hemlock.  They also will consume the leaves of many other trees. In fact, these voracious buggers attack more than 120 species of woody ornamentals, including deciduous shrubs and trees such as black locust, buckeye, elm, honeylocust, maple, sycamore, and willow.

Heavy bagworm infestations can lead to branch dieback.  Sometimes trees can be killed outright, especially after having been completely defoliated over one or two seasons.

These gourmands of the insect world intrigue me, mostly because of the spindle-shaped bags constructed by the young caterpillars or larvae as they feed.  Each larva builds a bag of silk and bits of leaves and twigs from the host plant so its appearance varies from plant to plant.

Unbeknownst to me, the bagworms larvae were feasting and toting their bags for 8 to 10 weeks; they gradually enlarge their bags with every molt. When the larvae reach full size, they stop feeding and secure their one- to two-inch long bags to a twig to pupate. About a month later in September and early October, the brown furry male moths with clear wings will emerge, fly to the wingless females, and mate with them inside her bag.

Although the female bagworm is a moth, she doesn’t look like one.  She has no wings, eyes, legs, antennae, or functional mouthparts.  In fact, her soft yellowish-white body never leaves the bag.  After mating, she lays 500 to 1,000 eggs inside her bag before dying, encasing her clutch with her mummified body.  There is only one generation a year.

The best course-of-action right now is to remove the bags by hand to interrupt mating and to reduce next year’s population. These bags may be difficult to remove without damaging the twig, so pruning shears may be necessary to cut the threads. From my single 5 ½-foot tall Atlantic cedar, I picked and discarded 132 bags. Sadly, my wife or daughter expressed no interest in this task; they didn’t believe me when I told them that it was like removing ornaments from a Christmas tree.

OK, I’ve learned my lesson. Next year I’ll be on the lookout for small bagworm caterpillars emerging in late May or June. Egg hatching begins when the black locust flowers begin to fade and is complete when the Japanese tree lilacs are in full bloom. When the young larvae start feeding and building their bags, I will consider applying the bacterial insecticide, Bacillus thuringiensis var. kurstaki (Dipel® or Thuricide®) or spinosad (Ferti-Lome® Borer, Bagworm, Leafminer & Tent Caterpillar Spray or Spinosad). See “Less Toxic Insecticides” for additional controls.

This weekend I felt that I was alone in my battle against bagworms, but I’m not.  Working in concert with my efforts are birds and several ichneumonid and chalcid wasps that parasitize the larvae.  Also, low winter temperatures can damage the overwintering eggs. I just hope that next year the birds, parasites, and parasitoids that relish bagworms pick up their game so I won’t have to.

© Bob Polomski 2015



Rose of Sharon double

June 28, 2014. SC Botanic Garden, Clemson, SC.

Rose-of-Sharon or shrub althea (Hibiscus syriacus) is a frequent denizen of old gardens where it often grows 8 to 10 ft. high and 4 to 6 ft. wide. The toughness and durability of this old-fashioned was eloquently affirmed by Felder Rushing in his 11th book, Tough Plants for Southern Gardens: “A drunk driver once ran over my great-grandmother’s old althea and it came right back with new flowering growth.  That’s one tough shrub if it can be pruned with a pickup truck!”

Double rose of sharon wide

June 28, 2014, SC Botanic Garden, Clemson, SC.

Rose-of-Sharon blooms in the torrid months of June to early September. Depending on the cultivar, flowers can be single or double in a range of colors that include white, pink, purple, blue and red. The flowers give rise to highly fertile seed pods, which can become a nuisance. I still remember a roadside rose-of-Sharon that I rescued more than a decade ago. I never realized that this single shrub would thank me with bazillions of offspring. Fortunately, there are new, sterile to semi-sterile cultivars that have been selected for their compact nature (older cultivars are prone to legginess) and gorgeous flowers.

Rose of Sharon single

June 14, 2013. Tybee Island, Ga.

Despite the availability of new releases, I’m old-fashioned and like to go retro with these 1970s releases from the U. S. National Arboretum: ‘Diana’ (white), ‘Aphrodite’ (pink), ‘Helene’ (white), and ‘Minerva’ (lavender). These sterile cultivars named after Greek goddesses have compact growth habits, leathery dark green leaves, and produce little or no seeds. Site them and any rose-of-Sharon in full sun.  Since they produce flowers on current season’s branches, prune these deciduous shrubs when they’re dormant in late winter, preferably with bypass pruners or loppers–not your granddaddy’s pickup.

