Then Athena held up her aegis, the bane of mortals, on high from the roof, and the minds of the wooers were panic-stricken, and they fled through the halls like a herd of cattle that the darting gad-fly falls upon and drives along in the season of spring, when the long days come.Homer, The Odyssey Book 22
High summer is high season for flies. Face flies, horn flies, horse flies, and deer flies. The month of July in Upstate NY belongs to Beelzebub.
All these flies feed directly off of animals, getting their meals through blood, saliva, mucus, or sweat. They are endlessly annoying and occasionally painful. At this stage of the summer, a cloud of flies follow the cattle through their pastures. During the day, when the flies are active, the herd typically bunches up into a “fly huddle”, a dense configuration that allows some cattle to rotate into the center of the group, where they can wedge themselves between other cattle and thus reduce the surface area exposed to attack from flies.
It is no surprise that agriculture has always treated flies as a nuisance, something to be controlled. At the very least, no farmer or herder has ever enjoyed the bites and nibbles, or even the incessant buzzing sound. Cattle can be harmed by the insects – flies can spread infections. The fly-borne diseases vary throughout the world, but in our area the most common is pinkeye. Cattle with pinkeye can temporarily lose some of their sight, and in more advanced cases, they become completely blind.
Insecticide to the Rescue?
Given these consequences, most herds are treated as a matter of course with some kind of fly control. These are pesticides that are fed in the minerals or feed, rubbed on using a mixture of oil and pesticide in a long sock that the cattle self-administer by back-scratching, or directly applied by the farmer or rancher (sometimes a slow-release pesticide treatment is included in their ear tags, or cattle will be herded through a chute to get a dose sprayed along their back, or – and this is probably the situation that would interest certain kids I know – they can get splatted with modified paintballs that are filled with insecticide).
But it won’t shock any of my readers to know that I’m not comfortable with the easy solution of poisoning my way to happiness. The pesticides used are all broad-spectrum killers, so flies aren’t the only insects being killed. All kinds of insects, arthropods, and worms die. The birds and mice that eat bugs concentrate these chemicals in their bodies, and then the insecticides become increasingly concentrated as they move up the food chain into larger animals such as skunks, owls, racoons, weasels, coyotes, and bobcats. A further concern is that these pesticide treatments are rapidly breeding more resistant pests, so the control measures need to constantly escalate the level of chemical warfare.
I’ve written before about the side effects of insecticides on the insects that help incorporate manure into the soil, such as dung beetles or yellow dung flies, so we don’t need to cover that in detail here. But it is sufficient to note that these insects are critical to the biological cycling of nutrients and the process of creating soil fertility. And there are other life-sustaining roles that are impacted by chemical treatments, most notably insect-based pollination. It is worth noting that the green-head horseflies (aka green marsh flies), are both blood-suckers and pollinators, so drawing lines between friend and foe is complicated.
Ecological Fly Control
There are some theories in the more regenerative side of farming that flies can be controlled by natural means. One often-cited idea is that a flock of laying hens following the cattle will eat the fly larvae from the manure. I’ve done a lot of work with this concept, but never found it to be effective. Hens will hunt down and devour fly larvae, so that’s unquestionably advantageous in creating a free source of chicken food. But I haven’t found chickens to be capable of reducing the fly population. Flies are so fecund, and their reproductive cycles are so short, that only a small fraction need escape the chickens to create a swarm.
There are other interventions we’ve tried. For several years we brought in predatory wasps. These wasps specifically target the larvae of some of the most pernicious fly species. Overall, this project was a failure. These wasps might be effective around confinement situations and barns where the cattle are constantly living close to manure piles, but in our rotational grazing situation with the cattle constantly on the move to new grass, the wasps could never keep up with the cattle.
One thing that does make a difference is the pattern of movement we use with our herd. Every day (or twice a day this month), we open up a fence and walk the cattle to new grass. Being on the move and getting away from manure helps with the worst of the fly buildup. But even this solution is limited because, obviously, flies can fly. Supposedly, the flight range of these flies is about a half mile per day, so if one had many thousands of acres, it might be possible to move the herd so far that they could keep ahead of any new larvae hatching. But we don’t have thousands of acres, so that option isn’t available. I’m not convinced that large migratory movements would actually work, as evidenced by research on biting fly populations found among herds of bison in Yellowstone that have hundreds of miles of territory over which they roam.
The approach we’ve taken with flies is to prioritize cattle health while creating a balanced ecosystem. Cattle and flies have always coexisted, as evidenced by my leading quote from Homer and the previous reference to flies on wild bison. In a healthy system, healthy cattle can coexist with healthy flies.
As a person who lives much of my life outdoors, I’d prefer to be left unmolested by all the blood-suckers. But I believe ultimately that all these pests are essential to a functioning environment. I don’t know what all their roles are, but my ignorance of their purpose doesn’t mean they are without purpose. It is seductively easy to conflate my ignorance with teleology. Mosquitos, ticks, and horse flies, for all their banefulness, are by virtue of their continued existence, evidently important to the world. And so are grazing herbivores. The world needs herbivores and it needs the bugs that bug them. So I think our best role as humans living in the middle of this tension is to ensure that our influence on the situation balances out the herbivores and their pests.
Any observer of animals finds that sick individuals attract pests. Gardeners have long noted a similar relationship where weaker plants can be swarmed while nearby stronger ones seem to be unappealing to the same insects. So our primary defense against insects lies in creating the best starting point from which the animals can thrive. Healthy cattle can handle flies. Weak cattle are wiped out by them.
Increasing grass and soil health, improving pasture management, and selectively breeding for cattle that can be successful in our particular environment, these all create the foundations for cattle to coexist with the flies that inevitably will be present. The path toward these fixes is traversed slowly and circuitously, so it doesn’t yield results with the satisfying instantaneity of opening a can of insecticide.
The closest thing we have to a quick fix is that during June, July, and August, we add Certified Organic garlic powder to the salt the cattle lick. We stir in one pound of garlic powder for every fifty pounds of salt. Garlic is a traditional herbal fly remedy that seems to be useful to our cattle. We have also experimented with adding sulfur to the salt, and while some people swear by it, I’m not sure if it is effective for our cattle, or maybe it isn’t effective for the mineral balance our cattle need. Neither garlic nor sulfur eliminate flies, but they both apparently help support the health of cattle during peak fly season.
When fat flies are landing all over my face, I do sometimes find myself wishing for quick fixes. But I can’t abide the thought of waging chemical warfare on my farm’s insects. And I wouldn’t want to eat beef that contained a dose of pesticide residues.
Can I love the flies? Probably not. But I think they need to have their place here too.