On control measures: Stinkbug invasion reveals good data

When farmers have a bad year with a particular insect, researchers usually gather their most reliable data on the pest.

In 2001, this Catch 22 occurred when stinkbugs caused significant damage in Mid-South rice fields, costing growers $30 million in Arkansas alone. Conversely, researchers harvested some of their best data to date on two methods used to control stinkbugs in rice — Karate and methyl parathion.

Lately, stinkbugs are becoming more persistent pests in rice, causing broken kernels at harvest and reduced quality and yields, along with dockage by the mills.

In 2001, University Extension personnel and rice consultants in Arkansas conducted several large-scale trials comparing the efficacy and quality impact of Karate with Zeon technology and methyl parathion. Fields in the study were 60-80 acres. Eight trials were conducted.

“In most cases, Karate was at least as efficacious as and, in many cases, did a better job than methyl parathion for rice stinkbug control,” said Gus Lorenz, Extension specialist with the University of Arkansas.

Rice also benefited from residual control with Karate, “which took out a lot of the nymphs that had come out after the first treatment,” said Steve Harrison, with Syngenta, which markets Karate.

The study showed that the number of stinkbugs caught per 10 sweeps were 0.8 and 1.4 for Karate Z and methyl parathion, respectively, three days after treatment. At seven days after treatment, the numbers were 2.8 and 10.4, respectively. At 14 days after treatment, the number of stinkbugs per 10 sweeps had risen to 22.7 for methyl parathion versus only 6.4 for Karate Z.

Rice samples were taken to determine the effects on milling quality, percent peck and grade. Overall, Karate Z gave a premium of 21 cents per bushel across all measurements compared to methyl parathion. In addition, Karate Z gave higher values for both whole and total kernels than methyl parathion, according to Harrison.

Karate Z reduced peck by 50 percent compared to methyl (1.4 percent rating vs. 2.9 percent rating). USDA grades for Karate Z samples were 1 compared to 3 for methyl.

Stinkbug feeding on kernels in the pre-milk stage will stop development and result in severely reduced kernel sizes. In the milk or soft dough stages, stinkbugs remove portions of the kernel and expose it the fungal pathogens that cause kernel discoloration.

Syngenta also released the results of a grower trial on the value of fungicide applications on rice. The study evaluated the yield response between treated and untreated plots.

“The tests I've completed the past two years showed a $75 increase per acre on my Quadris-treated plot in 2001,” said Chad Elms, a Richmond Texas producer. “In addition, I'm getting higher milling yields and less smut with Tilt.”

Sheath blight is the number one disease problem in rice. If left unchecked, it can reduce yields up to 25 bushels per acre, with severely infested fields, up to 50 percent. Panicle blast, although not as common as sheath blight, is one of the most damaging diseases in rice, capable of inflicting yield losses up to 90 percent.

Kernel smut dramatically impacts quality, potentially costing growers three to six head rice points and reducing yields by 10 to 15 percent.

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