Controlling Chiggers 1967 -- Entomology Research Division Agricultural Research Service Home and...|
Controlling Chiggers |
Entomology Research Division
Agricultural Research Service
Home and Garden Bulletin 137, USDA, 1967
Issued December, 1967
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II. S. DEPARTMENT OF AGBQ1TK
Home and G a r d e n B u l l e t i n No. 137
U.S. DEPARTMENT OF A G R I C U L T U R E
Entomology Research Division
Agricultural Research Service
This bulletin supersedes Leaflet 403, "Chiggers: How To Fight Them."
Washington, D.C. Issued December 1967
For sale by the Superintendent of Documents, U.S. Government Printing Ofllce
Washington, D.C. 20402 - Price 10 cents
Chiggers, sometimes called red
bugs, make up a family of mites.
Five species found in the United
States commonly attack man.
Chigger bites cause intense itch-
ing and small, reddish welts on the
skin. You may notice these symp-
toms in the summer after working
in the garden, walking in the woods
or fields, picking berries, or mowing
the lawn. The symptoms may be
your only way of knowing that you
have been in an infested place, be-
cause chiggers are so small that most
persons cannot see them without a
Chiggers are found throughout
the continental United States.
You can use a repellent to prevent
attacks by chiggers if you go in an
area known to be infested. If you
get in an infested area without
knowing it, you can reduce itching
by bathing and by applying an anti-
septic and a local anesthetic to the
welts. You can get rid of an infesta-
tion by spraying or dusting the in-
fested area with an insecticide.
Adult chiggers pass the winter in
protected places and become active
in the spring. A few days after the
females becomes active they lay eggs
in sheltered places. These eggs hatch
into the first generation of the year.
The young chigger is known as a
larva. It is the troublemaker. It is
a parasite—feeds on man and ani-
mals. The larva transforms to a
nymph, and the nymph to an adult.
Neither the nymph nor the adult is
Chiggers raised experimentally
complete the life cycle—from egg to
egg —in about 50 days.
In southern Florida and southern
Texas, chiggers may be present
throughout the year. In other
States, the chigger season begins in
May, June, or July and lasts until
September or the first frost.
In the larval stage chiggers are
orange yellow or light red. They are
less than y
inch in diameter. The
bodies are hairy. A larva has three
pairs of legs. Its mouth parts in-
clude two pairs of grasping palps,
which are provided with forked
The nymphs and adults have four
pairs of legs. The bodies are hairy,
inch long, and usually a
brilliant red. There is a marked
constriction in the front part of the
Young chiggers attach themselves
to the skin of people or to the skin
of domestic animals, wild animals
(including reptiles), poultry, and
Before settling down to feed,
chiggers scurry around for a suit-
able location. The preferred loca-
tions on people are those parts of
the body where clothing fits tightly
over the skin, or where the flesh is
thin, tender, or wrinkled.
Like ticks, they attach themselves
by inserting their mouth parts in
the skin—frequently in hair follicles
or pores. They inject a fluid into the
skin; the fluid dissolves the tissues;
the chiggers suck up the liquefied
A Species of Chigger
1. Unengorged larva
2. Engorged larva
From" Mich en er. Ann. Ent. Soc. Amer.
When they attach themselves to
animals, they become engorged in
about 4 days. Then they drop off
and change to nymphs.
Nymphs and the adults feed on
insect eggs, small insects, and orga-
nisms found on or near woody
EFFECTS OF ATTACK
The fluid injected into the skin by
the chiggers causes reddish welts to
appear. It also causes swelling, itch-
ing, and (in some persons) fever.
Chigger bites have a more severe
effect on some persons than on oth-
ers. Persons who are exposed re-
peatedly may develop immunity to
A chigger attached in a pore or at
the base of a hair may be so en-
veloped in swollen skin that it ap-
pears to be burrowing into the skin.
This fact sometimes leads persons to
believe, mistakenly, that chiggers
embed themselves in the skin, or that
welts contain chiggers.
Any welts, swelling, itching, or
fever will develop within 24 hours
after the attack. Itching may be in-
tense and, if nothing is done to re-
lieve it, may continue a week or
longer. Scratching a bite may break
the skin and result in infection.
Chiggers attacking in large num-
bers can cause serious injury to
poultry. They sometimes cause the
death of young chickens.
See Leaflet 383, Poultry Mites: How
To Control Them, which may be obtained
from the U.S. Department of Agriculture,
Washington, B.C. 20250. Send your re-
quest to the Department on a post card.
Please include your ZIP Code.
