January 15, 2010

5 Min Read

The boll weevil and tobacco budworm are no longer economic pests in most areas of the Cotton Belt, but they’ve been replaced by secondary pests like the tarnished plant bug, which are proving to be costly bugs to control as well.

Additional insect control costs are coming from increasing foliar sprays, higher technology fees and pest resistance, according to Jeff Gore, research entomologist at the Delta Research and Extension Center, speaking at the 2010 Beltwide Cotton Conferences in New Orleans.

Gore adds that decisions growers make on insect control are changing, too, based on developments such as the shift from granular, at-planting insecticides to neonicitinoid seed treatments and the transition from single gene Bt cottons to dual Bt gene cottons.

“We also have a more of a diversity of crops. In Mississippi, we’re growing a lot more corn and soybeans than we’ve ever grown in the past, and we’ve reduced our cotton acreage. This is also impacting the pests that we’re dealing with in cotton.”

When these costs are added to other rising input costs such as fertilizer, fuel and equipment, technology frees and seed treatments, “we’re essentially spending a lot more on cotton production than we ever have in the past.”

Gore said that in 1995, the cost of planting an acre of cotton ranged from $12.75 an acre to $24 an acre depending on at-planting insecticide and fungicide treatments. “In 2005, if you had planted Bollgard, Roundup Ready cotton varieties with a Cadillac seed treatment, you would have spent about $52 an acre. Now in 2010, with Bollgard II and Roundup Ready Flex, you’ll be spending $85 or more an acre. This is also impacting our insect management throughout the season because we’re front loading so much of our cost, and it’s becoming more and more difficult to make those insecticide applications later in the year.

“And with the weed resistance likely to increase our weed control costs at the beginning of the year, it could also impact some of the decisions later in the season in terms of insect management.”

Research indicates that Mississippi cotton producers are starting to increase foliar applications directed at the bug complex, according to Gore. “The trend line for foliar costs dropped significantly with boll weevil eradication and Bt cotton. But for the past four or five years, we’re seeing a significant upward trend on foliar costs. It’s approaching where we were before Bt cotton and boll weevil eradication.

“In Mississippi, we have growers who are spending well over $100 for foliar insect control. You add that onto technology fees and seed treatments, you understand why our cotton acreage is decreasing.”

Varieties with no traits or single traits “are becoming extremely limited,” Gore said. At the same time, “two-gene Bt products are definitely not bulletproof. We’re still having to make some applications, although fewer, on caterpillar pests.”

Mid-South growers have asked Gore about the wisdom of planting a non-Bt variety, especially with the higher costs of Bt technology. “We have a few growers planting small acreages of non-Bt cotton, and they’re probably going to see benefits from that.

“But if we start shifting back to non-Bt cotton, I promise you, the tobacco budworm will come back, and we don’t want to be making foliar applications for resistant tobacco budworms, in addition to treating tarnished plant bugs. The amount of money we would have to spend in that situation would be astronomical.”

Gore says growers also question the cost and value of resistance management, a major selling point of two-gene, Bt cotton. “From my standpoint as a researcher, resistance management is worth it, but I can also understand the sentiment of growers trying to survive, and the difference they’re paying between Bollgard and Bollgard II may be what they need to stay in business next year.”

Shifts in the pest complex have also compelled research to rethink scouting methods and thresholds historically used in cotton to scout worms and boll weevils, not bugs. “So there’s a general lack of confidence in our sampling procedures and thresholds for bugs in cotton.

“One of the things the Southeast has done is to develop some injury thresholds for stink bug, a major pest of the region. The threshold changes throughout the season and should help to limit some applications.”

Gore notes that the plant bug has now been the No. 1 pest in the Mid-South for the past four to five years. “It’s this pest which is driving a lot of cotton out of the Mississippi Delta. I was talking to a farmer the other day who was adamant about being a cotton grower. I asked him how much he grew last year, and he said he didn’t grow any. He just couldn’t afford to spray plant bugs.”

Spider mites are also gaining a reputation as budget busters in the South, along with aphids and stink bugs.

In 2009, Mississippi averaged six plant bug sprays per acre, with the average cost of application at $11.50. “We’re spending about $75 on average for foliar tarnished plant bug control.”

In addition, plant bugs and spider mites are becoming resistant to the insecticides used to control them, Gore says.

“Over the past 15 years, we’ve essentially doubled our application rates with Bidrin and tripled our application rates with acephate. So we’re not only spraying more often, we’re applying higher rates that cost more.”

Gore said a side effect of relying on neonicitinoids for plant bug control “is that we are starting to see some tolerance in cotton aphids. We’re starting to hear lots of complaints from consultants across the Mid-South.”

It’s no surprise, Gore says. “They are also used as a seed treatment on almost every crop we grow, plus we’re making two to three foliar applications pre-flower for aphid and plant bug and we’re making additional applications mid- to late season, for plant bugs. And there are foliar labels for subsequent use in other crops.”

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