Cotton
Spraying: The Pests Died - Or Did They?
(Beyond Pesticides, September 26, 2003) This week's Photo
Story comes from retired beekeeper David Green and his website at
www.gardenbees.com.
Mr. Green's photographs show an aerial pesticide application made to
a cotton field near his home, as well as the photographs of which insects
did and did not survive the spraying. Below is an excerpt from his account
of the spraying. His full story can be viewed here.
An aerial applicator began spraying a large cotton field at about 1:15 PM on August 11. The plane began making passes from east to west and west to east along the south margin of the field. I observed from the west end of the road frontage. Each time the plane pulled up over the road spray could be observed to follow across the road and into the woods on the east side.
The cotton plants were in bloom and there were abundant wild flowers along the road, with honeybees and bumblebees visiting the wildflowers. Presumably they were also visiting the cotton blossoms. The most noticeable feature was the large number of dragonflies. I would estimate that there were at least 1000 dragonflies along the road frontage of this field. There were also large numbers of sulfur butterflies along the ditch. Swallowtail butterflies could also be seen sipping at the vervain and moving on. There were about a half dozen of these on the road frontage. A couple red spotted purple butterflies were also present. Gulf fritillaries were not; for some reason they have been few in number so far this year.
I took a number of photos of the plane. As it worked its way toward me I was able to get some good shots. When it was about half done with the field, I rolled up my car windows and drove to the east end of the road frontage, where I took additional photos. As I was in the area already sprayed (by drift from the field) I noticed only a few dragonflies still flying. Their flight was much more erratic, and some were on the road surface obviously dying.
I left the area when the applicator moved on to another field, and returned about an hour and a half later to look at the scene and take photos. I did look briefly in the grass on the road shoulder, but it was too dense to see much, so I made most observations along the edges of the pavement, and took photos. I observed many dead insects. The most common were polistes wasps, but there were also bees, dragonflies, grasshoppers and moths. No dragonflies were seen alive, in stark contrast to their intense activity a few hours earlier. No bees or other insect visitors could be found on the wildflowers alongside the road except I saw one cotton bollworm adult visit Eupatorium (photo below). One beetle that I thought dead, ran for cover when I tried to photograph it.
The day after spraying, I returned to the scene. It is eerily quiet, as I am used to seeing a lot of activity along this road. Not a single dragonfly was in evidence, nor any bees, nor butterflies. After watching for awhile I saw a silver-spotted skipper on the vervain. I found the stillness disconcerting, and I went along the road, away from the field to see if I could find normal life. It was a half mile before I saw a single dragonfly. A little further and there were many. I stopped to watch awhile, relieved to see the sulfur butterflies flitting everywhere and dragonflies and bees like they had been at the cotton field the day before.
The Survivors: They were four species of insects seen alive two hours after the application. One was a small white moth, fairly numerous, which I was unable to photograph or identify because it was very active and tended to hide in the grass. I strongly suspect it was a pest insect. The other was Helicoverpa zea, known as the corn earworm or the cotton bollworm. They also were quite active, but I was able to capture these blurred images of two by telephoto.
The third species seen were fire ants, which seem to be quite resistant to pesticides. They were scavenging the corpses of some of the dead insects. A fourth species, not identified, was a small beetle, which I thought was dead, but when I attempted to take a photo, it scurried for cover.
The Casualties: A number of dead or dying insects were seen along the roadside. The most common were polistes wasps. These are predators of caterpillars, which they feed to their brood. I have seen them highly active in unsprayed cotton in the past, busily searching throughout the foliage. Judging from the numbers seen in this small area, there must have been thousands of these beneficial insects killed in the field and overspray area.
The second most common casualty was the dragonflies. These are predators upon flies and mosquitoes, and the larval forms are even more voracious predators upon larval mosquitoes in standing water. No dragonfly survivors were seen.
Also among the casualties, there were one each: honeybee, male velvet ant, cotton bollworm, katydid, and grasshopper. Since the sample size was small, there were indubitably many more of each killed. Honeybees are highly beneficial insects. No dead bumblebees were spotted, but they were conspicuous by their absence the next morning.
There are special laws pertaining to bees, which will be discussed below. Of course honeybees are one of the most beneficial insects known to mankind. Half of the US beehives are trucked each year to California for almond pollination, then most of them are used again to pollinate apples, cherries, blueberries, strawberries, seed legumes, vine crops, and many others during the rest of the season. Wild honeybees have become scarce due to parasitic mites, pesticide damage, new diseases, and changing agricultural practices, such as the decline in use of clover, buckwheat and other crops that are high in nectar yields, and the mowing of alfalfa for hay prior to bloom.