Green Thumbs Up: Coping with bugs, slugs and other thugs

Suzanne Mahler

For many perennial gardeners, the July garden is the highlight of the growing season.

Dazzling displays of daylilies paint the landscape with riotous colors, while delightful daisies, large and small, offer colorful complements, attracting throngs of butterflies that perch on their petals while sipping nectar from the multitude of tiny flowers in the central disks.

The stunning spires of rosy purple gayfeathers (liatris), blue veronicas, and lavender catmints (nepeta) provide pleasing contrasts. Boisterous bee balm in vivid shades of red, pink, and violet entice hummingbirds to hover at their unique whorled flower heads.

The early weeks of summer are a time to step back and admire the fruits of our labors before the inevitable heat, drought and war of the weeds impact our landscapes.

As I wandered through the arbor into my backyard sanctuary to survey my luxuriant shady borders, I was startled by a huge form rising from the edge of my tiny water garden.

For several weeks, my small collection of goldfish seemed to be dwindling, and as the elegant but infuriating great blue heron took flight, awkwardly perching in the branches of a nearby birch tree, my suspicions about this giant culprit were confirmed. In years past, I have resorted to a variety of remedies, including netting the surface of the small pond, but none of the half-dozen recommended deterrents has been particularly effective.

Continuing on my stroll, a furry little beast darted across the lawn and disappeared into a nearby perennial border. Closer inspection revealed that a family of woodchucks has taken up residence at the base of a large shrub in the middle of my garden, a sandy mound a telltale entry to the gaping tunnel that leads to their humble abode.

Nearly every coneflower (echinacea) has been stripped of its leaves by the miserable little varmints, while other delicacies throughout the yard are bent, broken and devoured. In the weeks to come, repellents will be the first line of attack while more drastic measures are sure to follow. 

From the day we turn over our first bit of earth and plant our first tree, lawn, shrub, vegetable garden or flowerbed, the forces of nature suddenly take on new meaning. Bugs, slugs, grubs and critters seem to materialize overnight, attacking precious acquisitions at every turn, and many a garage becomes an arsenal of chemical warfare.

Many of these intruders do their ravaging under the cover of darkness, making it difficult to determine the source of the damage.

Clever or cowardly, depending upon your perspective, slugs, snails, caterpillars and furry creatures munch away while we sleep, disappearing by dawn’s early light. Other invaders, such as spider mites or chinch bugs, are so tiny that gardeners may not realize their presence until much of the damage has been done.

Still others, like the incredibly grotesque tomato hornworm or the green cabbage worms, are so perfectly camouflaged that they go undetected until they reach gargantuan proportions or leave the plants riddled with holes.

Beetles are some of our more troublesome pests. Japanese beetles (metallic blue or green with copper-colored wing covers), European chafers (rusty red) and one of the newest arrivals, Oriental beetles (tan with darker brown spots), are beginning to emerge.

Their grubs devour our turf and the adults skeletonize our roses, hollyhocks, grapes, raspberries and many other trees, shrubs and perennials. Several pesticides are effective on the adults including Imidacloprid (Merit) or Sevin, but the latter is toxic to bees and wildlife and should be considered only as a last resort.

Controlling grubs in the lawn with will reduce their numbers but will not prevent these flying insects from traveling to your garden from other areas. 

In recent years, the Asiatic lily leaf beetle has been added to the list of repulsive intruders, particularly in the larval phase, when the larvae encase themselves in their excrement and appear as tiny globs of gray goo on the foliage. This Chinese-lacquer-red, elongated beetle primarily affects lilies that grow from bulbs, not daylilies, which are fibrous-rooted perennials.

Spring-blooming fritillaria (grown from bulbs) and some fall-blooming toad lilies (tricyrtis) have also shown damage from this nuisance. Adult beetles hibernate in the soil through the winter, emerge in early spring, and begin devouring all parts of the lily as they multiply at an alarming rate. Rows of cinnamon-colored eggs are laid on the underside of the leaves.

Manual removal of beetles is tedious, especially the lily leaf beetles, as the adults move quickly and fall to the ground, brown belly-side up, and the gooey larvae are disgusting.

Neem products are quite earth-friendly and have been reported to be effective on lily beetles, particularly in the early stages when larva first begin chewing. An application of the systemic Imidacloprid (Merit) as a drench around lily bulbs in early spring or as a spray (Bayer Rose and Flower Insect Killer) has also demonstrated some positive results in reducing the devastating effects of this scourge.

A lily beetle parasite has been released in both Massachusetts and Rhode Island and hopefully offer some control of this destructive pest in years to come.

Suzanne Mahler is an avid gardener, photographer and lecturer who has been developing the 1.5-acre property surrounding her home in Hanover, Mass., for more than 30 years. Her weekly gardening column 'Green Thumbs Up' has appeared in Community Newspapers for more than a decade. She is a member of two local garden clubs, past President of the New England Daylily Society, an overseer for the Massachusetts Horticultural Society and is employed at two garden centers.