Potassium Deficiency in Soybeans

I have been out looking at some soybean fields and have started to see some potassium deficiency in some fields. Every year I see some fields with potassium deficiency in our sandy soils in the south. It is not uncommon to see in double crop beans where the straw is baled. Potassium deficiency is seen as yellowing or browning and sometimes necrosis along the edges of older leaves. As the deficiency becomes more severe the symptoms move higher up the plant. Below is a picture of potasium deficiency in soybean. Potassium deficiency should not be confused with manganese deficiency. With manganese deficiency the veins of the leaves remain green.

Bill Bamka

Leaf Hoppers

We are starting to see continued increases in leaf hopper populations in alfalfa fields. Also while scouting soybean fields I was also finding leaf hoppers. Keep an eye on alfalfa fields as the nymphs can cause damage pretty quickly. Once you start to see yellowing or "burn", yield has already been reduced. The threshold for 4-6 inch tall alfalfa is 50 leaf hoppers per 100 sweeps. Soybeans in the seedling stage are most susceptible to injury. If you see plant damage and average 8 leaf hopper per sweep, control may be necessary.

Bill Bamka

European Corn Borer

I was called to look at some field corn in Burlington County because of insect damage. The damage was due to some significant populations of european corn borer larvae. This is not suprising given that the RCE Vegetable IPM program was reporting very high populations of adult moths in black light traps earlier this spring. Those of us in field crops tend to forget about ECB because of Bt hybrids. Remember though we can still treat for ECB in the required non-Bt refuges and non-Bt planted fields. Rescue treatments are not that effective when the larvae are deep in the whorl or in the stalk. Information on scouting and treatments for ECB can be found in the Mid-Atlantic Pest Management Recommendations for Field Crops. Keep in mind that ECB can also attack sweet corn and peppers.

Bill Bamka

Mid-Atlantic Regional Agronomist Quarterly Newsletter June 2011

Dr. Richard W. Taylor's Mid-Atlantic Regional Agronomist Quarterly Newsletter is available for download. 

Please note in the calendar of events that a number of meetings are coming up both this week and next week so check the calendar over carefully. Also feel free to forward the newsletter on to anyone else you think might be interested in the information. - R. Taylor

To subscribe, send request to: rtaylor@udel.edu

Rabin

Manganese deficiency in soybeans

Over the past few days I have begun to notice manganese deficiency appearing in some of our earlier planted soybean fields. As many of us know manganese deficiency on soybean can be a common and recurring deficiency on our sandy soils in the southern portion of the state. Deficiency results in reduced leaf chlorophyll content. The common symptom in soybeans is interveinal chlorosis (the tissue between the veins turns yellow while the veins remain green). Manganese deficiency can result in reduced yields. Extensive research by our extension soil fertility specialist Dr. Joe Heckman has shown an economic benefit of applying foliar applications of manganese fertilizer to soybeans deficient in manganese. More information is available on manganese deficiency in the RCE publication Soil Fertility Recommendations for Soybeans.

This photo shows a soybean plant with typical symptoms of manganese deficiency.


Bill Bamka