Scarlet lily beetles and other pests

The February 2015 meeting of the Garden Club of PEI featured Christine Noronha, Entomologist with Agriculture and Agri-Food Canada.  She talked about the most common insect pests we encounter in our gardens.

Scarlet Lily Leaf Beetle appeared on PEI in 2004.  It has since spread across the province.  It is native to Europe and Asia.  It was first seen in North America in Montreal in 1943, and has moved across eastern Canada and as far west as Alberta. It is thought to have spread through the importation of plant bulbs.

These beetles overwinter in the soil as adults.  They emerge in early spring and lay about 450 eggs in batches of about 12 on the underside of leaves.  The larvae feed under the leaves.  They are reddish, but are identifiable as black blobs, because they cover themselves in their own frass (excrement) which makes them unattractive to predators.  Mature larvae drop to the ground, burrow into the ground, and make a cocoon.  One generation per year is produced.

Host plants:  mostly lilies.  asiatics are most susceptible.  They also feed on fritillaria, lily of the valley (convularia), flowering tobacco (nicotiana), hollyhock, hosta, potato, and solomon’s seal (polygonatum).

To manage these pests:

·         hand pick adults and crush or drop them into a container of soapy water.  The soap will prevent them from breathing.

·         spray with diluted neem oil.  Neem degrades quickly in warm weather, and must be reapplied at least every 5 to 7 days.

·         young larvae are more susceptible to insecticides than adults.  Spray the underside of leaves where larvae feed. 

·         floating row cover may be effective.

A parasitic wasp, Tetrastichus setifer, lays its eggs in beetle larvae.  When the eggs hatch, the wasp larvae eat the beetle larvae from the inside.  PEI has a low number of species of naturally-occurring parasitic wasps (4) vs Ontario (12).

According to http://lilybeetletracker.weebly.com/ this wasp was introduced in Ottawa in 2012 and a researcher at Carleton Univerisity wants to introduce the wasp to other areas across Canada.  According to her studies, the wasp attacks only lily leaf beetles, and it survives the winter.  Gardeners are welcome to sign up to introduce pupae and eggs to their gardens.

Aphids are soft-bodied, tiny, pear-shaped insects that can be brown, black, green, white, or grey.  They can be identified by short tubes protruding from the base of the body, and a waxy or woolly coating. 

Females produce live babies.  They are like Russian dolls - one inside the other.  Babies are born already pregnant, and the babies inside the babies are also already pregnant!  For that reason, aphids reproduce very quickly.  The babies produced are wingless, but if populations become too large and food becomes scarce, babies are born with wings so that they can fly to a new food source.  During the summer, all babies born are female.  In fall, both males and females are born with wings.  They mate and lay eggs, which overwinter. 

Aphids have mouthparts that pierce the stems of plants to suck out plant juices.  Because they attack multiple plants, they can spread disease.  This is a problem for commercial growers.

Aphids feed in large groups on the undersides of leaves.  Predators include lady beetle larvae and adults and predatory wasps, which lay eggs inside the larvae. Spraying with insecticidal soap is effective, but you can also just spray with plain water to knock them off the plants.

Greenhouse growers use Aphidius colmani - one package per square metre.  A BC company called Bug Factory sells these.  This is not as effective in open areas.

Earwigs – males have curved pincers, females have straight pincers.  The females are very good mothers.  They lay eggs in a nest in the ground and feed and protect their young for several weeks until they are ready to leave the nest in early July.  Babies hatch looking like smaller adults – no larvae stage.   

Earwigs are most active at night.  In the late fall, their blood is replaced with a substance that acts as antifreeze, and they are able to withstand the winter.  Adults emerge in spring, lay eggs, tend their young, and then die.

Management: 

·         break up soil and expose eggs on surface for predators. 

·         rolled up newspapers or pieces of garden hose will attract them during the day.  Shake the paper and hose into a bucket of soapy water.

Mites feed on the undersides of leaves.  Females lay about 300 eggs on the branches or stems of their host plan and overwinter there.  They hatch in early spring and begin feeding.  They grow from egg to adult in just 5 days when it is warm, longer when is cool.  Several generations are produced in one year. 

Management:

·         bring in lady beetles, lacewings, or predatory wasps.  This works best in confined space like a greenhouse

·         spray with insecticidal soap, neem, or a registered insecticide.  To be effective, there must be direct contact with the insect.

Thrips have lacy wings that look like feathers.  There are 6 stages to the life cycle:  egg, 2 larval stages, prepupal, pupal, adult.  One generation takes one month to complete.  They are poor fliers, and are carried by the wind.  Thrip damage makes leaves appear brownor mottled silver, and dry rather than wilted.  They feed on the underside of leaves. 

Management:  Biological controls are not successful.  Because they feed on weeds, keep weeds controlled.  They also will attack stressed plants, so keep your plants well watered and healthy. 

damage from carrot rust fly larvae

Carrot rust fly larvae feed on the tissue of carrots.  It is very small, with red eyes, orange head, a shiny back, and clear wings.  They lay eggs in the soil at the base of carrots.  Eggs hatch in 6-10 days.  Larva feed on carrots, celery, parsley, parsnip, dill, caraway, and fennel.

