Insect Pests To Be On The Lookout For In The Garden

Tent Caterpillars

Eastern tent Caterpillar Nest. Photo credit: William H. Hoffard, USDA Forest Service,
Eastern Tent Caterpillar (Malacosoma americanum) Photo credit: USDA Forest Service – Region 8 – Southern , USDA Forest Service,

Tent caterpillars construct their silky tent like nests in early spring in the crotches of trees such as cherry (Prunus) and apple (Malus). They feed during the day, then at night they return to the tent for protection. Your first line of defense should be to begin looking for these nests in early spring, about the time saucer magnolia (Magnolia x soulangiana) and crabapples are at bud break. Once located remove the nests and burn them, where permitted. Alternatively cut the tent open and hand pick the caterpillars throwing them into a bucket of soapy water. These 2 methods are most effective because large numbers can be removed at once. (Be sure to wait until they have returned to the nest for the evening before removing the nest). Your second line of defense is spraying them with Btk (Bacillus thuringiensis var. kurstaki). Check for egg masses in the fall and spring and remove any you may find by scraping the clusters with a knife; prune trees in late fall or early spring also helps to keep populations low. Some natural enemies of tent caterpillars are birds and rodents. If physical and biological measures are not effective, use a pesticide which will have a minimal impact on both you and the environment. Apply dormant oil in late winter to kill the eggs before they hatch. An insecticidal soap is another option for control of the eastern tent caterpillar.

Slugs and Snails

A snail Photo by

In areas where slugs have posed a problem in the past till the area well or hand dig in the spring the reduce populations. Slugs prefer heavy, wet soils, particularly for laying their eggs. They also like weedy areas with plenty of soil spaces to hide in, try to avoid such conditions. Sprinkling sand, ashes, broken eggshells and soot around vulnerable plants is a fairly effective deterrent, but they require constant reapplication (diatomaceous earth works in the same way). These barriers are scratchy and sharp serving to dry up the slugs mucous glands which are necessary for their movement. Hand picking still remains one of the most effective ways to reduce slug populations. Drop them into a bucket of warm soapy water or squash them under foot. Dusk and overcast days are the best times to go out picking. To encourage ground-living insect predators within the beds try laying down wooden boards. The predators hide under these during the day, emerging at night to perform their duty. As an added bonus slugs and slug eggs also collect there. Scrap them off into a bucket of warm soapy water once a week to further reduce your slug populations. 

Viburnum Leaf Beetles:

Viburnum leaf beetle (Pyrrhalta viburni) Photo credit: Paul Weston, Cornell University,

Viburnum leaf beetles only infest viburnums but they can nearly skeletonize the entire shrub. Adult females lay up to 500 eggs on viburnum twigs in summer and early fall. The eggs overwinter and hatch in spring. Larvae feed on foliage until early summer, then crawl down the shrub and pupate in the soil. Adults emerge from the soil in midsummer, feed again on viburnum foliage, and mate. From egg hatch to adult takes just 8 to 10 weeks. Egg-laying sites are easiest to spot when viburnums are leafless. Look for infested twigs between early October and mid-April and prune them out. This is probably the single most effective measure you can take to limit beetle populations.


Large Yellow Underwing aka. Winter Cutworm (Noctua pronuba). Photo by Kimberley Pacholko

Cutworms are a common pest of many vegetable crops. They consist of the larvae of several species of night-flying moths. Cutworms feed at night and will not generally be observed on plants or on the soil surface during the day, but you will know they are present by their characteristic damage, finding seedlings that have been ‘cut’ off at ground level. If you find this type of damage dig down around these plants to a depth of about 5 cm to find the cutworm(s) and destroy it/them. Cutworms lay their eggs on the soil; weedy areas, fields of grasses or pasture are ideal sites for cutworms to overwinter. Placing protective collars (like toilet paper rolls) around young seedlings is an effective way for the small home gardener to protect their young seedlings against cutworms.