© Bob Polomski

The Spooner Oak – A possible new national champion live oak

I received this email from Susan Granbery on July 16, 2015 3:48 PM:
Check out this live oak in Iron City, GA (far southwest corner of GA near the Alabama line). The folks from the Big Tree Registry are flying down


“Recently discovered” lIve oak (Quercus virginiana) in Iron City, GA.

tomorrow to measure it for national champion status. Our forester says it’s a 20 minute drive from the nearest Dairy Queen. No one ever knew it existed. Look out Seven Sisters of Louisiana!   Susan Granbery, Urban & Community Forestry Coordinator, Georgia Forestry Commission
6835 James B. Rivers/Memorial Dr., Stone Mountain, GA 30083.
The current champion is a live oak (Quercus virginiana) in St. Tammany Parish, Louisiana. According to the American Forests Champion Trees site, this “big tree” made the list in 1976 and “is the largest known tree of its species in the country.” This 68 ft. tall live oak has a crown spread of 139 ft. and a trunk circumference of 467 inches. Do we have a new champion?
In South Carolina, our biggest live oak is 62 ft. high with a crown spread of 129 ft. wide and  a trunk circumference of 385 inches. Sadly, its canopy was damaged in a storm.

Got mulch?

Mulch is as important to southern gardens and landscapes as sausage gravy is to biscuits or as corn bread is to pinto beans. That was no surprise to me I read the results of a nationwide survey of 105 million U.S. households by the Garden Writers Association Foundation. When asked, “What do you plan to purchase for your yard or garden this fall?”, the #1 response from Southerners was mulch. Buying shrubs and trees came in second.

Mulch not only enhances the appearance of our plantings, but it’s the right thing to do. A shallow layer of organic mulch conserves moisture, suppresses weeds, and supplies nutrients as it decomposes. Covering bare soil with mulch reduces erosion.

A common question that arises is which mulch is best? My answer: anything that looks good and is affordable. During my travels throughout the South I’ve seen a wide variety of mulches used by gardeners. They include newspapers, old carpeting, salt hay, cocoa and pecan hulls, and eucalyptus chips. Mulch, in my opinion, is a lot like barbecue sauces: there are regional differences. For example, pine straw is commonplace from the Midlands to the Coast. Along the Coast, besides pine straw, you’ll find seashells, white marble chips, and pea gravel. In the Piedmont shredded hard-and softwood mulches are commonplace.

Colored woody or rubber mulches are in vogue right now. Tired of earth tones, then consider mulches made of recycled tires in “Bright Blue,” or “Real Teal.”

Whatever mulch you apply, apply it properly by following these simple guidelines:

  • Apply a shallow 2 to 4 inch layer of mulch. For annuals and perennials, apply a mulch layer one to two inches thick. Avoid the temptation to create a “mulch volcano” that’s a root-suffocating two to three feet high with sloped slides. Volcano mulching will not impress passersby (”Hey, look everybody, Bob mulched his trees!”), but it can kill trees. The bark of shrubs and trees needs to “breathe” and it needs to be dry. Keep the mulch at least 3 to 6 inches away from the trunk of young trees and shrubs and 8 to 12 inches away from the trunks of mature trees. Also, by keeping the trunk free of mulch discourages bark-feeding voles which like to be hidden from predators.
  • Mulch individual trees out to their outermost branches or drip lines, if at all possible. Because the root system can extend two to three times farther than the branches of a plant, mulch as large an area as possible. To avoid “slalom mowing” in and around individual plantings of trees, unite them with a single bed of mulch.
  • Every two or three years submit a soil sample from your mulched beds to your Clemson Extension office. Mulches, such as pine straw or pine needles, are high in nitrogen and phosphorus, but they also acidify the soil as they decompose. Florida researchers reported in the Journal of Arboriculture (March 1999) that a 3.5 inch layer of pine needles reduced the soil pH from 5 to 4.4 over the course of a year. While this makes pine straw an ideal mulch for acid-loving plants, other less acid-tolerant plants would benefit from the addition of calcitic or dolomitic limestone to increase the soil pH to the optimum level as recommended by the results of the soil test. Also, adjusting the pH to the right level will avoid potential nutrient deficiencies caused by a low soil pH, especially nitrogen, phosphorus, potassium, calcium, and magnesium.

So this weekend if you’re looking for something to do in the landscape, throw some mulch around. And if you’re feeling really adventurous this year, toss out a Caribbean Blue colored mulch with a sprinkling of last summer’s seashells on top. Guaranteed, your neighbors will know that you’ve mulched your landscape.

