Advertise in Print | Subscriptions
Published July 20, 2010, 08:31 AM

NDSU: Stay ahead of pests

FARGO, N.D. — The latest NDSU Crop & Pest Report came out July 15. Among the report’s highlights and alerts:

By: Mikkel Pates, Agweek

FARGO, N.D. — The latest NDSU Crop & Pest Report came out July 15. Among the report’s highlights and alerts:

Grasshopper, aphid alert

Montana State University reports grasshoppers feeding on lentils in eastern Montana. When hoppers are found in lentils shortly before bloom, economic damage thresholds are “very low, only two grasshoppers per square yard” to require treatment, says NDSU Extension entomologist Janet Knodel, citing MSU data.

Grasshopper nymphs and adults are reported defoliating some sunflower field edges. As cereals come out in late July, adult grasshoppers will migrate to sunflower, flax, soybean and other green crops, Knodel says. Information: www.ag.ndsu.edu/pubs/plantsci/pests/e1143w1.htm.

Scout aphids on late wheat and barley. Late-planted wheat is at a relatively higher risk for cereal aphids, and the increased numbers can signal barley yellow dwarf virus. Scout and treat wheat/barley fields that have 85 percent or greater incidence of 12 to 15 aphids per stem prior to the completion of heading, Knodel says.

Moth egg scouting

Scout for banded sunflower moth eggs in the preferred egg-laying stage of R2 to R3, Knodel says. The potential for damage is figured by counting eggs on floral bracts. Use a magnifier to count the small eggs.

“We recommend using a head-mounted 3.5X magnifier to leave both hands free for manipulating the bud being observed,” she says.

Make egg counts when most plants in the field are at the plant stage R3, where a distinct bud elongated ¾ inch above the nearest leaf, and the ray petal is not visible.

- Divide each side of the field into two sections.

- Sample the center of each section at 20 feet into the field from the field edge.

- Randomly select five buds.

- From each bud, randomly select six bracts from the outer whorl and count the eggs on each bract.

- Average the egg counts from the five buds and then map the average egg counts from each sample site to a diagram of the field.

A spreadsheet is available at the NDSU Extension Entomology website to automatically calculate your egg EIL. Click on “Banded Sunflower Moth Calculator for Egg Sampling” at http://bit.ly

/cn4djo.

Canola pests up;

corn pest MIA

Some growers are spraying flowering canola for Lygus bugs near the towns of Pillsbury and Oriska, N.D., in Barnes County, says Knodel. Other Lygus outbreaks have been reported in Minnesota’s Red Lake Falls, Red Lake County, Thief River Falls areas.

Immature and adult Lygus bugs feed on growing points, buds, flowers and green pods, Knodel says. The bugs inject a toxic saliva, causing “blasting” of flowers or buds and shriveled seeds. Blasted canola turn white in 24 hours and quickly fall to the ground.

Scout just before bud formation through flowering until seeds in the pods are firm. Lygus will migrate to canola from alfalfa — the preferred host — when it is cut. Canadians recommend an economic threshold of 15 bugs per 10 sweeps from bud stage through petal drop, and 20 Lygus bugs per 10 sweeps after petal drop. Crops can compensate for bud feeding if soil moisture is good.

Illinois and Iowa are reporting record-low European corn borer densities. North Dakota is seeing “fewer and fewer fields infested with ECB as well,” Knodel says. It’s likely 2010 flights will stay low, probably because of Bt hybrid use and new “pyramid genes expressing multiple Cry proteins with decreasing refuge size.”

Farmers can use a degree-day model for watching the disease. For information, go to http://ndawn.ndsu.nodak.

edu/corngdd-form.html.

After prevent plant

Want to plant winter wheat on your prevent-plant acres this year? NDSU Extension agronomist Joel Ransom says results are best when winter wheat is planted into fields that will catch and retain snow. Fields with standing stubble are ideal for direct-seeded winter wheat. Growers need to manage weeds and volunteer crop plants prior to planting, Ransom says. Volunteer wheat plants and other grassy weeds can harbor wheat curl mite, which can carry wheat streak mosaic virus infections.

A residue crop must remain erect during fall and winter to be effective. Cereals that don’t reach the boot state before a killing frost will lie flat on the soil and won’t capture much snow.

“The most effective residue crop is probably flax,” Ransom says. Some tips:

- Establish as a lightly seeded solid stand in 3- to 4-foot row spacing, or as strips.

- Set the drill at a “high” seeding rate of 40 to 60 pounds per acre.

- Tape drill spouts shut to obtain desired spacing.

“Flax planted in late July, or early August, followed by winter wheat, should be a viable and profitable option for dealing with land that was too wet to plant this spring,” Ransom says.

Sunflower rust

Sam Markell, NDSU extension plant pathologist, says five out of six fields he has scouted between Minot and Langdon on North Dakota Highway 83 have sunflower rust. The dusty-brown pustules only were found on lower leaves and all but one infestation was light. Markell advises scouting fields.

Research shows that fungicide is economical when disease severity is 1 to 3 percent before the R6 stage. When the disease is severe in the vegetative stages, two applications may be beneficial — the first in early reproductive stages and the second in the bloom, Markell says.

“Folicur and tebuconazole generics, Headline and Quadris are all labeled for rust. When severity is approaching 3 percent, tebuconazole will have an edge over strobilurin products (Headline and Quadris),” Markell says.

Information: Information: www.sunflowernsa.

com/uploads/Markell_Controlling

Rust_10.pdf.

Roundup Ready volunteers

More farmers are seeing volunteer Roundup Ready canola as a weed. It likely is introduced as “a contaminant in dry fertilizer and cover crops or dropping off rail cars on railroads,” says Jeff Stachler, NDSU weed scientist.

It’s important to stamp it out. Most canola plants already are in late reproductive stages, making “immediate removal necessary,” Stachler says.

It’s too late this year to control it in Roundup Ready sugar beets, “leaving hand-removal as the only option,” he says.

In soybeans, Flexstar should suppress additional flowering and potentially reduce seed production.

Information: http://bit.ly/9ItZOP.

Tags: