An unbelievable 12,000 aphids on some soybean plants last year provided a buffet bonanza for hungry beneficial lady beetles. But depending on nature to control most bad bug outbreaks in soybeans or corn may not be economically feasible for most farmers.
A good integrated pest management (IPM) program will probably feature some naturally occurring beneficial control of aphids, caterpillars and borers. But it will also include timely application of insecticides, which can be vital in any knockdown or elimination program.
“You can't rely on any one tactic to control soybean aphids or other damaging insects,” says Robert Wiedenmann, an entomologist involved in biological control and other research for the Illinois Natural History Survey in Champaign. “Most of the time biological control agents don't act fast enough to knock down a major outbreak.”
The notion of buying large quantities of commercially produced and marketed beneficial insects has been around for a long time. After all, the multicolored Asian lady beetle, lacewings or Trichogramma are predators and parasites that devour enemy insects by the tens of thousands.
But with massive outbreaks like those seen in the bean belt in 2003, “you couldn't buy or put out enough lady beetles to knock down soybean aphids,” says Wiedenmann, noting that “astronomical” numbers of aphids, 6,000-12,000/plant, were seen in some fields. “The aphids can double their population in a matter of days. It would take three to four weeks for a new generation of lady beetles to reproduce. You would play catch up all the time.”
Mike Gray, University of Illinois entomologist, says pesticide applications were imperative to encounter the huge aphid outbreak. “But it's hard to tell how many more fields would have required spraying if the lady beetles had not provided some late season control.”
Entomologist Frank Junfin, owner of Kunafin “The Insectary,” and his family have operated their facility (www.kunafin.com) and service since the 1970s in Quemado, TX, in the lower Rio Grande Valley.
The bulk of their business is in fly parasites for fly control around feedyards, dairies and other livestock operations. But they also deal in lady beetles or ladybugs, lacewings and Trichogramma. And he sees a time when Trichogramma can be introduced in combination with a Bt corn program.
“In Bt corn, earworm moths are still going to hatch,” he says. “What is going to happen if there is an eventual resistance to the Bt gene? By getting a build up of Trichogramma, growers will not have to rely as much on Bt corn.”
He says for $2-5/acre, growers can release the beneficial bugs.
“The Trichogramma will recycle in about 10 days,” says Junfin. “They will continue to provide an additional tool against corn borers or earworms, which are the same as cotton bollworms, tobaccos budworms and soybean pod worms.”
The cost of lady beetles can run as much as $78/gal., or 72,000 bugs, says Jim Kluttz of The Beneficial Insect Co. (www.thebeneficialinsectco.com), Glendale Springs, NC. He sells lady beetles, lacewing and other beneficials, mainly to gardeners, greenhouses and some smaller organic operators.
“One gallon of ladybugs will treat from one to five acres,” he says. “When comparing that to the cost of chemicals, there is much less labor involved in releasing beneficials.”
Junfin says $1/1,000 lady beetles is a common price. He suggests releasing the bugs at 5,000 at a time “to help build up a cycle.” He also says his company provides a natural food source for lady beetles before they are shipped. “That way they can be ready to start laying eggs when they are released,” he says.
USDA has released the multicolored lady beetle to help control bad bugs in pecans and some field crops. That could be one reason behind population buildups and an unwanted migration inside homes.
“I have heard of people vacuuming them up,” says Junfin, noting that commercial availability of the lady beetles can sometimes be short. “Those people should keep them and sell them to farmers.”