Mites

"All life is important, no matter how small".
- Unknown

introduction

Mites are small arachnids with eight legs, and are typically very tiny, topping out around 0.04 inches in length. Their small size means that they are generally overlooked unless they appear in large infestations or cause damage to human or plant life. Some species of mites live in water, others are soil decomposers, and still others live on plants. There are even some species of mites which are parasites and predators.

Like their spider relatives, mites have two body regions, a cephalothorax and an abdomen. They are more fused together, however, than the body parts seen in spiders. Mites have eight legs, each with six segments Many species are blind, and most have bristles on their bodies. They are typically various shades of brown, but can also be red, orange, black, green, or a combination. Most mites lack a heart, and most of their internal fluid is moved using muscle contraction. Male and female mites look pretty similar; most differences cannot be discerned by looking at them with the naked eye. Mites lay eggs, which can take up to six weeks to hatch. They go through various life stages before reaching adulthood. Mites have short lifespans, from a few days up to a few weeks, and most require access to a host to survive at all. The smallest mites are 79 micrometers long (0.079 millimeters), and the largest mites are about 6 millimeters long.

Mite Behavior

Mites fill many different roles, including as decomposers, predators, and parasites, and have occupied a wide array of habitats worldwide, including freshwater and saltwater. Mites hold all-time speed and strength records (relative to their size). Most mites are parasitic pests of plants and animals, and live on their hosts or in close proximity to them, for example in their nests or burrows.

Nest mites are a group which primarily lives in the nests of birds and other animals, and feed on blood, skin and keratin.

Ticks are also a prominent group of mites that are easily recognizable. They are parasites of vertebrates (mostly mammals and birds) and feed on blood with specialized mouthparts.

Dust mites are a group of mites that feed mainly on dead skin and hair shed from humans.

Parasitic mites also infect insects, some attacking honey bees and living in their tracheae, and others parasitize ant species. Plant pest mites include spider, thread-footed, blister, rust, erineum, bud and gall mites. There are also mites that affect human health, including those known as chiggers, ticks, and scabies. Each type of mite has its own unique behaviors, depending on their chosen environment and feeding habits.

Mite Species

About 48,200 species of mites have been formally described, and there are estimated to be about a million or more that are not as of yet documented. The list below includes commonly encountered mites in the garden, as well as some that will enter homes, and others that affect our health and wellbeing. It includes commonly-encountered mites that exist in western North America; If you are in another area, make sure to do some research on which mite species are common in your area.

Mites Affecting Outdoor Spaces

Acalitus essigi
(Redberry Mite)
These mites affect Raspberry and Blackberry plants, overwintering in nooks where buds form. They cause hardened, red drupelets.

Anystis spp.
(Whirligig Predatory Mites)
These large mites are predators of spider mites, leafhopper nymphs, and other arthropods.

Aculops fuchsiae
(Fuchsia Gall Mite)
These organisms affect Fuchsia and other related plants, distorting and thickening leaves, and causing foliage to redden.

Aculops lycopersici
(Tomato Russet Mite)
These very tiny mites cause bronzing on tomato plant leaves and stems, starting at the base of the plant and moving upward over time.

Bryobia rubrioculus
(Brown Mite)
Becomes active in late winter, and is larger than most other spider mites. Feed on both sides of leaves, causing mottling and stunted growth.

Colomerus vitis
(Grape Erineum Mite)
These mites affect grapevines primarily, and cause warty swellings on leaves.

Eotetranychus sexmaculatus
(Sixspotted Mite)
Affects Plumeria and Avocado plants. These spider mites feed on lower leaf surfaces only, and can cause premature leaf drop.

Epitrimerus pyri
(Pear Rust Mite)
Affecting Apple and Pear trees, these mites are very small, and cause browning on leaves and fruit tissues. They can stunt growth of young trees.

Eriophyes cynodoniensis
(Bermudagrass Mite)
Feed on Bermuda Grass, sucking juices from stems and leaf sheaths. Plants will be stunted and swollen. Worm-like shape.

Eriophyes mackiei
(Live Oak Erineum Mite)
These mites cause green glossy blisters to occur on Oak species, and form felty masses on leaf undersides.

Eriophyes pyri / Phytoptus pyri
(Pearleaf Blister Mite)
These mites attack Pear trees, causing discoloration on fruit and leaves, and reducing fruit yield.

Eriophyes sheldoni
(Citrus Bud Mite)
Cause severely deformed blossoms, foliage and fruit of lemon trees.

Euseius spp.
(Euseius Predatory Mites)
These mites prey on nymphs of scale insects, thrips, whiteflies, and spider mites.

Neoseiulus spp. / Amblyseius spp.
(Neoseiulus Predatory Mites)
These mites feed on spider mites primarily, but will also eat thrips, other species of mites, and small arthropods.

Oligonychus perseae
(Persea Mite)
These spider mites form round patches of silk under which they feed on leaves. Causes circular brown-yellow spots visible on both leaf surfaces.