Chiggers are not known to trans-
mit any disease in this country. In
some parts of the world, particu-
larly in parts of the Far East, they
transmit scrub typhus, a serious dis-
ease similar to spotted fever. In this
country spotted fever is transmitted
Chiggers are most often found in
low, damp places where vegetation
is rank—for example, berry patch-
es, orchards, woodlands, and mar-
gins of lakes and streams. But some
species are adapted to living in drier
places where vegetation is low, and
heavy infestations may be found in
lawns, golf courses, and parks.
You cannot tell by looking at a
place whether it is infested. Chig-
gers may be numerous in a place one
year, and scarce or absent another
year; and they occur in some places
only for short periods.
Before going into a place where
chiggers may be, protect yourself
against them by using a repellent.
Several highly effective repellents
are available. They do more than
repel. Chiggers that attempt to
crawl over clothing or skin areas
treated with the materials are
Kepellents can be used to obtain
either temporary or long-lasting
protection. Used the first way, they
are effective several hours; the oth-
er way, several days.
The following repellents are ef-
fective against chiggers—deet (di-
ethyltoluamide), dimethyl phthal-
ate, dimethyl carbate, and ethyl
hexanediol. They are also effective
against mosquitoes and some other
insects. Go to a drug store, hardware
store, or any other store where in-
secticides are sold. Ask for any one
of the repellents by name. You may
be offered a product that contains
two or more of the repellents. Such
a product is acceptable. The repel-
lents are effective individually or in
Apply the repellent to clothing by
rubbing it on, by applying it direct-
ly from the bottle, or by spraying it
on. Rayon and some other manmade
fabrics may be harmed by the re-
pellent ; nylon, cotton, and wool will
not be harmed.
Applying repellent to socks and cuffs
of trousers for protection against
Apply the repellent lightly, with
the fingers, to the arms or legs if
they are not covered by clothing.
Treat socks or stockings after you
put them on. Apply a ring of
repellent just above your shoe tops.
Treat all the way around the upper
edges of the hose. Cotton and wool
socks absorb repellent better than
other materials and are preferred
for wearing in chigger-infested
In treating other clothing, apply
the repellent along the edges of all
openings, inside and outside. Be-
sides treating openings that are but-
toned, zippered, or otherwise fas-
tened, treat such openings as the
In trousers and slacks.—Cuffs
In shirts and blouses.—Cuffs (or
armholes) and neckband.
In skirts.—Hem and waistband.
In dresses.—Neckline and skirt
hem; cuffs, sleeve hems, or arm-
To rub a repellent on clothing,
pour about a dozen drops in the
palm of one hand, rub the hands to-
gether, then rub lightly the parts of
the clothing to be treated.
To apply it directly from the bot-
tle, press the bottle opening against
the clothing and move it over the
parts to be treated.
To spray a repellent on clothing,
use an ordinary hand sprayer—the
kind used in homes for applying fly
Do not saturate the cloth with re-
pellent. If a garment is moist with
repellent along all openings—inside
and outside—it has been adequately
If the infested place is one in
which the vegetation is low, if you
intend merely to walk in it, and if
you are wearing trousers or slacks,
you need only apply repellent to the
cuffs of the trousers or slacks and
to socks or stockings.
Long-lasting protection against
chiggers is needed chiefly by men
who work regularly in infested
areas and by others—such as camp-
ers, hikers, and hunters—who may
be in such areas several days at a
The protection is obtained by im-
pregnating clothing with a diluted
repellent or by spraying an undi-
luted repellent on the clothing.
Buy 50-percent deet, or full-
strength dimethyl phthalate or ben-
Impregnating the Clothing
Two fluid ounces of repellent
are needed to treat an ordinary set
of work clothes—shirt, trousers (or
overalls), and socks.
Prepare a solution by adding
the repellent to 3 pints of any dry-
cleaning fluid. After all parts of the
garments have been saturated with
the solution, let the cleaning fluid
Prepare an emulsion as follows:
(1) Put % ounce of soap powder
(but not synthetic detergent) or
thinly sliced soap in 1 quart of water
and stir until the water is soapy.
(2) Take 1 cupful of the soapy
water, add 2 ounces of the repellent,
and stir vigorously. (3) Pour this
into the rest of the soapy water and
Place the clothes in a container
and slowly pour on the emulsion.
Work the clothes around in the
liquid. Wet them uniformly but do
not let them soak. Wring them and
hang them out to dry.
Deet or dimethyl phthalate gives
protection for at least a week, un-
less washed out of the clothing.
Laundering washes out the repel-
lent ; a heavy rain may do so. Repel-
lent in trousers and socks is washed
out if the wearer wades through
water. Re-treat the clothing after
Benzyl benzoate is effective long-
er than deet or dimethyl phthalate,
and it washes out less readily. It
gives protection even after clothing
has been laundered twice. Clothing
that has been laundered twice since
being treated should be re-treated.
