April 0, 2023
This calendar is an ever-expanding database on information about life cycle events for common Missoula County plants, pests, and diseases. Below, you will find information about LEAST-TOXIC treatments (those that have the smallest impact on humans, pests, wildlife and insects, like bees and ladybugs, which benefit the garden) as well as HARD PESTICIDE treatments (those that have greater impact on humans and the environment).
Integrated Pest Management (IPM) strives to optimize plant health by:
- Managing garden and landscape soils for good drainage and aeration
- Building soil by adding organic matter and properly timed fertilizers
- Pruning and irrigating according to the needs of particular plants
- Knowing the plant's level of susceptibility to pest damage
IPM also means knowing as much about each pest as possible.
- When is the pest MOST vulnerable, infective, or invasive?
- When is the pest most vulnerable to least-toxic management strategies?
- What is the least-toxic management tool that can be used successfully?
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Saturday
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Insect Prevention29
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Last Call for tree pruningApril 1, 2023
Last Call for tree pruning
Check for diseased branches, injured or water sprout branches now before buds break dormancy.2
Last Call for tree pruningApril 2, 2023
Last Call for tree pruning
Check for diseased branches, injured or water sprout branches now before buds break dormancy.3
Dormant SpraysApril 3, 2023
Dormant Sprays
If you had problems with mites, aphids, scale, or leaf rollers last year, you might want to consider applying an insect-preventative horticultural oil spray when tree and shrub buds begin to swell and show the first green color. Research indicates that oils are most effective (especially on scale and leaf-curling aphids) if you wait until the very first tips of green leaves begin to emerge before you apply oil. Oils smother newly hatching insects and insect eggs that are just about to hatch. Oils are less effective on insect eggs that are not yet ready to hatch; these eggs are thicker and tougher (in order to get through our cold winters). As days lengthen and temperatures warm, insect eggs become less thick and more susceptible to the smothering effect of horticultural oils. Most spray oils are petroleum based, but vegetable, fish, neem, and citrus oils are also available. Petroleum oils stand up to weathering best, and thus last the longest. Oils can burn tender new leaf tissue, so apply them carefully. Lighter, lower concentration oil sprays are less likely to burn leaves. Use oils when temperatures are above 40 F, but below 80 F. Oils should dry completely before they are exposed to freezing temperatures. Apply oils several hours before night temperatures drop. The advantage of oil sprays is that they have relatively low hazard to humans and non-target organisms, such as beneficial, biological control insects. There are limitations, however. Oils must contact the insect (or insect egg) to kill it. So, dormant oil sprays are completely ineffective unless the pest for which you are aiming has spent the winter, and is still present, on the tree or shrub you are spraying. Another limitation is that oil sprays generally kill only smaller, soft-bodied insects. If you had disease problems last year, you can also apply disease-preventative sprays to trees and shrubs. If bacterial diseases, such as Fireblight, were a problem last year, the least-toxic disease preventative spray is copper or Bordeaux mix. Bordeaux mix is a combination of copper and lime. If fungal diseases caused spots on leaves last year, Lime sulfur is the least-toxic disease-preventative option. Wait until day time temperatures are between 55 F and 65 F before spraying copper-containing or lime sulfur sprays.4
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Honey locust tree podgall midgeApril 5, 2023
Honey locust tree podgall midge
When honey locust trees start to break bud it's time to treat for the podgall midge that creates seed-like galls on leaves6
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Tent CaterpillarsApril 10, 2023
Tent Caterpillars
When apples are showing 1/4" to 1/2" of green and dandelions bloom, check your trees for the first 1/4" to 1/2" tent caterpillarsForest and Western Tent Caterpillars
Both species have similar appearances. Small larvae are black with long hairs and feed gregariously. Mature larvae are dark brown with bluish heads and blue-black sides. There is a row of whitish or yellowish keyhole-shaped spots on the back with patches of fine orange lines. Mature larvae feed singly.
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Ash leaf-curl aphidApril 14, 2023
Ash leaf-curl aphid
Ash leaf-curl aphids emerge when buds swell and leaves begin to expand.. Treat Now!
Very small (1/10 to 1/8 inch long), pear-shaped, soft-bodied insects ranging in color from light green through dark green, and pinkish to black. Aphids cluster on stems and/or undersides of leaves and produce "honeydew", a sugary protein mixture which is fed upon by ants and many of the aphids' natural enemies. Aphids move very slowly, if at all, and often appear to be attached to the plant surface by their sucking mouthparts. Young aphids, or nymphs, are wingless. Adults can be winged or wingless, depending on the species, environment, and time of season. There are many different kinds of aphids, most of which are specific to particular species, or genera, of plants. However, there are some aphids that attack many species of plants. Different species of aphids are often present at different times of the season.
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Ash leaf-curl aphidApril 16, 2023
Ash leaf-curl aphid
Ash leaf-curl aphids emerge when buds swell and leaves begin to expand.. Treat Now!
