Department of Entomology
Insect Note - ENT/rsc-2
On a world-wide basis, mites are important nuisance pests and some are capable of transmitting disease agents. Fortunately, the mites that we commonly encounter in North Carolina do not transmit disease agents that affect people. The majority of mites are free-living, but thousands of species are parasites of animals or plants. Most of these are external parasites (i..e., they feed on the exterior of their hosts), but some species inhabit the ear canals, lungs, intestine and bladder of vertebrates, particularly domestic animals. Their biting and bloodsucking behavior causes considerable discomfort to their hosts and a few species also cause serious allergic reactions, such as asthma, in people. Because of their relatively small size, mites are often the "suspects" of a whole range of biting/itching problems. Understanding mite biology and the symptoms associated with mite infestations can help determine if they are the actual cause of a particular problem.
|Mite Biology||Scabies Mites||Chiggers Mites||Clover Mites||Dust Mites|
|Relief for Mite Bites||Straw Itch Mites||Bird Mites||"Paper Mites"and unidentified bites|
Mites are not insects; they are more closely related to ticks and spiders.
Most mites are visible to the unaided eye and usually measure 1/8"
or less in length. Their life cycle has four basic stages: egg, larva,
nymph and adult. The egg hatches into a larval stage, which molts to the
nymphal stage. After 1-2 more times, the nymph matures into an adult. Mites,
like ticks, have three pairs of legs as larvae and four pairs of legs
as nymphs and adults. The life histories of some common mites associated
with people are described below.
The rash and intense itching associated with scabies occurs when the nymphs burrow into the skin and begin feeding. These symptoms usually appear several weeks to a month after the initial infestation. The majority of mites are found in lesions in folds of skin between the fingers, on the sides of the feet, on the wrists and genitals, and in the bends of the knees and elbows. After feeding on tissue fluids, the nymphs molt to become adults. The life cycle, from egg to adult, can be completed in about two weeks. Scabies mites are readily transmitted within families and within institutions such as nursing homes. Personal contact, particularly holding or shaking the hands of an infested person, is a principal method by which the mites are spread. Intimate contact and sleeping with an infected person can also spread the mites.
Proper treatment and control of a scabies problem requires:
Chigger (Red Bug)
are very small, reddish mites that feed only in the larval stage on
humans and other animals, particularly rodents. The red color of the
larvae is not blood but a natural red pigment. On animals, chigger larvae
remain attached to the skin for several days but on humans, they are
usually dislodged within several hours of attachment. Unlike scabies
mites, chiggers do not burrow into the skin. They feed at the base of
a hair follicle or in a pore. Chiggers generally attach to those areas
of the body where clothing fits tightly, such as at the sock
line and waistline. Larvae ingest lymph and partially digested cells
after the chigger attaches. The bites commonly cause itching in about
3 to 6 hours and dermatitis develops in about 10 to 16 hours. Some people
experience allergic reactions to the bites and develop blister-like
lesions. Chiggers do not transmit any disease agents to people. The
adults and nymphs are free-living predators of insects. In the South,
chiggers are active virtually year round. They are commonly encountered
at the woodland borders, along the periphery of swamps, and in shrub
thickets and unmowed areas of lawn. Areas that contain thick layers
of pine straw, leaf litter or thatch are suitable habitats for chiggers
and their prey. Treating chigger-infested areas with a pesticide spray
will provide some control. Ground cover in these areas should be wetted
down to the soil surface. Avoid excess treatments that can lead to pesticide
runoff into creeks, streams and storm sewers. For personal protection,
use insect repellents. DEET or Permanone (permethrin) can be applied
to clothing. DEET is
appropriate to use on exposed skin. Repellents should be used in moderation
by children and pregnant women. For more information about repellents,
see Insect Note - ENT/rsc-5.
Straw Itch Mites
Pyemotes tritici commonly breed in stored grain, dried beans and peas, wheat straw, hay and other dried grasses . They are frequently a problem for people doing landscaping or feeding horses and other livestock. The mites are actually beneficial because they attack insects that feed on stored grain and similar materials. People who handle mite-infested materials will be attacked. The bites of straw itch mites are characteristically found on the trunk of the body and on the arms.
