By: Mary Lou Jay, Contributing Writer
Agricultural aviation plays a small but important role in the production of citrus fruits, which are a welcome addition to the American diet during the fall, winter and spring months. Although oranges, tangerines, tangelos, grapefruit, lemons and limes are grown commercially in four states, Florida is by far the largest producer in the U.S., providing 7.5 million tons in 2004/2005. In that same year, California grew only 3.3 million tons, Texas .33 tons and Arizona just .12 tons.
Over the last few years, however, weather and disease have drastically decreased Florida’s crop yields. Aerial applicators are seeing the impact of this reduction on their own businesses.
Aerial spraying has a limited role in citrus production because many chemicals used on the trees require ground application. In addition, there are not many chemicals currently approved for citrus applications, says Chuck Stone, owner of Southeastern Aerial Crop Service of Ft. Pierce, Florida. “Citrus is considered a minor use crop by the chemical people, and it costs a lot to get an aerial label these days.”
Finally, agricultural aviators in the state, like those throughout the country, are facing opposition from people moving into areas that were once rural. Bill Malone, owner of Sunniland Aircraft in Okeechobee, says he has sometimes turned down work on citrus that’s too close to residential areas. “I don’t need the drift complaints, and the owner doesn’t need to get in trouble,” he says.
Still, the sheer size of Florida’s citrus groves has made citrus an attractive niche market for some pilots. Stone, for example, has been spraying citrus for 58 years, and it makes up about 90 percent of his agricultural aviation business. His operation is located in Ft. Pierce, Florida, halfway between Miami and Jacksonville and 40 miles north of West Palm Beach.
“We spray for rust mites and spider mites and also apply fungicide for greasy spot and scales,” Stone says. Spider mites are more prevalent in cooler weather and rust mites during warmer months, “but we’re liable to spray any time of year, since it’s summer here practically all the time.” Citrus harvest times run from the end of September through July, and treatment times vary because of the many different varieties of fruit that are grown.
Spraying for rust mites is done primarily for whole fruits destined for supermarket. That’s because the brown tinge that the microscopic mites leave on the citrus skin makes it less attractive for sale, explains Malone. “It’s not as big an issue for fruit that’s going to be used for juice.”
Malone, who has been spraying citrus since 1974, says he treats about 75,000 land acres of citrus twice a year. He rarely uses insecticides for rust mites, he says. “Insecticides have gotten pretty pricey. If you can get an early jump on them, before the populations build, you can control them with crop oil. If they get a little out of hand, you can use sulfur. It’s really a matter of staying on top of things, and putting it out at the right time. You can put as much as 10 pounds of sulfur in 15 gallons of water and spray that.” Since owners want to get as much benefit as possible from each pass, Malone says they’ll often request applications that combine two treatments into one. That could mean applying a fungicide and rust mite treatment at the same time, or treating for both rust mite and fire ants.
Stone uses primarily copper, sulfur and Kelthane in his operations, applying them at a 15 gallons per acre rate. Like Malone, he sprays in early morning, before the winds come up. “With the trees like a big canopy, it’s very easy to get too much on one side of the tree and not any on the other,” he adds.
Spreading Birth Control for Ants
Another job that aerial applicators can perform for citrus grove owners is control of fire ants. “Fire ants like young trees, and they will suck out the moisture from the trees if they go unchecked,” Malone says. “And sometimes the fire ants will get so bad in the groves that the fruit pickers will refuse to go in because the ants are biting so much.”
The biggest damage from fire ants, however, may be to the systems that support the young trees. “We had a customer down here who had 10,000 acres of trees, and every year we’ve spread this fire ant bait out for them. But one year they cut it out of their budget. They lost a lot by not keeping them under control that one year,” Malone says.
“The ants were looking for water, and they got into the irrigation system and clogged up the emitters, which then couldn’t drip water onto the young trees. They lost 100,000 trees, scattered throughout 10 square miles. They had to go out and repair the irrigation system and replant new trees. That little mistake cost them over one million dollars.”
