Unprotected soybean roots ought to be scared. Root-crunching critters, called nematodes, continue to proliferate in fields where farmers plant soybeans and other row crops. Also known as roundworms, nematodes are documented to represent nearly 80% of all animal life — and they live in the dark, below the seedbed, where roots reside.
Iowa State University studies, funded by the National Soybean Checkoff , reveal an average 15% to 30% yield reduction from soybean cyst nematode (SCN) feeding in susceptible soybean varieties — even on plants that show no visible, aboveground symptoms. “SCN feeding damage is a very common problem in the Midwest,” says Greg Tylka, ISU Extension plant pathologist.
Finding an effective solution to SCN should help farmers overcome chronic soybean yield challenges.
“There’s still no quick fix for the current yield plateau in soybeans, but both nematode and disease control are part of the equation for significantly boosting yields,” Tylka says. “For now, farmers can choose from an ever-expanding selection of seed treatments that could help provide early-season protection from SCN feeding.”
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In 2013, the market offered three soybean seed treatment choices for nematode protection, says Tylka. They were Avicta, sold as Avicta Complete Beans , from Syngenta; VOTiVO , sold as Poncho/VOTiVO seed treatment, from Bayer CropScience; and N-Hibit , from Plant Health Care Inc.
“Starting in 2014, a fourth one will become available, called Clariva, from Syngenta,” says Tylka. “Clariva will provide protection specific for SCN, whereas the other three seed treatments are reported to provide protection to many different nematode species.”
Still, farmers who want third-party, research-centered advice on product performance will have to wait. “At this point, based on our experiments at ISU, we don’t have enough information to guide purchase decisions, whether for Avicta, VOTiVO or N-Hibit — or for Clariva, which we haven’t studied,” says Tylka. “What they do and how effective they are in different agronomic environments is complicated — that pretty much summarizes the entire situation.”
What remains clear, however, is that “every one of these products has a radically different mode of action,” notes Tylka. “Avicta is a nematode nerve transmission inhibitor; Clariva is a bacterial parasite of the soybean cyst nematode; N-Hibit is a protein that stimulates natural plant defenses; and VOTiVO is bacterially based [for root protection].”
Clariva Complete Beans is Syngenta’s newest product available for SCN protection, says Palle Pedersen, Syngenta Seedcare technology manager. “Clariva is a revolutionary way of managing SCN,” he says. “It is the only nematicide on the market that will get in direct contact with the nematode, attach itself, penetrate and over time kill the nematode.”
Clariva’s active ingredient is the soil bacterium Pasteuria nishizawae, “with specific activity against SCN,” says Pedersen. “This product gives full-season protection, even in fields where SCN-resistant varieties have been used for a long time and the SCN population in the soil is characterized as HG type 2.”
Here’s how it works: “After treated seed is planted, P. nishizawae spores are released into the soil around the seed and developing roots,” Pedersen says. “The spores attach to the outer layer of the SCN as they pass through the soil. Once attached, the nematode’s body is infected with spores of P. nishizawae, which depletes the nutrients within the nematode and reduces reproduction. The nematode eventually dies, and the spores are released back into the surrounding soil.”
Syngenta’s multi-year field studies show a 3% to 5% average yield increase from Clariva use with an SCN-resistant variety in SCN-infected soils compared to CruiserMaxx Beans, notes Pedersen.
Poncho/VOTiVO, from Bayer CropScience, is in its second full year in the soybean market. “It performed very well despite the tough conditions last year with the drought,” says Ethan Luth, seed treatment product manager. “Last year, growers saw a 5- to 8-bu. yield increase with Poncho/VOTiVO in soybeans vs. the fungicide seed treatment alone.”
Poncho/VOTiVO works by utilizing a bacterium (Bacillus firmus strain I-1582) that grows with the root system, he points out. “Poncho/VOTiVO blocks the ability of the nematodes to sense the food source (roots) that they would normally be drawn toward,” says Luth. “It acts as a protective mask. The protection lasts through the early growth stages, which are the critical growth stages for maximizing yields.”