The best control
strategy is to eliminate the mite's host insects. If possible, clean storage
areas thoroughly and treat it with a pesticide, such as cyfluthrin. Treating the straw is difficult because the mites are inside the bales as well as on the surface. Plus, there are currently no insecticidal sprays labeled in North Carolina for application to hay used as feed for animals. If necessary,
stored commodities can be fumigated with Phostoxin® to disinfest them. Fumigation should
be performed by persons holding the appropriate North
Carolina F-phase structural pest control license or certification.
The northern fowl mite (NFM),Ornithonyssus sylviarum, is a common pest of domestic fowl, pigeons, starlings, house sparrows and other wild birds commonly associated with people. Mite populations build up rapidly and a generation can be completed in 5 to 12 days. Several generations occur each year. Northern fowl mites spend virtually their entire life on the host bird. They can survive off a host for about a week or so. Mites that fall off host birds may be found wandering indoors. In poultry houses, they are sometimes found in the litter or on eggs, crates and cages.
Dermanyssus gallinae, the chicken mite (or red mite of poultry), is similar to the fowl mite in its host preferences. Unlike NFM, the chicken mite spends much of its time off the host bird, hiding in cracks and crevices during the day and feeding at night. They can survive for extended periods (as much as 8 months) off a host. It can be a serious problem to workers who handle birds. Around residences and other structures, mite problems tend to be more sporadic. Bird nests are often located in chimneys and tucked under eaves or window-mounted air conditioners. In the spring, nestling birds may be parasitized by thousands of mites. When the nestlings mature and leave their nest, mites may invade buildings in search of alternate hosts.
In some areas
of the state, bird mite problems may continue year round because hosts
such as pigeons are constantly present. Mites that find their way indoors
are easily removed by vacuuming or can be killed with an aerosol insecticide.
The key to reducing bird mite problems is to prevent the birds from nesting
on/in structures and to remove abandoned nests quickly. Although pigeons,
starlings and sparrows can be removed readily, birds such as chimney
swifts are protected under the 1918
Federal Migratory Bird Treaty Act and cannot be disturbed.
The best approach is to install a screened chimney cap in the early spring
or fall when the birds are not nesting.
House Dust Mites
Dermatophagoides pteronyssinus and D. farinae are the most common species of house dust mites in North Carolina . These tiny mites are most abundant in warm, humid areas. House dust mites do not bite or sting, but they may cause a skin reaction. They feed on "dander", shed human skin scales that collect in the dust on furniture, particularly mattresses and on carpeting below beds, couches, and chairs where people spend significant time. House dust mites are important medically because they produce allergens in their secretions and excrement. Inhaling airborne house dust containing mite feces and cast skins is a common cause of asthma in young children.
Products containing benzoyl benzoate and other ingredients are often used for severe infestations of house dust mites. Since dust mites can cause respiratory problems, avoid using insecticides that may further aggravate such conditions. The long-term solution to reducing a house dust mite problem is sanitation and environmental modifications:
For additional information, visit Bioaerosols in the human environment
[Top of Page ]
Bryobia praetiosa is a small (1/32") mite easily recognized because of its reddish-brown color and long pair of front legs that are often mistaken for antennae. Clover mites do not bite. They are a nuisance because hot dry weather in the spring and early summer nay cause clover mites to migrate indoors. In the fall, the mites may also migrate indoors seeking shelter from low winter temperatures. In attempting to remove the mites, homeowners often crush them, leaving red stains on furniture and drapes. Mite invasions are most common from vigorously-growing lawns and other vegetation surrounding homes, especially if shrubs are close to or touching the walls.
There is some anecdotal evidence that suggests that applying too much nitrogen fertilizer may worsen clover mite problems. A simple, non-chemical control method involves leaving a strip (12-18 ") of bare soil or gravel mulch around
foundation walls. This plant-free zone discourages mites from migrating
onto the walls and provides an area that is easily treated if needed.