Sponge Moth aka. Gypsy Moth (was renamed in 2022)

Spongy Moth aka. Gypsy moth caterpillar. Photo by Kimberley Pacholko

The Spongy Moth aka. European Gypsy Moth (Lymantria dispar), was renamed in 2022 by the entomological society of America due to many Romanian people finding the term gypsy to be derogatory. Name aside it is still considered a major pest in North America. The caterpillar, or larva stage of the insect, eats approximately 500 species of trees. Broad-leaved trees are preferred, mainly red and white oak, poplar and white birch. The eggs hatch into caterpillars just as the tree buds are beginning to open and feed voraciously for up to 7 weeks. Therefore, it is important to control gypsy moth infestations early in the growing season. When gypsy moth populations get out of control cities will often conduct an aerial and ground spray programs to control the outbreak. Btk (Bacillus thuringiensis subspecies kurstaki) is often used and is a safe and effective treatment for gypsy moths. Apart from large scale intervention there are many things the home gardener can do to reduce their populations. First and foremost is seeking out and destroying egg masses. Egg clusters are usually ¾” and oval in shape. They look like a piece of felt or velour and are buff colored when first laid but may bleach out over the winter months when exposed to direct sunlight and weathering. Common hiding places include the underside of branches, tree trunks, fences, firewood, outdoor furniture, swing sets, boats, and trailers and under the eaves of buildings. When an egg mass is observed it should be scraped off with a knife and dropped into a bucket. Destroy the eggs by burning, crushing or by pouring scalding hot water over them.

Lily Beetles

Lily Beetle (Lilioceris lilii)
Photo by Alex Andrews on

Lily Beetles are brightly coloured orange beetles with black bellies, head, antennae and legs. They measure about 8mm in length. Their wings are quite shiny with tiny dimples on them. They eat the leaves, stems, buds and flowers of Lillium species such as asiatic lilies, oriental lilies, Easter lilies, tiger lilies as well as fritillaries. They overwinter in the soil and come out early in spring. These brightly coloured orange beetles measure about 8mm long. Their wings are quite shiny with tiny dimples on them. As soon as the lilies break through the ground the adults begin feeding and mating. Eggs are laid on the in underside of leaves in May. These eggs quickly hatch in 4-8 days and larvae begin feeding on the underside of leaves piling their own excrement on themselves to protect them from predators. These can sometime be dislodged with a strong jet of water. They feed for about 16-24 days then drop to the ground to pupate in the soil. Winged adults emerge 16-22 days later and continue feeding the rest of the season.

Neem oil is effective when applied weekly to the early stages of larvae. Handing picking, knocking them into a bucket of warm soapy water, still remains the most effective treatment. It can be helpful to place a light coloured material beneath your lilies before picking as they tend to drop off when the plant is disturbed with their black undersides pointing up. For regions permitted, spinosad may be effective as well as chemical soil drenches and foliar sprays labels for use against lily beetles.

Soft- Scale

Soft scale on a magnolia tree. Photo by Kimberley Pacholko
Soft scale on a purple sand cherry (Prunus x cistena). Photo by Kimberley Pacholko.

Soft- Scale are typically found on woody and foliage plants. They feed on the sap causing yellowing of leaves and overall plant decline. They also secrete a sticky clear substance known as honeydew which provides the ideal environment for “sooty mold”; a fungus which can be more damaging than the scale itself. This honeydew also attracts ants which then carry the scale to non-infested plants as well as protect them from natural enemies such as predators and parasites. The first nymphal instar is called a crawler and has functional legs, while the remaining instars are attached to the leaf or twig and (with the exception of green shield scale) do not move.
Dormant oils are somewhat effective at suffocating over wintering scale. Contact insecticides can be effective, but only if they are applied to the unprotected crawler stage of the scale. Thus, timing of contact insecticide application is critical to effective control. Parasitic wasps whose adults lay their eggs inside of soft scale may further serve to reduce scale populations. Metaphycus prefers young stages, Encyrtus the adult.

