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Common Pests and Organic Controls

PEST TREE SPECIES AFFECTED WHAT IS IT? PREVENTION CONTROL
Aphids tulip tree, nannyberry, maples, alders, birches, dogwoods, basswood Tiny green to black, reddish brown, or dusty grey insects usually found in colonies which suck plant sap. do not over fertilize with nitrogen encourage native predators and parasites
spray plants frequently with a strong stream of water to knock aphids off
use mild soap spray or homemade garlic spray
Borers and Bark Beetles maples, cherries, pines, ashes, oaks, alders, basswood Larvae of beetles bore into wood of trees. Attacked patches of bark exude gummy sap, turn dark and die. If bark dies entirely around trunk, the tree will die. avoid injury to bark remove injured limbs as soon as damage occurs
Webworm ashes, pines Caterpillars feed on leaves, eating holes until only a dry leaf skeleton remains. attract parasitic wasps with nectar or pollen knock caterpillars off leaves into pail of soapy water
remove host weeds in garden vicinity remove webs and destroy by burning or immersing in soapy water
Gypsy Moth basswood, birch, oaks, serviceberry, pines European Gypsy Moth is a defoliating insect that can severely weaken or kill trees. It is a major introduced pest to North America. attract birds to your yard by planting appropriate plants in spring, trap caterpillars by wrapping burlap around trunk of tree destroy caterpillars from this shelter every afternoon
scrape brown or yellow egg masses of trunks into bucket of soapy water
Leaf Miners birches, oaks Larvae of these insects tunnel between leaf surfaces, feeding on leaf tissue. encourage native parasites with nectar plants destroy overwintering sites for insects by collecting and removing fallen leaves in Fall
Leaf Skeletonizers hackberry, birches, oaks, cedar, basswood Insects that specialize in eating the soft green tissue of leaves, but leave the network of veins. Often leave the top and bottom layers of leaf skin, giving leaves brown, papery appearance. maintain plant health destroy overwintering sites for insects by collecting and removing fallen leaves in Fall
insecticides are often ineffective as the pests are inside the leaves and do not have contact with sprays
Spider Mites spruces, pines, cherries, basswood Minute, 8-legged bugs which suck juice from cells on the undersides of leaves. attract parasitic wasps and woodpeckers place a ground sheet under tree to catch larvae and destroy daily in soapy water
Scales ashes, hackberry, oaks, maples, redbud, alders, birches, dogwoods Small insects which suck plant sap, weakening the plants. attract native predators and parasites with nectar and pollen plants prune and destroy infested wood
release predatory beetles
Tent Caterpillars alders, birches A native insect that rarely occurs in large enough numbers to cause tree death in Toronto. Populations peak every 10-12 years, then quickly return to tolerable levels. attract natural predators insecticides are generally ineffective against mature larvae
caterpillars return to their tents during cool, wet weather and in evening prune and destroy nests during this time
Weevils pines, spruces Small beetles that feed at night consuming needles. Worst damage is from larvae feeding on roots and burrowing in crown of plants. avoid injury to tree destroy overwintering sites
drench soil around roots with parasitic nematodes
Adelgids pines, hemlock Insects that suck sap from undersides of limbs. They cover themselves with white powdery material spray with soapy water solution
spray with dormant oil in late winter before growth begins
Carpenter Ants any tree with decayed wood Large (8-11mm in length) black ants that live in colonies. They do not eat wood -their presence is usually an indicator of wood decay. Because carpenter ants only chew decayed wood, preventing wood decay is most important in preventing colonies of ants from colonizing a tree Monitor tree and have it assessed for safety by a certified arborist
do NOT seal or fill cavity
Fall Cankerworm oaks, ashes, maple, basswood, beech, birch, elm, hickory Insect larvae, also known as loopers or inchworms, that feed on buds and new leaves in severe infestations causing heavy defoliation. May result in tree death if coupled with other stresses. Encourage parasitic wasps, virds, and ground beetles
Maintain plant vigour - healthy trees can releaf after being defoliated in early summer
Leaf Rollers willows Green caterpillars with brown heads that spin webs at branch tips, pulling leaves together and feeding on enclosed buds, leaves and developing fruit. encourage parasitic wasps such a Trichogramma apply dormant oils sprays just before buds break in spring to kill egg masses
check branches of young trees weekly and remove caterpillars
Lace Bugs alders Small insects with distinct lacelike pattern on wings and heads that suck plant juices on undersides of leaves, resulting in speckled white or grey blotched appearance on leaf surfaces. Spray with insecticidal soap
Sawflies pines, tamarack, spruces, ashes, birches Insect larvae that look like hairless caterpillars that feed in groups and can quickly defoliate portions of a tree. There are many different species of sawflies, each prefers specific plants maintain plant health hand pick larvae and drown in bucket of soapy water
monitor trees in spring for caterpillars knock caterpillars off tree with strong water spray
spray with insecticidal soap
Spruce Budworms spruces, balsam fir, tamarack, hemlock Caterpillars 1"" long, dark reddish-brown with white spots and black head that eat needles. Infestations can reduce tree growth and, if prolonged, lead to tree death maintain plant health hand pick larvae and drown in bucket of soapy water
knock caterpillars off tree with strong water spray