© Bob Polomski

Invasion of the neon-colored blob

Over the years I’ve promoted the use of organic mulches (see tomorrow’s entry). Occasionally, unexpected “issues” arise, such as the phallus-shaped dog stinkhorn fungus (Mutinus canines) or the neon yellow, foamy-looking slime mold that looks like a colorized version of the blob. These invaders may be unsightly, but they are harmless.

The neon yellow slimes molds are called scrambled-egg slime or the “dog vomit fungus.” They appear from spring through fall, usually when moisture is vomit fungus1

Slime molds spread by spores, which could have already been present on the mulch or were blown in by the wind. When the spores come into contact with water, they burst and release amoeba-like cells. These cells eventually unite with other cells to produce a plasmodium, that scary, frothy-looking mass. It flows over mulch, sidewalks, and driveways in search of fungi, bacteria, and decaying organic matter. Scientists have discovered that the plasmodium moves as much as 2 feet or more per day in response to light and food. Eventually, the slime mold reaches the reproductive phase when it dries and develops mushroom-like fruiting bodies that release the dustlike spores.

Because this curiosity eventually dries up and disappears, no control is necessary. However, if its appearance bothers you, break it apart with a garden rake with water from the hose. Slime mold invasions can be avoided by adjusting the irrigation system to prevent the mulch from becoming too wet. Also, periodically fluffing up the mulch with a rake will help aerate it and speed up drying.

© Bob Polomski

To water or not to water my lawn….

Ben Franklin was right when he wrote in his self-titled autobiography: “When the well is dry we know the value of water.” We’re not sharing the same experience as California residents who are receiving rebates for replacing their front lawns with drought-tolerant plants or rocks and pebbles, installing synthetic turf, and painting their brown lawns with nontoxic green paint, but we know drought. In fact, our state has experienced drought conditions eight of the last ten years. We need to respect water—especially potable water—now and in the future, and use it wisely, especially when it comes to summer lawn care.

Know that you have the choice to water or not to water your lawn. If you choose not to turn on the spigot, don’t be alarmed by the dead brown leaves. The lawn grasses have gone dormant. Grass plants possess buds in their crowns and rhizomes (underground stems) that may remain alive and grow when more favorable conditions return.  Tall fescue is an exception because it has no means of escape. Three weeks or more without rain in the summer can injure or kill tall fescue. Nevertheless, any bare areas that arise can be easily repaired in the fall with seed or sod.

If you choose to irrigate your lawn, water efficiently:  water the lawn when it exhibits drought stress symptoms; apply an appropriate amount of water; and water at the right time of day.

A “thirsty” or drought-stressed lawn develops a bluish-gray cast, footprints stay in the grass after you walk over it, and leaves become wilted and rolled.

To prevent the lawn from going dormant, apply about one-inch of water to your lawn. (It takes 640 gallons of water to irrigate 1,000 square feet with one inch of water.) This amount wets most clay soils to a depth of 6 to 8 inches. If all of this amount cannot be applied at once because water runs off the lawn or puddles up, then apply one-half inch at a time.  Allow the water to soak in before continuing.

To apply the right amount of water, calibrate your watering system by following these simple steps:

1.      Place several equally-sized coffee cans or other straight-sided, flat-bottomed containers randomly throughout the area to be irrigated.  For above-ground, portable, hose-end sprinklers, arrange containers in a straight line away from the sprinklers to the edge of the water pattern.

2.      Turn the irrigation on for 15 minutes.

3.      Turn the water off, collect the cans and pour all of the water into one of the cans used.

4.      Measure the depth of water you collected.

5.      Calculate the average depth of water by dividing the total amount of water in inches by the number of cans. For instance, if the total depth was three inches, and you used six containers, then the average depth would be 3/6, or 0.5 inches.

6.      Multiply the average depth by four to determine the application rate in inches per hour. For example, one-half inch multiplied by four equals two inches per hour.  If you run the system for one hour, it will apply two inches of water; run it for half an hour, and it will apply one inch.  If, during irrigation, water runs off the lawn, apply a half-inch, stop the system and let it soak in, then apply more.

Water late at night or early in the morning when dew has already formed. Watering at night cuts evaporation in half, to 15 to 20 percent.

Whether you choose to water or not to water the lawn –stick with it.  Flip-flopping between the two can weaken and injure your lawn.