Two types of buffalo fly traps are used in Australia. They differ in the way they dislodge the flies from cattle. One uses a change in light, the other mechanically brushes off the flies. Insecticides were historically used to kill the dislodged flies, but modern traps use heat and dehydration.
The buffalo fly tunnel trap consists of a short, darkened tunnel through which the cattle walk, with cages for trapping flies mounted on the sides (Figure 1). The change in light intensity on entering the darkened interior causes flies to leave the cattle and become attracted to light shining through the flyscreen on the sides. The flies then fly upwards in the compartment through the gap in the baffle and become trapped in the cages where they are killed by high temperature and low humidity. Usually ants find the dead flies and rapidly remove them from the cages, so manual removal of the flies is seldom necessary.
In certain weather conditions tunnel traps have been shown to reduce buffalo fly numbers by 60% to 70% when placed in positions where cattle use them frequently. There are a number of advantages to this type of trap. First it can be easily and cheaply built by a producer, with plans for construction available on the Queensland Government website. Secondly, cattle can be easily trained to use the trap because there are no internal obstructions.
Figure 1. Buffalo fly tunnel trap, a) general assembly and b) a side view and c) cross section view of the cage frame and baffle. Image courtesy of the Queensland Department of Agriculture and Fisheries
The second type of trap is the buffalo fly brush or curtain trap which consists of a translucent plastic ‘tent’ that the cattle walk through. There is a set of brushes or curtains halfway along the trap that the cattle must push past. The brushes dislodge the flies which fly to the light at the sides and top of the tent (Figure 2 and Figure 3). More recent designs walk the cattle through multiple sets of curtains as they pass through the tent. The flies move to the top of the tent where they become trapped in a second compartment, behind a ‘false ceiling’ in the dome of the roof, where the air is hot and dry. The heat and low humidity in this compartment cause rapid death of the flies by dehydration.
Figure 2. Basic buffalo fly curtain trap design. Image modified from Sutherst and Tozer (1995) Aust. J. Agric. Res.
The use of a light chamber rather than a dark chamber is a major advantage of this design of trap as more of the flies remain on the cattle as they enter the trap and only leave cattle when dislodged by the brushes. Brush traps can remove more than 90% of flies each time the cattle pass through. However, they are less robust than the tunnel traps, the brushes can become worn over time, the plastic covering of the traps is subject to damage in severe storms and the sides must be protected from damage by cattle.
The key to obtaining good effect from traps is positioning them in areas where cattle will pass through them frequently, such as in gateways or laneways, accessing water or feed, or in leadup races to dairies. If necessary, food supplements or salt blocks can be used to induce cattle to use them. The traps are generally most effective when positioned in full sunlight as this provides good light contrasts and the most efficient conditions for fly trapping. The traps should also be placed at a well-drained site so that puddles do not form in depressions, and walkways do not become muddied. It will usually be necessary to train cattle to use the traps. With the brush traps, or traps that use curtains, this may be assisted by temporarily removing the brushes or curtains.
Figure 3. Buffalo fly brush trap. Image courtesy of CSIRO
Vacuum tunnels and ‘Fly Vacs’
There are a number of more elaborate designs now marketed for horn fly control in the USA, which use various configurations of vacuum systems and blowers to aid the collection of flies. The blowers help dislodge flies on the belly and other areas not easily accessed with brushes or curtains, while strategically placed vacuums ‘suck up’ flies that in other trap designs may leave cattle as they enter the traps and then re-join the animals at the other end of the race. This is claimed to increase the effectiveness of trapping. The fly trap ‘Cow vac’ is smaller than other traps and can be retrofitted to yards and races. These designs are generally more expensive than the earlier traps, require access to a power source for operation, and have a much more complex design. These systems may have a place on organic enterprises or larger dairy operations. However, beef or dairy producers would need to evaluate whether the higher trapping efficiency would justify the extra purchasing and running costs. These systems are not currently being marketed in Australia.