In addition to providing complete
protection against chiggers, either
of these treatments gives consider-
able protection against ticks.
Spraying the Clothing
In spraying to obtain long-lasting
protection, you apply the repellent
to the entire garment—not just to
the openings. Using a hand sprayer,
apply a mist of full-strength di-
methyl phthalate or benzyl benzoate
on the outside of the clothing and
on your shoes and socks; continue
until the clothing is slightly moist,
but not wet. Do not apply more
than 2 ounces of repellent to a set of
work clothes. Let the clothes dry for
several hours before wearing them.
Deet is available at 12 to 15 percent
in pressurized spray cans. Follow
directions on the labels.
It is easier to spray clothes than
to put them through the impregna-
tion treatment, but it is difficult to
apply the spray uniformly. Also,
sprayed-on repellent loses its effec-
tiveness a few days sooner than re-
pellent applied by impregnation,
and it is washed out more easily.
REDUCING THE ITCHING
If you get in a chigger-infested
place without the protection of a re-
pellent, attack is almost certain.
You may not know that you have
been attacked until welts appear on
the body and itching begins.
Take a bath as soon as possible.
Apply a thick lather, then rinse it
off. Do this several times. The bath
kills most, or all, of the attached
chiggers, and any others that may
not yet be attached.
Next, apply a dab of antiseptic to
each of the welts. This will kill any
chiggers not killed by the bath, and
it aids in preventing infection.
Destroying the chiggers reduces
the itching, but does not stop it. The
fluid injected by the chiggers causes
the itching. No practicable way to
remove it has been found, and no
treatment is known that will give
permanent relief from the itching.
To get temporary relief, apply a
local anesthetic. The following for-
mula has been found helpful:
Methyl salicylate, 2 percent.
Salicylic acid, 0.5 percent.
Ethyl alcohol, 73 percent.
Water, 19.5 percent.
Take the formula to your drug-
gist for compounding. Apply the
Proprietary ointments containing ben-
zocaine are also useful.
Applying insecticide with a rotary hand duster.
material to each welt with a piece
of cotton. One treatment gives relief
for an hour or longer. Repeat the
treatment as often as necessary.
Some persons who have had ex-
perience with chiggers can detect
an attack without the evidence of
welts and itching. They feel the
slight irritation that is produced
when the chiggers begin to attach,
and they know what is causing it.
They may feel the movement of
chiggers as they crawl on the body
seeking a place to attach.
If you become aware of sensations
that cause you to suspect the pres-
ence of chiggers, examine the skin.
Look carefully at the bases of hairs.
You may not be able to see the chig-
gers, but you may be able to see
small reddish spots where they are
The more quickly you detect the
chiggers, the better results you will
get from the soapy bath. If you can
take the bath within an hour after
the chiggers get on you, it will prob-
ably kill most of them before they
You can wipe out a chigger in-
festation by applying an insecticide
spray or dust in the infested area.
Apply the spray or dust to grass,
logs (and the ground around them),
and ground litter. Apply it around
bushes and high weeds.
The recommended insecticides are
chlordane, toxaphene, and lindane.
They can be purchased in insecticide
supply stores, and are generally
available in the form of emulsifiable
concentrates, wettable powders, and
dusts. Select any one of the insecti-
cides, and decide in what form you
wish to buy it.
An emulsifiable concentrate or
wettable powder is mixed with
water to make a spray. A dust is
ready to use when purchased.
An emulsion spray, prepared by
mixing an emulsifiable concentrate
with water, usually gives better re-
sults than a wettable-powder spray
or a dust.
Locating the Chiggers
Before you start applying an in-
secticide, have a clear idea of where
Applying insecticide with a garden-type compressed-air sprayer.
HOW TO PREPARE SPRAYS FOR CHIGGER CONTROL
FORMS IN WHICH INSECTICIDES MAY BE
CHLORDANE OR TOXAPHENE
AMOUNT OF PURCHASED PRODUCT
TO Mix WITH —
5 gallons of water
\\% pounds .
% cup _
100 gallons of
the chiggers are. If the area is a
large one, such as a picnic ground,
a golf course, or a large lawn, it may
be advisable to make a simple sur-
vey. The chiggers may be concen-
trated in a few spots within the
area. Treating the trouble spots is
quicker and less expensive than
treating the whole area, and less
likely to damage wildlife.
Place a piece of black card-
board edgewise on the ground. Ob-
serve it for a few minutes. If chig-
gers are present, they will climb to
the top edge and congregate there.
Make the test in about a dozen spots
over the area. Pick out spots that
have different kinds of cover, such
as solid growths of grass, tufts of
grass, dead leaves, and decaying
twigs. Remember, you are chigger
hunting; you should be protected
by a repellent.
