John farms 2,500 acres of mixed grains and oilseeds, including wheat, oats, canola, and flax, in addition to the odd season growing clovers and specialty crops, such as borage and hemp.

It was mid-June when John contacted me about one of his canola fields. He was convinced the Group 10 herbicide he’d applied to his herbicide-tolerant canola had damaged his crop.

“The crop looks almost burnt,” he said. “I think it’s surfactant damage with the way the leaves are drying up.”

The plants in some areas of the field were severely wilted, with the headlands and regions nearest the river being the worst hit, he said.

On June 15, I arrived at John’s farm, which is located near Carrot River, Sask., around midday, thus giving the crop a chance to perk up, as we had been experiencing cooler temperatures at night. Temperatures during the day were in the mid-teens to the low 20s.

There was an observable difference in the plants’ development in some areas of the field, which was set back, especially on the headlands and riverbed regions. In addition, the plants’ leaves were cupping, however no purpling or discolouration was observed, which would have led me to believe we were dealing with either a residual chemical, or possibly a sulphur or other nutrient deficiency.

John thought the Group 10 herbicide he applied had damaged the herbicide-tolerant canola crop somehow. After determining his spray rates and water volumes were correct, and following an explanation of how glufosinate-ammonium (the Group 10 herbicide) works with the herbicide-tolerant canola variety, John and I agreed it was unlikely the herbicide had injured the plants.

We decided to meet up again in two days to give the crop time to pop back, just in case the symptoms were directly related to the -5 C frost the area received May 29. During that time, John could check his spray records to determine if he’d sprayed any residual herbicides on the field in question.

Two days later, there was a dramatic change to the plants’ appearance and development in the affected areas. Not only did their development continue to be set back, the injured plants had severe cupping and purpling. It was now obvious the crop had been damaged by a residual herbicide.

At this point, we examined John’s spray records. Everything was in order — the correct water volumes and herbicide rates (Group 10 and Group 1) had been used, the field was sprayed under blue skies during the heat of the day at a temperature of 19 C, with relative humidity at 31 per cent.

However, John had sprayed a quarter section of peas the previous day with a herbicide containing Groups 1 and 2 to control broadleaf and grassy weeds in that crop. Were we dealing with Group 2 residue damage? It now looked like that was a good possibility. This incident may have happened as a result of a tank cleanout issue.

John’s spray unit includes a polyethylene sprayer tank. We reviewed John’s entire rinse procedure, and it was impeccable. His cleanout method included several rinses of the tank, booms and filters using a spray tank detergent/decontaminator, which neutralizes and solubilizes certain herbicides, and ammonia, which helps raise the pH of the cleaning solution, aiding the dissolution of herbicides. It was evident he understood tank residues.

How was it possible we were observing residual herbicide damage with John’s cleanout regime?

Crop Advisor’s Solution: Rigorous tank cleanout reduces risk of residue injury

John’s spray records indicated he’d sprayed the herbicide-tolerant canola with a Group 10 herbicide at the correct rates. However, when examining all spray records, we noticed John had sprayed a quarter section of peas with a herbicide containing Groups 1 and 2 the day before spraying this canola field.

Despite John’s correct tank cleanout procedures, the symptoms of the injured canola pointed to residual herbicide damage. I’ve come across numerous Group 2 residual damage incidents in the past, which were easily diagnosed as improper cleanout methods due to hasty rinse procedures, or lack of knowledge of the proper steps.

Yet, in some cases, like John’s, the producer understood and implemented correct cleanout methods. These cases were less straightforward; however, after consulting sprayer manufacturers, chemical reps and other producers, I realized it wasn’t the growers’ cleanout procedures at fault, but simply how well the cleaners were working in removing any residual herbicide etched into the polyethylene tank walls.

Many growers have shared with me the different ways they have tackled this issue. The only clear fact is there
is no single solution, but using strong detergents with adequate concentrations of ammonia, in addition to more rigorous tank and boom cleanout is key when dealing with Group 2 or 4 residual damage issues. Your crop advisor or agronomic consultant will also have some good suggestions to eliminate the risk of residual herbicides damaging your crops.

