The
stable fly is the most significant
pest of livestock in America; because of its painful bite and blood feeding
behavior, cattle self-inflict stress and injury trying to escape attack. The impact of the stable fly is noticeable
with populations of more than 20 flies per animal, which can adversely affect
animal health and significantly lower income for livestock producers. Evidence shows that heavy infestations of stable
flies on beef cattle have reduced weight gain by 25 percent and, in dairy
cattle, have decreased milk production by 10 to 20 percent. To suppress stable flies effectively and economically, it is important to:
- Be able to identify them properly;
- Understand the insect’s life cycle; and
- Use a combination of control strategies.
Identification
The stable fly, Stomoxys
calcitrans, looks like the house fly, but it is smaller (1⁄4 inch). Unlike the house fly, stable fly mouthparts resemble a
bayonet that can easily be seen protruding from the head. The stable fly differs from the housefly in that
it depends on blood as food and has an extremely painful bite. Stable flies primarily attack the legs of livestock and the ears of dogs.
An
animal’s reaction to being attacked by stable flies consists of objectionable
behavior such as stomping and kicking their legs, this makes it difficult to milk dairy cows. Unrestrained animals will typically bunch
together when attack, causing an increase in heat stress.
Biology and habitat
The stable fly has a complete life cycle with egg, larval
(maggot), pupal and adult stages. Populations can increase quickly: Under
optimal conditions, the egg to adult cycle is about 3 to 4 weeks; therefore
several generations can develop each year.
A female stable fly lives for 3 to 4 weeks and lays 500 to 600 eggs
during its lifetime.
The eggs are typically laid in wet straw, wet hay bales or in other decomposing vegetation mixed with urine and feces produced by
the animals.
Management
To suppress stable fly populations efficiently, producers should
use an integrated pest management (IPM) approach. IPM relies on three tactics
for successful suppression of an insect pest: cultural, biological and
chemical.
Cultural control: Cultural control
methods involve manipulating the environment to reduce insect pest populations.
The most economical and effective method for suppressing stable fly populations
is sanitation.
In confined animal facilities, a top priority should be to
eliminate stable fly breeding sites as often as possible. To do this, remove
and spread decomposing vegetation or bedding material that has become mixed
with urine and feces. Spreading the bedding will allow the material to dry
faster and prevent colonization by the stable fly.
Another tactic for confined animal areas is to design the stalls
to allow for complete manure removal and drainage. Cleaning out the wet feed
remaining in the ends of troughs should be done weekly because the wet feed serves
as a breeding site for flies.
For small to moderate fly populations of adult flies, sticky traps and other mechanical methods, when combined with sanitation, are
effective in confined areas. However, sticky traps will not substantially
reduce fly numbers if used alone. Sticky traps
should be changed weekly because they become coated
with dust or “saturated” with flies.
Spreading decomposing vegetation (unused hay) should also be implemented for
range or pasture cattle. Throughout the year, hay bales are often provided as supplemental
feed for cattle. Over the course of the winter, the sites where hay bales have
been placed become ideal stable fly breeding areas. Using hay rings will help to reduce stable fly populations in the field/pasture by reducing the amount of wasted hay trampled into the soil. Also, moving the feeding site regularly reduces
the accumulation of wasted hay at a site and eliminates breeding
sites. Spreading the accumulated wasted hay, will help dry out the site and prevent continual stable fly breeding.
Sticky Traps: The use of sticky traps provides a non-chemical approach to controlling stable flies, both males and females. The sticky traps are attractive to the adult stages as a resting location during bloodmeal digestion but prevent the stable flies from leaving. These traps can be used at any number of facilities but are best placed out of reach of animals.
Biological control: This IPM tactic uses
natural predators (fire ants), parasites (like the wasp Spalangia sp.) or pathogens (Bacillus
thuringiensis) to suppress pests.
The parasitic wasp, Spalangia
sp., is available commercially. The
wasp lays an egg into the pupa of the stable fly. The immature wasp feeds on
the pupa, eventually killing the pupa.
The wasp develops into an adult and emerges from the pupa to start the cycle
again.
At this point, there is no clear answer to the effectiveness of
using parasites to reduce fly populations.
Chances for success are greatest when coupled with waste and water
management, and chemical control as needed.
Chemical controls should be limited to sprays or other application
techniques that will not come in contact with breeding sites and kill the
parasites. Wasp releases have to be conducted on a set schedule and are needed each
year; do not count on establishing a population on your farm. Wasps may supplement an integrated program
based on sanitation but are unlikely to provide adequate control when numerous
breeding sites are available.
Chemical control:
If a stable fly problem persists, an insecticide can be used.
Many compounds are available for suppressing adult and larval stable fly
populations. Always read the pesticide label in its entirety before making any
applications.
Animals can be treated as needed with sprays containing permethrin
(Catron, GardStar, Permectrin II, Permethrin and Tengard), Ravap® EC (23%
tetrachlorvinphos) and Vapona® EC (40.2% dichlorvos). Residual wall sprays such as Atroban®
11% EC (permethrin), Demon®WP (cypermethrin), Ravap®, and Vapona® can be applied to surfaces where the
insects rest. These products can be used in backpack or truck sprayers for
range or pasture cattle or used in misters daily on dairy cattle for protection
against stable fly feeding. Brahman and
Brahman cross cattle should not be treated due to hypersensitivity to
organophosphates. One day withdrawal is
required for beef cattle sprayed with Vapona®.
Many premise products are available (Annihilator®, Atroban®
11% EC, Brute®, Demon® Max, Durashield®, Elector® PSP, GardStar®, Grenade®, Permectrin
II, permethrin, Rabon® 50 WP,
Ravap® EC, Tengard®, and Vapona®) that can be
sprayed around a livestock facility and on side walls that are used as resting
sites for fed stable flies. Always follow product labels for conducting premise spray applications.