If mites become a problem, application of a miticide to nearby foliage
and lawns may help. Insecticides applied to foundation walls, door thresholds
and window ledges make an excellent barrier. Indoors, the mites are easily
killed with aerosol insecticide sprays, but vacuuming is a preferable
alternative. SevinŽ, cyfluthrin, bifenthrin, and permethrin sold under
a variety of brand names are examples of pesticides that are currently
labeled for such use. Read the pesticide label carefully and select products
appropriate for use indoors or outdoors as needed. For additional information about clover mites as a pest in turf, refer to Insect Note ENT/ort 124.
Complaints about bites and rashes for which a specific cause cannot be found are often attributed to so-called (and non-existent) "paper mites" or to one of the other mites mentioned above, particularly scabies and bird mites. Other biting/stinging pest such as fleas and bed bugs are easily seen and produce very noticeable and characteristic bites and other evidence of their feeding. Although mites are extremely small, they are usually detectable with the unaided eye (as in the case of bird mites) or by skin scrapings or biopsy or other samples collected and examined by a physician. In the case of scabies and straw itch mites, the rash or bites caused by these mites help in identifying them as the cause of the problem. However, bit marks (or presumed bite marks) are not entirely reliable on their own to confirm the cause of the problem.. Very often we unconciously and repeatedly scratch irritated areas of the skin (particularly at night while sleeping) and this will only worsen the condition. Bird mites, "black pepper mites" and "paper mites" are often used as reasons to justify pesticide treatments in homes and offices. Pesticide applications made without first identifying a specific pest problem (and target application site) are usually ineffective and should not be used. More importantly, repeated and widespread pesticide applications are potentially hazardous to you and others around you. This includes constant (and multiple) applications of insect repellents and other insecticides to your skin (which can cause rashes and irritation) and to your clothing and/or bedding. You need to identify the cause of a problem before you resort to spraying any pesticides in your home.
Here are some tips for collecting specimens for identification.
If no insects or mites can be found, then you need to keep a broad perspective and consider other possible non-arthropod (insects, mites, spiders, etc.) causes
for your symptoms. A previously unidentified (or recently developed) allergy or sensitivity may a mimic biting sensation and bite-like marks or rashes. These allergies can include: certain foods, chemicals (including laundry detergents), dust, pollen, as well as interacitons among medications (and even medications with various health supplements). Even changes in your indoor environment (e.g., changes in humidity) and stressful situations can trigger skin reactions and sensitivities. Repeatedly using "natural" treatments or frequent (several times daily) bathing or showering can dry your skin too much and cause iteching or sensitivity. For that reason, you should consult your family physician or prefeably medical specialist such as a dermatologist or allergist.
Relieving the Itch of Mite Bites
When mites attach to skin, the saliva they secrete causes the intense itch that may be felt for several days after the mite is no longer attached. As soon as possible after walking through chigger-infested areas or being exposed to other mites, you should bathe in hot, soapy water and scrub down with a wash cloth. Oral antihistamines and/or application of a hydrocortisone cream to bites may help to relieve itching. If you develop a severe reaction, then consult your physician.
[Top of Page ]
Pest information and control recommendations presented here were developed for North Carolina and may not be appropriate for other states or regions. Any recommendations for the use of chemicals are included solely as a convenience to the reader and do not imply that insecticides are necessarily the sole or most appropriate method of control. Any mention of brand names or listing of commercial products or services in the publication does not imply endorsements by North Carolina Cooperative Extension nor discrimination against similar products or services. All recommendations for pesticide use were legal at the time of publication, but the status of pesticide registrations and use patterns are subject to change by actions of state and federal regulatory agencies. Individuals who use chemicals are responsible for using these products according to the regulations in their state and to the guidelines on the product label. Before applying any chemical, always obtain current information about its use and read the product label carefully. For assistance, contact the Cooperative Extension Center in your county.
Distributed in furtherance of the acts of Congress of May 8 and June 30, 1914. North Carolina State University and North Carolina A&T State University commit themselves to positive action to secure equal opportunity regardless of race, color, creed, national origin, religion, sex, age, or disability. In addition, the two Universities welcome all persons without regard to sexual orientation. North Carolina State University, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.