At the other field tour stop, Monsanto’s Jorge Cuarezma, Monsanto technology development, said root knot nematodes cause severe crop injury and also exacerbate Fusarium wilt problems in cotton. Seed treatment control, he said, often breaks down after a few weeks, especially in areas of high nematode pressure.

Nematode infection symptoms include yellowing of leaves, stunting of the plant and taproot, tell-tale galls or knots on the tap and lateral roots, along with a lack of secondary hairs on the roots. “Because root knot nematodes attack the root system, reducing the plant’s ability to take up water and nutrients, symptoms are most noticeable during periods of stressful environmental conditions. Lighter soils, such as sand that are more susceptible to nutrient leaching, are more likely to show visual symptoms of damage.

“With heavy populations, we need a resistant host,” Cuarezma said. Resistant varieties, he added, show significantly fewer galls on the roots and disrupt nematode reproduction. “Breeders are finding resistant genes in cotton plants. Deltapine’s two experimental nematode resistant varieties—13R341 and 13R347— are part of Monsanto’s New Product Evaluator (NPE) program and are candidates to be on the market for the 2014 season.” Those are research numbers and will change when the varieties are released.

Cuarezma said nematodes obstruct the vascular system of plants and hinder growth. Nematode infection also has an effect on Fusarium wilt and limits yield and performance of the cotton plant.

The number of nematode eggs on resistant cotton variety roots is “much less and the resistance reduces the number of root-knot nematodes in the soil profile,” he said.

Monsanto’s Dave Albers said growers need varieties that are not only resistant to root knot nematodes but “are also good performers where there is no nematode pressure.”

The new varieties will be mid- to full-season, and 347 is slightly later than 341.

Ongoing tests this season also evaluate nematode injury, based on soil moisture readings from the root zones. “We hope to put a value on nematode traits,” Albers said. “And we hope to extrapolate that back to yield.” Marker-assisted breeding helps isolate the genes linked to nematode resistance. “These are breeding traits, not biotech.”

“We hope to launch these varieties where they will best fit,” Cuarezma said.

“We need something like this in this area,” said Manda Anderson, Texas AgriLife Extension integrated pest management specialist. “I think nematode damage is right behind Verticillium wilt, which only comes in wet years. With a high level of nematode infection, seed treatments tend to break early.”

 

Also of interest:

Across the Sunbelt, herbicide resistance changes production options

Weed resistance now an issue in Texas

Prevention is best strategy for resistant weed management