Management:

·         They are poor flyers, so putting up a low barrier can deter them

·         cover with floating row cover

·         avoid bruising carrot leaves – they are attracted to the scent

·         seed carrots later in the season to avoid the larvae’s life cycle

·         harvest carrots before the second week in September to avoid major damage

·         Resistafly is a variety of carrot seed available at Vesseys.com.  It’s leaves have no scent, and does not attract carrot rust fly.

Cutworms overwinter as eggs, larvae, pupae and as adults.  They feed by cutting young seedlings at their base.  They are attracted to weedy areas. 

Management: 

·         cultivate soil to expose cutworms to predators

·         planting late starves them

·         they are nocturnal – hand pick at night

·         put a collar of cardboard or foil around each plant

·         they overwinter in debris – clear away their habitat

·         ground beetles and birds are great predators

Chinch bugs have sucking mouthparts that feed on grass blades and roots.  Adults are black with white spots and white wings.  The nymph is bright red with white bands across the back.They are attracted to poorly tended lawns and compacted soils with lots of thatch buildup and lack of moisture.

Management:

·         aerate and remove thatch from lawns

·         use slow-release fertilizer and lime

·         keep lawn moist

·         do not cut lawn too short, which stresses the plants

from left:  larva of Japanese beetle, European chafer, and June beetle

June beetles have a 3-year life cycle.  Grubs eat grass roots.  In June, adults lay their eggs in the soil.  They hatch in 2 weeks.

Management:

• a healthy lawn is the best protection against grubs
• skunks and crows are dig up the lawn to feed on grubs
• parasitic nematodes will control them – need the right kind, and the soil must be moist to be effective

Japanese beetles have invaded PEI in the last 4 years.  There is a huge population in the Charlottetown, Cornwall, Canoe Cove area. They attack trees such as crab apple, elm, maples, but mostly concentrate on roses.  The beetles are very beautiful, with iridescent bodies, but very destructive.  The larvae are in the ground where they attack roots.  The adults can skeletonize leaves very quickly.  They overwinter as grubs that are smaller than June beetles.

Management: 

·         hand pick and knock into jar of soapy water

·         insecticidal soap must make direct contact with beetle

·         pheramone use:  be cautious, because this attracts more to your area

·         check soil in late summer:  more than 12 grubs per square feet means you need to treat the lawn

Colorado Potato Beetle attacks potatoes, tomatoes.  The yellow eggs are laid on the underside of leaves.  The young and the adults feed on leaves.  The young shed their skin 4 times as they grow (instars) and overwinter in the ground. 

Management:

·         hand pick and knock into jar of soapy water

·         kill eggs by crushing

·         Bacillus thurengis may work on larvae

Striped Cucumber Beetle overwinters as an adult.  It lays eggs in the soil.  Adults eat leaves, pollen, and flowers of cucumber plants.  The larvae eat the roots and stems.  It can spread bacterial disease, which appears as bacterial wilt.  Infected plants cannot be saved.

Management: use floating row cover to keep them away from plants.

Sawflies – Rose Slug look like tiny caterpillars.  When you disturb the larvae, they raise their back end, which caterpillars do not do.  Adults lay eggs on leaves, and the larvae eat all spring and summer, skeletonizing the leaves.  Host plants include roses, raspberries, ash, elm, dogwood, willow.  They are hard to remove from the plant because they are on the undersides of leaves.

damage from viburnum leaf beetle

Viburnum leaf beetle is greyish-brown. The yellow and black larvae eat holes in viburnum leaves, leaving only the large veins behind.  To check for an infestation, check stems of plants.  Rows of bumps mean there are eggs buried in the stem.

Management:

·         They are too numerous to hand pick.

·         In fall when leaves have fallen, cut off infected stems

·         Spray insecticide when larvae are young

·         They crawl down the stem to the ground to pupate.  Covering stems with tanglefoot can trap them.

Brown marmorated stink bug, an insect not previously seen on our continent, was accidentally introduced into Pennsylvania. It was first collected in 1998. 

Adults are approximately 17 mm long and are shades of brown on both the upper and lower body surfaces.  They have the typical “shield” shape of other stink bugs, almost as wide as they are long. To distinguish them from other stink bugs, look for lighter bands on the antennae and darker bands on the membranous, overlapping part at the rear of the front pair of wings. They have patches of coppery or bluish-metallic rounded depressions on the head.

The name “stink bug” refers to the scent glands located on the dorsal surface of the abdomen and the underside of the thorax. It releases a bad odour if crushed.

In its native range, it feeds on a wide variety of plants, including apples, peaches, figs, mulberries, citrus fruits and persimmons. This true bug has also been reported on many ornamental plants, weeds, soybeans and beans for human consumption. Feeding on fruits such as apple results in a characteristic distortion referred to as “cat facing,” that causes the fruit to be   unmarketable.

These bugs are a big problem in the US and have been found in the Niagara region of Ontario, where they are a major threat to fruit production.  They were spread by hitching rides on Home Depot trucks moving goods from the US to Ontario, and have been found on trucks on PEI as well.  These bugs even survive going through the washing machine.

If you find this bug on PEI, please catch it in an escape-resistant container and bring it to Christine Noronha at the Agriculture and Agri-Food Canada building on University Avenue in Charlottetown, or call her at 902-394-1350.