As part of the ecosystem, our gardens are constantly fighting large and small attacks. Common mites (Polyphagotarsonemus latus) are tiny but destructive beetles that reproduce quickly and can cause great damage to vegetables and ornamental plants. They are documented on over 60 plant families. This mite is a problem in areas of the world without freezing temperatures in winter and poses a serious threat to greenhouse growers.
In recent years, breeders in parts of the United States with mild winter temperatures have seen an increase in the broad population of mites. Large mites are usually killed by the cold, but can hibernate in leaf litter at temperatures close to freezing.
The common mite is a major agricultural pest domestically in temperate states such as California, the Carolinas, Florida, and Virginia, and abroad in parts of Asia, South Africa, and Mexico. Fruits like blackberries and strawberries, apples, melons, citrus fruits and grapes are just as susceptible as vegetables like potatoes and beans. Ornamental plants such as African violets, dahlias, azaleas, begonia and zinnias are also part of his long list of victims.
Broad mites encourage new growth and young buds on plants and can be particularly problematic for plants harvested for that growth, such as tea and cannabis.
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Overview of the broad mite
Wide mites are extremely small and difficult to see. Source: David B. Langston
The average width mite (Polyphagotarsonemus latus) is much smaller than spider mites and grows to be less than 0.2 mm long. The common mite is very difficult to see with the naked eye. These predatory mites feed on sap and cause discoloration and browning of the leaf surfaces. Heavy infestation with broad mites can lead to stunted plant growth, deformed fruits and even plant death.
Mites can range from translucent to light yellow or brown in color and have four pairs of legs. Adult female mites have three pairs of legs with the last pair ending in long hair, and adult males have three pairs of legs with the last pair ending in strong claws. Broad mites reproduce sexually and have a very short life cycle of between 5-13 days. An unpaired female common mite only lays male eggs. After mating with a male, she lays 4 female eggs for each male egg. These eggs are oval and translucent with white spots on the surface. This unique looking egg pattern is one of the most distinctive features of this species.
Life cycle of the broad mite
Eggs hatch into 6-legged larvae within a few days and immediately start feeding on plants. After two to three days, the larvae enter the resting or inactivity phase. Adult males develop before the females, carrying dormant females with them, waiting for them to become active again to mate. Adult males can transport adult females to a new leaf or host plant to spread the mite population. The population can grow rapidly as there can be up to 130 eggs per square centimeter of leaf surface.
Common living spaces
Rough, leathery texture as well as deformations and curling leaves are symptoms of widespread mite infestation. Source: Scots Nelson
Since broad mites prefer new growth, look for them near the terminal leaves and buds of your plant. Because these 0.2mm long mites are so difficult to see, it may be easier to look out for symptoms such as misshapen leaves and stunted growth first. The mites can also be in crevices and on the dark side of fruit. Eggs are on the underside of the leaves.
What do broad mites eat?
The broad mite is not a very picky eater and will attack a wide variety of hosts. Nightshade plants such as tomatoes, peppers, and eggplants can host broad mites. Typically, mite symptoms in these plants may initially look like a viral infection with leaf curls and deformed fruits and flowers. Young pepper plants have a particularly low tolerance to broad mite infestation, and five mites on a pepper can impair fruit development. Broad mites also infest many ornamental plants such as impatiens, berbera, marigold, and cyclamen to name a few.
Because a broad mite is more likely to survive in cozy greenhouse conditions, it is a threat to plants grown under covers. For example, the growing cannabis community has many resources to combat widespread mite infestation.
How to fight wide mites
Wide mite damage on paprika leaves. Source: Scots Nelson
The main problem with wide mite damage is that symptoms are usually not very noticeable until there is a significant mite population after 20-30 days of infestation. The saliva of the common mite contains a toxin that deforms the leaves. A plant adjacent to the visibly infested plants could actually be home to the largest population as the mites can migrate from plant to plant.
If you suspect you have a broad mite problem, carefully examine your plants with a 10-20x magnifying glass or send a sample to your local university agricultural advisory service. After positive evidence of common mites, treat all plants and not just those showing symptoms of infestation.
Organic or chemical control
Commercial kindergarten administrators can use an acarid with an active ingredient such as abamectin, chlorfenapyr, or spiromesifen. These are not available for home use. However, home gardeners can remove and destroy infested plants and treat these and adjacent plants with pyrethrin, insecticidal soap, or horticultural oil. These biological controls can help, but are typically less effective than commercial chemical controls.
If you're using a biological treatment like insecticidal soap or horticultural oil, apply the spray liberally. Be sure to spray the underside of all leaf surfaces and near the growth tips. Use multiple applications 7-10 days apart. As always, carefully follow the directions on the package and do a test spray before applying a full biological pesticide treatment.
Proper hygiene is important in your garden and greenhouse. This includes removing infected plant tissue, cleaning and disinfecting workplaces, and disinfecting tools. Following these best practices can help reduce the likelihood of transmission or transport of diseases and pests – including the broad mites.
It is known that common mites hitchhike on the legs of whiteflies. If you see white flies in your yard or greenhouse, you may also need to watch out for wide mites.
Greenhouse managers can also employ biological controls by releasing Amblyseius swirskii, a predatory mite that feeds on broad mites and other pests such as thrips and whiteflies. Managing an ecosystem can be difficult and managers may need to release several rounds of these predatory mites, carefully monitor the climate in these greenhouses, and replenish broad mites with additional food sources.
Wide mites are very sensitive to heat. If you suspect common mites on your potted plants, remove the infested leaves first. Then, submerge your plant, including its pots, in hot water (110 ° F water) for 30 minutes. This temperature should be hot enough to kill the mites but not hot enough to harm the plants. This treatment is not suitable for all plant species, so do your research before using this method.
frequently asked Questions
Wide, mite-induced curling on a coffee leaf. Source: Scots Nelson
Q: How do you know if you have wide mites?
A: Examine the underside of the plant leaves with a 10-20X magnification for signs of large mite eggs. You will be covered with a very distinct pattern of white dots. You can also send plant samples to your local counseling office or plant pathology department.
Q: Where do wide mites come from?
A: The broad mite is found in temperate climates around the world and can be transported by other insects such as whiteflies.
Q: Can plants recover from wide mites?
A: Yes, plants can recover from damage from wide mites if the population can be controlled or eradicated.
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