Hard- Scale

Hard scale on a euonymus shrub. Photo by Kimberley Pacholko

Hard- Scale: differ from soft scale in that they generally have two or more generations per year. They do not produce honeydew and typically overwinter as eggs underneath the body of the dead female. (with the exception of euonymus scale which lay their eggs in early spring).They usually appear circular or rounded in shape and their crawlers tend to be less active.

Spider mites

Spider mite. Photo by Kimberley Pacholko

Spider mites: Spider mites are common plant pests. They thrive in hot arid conditions thus irrigation and moisture management can be important cultural controls for spider mites. They also thrive in high nitrogen soils and dusty environments. They feed and lay their eggs on the underside of leaves. Symptoms of injury include speckled leaves, discoloration (bronzing) and scorching of leaves. Injury can lead to leaf loss and even plant death. Natural enemies include small lady beetles, predatory mites, minute pirate bugs, big-eyed bugs and predatory thrips. To control spider mites they can be sprayed with a strong jet of water, a summer oil spray or a chemical miticide where permitted.


Red aphids on a rose bud. Photo by Kimberley Pacholko

Aphids are small, soft bodied insects with piercing mouth pieces that suck plant juices from a wide variety of plants. They vary greatly in size and colour. Damage includes spotty yellow leaf discolourations, curling or distorted leaves and stunted new growth. As aphids feed they secrete a sticky substance called honey dew, providing (in humid conditions) the perfect breeding ground for black sooty mold. Insecticidal soaps and dormant oil are some what effective in controlling populations. Spraying them with a fast jet of water is also helpful. Lady bugs are a natural predator.

Mealy bugs

Mealy bug Photo by: Kimberley Pacholko

Mealy bugs: Females are oval, eight to ten mm long and five mm wide. The body is
red in colour, segmented and covered with white, waxy secretions. White, waxy filaments also extend down the sides of the body. Like the aphids and scale insects, they feed by piercing the plant material and sucking the juices out. Sticky honeydew coats the plant surfaces and ground below attracting ants, wasps. Their are several mealy bug species (some even on the invasive species list), that feed on wide variety of plant material both out doors and in. Indoors they are particularly fond of ivies and pothos as well as other tropicals. Outdoors you will find them on grape vines, Yew, Rhododendron, maple, citrus, linden, dogwood and other many other woody plants. The immature crawlers (live young), overwinter under bark scales or beneath the waxy covering of a dead female. There are 2-4 generations a year. Typically 2 outdoors and 3-4 indoors and in warm climates. They can be difficult to control. Small infestations can be removed by hand with a cut tip dipped in rubbing alcohol. Larger infestations may require a systemic insecticide.

Japanese Beetle

Japanese Beetle Photo by Kimberley Pacholko

Japanese Beetles are a destructive pest to hundreds of different species. They appear about 1/2″ in length with metallic blue/green heads and copper coloured backs. They tend to feed in groups and are usually observed in a mating position. They skeletonize plant leaves and chew holes in flowers and flower buds. When disturb they drop to the ground on their backs and they are difficult to spot as their bellies are the colour of soil. They lay their eggs in the soil in June which develop into white grubs.

Controlling Japanese beetles is challenging. Japanese beetles make their appearance in July. Hand pick them by knocking them into a dish of warm soapy water. Japanese beetles drop to the ground when disturbed so hold your bowl under them. Pheromone traps are available if you opt for one be sure to place it at least 9meters (30′) away of vulnerable plants further if possible. If you are on an acreage or large property 76 meters (250′) is ideal. Place them in a non-flowering tree, like a pine or spruce about 4′ high. Note: these traps will lure about 4 times as many Japanese beetles to your yard then you would normally have; they trap about 75% of those lured…meaning you have not in the end really reduced their numbers.

Updated on Mar. 7, 2022

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