Ash trees are one of the most widely planted trees in Colorado. Ashes are tolerant of difficult soils and tough weather conditions. Ash availability, successful planting, and moderate growth rate encouraged the extensive use in the landscape. Many were planted as replacement trees when American elms fell to Dutch elm disease in the early 1970’s.
In Colorado, many insects are associated with ash causing both aesthetic and health harm. With the discovery of emerald ash borer in Colorado, ashes are being closely scrutinized for insect infestations. Emerald ash borer is
Aphids and scales are known as the piercing and sucking insects. Their mouthparts pierce plant cells and suck the sap from the tree.
Aphids are a nuisance and can be a serious pest. In ash, the aphids can be found by uncurling the leaves revealing a sticky mass of 1/8 inch long pale colored, pear shaped insects. When abundant, aphids remove large quantities of sap, reducing the growth and vigor of the plant. The aphids cause the leaf to curl and distort. Heavy infestations will result in leaf drop, sparse canopy, and also a sticky honeydew secretion from the leaves.
Scales include oyster shell and common falsepit. Scales are unusual looking and many people do not at first recognize them as insects. Oyster shell is aptly named as the scale resembles an elongated ¼ inch brown shell. Common falsepit scales are about 1/6 inch in diameter, rounded and cream colored. Scale insects attach themselves to the bark of twigs and branches causing injury by sucking plant juices, sometimes killing a branch or entire stem.
How to Get Rid of Thrips in American Mountain Ash Tree
Thrips are tiny insects that can cause major damage to American mountain ash trees. If left uncontrolled, thrips infestations can significantly impact the health and appearance of these ornamental trees. In this comprehensive guide, I will provide key information on how to identify, prevent, and get rid of thrips in American mountain ash trees.
What Are Thrips?
Thrips belong to the order Thysanoptera and there are over 5,000 known species worldwide. They are slender insects measuring around 1/20th of an inch in length Thrips can vary in color from yellowish to dark brown These insects use their rasping mouthparts to pierce plant tissues and feed on the contents. This results in stippling, discoloration, and deformation of leaves, flowers, and fruits. Thrips can complete multiple generations in a single year and populations can build rapidly in favorable conditions.
How to Identify Thrips Infestation
It is important to regularly inspect American mountain ash trees to spot thrips infestations early Some key signs to look out for
- Silvery flecking or bronzed appearance on leaves
- Stunted and distorted growth
- Premature leaf drop
- Black specks of fecal matter on foliage
Shaking branches over a white sheet of paper can help dislodge thrips for easier viewing. Check for the presence of tiny, slender insects with fringed wings. A hand lens may be required to see them clearly.
Natural Remedies to Control Thrips
When dealing with a minor thrips infestation, start with some natural and organic treatment methods:
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Prune off heavily infested branches and dispose properly to reduce pest numbers.
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Release beneficial insects like ladybugs, lacewings, and predatory mites which feed on thrips.
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Make foliar sprays using neem oil or insecticidal soap to control thrips populations.
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Use sticky traps near trees to monitor and trap adult thrips.
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Maintain tree health and avoid overfertilization which encourages thrips.
Chemical Treatments for Severe Infestations
For heavy thrips infestations that persist despite natural remedies, chemical insecticides may be required. Some options include:
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Insecticidal soaps which suffocate thrips on contact. Ensure thorough coverage of leaves.
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Pyrethroid based insecticides that disrupt the nervous system of thrips.
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Systemic insecticides like imidacloprid applied to soil to be taken up by the tree roots.
Carefully read and follow all label directions when using insecticides. Avoid applying them during bloom period to protect pollinators. Rotate chemicals from different modes of action to reduce resistance in thrips.
Preventing Thrips Infestations
Here are some key tips to help prevent thrips problems in American mountain ash trees:
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Maintain proper fertilization, watering, and mulching practices to keep trees healthy.
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Prune trees to open up the canopy and improve air circulation.
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Remove weeds, flowers, and debris from around trees that can harbor thrips.
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Check new plants and nursery stock for signs of thrips before bringing home.
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Consider preventative neem oil or insecticidal soap sprays in early spring.
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Hang sticky traps early in season to detect thrips activity.
