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ISSUE 16  August 22, 2002



The National Sunflower Association and North Dakota State University are hosting a sunflower field day on September 5 at the NDSU Carrington Research Extension Center. Sunflower growers, industry representatives, crop consultants, and other interested persons are invited to attend the event to receive updates on sunflower production research and recommendations. The event begins at 9:30 a.m. with registration and refreshments. Field tours begin at 10 a.m. and conclude at noon with a sponsored meal.

Tour participants will be able to view and/or hear discussion about new sunflower hybrids, sunflower hybrid tolerance to sclerotinia trial, weed management strategies with herbicide-tolerant sunflower, insect management, and sunflower industry update.

Additional information about the event can be obtained by contacting the Carrington Center - telephone: 701-652-2951, website:


or the National Sunflower Association - telephone: 701.328.5100, website:


Greg Endres
Area Extension Specialist/Cropping Systems
NDSU Carrington Research Extension Center



A killing frost is a temperature which kills the plant tissue. If you have frost (low temperature) damage it is the result of tissue death.

Critical stages and temperatures for various major crops are described as follows:

Wheat, durum and other small grains:

Temperatures below 32EF will cause sterile spikelets if the plant is in the late boot through the flowering stage. In the milk stage it will create shriveled kernels. Frozen immature spikes will turn white. After mid-dough stage, temperatures as low as 25EF will result in bran damage, some kernel shriveling and possible germination reduction. The bran damage will change test weight and probably will be discounted in the market. Grain may be saved for conditioning for seed and should be tested for germination and seed vigor.


Most susceptible during flowering and early boll stage. Immature seeds can be killed by temperatures of 28-32EF. After flax reaches dough stage it is more resistant to frost.


Most susceptible at bud and flowering stage. Temperatures of 28E and 30EF can result in damaged buds and sterile sections or rings in the flowering head. After pollination and petal drop sunflower can withstand temperatures as low as 25EF with only minor damage. Twenty-five degree temperatures at the bud stage will often damage leaf and stalk below the bud and seeds will not develop.


Easily damaged by light frosts in 28E- 32EF range. Beans that are still green and soft will shrivel. Stems rapidly turn dark green to brown and will not recover. Beans in pods that have turned yellow will mature normally. Some beans will turn yellow after 30-40 days of storage.

Pinto and navy beans:

Very sensitive to frost (30-32EF range). Earlier pods with yellow to brown color are sufficiently mature to escape damage. Late green pods or flowers are easily damaged by frost. Green beans will shrivel but should be left in field until dry in order to separate from mature beans.


Usually damaged by temperatures in the 28EF range or less. Corn is usually physiologically mature 50-55 days after the 50% silking date. Colder temperatures will kill entire stalk. If only leaves above ear are frosted kernel development will continue. If entire stalk and leaves are frozen kernel filling will cease and soft shriveled corn will result. If corn is at around 35 percent moisture or if black layer has formed at base of kernel the plant is physiologically mature and kernels will develop normally despite frost. Frosted immature corn is best used for silage or fodder.

Duane R. Berglund
NDSU Extension Agronomist



Farmers who have cattail choked sloughs that harbor blackbirds in the fall have a golden opportunity to get those cattails sprayed by USDA’s Wildlife Services. Some sloughs that had previously been signed up for spraying have been tilled under due to the dry conditions. That leaves an opportunity for more acres to be sprayed this August. Farmers with cattail sloughs of approximately 10 acres or more in standing water need to call 701-250-4405 in ND and 605-224-8692 in SD. Land descriptions are required.

Source: Natural Sunflower Association Newsletter 7/26/02

Duane R. Berglund
NDSU Extension Agronomist



Birdshield is a new product labeled for blackbird control in sunflower and corn in North Dakota. The active ingredient is a concentrate formulated from food grade products. The label recommendations are as follows for corn and sunflower.

Corn: Apply at a rate of one pint per acre by aerial application. Begin application 10 days before the crop begins to ripen or birds begin feeding. Reapply at 5 day intervals until harvest. Harvest 5 days after last application.

Sunflower: Apply at a rate of one pint per acre by aerial application. Begin application when birds begin feeding on the crop. Repeat as necessary to keep repellency. Harvest 7 days after last treatment.

The cost is $6 to $7 per acre plus application costs. More information at:


Duane R. Berglund
NDSU Extension Agronomist

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