Dairy/Field Crops 102GFSDI-1 1989
Bovicola bovis
Linognathus vituli
Haematopinus eurysternus
Solenopotes capillatus
Cattle lice are among the most important arthropod (insect and mite)
pests affecting dairy cattle in New York State and elsewhere in the
United States. Lengthy, cool winters are particularly favorable to populations
of lice, which thrive on animal skin that is protected by the long,
winter-hair coat. Unlike fly pests, which feed on a variety of livestock
and engage in many behaviors off the animals, lice are very host-specific
and can survive for only very short periods of time off the host animal.
Management of lice populations below economically injurious levels requires
systematic monitoring and identification of these pests.
Adults
Four species of lice feed on dairy cattle in New York. The most common
is the little red cattle chewing louse (Bovicola
bovis, fig.
1). Adults of this species can be recognized by their relatively
broad head and characteristic reddish-brown and yellow coloration. These
lice do not feed on blood but instead use their mouthparts to rasp animal
skin and hair.
In addition, there are three species of blood-sucking lice on dairy
cattle: the long-nosed sucking louse (Linognathus
vituli, fig.
2); the short-nosed sucking louse (Haematopinus
eurysternus, fig.
3), and the little blue sucking louse (Solenopotes
capillatus, fig.
4). Sucking lice are blood-feeders, and can be easily recognized
by their firm attachment to the animals' skin and by the dark coloration
that their abdomens take on as they fill with blood.
Although there is some size variation among these four species of lice,
all of them are small insects that reach a maximum size of about 3.0
mm (1/8 in.; fig. 5).
They are permanent parasites, which means that they spend their entire
lives on the animals. Development from egg to adult takes four to six
weeks.
Eggs
Female lice lay their eggs, known as nits, by attaching them to hairs
with a strong glue to prevent them from falling off (fig.
6). The nits can be seen on heavily infested animals as white specking
on the hair coat (fig.
7). The hard shell of the nit protects it from most hazards, including
insecticide treatments.
Nymphs
Eggs hatch into nymphs one to two weeks after being laid. Lice have
a simple metamorphosis; therefore, the nymphs resemble the adult lice
quite closely except for their smaller size. The nymphs feed on host
animals in the same manner as the adult lice. Development from egg hatch
to adult is completed in two to three weeks, with the nymphs passing
through three instars (stages between molts).
Damage
Regardless of the species involved in an infestation, cattle lice cause
extreme annoyance to the host animals. In heavily infested milking cows,
milk production declines and the animals' preoccupation with rubbing
leads to hair loss, reduced feed conversion efficiency, and general
unthriftiness. Infested animals are irritable and difficult to work
with, especially during milking.
Heavy louse infestations on calves and heifers also contribute to the
many stresses that can have adverse effects on growth, time to first
lactation, and overall future production performance of replacement
animals. In addition, people working around heavily infested animals
are exposed to greater risk of injury and are annoyed by stray lice
acquired from infested animals during handling.
Infestations with lice are aggravated by other stresses on the animals.
Cattle that are stressed by crowding, infection, or inadequate nutrition
often have exceptionally severe louse infestations.
Monitoring
Lice are more abundant on young animals than on mature milking cows.
In general, infestations are heaviest during cool weather, although
high populations of lice are commonly found on calves as late as June,
as shown in the chart on this page.
Early detection and treatment is essential to prevent infestations
from causing economic losses. Therefore, animals should be monitored
between the months of September and June.
It is best to inspect 30 animals every two to four weeks; choose 10
calves, 10 heifers and 10 milking cows. Healthy-looking animals should
be inspected as well asnoticeably lousy ones in order to detect populations
approaching economically injurious levels. Ideally, a headband light
or hard hat-mounted light should be used so that both hands are free
to work with the animals (fig.
8).
The neck, shoulders and tailhead should be inspected on each animal
by parting the hairs and estimating the numbers of lice present per
square inch (fig. 9).
Animals should be treated if more than 10 lice per square inch are found.
If replacement animals are brought into the herd from off of the farm
they should be examined and treated, if necessary, before allowing them
to mix with the other animals.
Management
A form of cultural control that is highly effective is the use of individual
outdoor hutches for calves instead of housing the animals in collective
pens inside barns.
Many insecticides are registered for louse control. Read the label
carefully to insure that the insecticide may be used on milking animals;
concerns about residues may limit the number of choices. Most insecticides
require two treatments spaced 10 days apart to kill the nymphs that
hatch after the first treatment (eggs are resistant to most insecticides).
A variety of application methods are available for controlling lice,
including whole-animal sprays, mists, dusts, back rubbers, pour-ons
and dust bags. Each method has certain advantages depending on individual
production and management practices. Whole-animal sprays give good coverage,
but should be avoided during cold weather when chilling the animals
is a concern. Mist-blowers may be used to minimize the amount of liquid
required for treatment. Dusts are convenient, may be used any time of
the year, and require no mixing. Self-application and forced-use devices
such as dust bags are effective only if they are positioned so that
the animals make frequent contact with them. Consult local Cooperative
Extension personnel for a louse management program that is appropriate
for your farm.
Authored by C. Geden, D. Steinkraus, and D. Rutz Department of Entomology,
Cornell University, Ithaca, New York. Figures 1 through 6 and 8 by D.
Steinkraus; figure 7 by G. Matthysse and figure 9 by E. Schmidtmann.
Layout by C. Koplinka-Loehr. Produced through the New York State Integrated
Pest Management Program, jointly sponsored by the New York State Department
of Agriculture and Markets and Cornell University. Cornell Cooperative
Extension provides equal program and employment opportunities. 6/89 10 M
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