Major Wood Borers of Ash
The wood borers are difficult to distinguish from each other as they develop inside the tree, insects are not often seen outside the tree and the tree damage each insect causes is similar. Different species of wood boring insects may attack the same tree.
Wood borers of ash may be categorized by the holes they leave when they exit the tree. Emerald ash borer and the flatheaded appletree borer both produce a very distinct “D” shaped insect exit hole. The larvae of these insects have a distinct flat head. Lilac ash, red headed, and the banded ash borer all produce a ¼ inch roundish exit hole. The ash bark beetle forms a very small 1/16 inch round exit hole.
Emerald ash borer. It is highly unlikely that you will see the signs or symptoms of emerald ash borer in Denver before it infests an individual tree. Where emerald ash borer is common in the Midwest and Eastern United States, by the time you see the “D” shaped exit holes at eye level, the tree is very infested and often cannot be saved with insecticide applications.
In the spring of the year, the adult emerald ash borer emerges from the tree briefly feeding on leaves. The feeding as well as the insect is difficult to detect. Insects mate and females lay eggs on the bark surface of ash trees. Initially, most egg laying is concentrated in the upper canopy of the tree and near branch crotches areas. With continued insect attacks, egg laying occurs lower in the canopy. Eggs hatch and the larvae bore into the tree. Larvae of emerald ash borer are cream colored, have a small head with pronounced dark jaws, slightly flattened area behind the head, and have a very elongate and somewhat flattened body. Overwintering emerald ash borer bores deep into the wood. Young larvae may take two growing seasons to mature. In the spring of the year, the insect matures into an adult emerging through a characteristic “D” shaped exit hole completing the life cycle.
Symptoms of emerald ash borer infestations begin as a thinning of the ash canopy. Dead branches are a symptom of advanced infestations. Trunk and twig sprouts form. The bark begins to crack revealing the insect galleries. Also present are D-shaped exit holes in trunk and branches. Woodpeckers also visit the tree in search of the young emerald ash borers as a food source. Sawdust is not expelled in the exit holes.
Lilac/ash borer. Without question, the lilac/ash borer is the most commonly encountered wood boring insect in ash. Adults of this insect emerge from trees during warm days in mid spring. The adult borer mimics paper wasps and may be seen flying about the tree. Adult lilac/ash borer is a moth and does not feed on the ash foliage. When adults emerge from the tree the pupal skin is often pulled out and will remain for some time partially extruded from the trunk. The hole through which the adults emerge is generally round and somewhat irregular. Lilac/ash borer is the only ash wood boring insect on ash that produces sawdust visible on the outside of the trunk. The adult lays eggs in bark crevasses. Eggs hatch and the insect bores into the tree. Larvae of lilac/ash borer are cream colored with a dark head. The larvae overwinter in the ash tree emerging the following year completing the life cycle.
Lilac/ash borer will produce more generalized riddling of the trunk and limbs than do the other borers associated with ash. External symptoms of lilac/ash borer injury often include some areas of swelling on the trunk and some sprouts. Branches are killed. Repeated injuries weaken branches making them susceptible to breakage.
THRIPS?! How to kill thrips and save your grow.
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Do aphids damage American mountain ash trees?
They are a common pest that can cause damage to American Mountain Ash trees by causing leaf curling, yellowing, and stunted growth. Signs of aphid infestation include the presence of sticky honeydew residue on leaves, black sooty mold growth, and the presence of the insects themselves.
What should I do if my American mountain ash tree grows too big?
If your American Mountain Ash tree has grown too large or is encroaching on nearby structures or plants, you can reduce its size through selective pruning. Focus on cutting back long branches to maintain a manageable height and spread while preserving the tree’s aesthetics. 5. Removing Suckers and Water Sprouts
Do aphids eat ash trees?
Aphids are tiny, soft-bodied insects that feed on the sap of trees by piercing the plant tissue with their mouthparts. They are a common pest that can cause damage to American Mountain Ash trees by causing leaf curling, yellowing, and stunted growth.
What insects eat American mountain ash trees?
Beneficial insects: Introduce parasitic wasps or predatory beetles that prey on leaf miners. Scale insects are small, immobile pests that attach themselves to the branches and stems of American Mountain Ash trees, feeding on plant sap. They can weaken the tree and cause yellowing leaves, premature leaf drop, and dieback.