As bad as the injured areas of the canola crop looked throughout all growing stages that summer, John was pleased to inform me that his yield loss was minimal — only six to eight bushels per acre — at harvest.

Mike Wassill works for Richardson Pioneer in Crooked River, Sask.

The post Crop Advisor’s Casebook: The residual riddle appeared first on Grainews.

The pea field had been seeded the second week of May. Allan called me in mid-June, just before staging of early bloom. The peas in the lush green sections were all starting to show early blooms, while those in the pale green areas were not.

Allan told me he initially thought the problem could be a result of higher-than-usual spring rainfall. “It seems like the field is going backwards. Could it be caused by moisture?” he asked. “If so, why not the whole field instead of only certain areas? It’s starting to show up on some of the higher spots in the field as well, where the moisture isn’t as significant.”

When I drove out to Allan’s farm and had my first look at the pea crop, the first thing I noticed was that the field had a great stand and there were lots of plants. However, the difference in crop colour and development was stark. Pea plants in the pale green areas were small and struggling compared to the larger, healthier-looking plants in the lush green areas.

Upon closer inspection, there didn’t appear to be any aphid damage, a problem that can sometimes affect peas at an early bloom stage. When I asked about the fertility package for the field, Allan informed me he typically uses little fertilizer on his peas and that only 20 pounds of 11-52 product per acre had been placed with seed row.

The only chemical applied to the field up to this point was a common herbicide package called Odyssey DLX, which had been utilized before the sixth node stage. Allan told me the field’s prior crop had been Roundup Ready canola, and that the only chemical sprayed in the previous year was glyphosate.

As I was leaving the field, I made sure to collect some plant samples from both the pale green and lush green areas so that I could compare the roots and plant structure of the peas. A close look at these samples provided some telling clues as to the source of the problem.

Crop Advisor’s Solution: Root rot

Back in late spring, I got a call from Allan concerning a crop of field peas at his 2,000-acre mixed grain farm near Aylsham, Sask. Some troubling patterns were showing up in the crop, with pale green areas containing small, struggling plants appearing in stark contrast to larger, healthier-looking peas in lush green parts of the field.

Allan called me in mid-June, just before staging of early bloom. He said the peas in the lush green areas were all starting to show early blooms, while those in the pale green areas were not.

When I arrived at the farm, Allan told me he initially thought the reason plants in affected areas were not progressing was because of higher-than-usual spring rainfall. However, that did not explain why the problem appeared in only certain areas of the field, or why it was also showing up in higher areas of the field as well.

The answers to my questions about Allan’s fertility package and herbicide treatment for the crop didn’t sound any alarm bells, and the plants (pale or not) didn’t seem to be displaying any chemical damage either. I began to suspect that the answer lay with something in the soil or plant roots that was affecting nutrient uptake — which was confirmed upon closer inspection of plant samples from both the pale green and lush green areas of the field.

When I washed the soil off the roots of the plant samples in a testing pail, it was clear by the state of the healthy nodules and white roots of the unaffected plants that they were getting adequate nutrients. In contrast, the roots of affected plants were brown and shriveled and contained very few nodules.

The roots were obviously being affected by some sort of disease, either in the stem or soil-borne. Upon review and consultation with Richardson Pioneer agronomist, Dean McDermott, it was determined that root rot caused by a fungal infection was to blame.

This disease group included the pythium and fusarium species as well as rhizoctonia. The clear line between infected and healthy plants in irregular patches in the field indicated that soil-borne fungi was at work, which was confirmed when the plants were rinsed off with water.

I informed Allan that warm, moist weather conditions in the spring had allowed the disease to become active and infect the pea roots. Unfortunately, at this stage of crop growth, there was no effective treatment for limiting the spread of the disease and its damage. The only advice I could give Allan was to rotate away from peas for at least four years, and hope for a drier cycle of environmental conditions.

The post Crop Advisor’s Casebook: Puzzling patterns in a pea field appeared first on Grainews.