Aerial applicators keep the fire ants under control by applying one of several commercial products that contain ground-up corn grits, an attracting oil, and a growth regulator that acts like birth control. The worker ants bring the food into the nest, where the queen and the other ants eat it. Although the queen keeps trying to lay eggs, no new ants develop because of the growth regulator. All the ants die of old age in about six weeks and the mound dies off.
“One pound of this mixture will go over 43,560 square feet,” Malone says. “It’s so fine that you can’t see it with the naked eye, but those ants will forage up to 15 feet for it. It doesn’t take much to get it into the nest and the food chain, and that’s the end of the mound.
“But you have to go back and treat the area every year as part of a maintenance program,” he cautions. “Although you may be taking care of your grove, the owner of the grove next to yours may not be. The ants get wings during mating season, and will go downwind, land in your field and start a new colony. That’s why control is so important every year.”
Some people try to control the ants by ground, but aerial application is more economical, he says. “We can pick the ideal weather conditions, when the ants are actively foraging and the temperature is in a certain range. And we can treat 1,000 acres in a day’s time, where by ground they can treat only 30 or 40 acres. They just get a lot better extermination by air.”
Hurricanes and Disease Cause Dramatic Drop in Output
Florida’s citrus crops have faced many threats over the years, including periodic infestations by the Mediterranean fruit fly (Medfly) since the 1920s. Agricultural aviation has helped control these Medfly outbreaks, spraying a mixture of a minimal amount of insecticide and protein/sugar bait.
More recently, however, citrus crops have been experiencing problems for which there are no cures. Canker, which causes lesions on a citrus tree’s leaves, fruit, branches and trunk, was first found in Florida’s citrus groves in 1995. The bacterial disease is highly contagious to other trees but not to people or animals. It most likely came to the U.S. on a fruit or plant that came from an infected area in Asia.
To try to prevent the spread of the disease, the U.S. Department of Agriculture and the Florida Department of Agriculture and Consumer Services for several years paid for the removal of trees in a 1900-foot radius from the infected tree. “In Florida, we had roughly 700,000 acres of commercial citrus, and they pushed and burned close to 100,000 acres of those trees,” Malone says. “They’d have to remove 240 acres from just one tree find.” Cleared areas can not be replanted in citrus for at least five years to ensure that the canker is completely gone.
This approach had only limited success. In addition, the high winds from hurricanes in 2004 and 2005 (particularly Hurricane Wilma in 2005) spread the disease throughout the state to as many as 168,000 to 220,000 acres of citrus trees.
In January 2006, the USDA and the FDACS announced the end to the large-scale destruction of citrus trees to try and control canker. They are now taking a different approach. “They are burning an infected tree on the spot, and a few surrounding trees around it on a case-by-case basis,” says Malone. But the destruction (and the weather) have taken their toll on the crops. In 2006, for example, Florida is expected to produce just 151 million boxes of oranges, only two-thirds the amount it had produced before 2004.
If that wasn’t enough bad news for citrus growers, agricultural officials identified another disease on trees in south Florida in the fall of 2005. Citrus greening attacks a tree’s vascular system, preventing it from producing usable fruit and killing the tree in five to eight years. It is spread by an insect, citrus psyllid, which is widely found in citrus groves. There is no known treatment or cure for citrus greening, and it could even further reduce the number of acres used for citrus.
Of course, fewer acres of citrus growing mean fewer acres to spray, and that is affecting agricultural aviation in the state. “Our whole business is going down,” says Stone. But they may soon see at least a leveling off in the spraying business. “This year we’re looking forward to good citrus prices if you have any marketable fruit, so growers are taking care of it better than they did before when the market was nip and tuck about whether they make a profit or not,” says Stone. Better care often translates into additional aerial spraying.
Malone thinks the industry will finally get a handle on the diseases threatening citrus, but not without some more permanent losses. “We started out at 700,000 acres, it’s around 600,000 now, and will probably stay in the upper 500,000 acre range in the future,” he says. “I think that some growers are going to switch and grow something else on their land and never go back to citrus. We may, in the future, maintain a grower’s crop, but it may not be citrus.”