Oligonychus punicae
(Avocado Brown Mite)
Spider mite that affects Avocado trees, feeding on leaves as well as fruits.

Panonychus citri
(Citrus Red Mite)
These spider mites produce little to no webbing, and affect more than 100 plant species.

Panonychus ulmi
(European Red Mite)
Spider mite species common on Prunus spp. and Apples, causes stippling and mottling on leaves.

Phyllocoptes gracilis
(Dryberry Mite)
Affects Blackberry and Raspberry fruits, causing them to become hard and fail to develop a natural color. Also causes yellow leaf spots.

Phyllocoptruta oleivora
(Citrus Rust Mite, Silver Mite)
Affects orange and lemon trees, causing damage on the surface of fruits. Does not hurt internal quality of fruit.

Phytonemus pallidus
(Cyclamen Mite)
These mites affect many different ornamental and crop plants, and cause discolored and deformed buds, leaves and flowers.

Phytoseiulus spp.
(Phytoseiulus Predatory Mites)
These small garden critters eat plant-feeding spider mites.

Polyphagotarsonemus latus
(Broad Mite)
Affecting herbaceous ornamental plants, these mites cause stiff leaves and flowers and bud drop.

Rhizoglyphus spp.
(Bulb Mites)
These are relatively large mites with shiny, cream-white bodies. They affect bulbs in the ground or in storage, and cause them to become soft and decayed.

Mites Affecting Humans

Sarcoptes scabiei
(Itch Mite)
These mites, commonly called Itch Mites, cause the skin issue called scabies.

Demodex folliculorum / D. brevis
(Demodex Mites, Face Mites)
These mites cause issues when populations get too large, but otherwise go unnoticed, living inside of hair follicles.

Ornithonyssus sylvarium / Dermanyssus gallinae
(Bird Mites)
These tiny parasites feed on the blood of birds and can also bite humans.

Liponyssoides saguineus / Laelaps echidnina
(Rodent Mites)
These small, greyish mites can bite humans, causing irritation and dermatitis, but usually feed on rodents.

Otodectes cynotis
(Ear Mites)
These mites feed off of skin oils and ear wax, and are commonly found in animals, though they can jump to humans in close proximity.

Dermatophagoides farinae /
D. pteronyssinus
(Dust Mites)
These pests feed on dead human skin cells, and thrive in warm, humid settings. They can cause allergic reactions in sensitive individuals.

Ixodida spp.
(Ticks)
These commonly encountered mites have the potential to bite humans and vector serious diseases.

Trombiculidae spp.
(Chiggers, Berry Bugs)
These mites feed on skin, and their bites can cause redness and itching. They do not commonly vector diseases.

Mites in the garden

Many types of mites exist in the landscape, including harmful and beneficial species. Populations will increase during the warm, dry months of the year and are also high in greenhouses with low humidity. Plants that are under stress from other issues, such as drought, mechanical damage, or disease, are much more susceptible to mite infestations than healthy plants. When looking for mites in the garden, check leaves first, looking for stippling (patterns of small dots or spots), yellowing/browning, or death, especially on older leaves. Mites that create webs will spin them on the undersides of leaves, so it is a good idea to flip the leaves over and check there as well. Other signs of mites include eggs and shed skins. To confirm the presence of mites, a hand lens is usually required due to their small size. Mites can be difficult to detect in the landscape. Their damage can mimic many plant diseases, so it is important to be able to identify and differentiate mite damage from disease reactions in plants. Study the mite indicators listed below to learn more:

Pale or Yellowing Leaves
Many plants will indicate a mite infestation when they develop pale or unusually yellow leaves. It can almost look like the plant needs a dose of nitrogen fertilizer. This is an initial symptom of a mite infestation, though it can be caused by a variety of problems.

Stippling
Leaves that have been fed on by mites will have very tiny yellow or white spots where feeding sites are located. This is because when mites feed, they remove the chlorophyll inside leaf tissues, removing the leaf's green pigment. Large populations of hungry mites can result in leaves losing almost all of their pigment, but most commonly it is seen as a stippling pattern of smaller dots.

Bronzing
There are some types of leaves that will develop a bronze or brown cast to them in response to spider mite feeding, not yellowing or stippling. Depending on the plant type, bronzing can develop after, or instead of, stippling.

Dusty, Gritty Feeling Leaves
Spider mites are hard to see, due to their tiny size. Evidence of their presence, however, can sometimes be seen and felt on some leaves. Debris like fecal matter, fine webbing material, dead mites, and exoskeletons tend to collect on leaves, making them feel gritty when they are rubbed.

Webbing
Similar to spiders, many species of mites produce webbing, which is typically found on new growth and between leaves. A buildup of webbing indicates a severe infestation.

For more information on creating a comprehensive pest management system in your garden, consult the following page:

Pests & Pest Management