The Insects of May
Brownheaded ash sawfly: Watch for pin-hole
feeding on new ash leaves early prior to later, peak feeding damage on entire leaves.
Apply control sprays of soap or many ohter insecticides when sawflys are small.
Zimmerman pine moth: Overwintered larvae move
into the trunk so protective sprays should be applied early in the month.
Pinyon tip moth: Exposed larvae on bark can be controlled early in the
month; larvae tunnel into new terminals in late May.
Southwestern pine tip moth: Egg-laying begins with emergence of new
needles.
Pine needle scale: Egg
hatch begins in mid month around the time of peak lilac bloom Check infested plants.
Lila/ash borer: Flights of adults should reach their peak in mid month so
now is the time for protective sprays.
Oystershell scale: Crawler emergence begins in
late May. Check infested plants.
Spiny elm caterpillar: Small colonies of these caterpillars may be seen
on willow, hackberry, aspen and other trees.
Hawthorn mealybug: Overwintering insects move
to twigs to feed.
Hackberry psyllid: Adults return to trees to lay eggs on the
late-emerging leaves.
Honeylocust podgall midge: Adults begin laying
eggs on new growth. First generation begins.
Honeylocust plant bug: Nymphs hatch and begin
to damage new growth.
Elm leaf beetle: Adults return to trees to chew
holes in leaves.
Peach tree borer: Larvae cause peak injury to
un-protected tree bases this month.
Tent caterpillars: Larvae make tents on various fruit and shade trees.
Forest tent caterpillars are also active.
Slugs: Cool wet weather, newly emerging
perennial leaves, and new annual transplants can lead to a slug feast.
Spinach leafminer: Egg
laying and tunneling can be seen on older leaves.
Seedcorn maggot: Gardeners gambling by
planting corn and bean seeds before soil temperatures are thoroughly warm risk damage.
Flea beetles: Adults lay eggs on cabbage,
radish and related plants.
Narcissus bulb fly: Adults emerge to lay eggs at the base of narcissus,
daffodils and hyacinth.
Miller moths: Flights can be expected mid month
and will likely peak late in the month.
Information courtesy Whitney Cranshaw, Department of Bioagricultural Sciences and Pest
Management, Colorado State University.
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