Great Hope or Great Hurt? Growers Turn to New Pesticide in Bid to Halt Drop By KEVIN BOUFFARD | THE LEDGER October 5 SCOTT WHEELER | THE LEDGER (2013) Slideshow | Gene Albrigo, professor emeritus of horticulture at the University of Florida IFAS Citrus Research and Education Center, examines the damage in a Lake Alfred grove with pre-harvest fruit drop caused by greening. WINTER HAVEN | Scores, perhaps hundreds, of Florida growers are experimenting with a fungicidal chemical that has been shown to reduce pre-harvest fruit drop, a scourge for the past two citrus seasons with drop rates that reached as high as 31 percent on the 2013-14 Valencia orange crop. But scientists warn that increased use of the fungicide Headline could lead to the development of resistance among the various fungicidal pests it was meant to eliminate, rendering it and other fungicides useless and allowing the pests to spread unchecked across the state. Theres also concern about the long-term effect of the practice on tree health. Id say at least 50 percent of growers are using it (Headline) in some way or another, said Vic Story Jr. of Story Citrus Services Inc. in Lake Wales, which manages about 5,000 acres in Polk and neighboring counties. Some growers have waded in pretty deep, like I have, and some have held back. His company has applied Headline on about 90 percent of the 2,000 acres of early and mid-season orange groves he manages, Story said. Ellis Hunt Jr., president of Hunt Bros. Inc., a Lake Wales grower with about 5,000 acres split between Polk and South Florida, said he has sprayed Headline in all his early-mid groves. Hunt is also a member of the Florida Citrus Commission. Another citrus commissioner, V.C. Hollingsworth, an Arcadia-based grower with 4,500 acres in DeSoto and Hardee counties, agreed interest in Headline for drop prevention is widespread. Hollingsworth said hell try it on about 500 acres of his early-mid oranges to see whether it reduces drop. Everybodys trying it to see if it works, he said. If it works on my early-mid oranges, Ill use it on every acre of my Valencias. Early-mid oranges are harvested from October to March while the Valencia harvest runs March to June. BASF, the manufacturer of Headline, recommends waiting to spray the fungicide for drop control until a few weeks before harvest, growers said. Story agreed the decision to spray Headline on his Valencia oranges will depend on how well it works on his early-mid oranges. Several other growers told The Ledger last week they are experimenting with the fungicide for drop on at least part of their early-mid oranges. Im not happy about it, said Megan Dewdney, assistant professor of plant pathology at the Citrus Research and Education Center, about the increased use of Headline. Resistance is my largest concern. We actually have limited quality data on this (Headline for pre-harvest drop). I would say theres going to be long-term consequences. Like human pathogens that eventually evolve to resist bactericides and other medications, harmful plant organisms can develop resistance to pesticides and other chemicals used to kill them. That can happen fairly quickly, explained Dewdney, who said it took just five years for the common plant fungus alternaria to begin showing resistance in Florida. Headline belongs to a class of fungicides called strobilurins, or strobes, that are commonly used in Florida to fight fungal diseases including alternaria, black spot, greasy spot and post bloom fruit drop, which reappeared in Florida last spring after a roughly 20-year hiatus. But strobes are normally applied to young citrus fruit in the spring and summer, Dewdney said. There is no disease you would apply a strobe for now, she said. Gene Albrigo, emeritus professor of horticulture at the Lake Alfred center, echoed Dewdneys concern about fungicidal resistance and also warned about potential long-term damage from the practice on tree health. Albrigo has been studying the pre-harvest drop problem since it emerged in the 2012-13 season. Drop a greening symptom He and other scientists agree that the drop problem is another consequence of the fatal bacterial disease citrus greening, thought to have infected almost all of Floridas 515,147 commercial citrus acres. Pre-harvest drop occurs only on trees infected by greening, which appears to weaken their ability to hold onto the fruit. Albrigo also agreed there is little scientifically valid data on the use of Headline to diminish pre-harvest drop and worried that forcing infected trees to hold onto the fruit may hasten their decline. This year, you may improve your yield, but you may pay for it next year in accelerated greening decline, Albrigo said. These debilitated greening-infected trees may not be able to hold on to all that fruit. But Hollingsworth, Story and other growers responded that post-harvest drop is their biggest greening-related concern and that they cant wait for scientists to validate its use. These growers are looking at the short run and not the long run. If we dont do something, there may not be a long run, said Wauchula-based grower Jay Clark, who is spraying Headline in about 20 percent of his early-mid groves. Its an experiment. Nobody knows if it will work, but its worth a try. Clearly, growers worry about the short-term economic impact of pre-harvest drop. Once the oranges, grapefruit and tangerines hit the ground, growers cant legally sell them to a juice processor or fresh fruit packinghouse. In the 2013-14 season, 23 percent of early-mid oranges dropped from the trees before harvest, the highest rate in more than 10 years, said Mark Hudson, the chief statistician in Florida for the U.S. Department of Agriculture. That followed a drop of 28 percent the previous season. The drop rate of 31 percent on the 2013-14 Valencia crop was the highest in 44 years among Florida citrus seasons not affected by hurricanes or freezes, he said. The 2012-13 Valencia drop rate was 22 percent. HEADLINE HYPE According to Albrigo and several growers interview by The Ledger, the Headline boom began after some growers observed their drop problem in groves sprayed with the fungicide had lower drop rates than the rest of their groves. No other strobes besides Headline appeared to show that effect. That led Consolidated Citrus LP, the states largest citrus grower with about 26,000 acres, to conduct a trial in March in one of its Immokalee Valencia groves. Charlie Lucas, Consolidateds CEO, could not be reached for comment. But a 12-page Powerpoint from BASF, the German-based international chemical company that makes Headline, showed Consolidated reduced its pre-harvest drop by a cumulative 43 percent on Valencia trees sprayed with Headline versus an untreated control group. The Powerpoint also states Headline appears to reduce drop by increasing the amount of sugars the tree produces, thus increasing root growth, and reducing levels of ethylene, a gas that helps separate fruit from the stem. Research on greening in Florida also has noted lower sugar production, less root growth and higher ethylene levels in infected citrus trees. Word of the Consolidated trial spread through the grower grapevine, aided by BASF-sponsored meetings with growers. But Albrigo maintained that the Consolidated trial fell short of the rigorous standards required for most scientific research. One factor that could inhibit the widespread application of Headline for drop is the cost — Headline is the most expensive strobe on the market, Story and other growers said. Cost is a factor, said Clint Updike of Updike Citrus Services in Alturas, which manages about 2,500 grove acres and is experimenting with Headline on just 20 acres of early-mid oranges. Were going all season with nutritional sprays (for greening), and to add another $75 an acre on top of that and not knowing what it will do is a risk.
Posted on: Mon, 06 Oct 2014 10:32:48 +0000
Trending Topics
Recently Viewed Topics
© 2015