Tabanids and stable flies are important nuisances to livestock and sometimes humans. Nzi, Vavoua, and Biconical traps or insecticide‐impregnated blue screens are commonly used to attract and catch these flies. Such devices are made of a specific cotton or cotton‐polyester phthalogen blue fabric acting as a visual attractant. However, the cost of cotton fabrics is high, and they are no longer available due to toxic dyes. The present study compared four blue polyester fabrics produced in Thailand with a reference blue cotton‐polyester fabric made in France by TDV® to attract hematophagous flies. Vavoua traps and blue screens covered with a sticky film made with the five different blue fabrics were compared. The TDV® had the highest trapping scores; however, there was no significant difference between TDV® and some polyester fabrics. Among the tested polyester fabrics, CR Solon No.41 was nearly as effective as the TDV® in attracting biting flies. The mean attractivity indices of CR Solon No.41, NS No.1469, Globe 2000 No.21, Globe 2000 No.34 were 0.86, 0.79, 0.69, and 0.39, respectively. Thus, we recommend that CR Solon No.41 would be the appropriate fabric for the further development of low‐cost and optimized screens and traps in Thailand and other countries.
Livestock are seasonally subjected to the nuisance of haematophagous flies, such as tabanids and stomoxyine flies. Topical application of insecticides has short term efficacy (a week or so), is expensive, and generates pesticide residues in animal products and environment. Attractive insecticide-impregnated blue fabrics are used for tsetse fly control in Africa; however, they are expensive and were never evaluated for other haematophagous flies. In previous works, we defined specifications of a white and blue screen specifically attracting haematophagous flies, particularly Stomoxys spp. In the present study, an assay was carried out in Kantchanaburi Province, Thailand, with around 30 of such screen prototypes, made of a multilayer polyethylene film incorporated with deltamethrin. Screens (also called 'targets') were deployed in 12 test farms, to evaluate the efficacy of a so-called 'multi-target method' (MTM); four control farms were also enrolled. A Vavoua trap was deployed one day/week in each farm to follow-up the density of insects. In the test-farms, during the 4 months post treatment, the mean density of haematophagous flies was significantly and consistently reduced by 63-73% compared to the control group. Laboratory tests indicated that insecticidal activity of these screen prototypes lasted around 3-4 months. However, in the field, significant reduction of fly densities was observed in all test farms up to 7 months after screen deployment, possibly as a consequence of the early impact of the screens on fly population dynamics. The significant effects obtained in test farms provided evidence for the proof of concept that MTM is effective for on-farm control of haematophagous and common flies. Durability of the screens will be increased in the next prototype generation. This innovative control method will be evaluated more extensively and in other livestock and poultry farms.
Hematophagous flies are a pest for livestock; their direct impact reduces productivity, and they are vectors of parasites, bacteria and viruses. Their control using insecticides is inefficient and highly polluting. The validation of new control tools requires efficacy and cost-effectiveness evaluation. The quantification of hematophagous insects’ impact in livestock is a challenging prerequisite. Tail flicks counts can reliably evaluate fly-burden; however, visual records are tedious and time-consuming. In the present study, automation of tail flick counts was made through the use of pedometers attached to the tail, in two groups of feeder cattle. Group A was kept in a pen under the protection of a mosquito net, and Group B was kept in an open-air pen. The fly density of Group B was evaluated using fly traps. The apparent density per trap ranged from 130 to 1700 in the study. The mean pedometer records per 24 h ranged from 957+/−58 bits in Group A to 11,138+/−705 bits in Group B. The night/day records observed in Group A (200/800 bits) were drastically increased in Group B (1000–4000/4000–14,000 bits) and variable along seasons. A very high correlation was observed between fly density and visual records or pedometer records (PR). Two-hour PRs proved to be a reliable predictive tool for fly density. Moreover, the pedometers revealed an unsuspected but significant nuisance of mosquitoes, which should be thoroughly investigated.
Beside blood pathogens transmission, insects of the order Diptera affect livestock by visual and contact harassment; blood-feeders are responsible of painful bites and blood despoliation, generating behavioural modifications, anaemia and production losses. Knowledge of their economic impact is a basis for cost-effective control. Here, we measured the global impact of Diptera by comparing two batches of six feeder cattle, one in open air, the other protected by a mosquito net. Analytical data were: insect density in open air, and, for feeder cattle: tail-flick counts, hematocrit values (Ht), feed intake, feed conversion ratio (FCR) and live body weight gains (LBWG). Over a period of five months, results showed significant losses of LBWG of cattle exposed to insects, estimated at 8.0±1.5 Kg/month [2.7;13.3], with a total loss reaching 40.0±5.5 Kg/head. Main diurnal insects were Stomoxys spp. and M. crassirostris. There was a strong correlation between fly density and diurnal tail-flicks. Night trapping and tail-flicks showed a potentially important role of mosquitoes to be further explored. Ht of exposed animals was 3-4% lower than controls. FCRs indicated that exposed animals needed 33% more dry matter intake/Kg of LBWG. Economic assessment showed that dipterans were responsible of 10-11% loss of LBWG during the main growing period of feeder-cattle (10-15 months). A feedlot of 100 calves would register a total loss of 16,000$ within 5 months, which appears to be an unexpectedly huge loss caused by dipterans. Investing part of this money in fly control would probably be beneficial.
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