Very small (1/10 to 1/8 inch long), pear-shaped, soft-bodied insects ranging in color from light green through dark green, and pinkish to black. Aphids cluster on stems and/or undersides of leaves and produce "honeydew", a sugary protein mixture which is fed upon by ants and many of the aphids' natural enemies. Aphids move very slowly, if at all, and often appear to be attached to the plant surface by their sucking mouthparts. Young aphids, or nymphs, are wingless. Adults can be winged or wingless, depending on the species, environment, and time of season. There are many different kinds of aphids, most of which are specific to particular species, or genera, of plants. However, there are some aphids that attack many species of plants. Different species of aphids are often present at different times of the season.
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Check for aphidsApril 18, 2023
Check for aphids
When apples are at pink flower bud stage, check fruit trees, shrubs and green ash for aphidsVery small (1/10 to 1/8 inch long), pear-shaped, soft-bodied insects ranging in color from light green through dark green, and pinkish to black. Aphids cluster on stems and/or undersides of leaves and produce "honeydew", a sugary protein mixture which is fed upon by ants and many of the aphids' natural enemies. Aphids move very slowly, if at all, and often appear to be attached to the plant surface by their sucking mouthparts. Young aphids, or nymphs, are wingless. Adults can be winged or wingless, depending on the species, environment, and time of season. There are many different kinds of aphids, most of which are specific to particular species, or genera, of plants. However, there are some aphids that attack many species of plants. Different species of aphids are often present at different times of the season.
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Annual weedsApril 21, 2023
Annual weeds
If annual broadleaf weeds or grasses were a problem last year, check to see if they have germinated and hit with a non-selective herbicide such as acetic acid or oil formulations.22
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Annual weedsApril 23, 2023
Annual weeds
If annual broadleaf weeds or grasses were a problem last year, check to see if they have germinated and hit with a non-selective herbicide such as acetic acid or oil formulations.24
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Poplar Petiole Gall AphidApril 25, 2023
Poplar Petiole Gall Aphid
When poplar leaves expand, look for petiole gall aphids. Treat now!
Very small (1/10 to 1/8 inch long), pear-shaped, soft-bodied insects ranging in color from light green through dark green, and pinkish to black. Aphids cluster on stems and/or undersides of leaves and produce "honeydew", a sugary protein mixture which is fed upon by ants and many of the aphids' natural enemies. Aphids move very slowly, if at all, and often appear to be attached to the plant surface by their sucking mouthparts. Young aphids, or nymphs, are wingless. Adults can be winged or wingless, depending on the species, environment, and time of season. There are many different kinds of aphids, most of which are specific to particular species, or genera, of plants. However, there are some aphids that attack many species of plants. Different species of aphids are often present at different times of the season.
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GrasshoppersApril 26, 2023
Grasshoppers
Time to start scouting for Grasshopper hatches in South facing, open soil areas if you had problems with them last yearGrasshoppers are some of the most familiar of all insects, and more than 550 species occur in North America. Grasshoppers damage plants by chewing. Most feeding occurs on foliage, although immature pods and fruit may also be eaten. Bark from twigs is sometimes gnawed, causing girdling wounds.
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White Pine WeevilApril 28, 2023
White Pine Weevil
White pine weevils begin to feed on tops of Spruce trees now. Eggs laid now will hatch into larva that cause tree tops to wilt and die.The insect overwinters in the adult stage under leaf litter and in other protected areas. In late spring to early summer, weevils become active and seek out spruce trees. They feed on the cambium of main branches near the leader and insert eggs into the feeding cavities that are formed. Eggs hatch in 1 - 2 weeks and the grubs tunnel downward underneath the bark. Damage increases as the larva grow. Wilting of terminal branches becomes noticeable by mid-summer. By late summer, the top of spruce trees display a characteristic dead "shepherd's crook". When full grown, the larva tunnel deeper into the stem and form a cocoon made of wood chips in which they pupate. In about 2 weeks, adult beetles emerge leaving small holes in the bark. Adult weevils feed on the needles, buds, and twigs of spruce for several weeks before going into a dormant condition for overwintering.
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White Pine WeevilApril 30, 2023
White Pine Weevil
White pine weevils begin to feed on tops of Spruce trees now. Eggs laid now will hatch into larva that cause tree tops to wilt and die.The insect overwinters in the adult stage under leaf litter and in other protected areas. In late spring to early summer, weevils become active and seek out spruce trees. They feed on the cambium of main branches near the leader and insert eggs into the feeding cavities that are formed. Eggs hatch in 1 - 2 weeks and the grubs tunnel downward underneath the bark. Damage increases as the larva grow. Wilting of terminal branches becomes noticeable by mid-summer. By late summer, the top of spruce trees display a characteristic dead "shepherd's crook". When full grown, the larva tunnel deeper into the stem and form a cocoon made of wood chips in which they pupate. In about 2 weeks, adult beetles emerge leaving small holes in the bark. Adult weevils feed on the needles, buds, and twigs of spruce for several weeks before going into a dormant condition for overwintering.
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April Pest Breakdown