The Great Screwworm War

Jockey and Irradiated Boxes

The Great Screwworm War

Castrated flies from the sky

By Stephen L. Wilmeth

            In the midst of bawling calves and confusion, an order was barked. “Get the clicker out of my pickup?”

            “Where is it?” was the immediate question.

            “It’s in the jockey box,” was the response.

            Only one person in the crew knew where to look. The rest looked around and winced. More than one mouthed in silent, wide eyed incredulity to an onlooker, “Jockey box?”

            Upon returning, the person who understood the request noted she hadn’t heard that term since she left Idaho. Smiles were exchanged and the mystery remained intact.

            Jockey boxes … what a colorful but absolutely apropos term from our past, but there were other things as well. Castrated flies are an example.

            Castrated flies

            A few of us can remember finding unique cardboard boxes scattered across the countryside. The boxes were approximately 4×4×6” and gray in color. Actually, they could have been brown, but, by the time we found them, they appeared gray. It seems the printing on them was red, but it could also have been black.

            We knew exactly what the boxes were.

             Their presence was the result of one of the great science projects in history. The importance could be best characterized by first hand experience with the horrors of screwworms.

It was in late spring that the scourge would descend. It was concurrent with calving and dry, nasty spring conditions. Every calf was susceptible to becoming a living depository of eggs laid around its attached navel cord (or open wounds) by female screwworm flies, Cochliomyia hominivorax.

Within 12-24 hours, the eggs would hatch and the larvae would crawl into the living flesh and commence eating. Any serum or blood flow would attract additional females. If left untreated, the animal would fall victim to subsequent generations and could die within a week to 10 days literally being eaten from the inside out.

In five to seven days, the larvae would drop out, pupate, and a succeeding generation would begin anew. The economic damage was horrendous. Texas alone reported over a million livestock cases annually prior to 1962.

Ranchers rode daily in their calving herds. Calves were roped and a benzol or a pine tar product would be applied to their exposed navels for protection until healing would preclude successful hatching.

My Grandpa Wilmeth’s material of choice was an aerosol can of benzol. He carried it in a leather boot attached to the saddle strings on the left side of his back jockey.

In the boot, he’d also have his ‘kit’. If the calf was not infected, a preventive application of the spray would be applied. If it was infected, we’d clean the worms out and spray it thoroughly. The material was red and the color served to flag the treated calves.

It wasn’t just calves, though, that suffered.

Those horned Hereford bulls that dominated the Southwest were also ready victims. One of the experiences that stands out so vividly in my memory was a bull that had been hooked under his right leg. I am not sure if I was with him when he found him or if I was along only after he had gathered him and was treating him in the corral, but Grandpa and I were up under him in the old wooden run-up that doubled as the only chute available. We had trapped him in there against the gate in front and a pipe stuck behind him so he couldn’t back out.

We crawled under the fence and him lying on our backs looking up trying to see into the wound in preparation of cleaning and treating it. Grandpa just couldn’t reach him because of the limited space, but I could. I’d seen it done and I knew what to do.

I went to work.

It was when I was digging those worms out with a shaped paddle made out of bailing wire that my mother arrived in the corral. It was the only time in my memory that she was ever in a corral, but she threw a fit when she saw what was going on. She was screaming at me to get out from under that bull, but my grandfather calmly looked me in the eye and told me to finish what I was doing.

“You’re just fine. Now … finish.”

And, we did with me spraying the aerosol material as best I could into the open wound and around the entrance. When we finally finished and turned the bull out of the run-up, we walked out of the corral with my mother continuing to give us both an earful. I don’t remember any words from Grandpa, and I would have been silent in those cases anyway, but I do remember he had his hand around my shoulders. That was the only time he ever did that.

I was proud, and … reassured.

Tusklike mandibles protruding from the screwworm larva's mouth rasp the flesh of living warm-blooded animals.

From the border they came

The flies over wintered only in the most southern extremes of their United States range in southeastern California, southwestern and southeastern Arizona, southwestern New Mexico, south Texas and Florida.

The threat would reappear each year after the last frost when fly emergence took place and another leapfrog expansion northward commenced. Successive advancements would consume as much as 50-90 miles each generation. By October, there would be confirmation as far north as northeastern Kansas with reports all the way to the Canadian border.

As far back as 1938, work was done in Texas and the materials noted herein were proven to be effective for control if the extent of the treatment universe was domestic livestock. The problem was wildlife could not be covered and eradication was impossible. Something large scale had to be done if full elimination was to be successful.

 By 1961, the use of the sterile male program on a large scale was ready to be mustered. Research had shown that hatching could be disrupted if enough sterile male flies inundated the population. The results could be observed with as few as 38 sterile males per square kilometer. By increasing the population toward 100 sterile males, full control was manifested.

From a facility in Mission, Texas, large quantities of male flies were hatched and effectively castrated by exposure to radiation. The goal was to make sure that 80 viable, sterile flies per square kilometer were available across specified areas at calculated time intervals throughout the entire season. The harvest of male flies was 28,000,000 in July of that year. By October, the output was 75,000,000. The flies were boxed in the little cardboard containers and dropped from airplanes. The results were astounding.

By 1963, not a single case of screwworms was reported in New Mexico and Texas.

Arizona was declared screwworm free in 1964. California followed in 1965, but Mexico would prove to be a continuing problem. In 1971, Texas started reporting reoccurrences. With a Mexican government involvement, the United States began a stepwise eradication program in Mexico. In intervals, the pest was eradicated southward, and, by 1983, Mexico was free of the pest south to a point near the Yucatan Peninsula.

The facility in Mission stopped castrating male flies in 1981.

Boxes revisited

There should be one of those irradiated boxes in the New Mexico Farm and Ranch Heritage Museum, but I suspect there isn’t. In retrospect, they were immensely important in our history.

I can remember one box in particular. The year had to be either 1961 or 1962. It was on the flat just south from where Dusty now lives in the Mangus Valley. I was on Champ and we were going somewhere to do something that may or may not have been important. The box was lying where it hit the ground and cracked open. The flies, of course, were gone doing their important work.

I had just heard one of the planes that we knew dropped the boxes, but it had been further west and the box on the ground had likely been there for some time. I looked up, though, and tried to spot the plane.

Those were good days.

We might have gone to Cliff that afternoon for the mail. If we did, it was in the blue 1951 Chevy pickup. In the ways of my grandparents, it would have been clean and tidy. Nothing would have been in the bed if enough of us were along to have to ride there. If it was just me, I would have been up front with them talking. If there was a need for something in the jockey box, I would have opened it and retrieved it.

If you don’t know what a jockey box is, I am not going to tell you. The word will remain secret code to those of us who were western children of the ‘50s and ‘60s.

Like castrated flies, that’s just the way it works.

Stephen L. Wilmeth is a rancher from southern New Mexico. “Indeed, those were bonus days.”