The potential for controlling house flies (Musca domestica L.) in organic dairy operations with repellent essential oils and organic attractants
House flies are the primary non-biting dipteran pest of dairy cattle and their control is of paramount importance to operate a successful dairy operation. In a binary choice laboratory bioassay conducted to assess the effectiveness of 6 plant essential oils - basil, lemongrass, peppermint, pine, geranium and lavender - as repellents to adult house flies, all the oils repelled adult house flies, to varying degrees. At the two highest doses - 42.8 [mu]l/slide and 6.7 [mu]l/slide, all oils except pine, repelled >89% flies from feeding on sugar smeared slides. The persistence of all oils across all doses declined after 24 h and still further at 72 h. Repellency of the essential oils can be attributed to the volatile bioactive components of the oil. Assessment of the above mentioned 6 essential oils as repellents of house flies when mixed with a suitable breeding medium in organic dairy barns confirmed that geranium, basil and lemongrass repelled >80% of the flies at the three highest doses (10, 20 and 50 [mu]l/g of fly rearing medium). A fly rearing medium (wheat bran, milk powder, blood meal, brewer's yeast and water) and molasses were attractive feeding substrates, and attraction persisted over a 3 d period. It is suggested that repellents and attractants could be combined together to formulate a novel 'Push-Pull' strategy, whereby house flies could be repelled or deterred away (push) from a source of attractive stimuli (e.g., cattle, bedding material) by using repellents (e.g., essential oils). The flies could be simultaneously attracted (pull), using an attractive stimulus (e.g., fly breeding medium or molasses treated with insecticides), where they would be concentrated and eliminated.