Unless the entire area is infested,
treat only the parts in which con-
trol is especially desired, such as
grass around picnic tables or lawn
Emulsifiable concentrates and
wettable powders contain various
percentages of insecticide. The per-
centages shown in the accompany-
ing chart are those most commonly
found in retail products.
To prepare a spray, mix one of
the products with water in the
proportion indicated in the chart.
Apply the finished spray as follows,
but do not treat areas where live-
stock feed or graze:
Small areas.—To treat a lawn,
campsite, or other small area, use a
cylindrical compressed-air sprayer
or a knapsack sprayer Apply 2% to
3 quarts per 1,000 square feet (25 to
35 gallons per acre).
Large areas.—To treat a park,
golf course, or other large area, use
a power sprayer. To get uniform
coverage, apply twice as much spray
material as you would with a small
sprayer, but do not double the
amount of insecticide. Double the
amount of spray material by adding
Apply 50 to 70 gallons per acre.
An emulsion spray prepared and
applied according to these recom-
mendations is effective 4 to 8 weeks;
a wettable-powder spray, 2 to 6
weeks. A spray is considered effec-
tive for a stated period if few or no
active chiggers can be found in the
treated area during that period.
Apply 5-percent chlordane or
toxaphene dust at the rate of 40 to
50 pounds per acre (1 to 1% pounds
per 1,000 square feet), and 1-percent
lindane dust at the rate of 50 pounds
per acre (1% pounds per 1,000
square feet). A dust treatment is ef-
fective 1 to 4 weeks.
Dusts can be applied with any
equipment that is used for dusting
plants. A rotary hand duster is ex-
cellent for treating small areas. A
power duster is better for large
areas. Do not treat areas where live-
stock feed or graze.
Keep repellents away from your
eyes and mouth.
Do not treat underwear with a re-
pellent. Treated underwear may ir-
ritate the skin.
Do not apply a repellent to stock-
ings or other clothing that contains
rayon. Eepellents are damaging to
some kinds of rayon and to some
other manmade fibers; nylon is not
Do not let repellents touch paint-
ed surfaces or objects made of plas-
tic materials, such as fountain pens,
fishing rods, watch crystals, or
frames of eyeglasses.
Insecticides used improperly can
be injurious to man and animals.
Use them only when needed and
handle them with care. Follow the
directions and heed all precautions
on the labels.
Keep insecticides in closed, well-
labeled containers in a dry place.
Store them where they will not con-
taminate food or feed, and where
children and animals cannot reach
them. Promptly dispose of empty
insecticide containers; do not use for
any other purpose.
Do not apply insecticide to your
skin or your clothing to repel or kill
chiggers; use only recommended re-
pellents in this way.
After treating a lawn, sprinkle
it with water to wash the insecticide
from the grass into the soil. Ihis
reduces the hazard to children and
pets, and does not reduce the effec-
tiveness of the treatment.
Keep children and pets out of a
treated area until the spray dries.
Do not treat areas where livestock
feed or graze.
Avoid repeated or prolonged con-
tact of insecticide with your skin.
Avoid prolonged inhalation of in-
secticide dusts or mists.
Avoid spilling an insecticide con-
centrate on your skin, and keep it
out of your eyes, nose, and mouth.
If you get any on your skin, wash
it off immediately with soap and
water. If you spill any on your
clothing, remove the clothing im-
mediately and wash the skin thor-
oughly. Launder the clothing before
wearing it again.
After handling an insecticide, do
not eat, drink, or smoke until you
have washed your hands and face.
Wash any exposed skin immediate-
ly after applying an insecticide.
Avoid drift of insecticide to near-
by wildlife habitats, bee yards,
crops, or livestock. Do not apply in-
secticides under conditions favoring
drift from the area to be treated.
Many insecticides are highly toxic
to fish and aquatic animals. Keep
insecticides out of all water sources
such as ponds, streams, and wells.
Do not clean spraying equipment or
dump excess spray material near
Do not apply insecticides during
hours when honey bees and other
pollinating insects are active.
Have empty insecticide contain-
ers buried at a sanitary land-fill
dump, or crush and bury them at
least 18 inches deep in a level,
isolated place where they will not
contaminate water supplies. If you
have trash-collection service, thor-
oughly wrap small containers in
several layers of newspaper and
place them in the trash can.
If you have any questions about
the repellents or insecticides dis-
cussed in this bulletin, consult
your county agricultural agent or an
entomologist in your State extension
service or experiment station; or
write to the Entomology Research
Division, Agricultural Research
Service, U.S. Department of Agri-
culture, Plant Industry Station,
Beltsville, Md. 20705. Send your re-
quest to the Department on a post-
card. Please include your ZIP Code.
U.S. GOVERNMENT PRINTING OFFICE: 1967 O—268-519