Boxwood is a landscape plant that used to grow in a number of areas as a perennial shrub. It can be used in different areas like hedges, screen, background, planting and topiary pieces. Many types of insect and pest attack on this perennial shrub. One of the famous pests of this botanical shrub is a boxwood leaf miner (Monarthropalpus flavus). Its attack in an academic form on American boxwood but Japanese and English boxwood also vulnerable to its attack.
In this article, I will tell about the insect, its attack symptoms, etiology (life cycle) and all possible means to control its attack and protect this perennial shrub.
What is a boxwood leaf miner (Monarthropalpus flavus)?
Boxwood Leaf miner is an insect pest in which the larvae attack the inside of the boxwoods leaves. These insects feed inside the leaf among the upper and lower leaf surfaces. Larvae will crack into adults and disruption through the lower leaf surface of the leaf when it gets fully matured.
Dual-Sided Yellow Sticky
(Leafminers, Thrips, Midges And Other Flying Isecs)
Description of boxwood leaf miner insect?
The larvae of the boxwood leaf miner are whitish in color as they got hatch from the eggs but with the passage of time as they grow, they convert into bright yellow color and having the approximate length of 1/8 inch. A single leaf of boxwood shrub can act as a host for multiple larvae. On the other side, adult leaf miners having a size of 1/8 inch are transformed from yellow to orange color and they tend to swarm around and cling to the boxwood. The eggs of the leaf minor insect are crystal clear or white in color and tend to visible upon holding an infested leaf up to the light.
Damage Symptoms of pest:
The certain symptoms of boxwood leaf minor are:
- The formation of blistering and irregular shaped swellings on the leaves of the shrub.
- Blistering is most apparent on the lower side of the leaves and it is most obviously seen in the late-season attack.
- The affected leaves develop yellow and brown splotches, moreover, they are stunted in growth and drop prematurely.
- A strong attack of leaf minor on boxwood shrub may cause dangerous defoliation and even leads to the death of a boxwood plant.
At the larval stage, it causes the most damage to the boxwood plant. Larvae hide in winter under the leaf blisters. As soon as spring arrives and temperature rise, it acts as a signal for larvae to become active again and start feeding inside the leaves of boxwood. Even some larvae are enough sluggish which start feeding inside the boxwood leaves from spring to summer. Side by side adult young ones of leaf minor can emerge out of the leaf in summer. Adults look like small yellow or orange flies that can even swarm around the boxwood plantings. After the emergence of adults, they mate with each other. After mating and successful fertilization, they start depositing eggs into the underside of the boxwood leaves. they even start direct injecting the eggs into the leaves of the boxwood leaf miner. A female can lay 29 eggs on an average. The adult female dies in a short span in an hour after depositing their eggs. Again egg starts hatching in two to three weeks of injecting eggs. In this way, the cycle start gains as the eggs grow into larvae within the leaf in about two weeks. The larvae can feed and grow to maturity inside the boxwood leaf bringing a lot of damage to the boxwood plant as it starts feeding and stealing the nutrients from the plant itself.
How to manage the boxwood leaf miner attack?
There are many ways to manage the attack of the boxwood leaf miner.
The first step in the management of any pest in defined monitoring in which you identify the right stage of the pest development. There are the following stages you can monitor while seeing an infected shrub.
Larvae: you can inspect the presence of larvae from November through March.
Adult: for adult monitoring, you have to set yellow sticky traps and even you can observe them early in the morning 300-650 GDD at the end of May through June.
Egg: You can even check the newest from a pinhole in late June.
Monitoring symptoms and techniques:
- First, make sure it is not winter injury destruction because boxwoods are susceptible to this. Winter burn creates a brown discolored margin around the border of the leaf that making it look like the edges have dried out. In contrast, boxwood leaf miner damage appears all over the leaf surface.
- If you look carefully at the underside of the leaves then you will see small blisters caused by the larvae inside. And if you peel off a leaf apart then you will clearly see the maggots which are hard to miss.
- One of the most important features is color. Infested leaves turn into yellowish color which may appear in the form of spotted and also looks unhealthy. With the passage of shrub will eventually decline and die.
- A soon as an adult emerges from the infected leaves, you may see small rice-shaped things that hanging underside the leaves. These are the pupal skins that may be left behind by the emerging midges.
- In the form of heavy infestation, you will often see swarms of orange color or mosquito-like midges which flying around boxwood especially if you shake the shrub. You can also even hear a hissing and popping sound.
Through monitoring, you identify the stage of pest development and also the damage and attack severity on the host.
Control the damage level:
After identifying the development stages and level of severity of the attack and different symptoms of an infestation then next step is to control the pest to avoid certain damage.
“Precaution is always better than cure”, so our first line of defense is taken appropriate measure to avoid the attack of the boxwood leaf miner.
Resistant varieties: For avoidance, you have to choose those cultivars which are more resistant to leaf miner. Most of the American cultivar is more susceptible to attack, while the English boxwood varieties are more resistant to leaf miner. Here are some resistant cultivars: Buxus sempervirens, pendula, suffruticose, Handworthiensis, Pyramidalis, Argenteo- varigata and Varder valley.
Pruning: Another option is to prune the shrub before adults emerge in spring, or right after eggs are laid in May. This can be condensed the population overall.
If despite avoidance the shrub is infested, then you have to move towards natural friendly means to control the attack.
- If only a few parts of shrub are infested then try to squeeze the affected leaves hardly, it will kill the maggots inside it. However, it is not a practical approach for large parts of shrub and multiple shrubs which are infested with leaf miners.
- The best non-chemical way to control boxwood leaf miners is with good sanitation practices and leaf removal.
- Always dispose of the fallen leaves or remove leaves that contain overwintering larvae that hide in the winter season.
Another way is to encourage the presence of a natural predator against the leaf miner pest. The most beneficial insect against the boxwood leaf miner is spiders and green lacewings which can also minimize the use of broad-spectrum insecticides.
If by all means you are unable to protect the boxwood shrub, or the severity level is much higher than no need to worry. Use insecticides to control the population of leaf miners. Multiple chemicals and a large number of application proposition a leaf miner control. Always use contact insecticides like malathion and carbonyl in spring when leaf miners are hovering around the boxwood. When the larvae are burrowing in leaves then use a foliar systemic insecticide like acephate. Soil treatments with imidacloprid or dinotefuran also offer leaf miner control but it may take time more than two weeks. Keep in mind always follow manufacturer instructions while using an insecticide.
In this way by using all the above means to control, you can protect your boxwood shrub which gives an effective look to your landscape.
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