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Crop Advisor’s Casebook – for Jan. 24, 2011

In August of 2009, Ted, an experienced farmer who farms 3,700 acres of wheat and canola near Olds, Alta., presented me with a complex problem that required all of my diagnostic skills. Concerned that the pods on his canola plants — a glyphosate-tolerant variety located in one of his fields — were not forming properly, he called me at the beginning of the month. “I think there may be a problem with this variety,” he told me, because the other varieties of canola he planted were doing fine. According to Ted, the plants had flowered but the pods had not formed on the main stems or branches. Also, he thought the crop was flowering longer than neighbouring crops, thus delaying its maturity. “I don’t think this crop will be worth harvesting,” said Ted. He told me he was thinking about getting a neighbour to silage it!

Very concerned for Ted’s crop, I visited his farm to have a look for myself at the problem field.

The main stems and branch racemes of the canola plants certainly lacked the number of pods a healthy stand would produce. A few pods had formed at the bottom of the racemes, however, in the middle most of the pods were aborted, and the top of the plant was flowering. Overall, Ted’s crop was much further behind in maturity when compared to neighbouring crops.

Upon closer inspection of the canola plants, I noticed the bottom 20 per cent of the raceme had formed small underdeveloped pods, the pods on the

Kent Clifford is a crop input manager at Richardson Pioneer Ltd. in Olds, Alta.

next 55 per cent of the raceme had been aborted, and the top 25 per cent had flower buds and was beginning to flower. This abnormality was observed uniformly across the field. The plants did not appear affected in any other way — leaves, shoots and roots all appeared to be normal. Heavier residual straw in Ted’s field was the only other difference between his and other surrounding fields of canola.

The first factor to rule out when considering Ted’s immature pods was variety. We checked with neighbouring farmers to see how the canola stands of the same variety and seed lot had faired that season. Those canola crops were developing normally and did not exhibit any of the same symptoms as Ted’s canola plants. This confirmed that the variety or seed lot was not the problem after all.

THE MYSTERY OF UNDERDEVELOPED AND ABORTED CANOLA PODS

Next, I checked Ted’s fertilizer rate. Sulphur and boron deficiencies have been linked to flower blasting in canola, but the 120-35-0-20 blend Ted applied was certainly sufficient. Also, soil test and tissue samples did not indicate any nutrient deficiencies.

The plants did not exhibit symptoms of disease or pest pressure. We monitored for lygus bugs because they can be responsible for flower blasting (by feeding on the flower clusters). The numbers we found were too low to be responsible for the damage in Ted’s field, and the damage was much too uniform for lygus bug feeding.

Ted had sprayed herbicide at the 10 to 15 per cent flower stage. Beyond that, we could cross herbicide residue in the soil or tank off the list of factors causing Ted’s pod abortion — a soil bioassay revealed residue was not an issue and Ted’s records indicated herbicide contamination in the tank was not responsible.

The last factor to take into consideration was weather. With the exception of some high temperatures at the end of July, the weather was normal and neighbouring fields were producing healthy stands of canola.

It was only when considering all of these factors together that I started to form a theory about what happened to Ted’s canola.

WhyareTed’scanolapodsnotformingproperly? SendyourdiagnosistoGRAINEWS,Box9800, Winnipeg,MB,R3C3K7;email [email protected] orfax204-944-5416c/oCropAdvisor’s CasebookJanuary24.Bestsuggestionswillbe pooledandonewinnerwillbedrawnforachance towinaGRAINEWScapandaone-yearsubscription tothemagazine.Thebestanswer,alongwith thereasoningwhichsolvedthemystery,will appearinthenextCropAdvisor’sSolutionFile.

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