The bacteria from VOTiVO help to create “a protective barrier around the root,” he says. “As a result, diseases don’t have an entry point into the plant, as they would if nematodes were feeding on roots.”
An SCN-resistant trait is also built in with the Poncho/VOTiVO seed package. “There are two components to its nematode protection: a living bacteria and a resistant trait,” says Luth. “Keep in mind that certain nematodes in the environment are beneficial. Our product protects roots from the harmful nematodes, but it has no negative effect on the beneficial nematodes that naturally exist in the soil.”
Avicta Complete Beans, in the market since 2011, was Syngenta’s first nematicide seed treatment for soybeans, says Pedersen. “Avicta will be the main product for nematode control outside the Midwest,” he says. “Depending on nematode pressure and species, it provided an average 2- to 4-bu. yield increase. The largest yield responses were in the South, where a complex population of nematode species exists, including SCN and root-knot, lesion and reniform nematodes.”
Avicta’s active ingredient is abamectin, a compound made from fermenting the soil bacterium Streptomyces avermitilis. This compound moves on the root surface as the plant grows, disrupting the nematode’s nervous system as it feeds on roots.
N-Hibit, from Plant Health Care Inc., has been available for several years as a seed treatment “containing the harpin protein, to stimulate natural plant defenses,” says Tylka. “It’s applied to seed by the farmer or a custom seed treatment facility for management of the soybean cyst nematode to bolster the plant’s own natural defense mechanisms.”
Tackling corn nematodes
There are families of roundworms that dine on corn, too.
Soybeans aren’t the only crop that benefits from nematode protection — corn roots can also suffer significant damage from nematode feeding, says Greg Tylka, Iowa State University Extension plant pathologist.
“A summary of soil and root samples sent in to ISU from 2000 to 2010 showed that about 10% of the samples had damaging levels from nematodes that feed on corn,” points out Tylka. “However, a more recent survey in Illinois has shown much higher levels of damage from nematodes that feed on corn.”
The bottom line is that corn requires careful management to prevent yield loss from nematodes, he adds. “There is still one soil-applied nematicide product available for farmers to use, which is not available for soybeans, and that’s Counter by AMVAC,” Tylka says. “In Iowa, we have seen that Counter reduces nematode populations, but we haven’t yet seen consistent yield increases. There are instances where it has provided 20-bu./acre-yield increases on sandy soils infested with heavy nematode populations, but there are also instances where it provides no yield increase.”
Nematode-protectant seed treatments are another option gaining in popularity, says Tylka. “Until the mid-2000s, there was no such thing as nematode-protectant seed treatments,” he points out. “They first became available for cotton, where nematode control is even more of a concern than for soybeans or corn.”
Poncho/VOTiVO, from Bayer CropScience, “has been used in corn since 2010, on about 15 million to
20 million acres,” says Ethan Luth, seed treatment product manager. “Its performance on corn is excellent, especially where growers plant more corn on corn and where minimum tillage practices allow nematode populations to increase more than they would with a rotation to beans and conventional tillage.”
Also available since 2010, Avicta Complete Corn, by Syngenta, includes an insecticide, a nematicide and four fungicides, says Palle Pedersen, Syngenta Seedcare technology manager. “Demand for Avicta Complete Corn more than doubled in 2013, and its market share continues to accelerate for 2014,” says Pedersen.
N-Hibit, from Plant Health Care Inc., is a seed treatment that contains the harpin protein to “stimulate natural plant defenses” for corn, says Tylka.
NIMITZ, an experimental nematicide by MANA , could be available for corn in the near future. “Final EPA evaluations for NIMITZ are expected in 2014 for tomatoes, peppers and cucurbits,” says Herb Young, MANA brand leader. “We’ve also begun evaluations for row crops that need to be submitted to EPA.”
NIMITZ provides protection using a unique mode of action, says Young. “It’s a new chemistry lethal to nematodes within 28 to 48 hours. Its mode of action targets the egg, larvae and adult, so it creates a clean eradication zone for plants to build an early root system.”