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Soybean tissue sampling and corn disease watch are the key activities now

TAGS: Extension
Soybean tissue sampling and corn disease watch are the key activities now
Scout's Report 2015: Soybean tissue sample collection and the concern of Northern Corn Leaf Blight and Gray Leaf Spot in corn are hot topics.

With the next round of treatments for soybeans happening soon, tissue samples are critical to ensure the plant is getting what it needs, and applying nutrients that will benefit the crop. For soybeans, the best time to sample is when the first flowers open, or just before that happens. As long as the sample is taken before the first pod fills, the sample will be valid.

Scout's Report 7/15: Disease threatens corn in Indiana, while brace roots face trouble

Dark skies and humidity mean disease risk: Too much rain, plenty of inoculum, too much humidity and moderate temperatures could make a perfect storm for corn diseases. This is the time to watch them carefully, Kettler says.

The sample needs to be taken from the most recent fully developed trifoliate leaf at the top of the plant. Do not use a trifoliate that is not fully developed. For the best answer of how to treat the entire field, take between 30 and 50 samples from different areas of the field.

To get a sample from a plant, select the correct trifoliate and carefully pinch off the most fully developed leaf. Do not include the petiole. Place the sample in a paper bag labeled with which sample it is. The samples should be put in a paper bag for transport, plastic will hold moisture and can cause mold or skew results of tissue samples. Leave the bag open to allow air drying, this will usually take between 24-48 hours. Then close the bag and mail or deliver the sample.

The results from a lab will indicate levels of nutrients in the plant. Typical values tested are N, P, K, Ca, B, Mg, Mn, Cu, Mo and Zn. Values lower than the critical value indicate a lack of that particular nutrient. Soybeans will sometimes respond to fertilizer at the point after the flowers have opened. However, results may be more useful for management practices for next season.

High values are usually not going to harm the crop but should be noted as an unusual condition in the area that sample was taken. High values could indicate that there was not enough tissue to dilute the nutrient that was taken up by the roots.

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Disease threat intensifies
The continued rain and moderate temperatures are enabling the spread of northern corn leaf blight and gray leaf spot.

Continue scouting for the progress of the diseases and consider all factors when making a management decision. These factors may include price of inputs thus far, price of grain at market, yield potential, projected losses and other yield factors.

Purdue University Extension has information available to assist in projecting yield and making management decisions.

Scout's Report 7/9: Diseases making an appearance in Indiana

The traps throughout north central Indiana have shown the next wave of European corn borer moth flight action. I have found eight moths this week and expect those to be laying egg masses soon for the next generation to attack the fields.

Japanese beetles have also made an appearance in corn as well as in the traps. Check Purdue Entomology and Agronomy updates for more information.

Kettler is a Purdue University agronomy student. She is an intern For Beck's Hybrids as a crop scout this summer, working with Ben Grimme, Kris Johnson and Denny Cobb. Thanks to Beck's for making her scouting reports available weekly. She writes from Atlanta.

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