Janice LeBoeuf, OMAFRA Vegetable Crop Specialist, Ridgetown
In June, proactive examinations of tomato roots of healthy-looking plants showed that a number of tomato fields were showing root symptoms indicative of corky root, similar to those seen in 2009. Typical symptoms on the roots include a lack of fine feeder roots, a small root system, and brown bands on the roots. The outer layer of affected roots can often be stripped off very easily by pinching them between your thumb and finger. Some roots have stubby, swollen stumps where the end of the root has died off. In severe cases, the entire root systems turns brown and the outer portion of the roots rot off. (photos below)
In the last couple of weeks, above-ground symptoms of vine decline have also become evident in some fields. This shows up as premature yellowing and death of foliage that cannot be explained by the presence of other foliar diseases (photos below). Plants may also be stunted; not reaching the size that you would normally expect. In 2009, above-ground symptoms seemed to come on very suddenly when hot, dry weather hit.
A number of research projects are underway in 2010 to learn more about the vine decline syndrome, the pathogens involved, and how to manage the problem. Experience in other areas shows that there is no easy solution.
For now, the best advice is to focus on the factors that you can control – be on top of your management to minimize other stresses on the crop and maximize potential. Do the best job you can on controlling other diseases and weeds. If you irrigate, monitor soil moisture closely to maintain optimum moisture levels (not too wet or too dry). Avoid piling more costs on a field that is struggling with vine decline – there is no evidence that foliar fertilizers or other in-season treatments will help.
Try to maximize soil quality in your fields in preparation for future tomato crops. You want the crop to build a strong, healthy root system. Soil compaction is a major constraint to this goal. If you start with a restricted root system, you are going to be that much farther behind if root disease sets it. Build soil structure with cover crops or other organic amendments, a good crop rotation, less tillage. Review “Soil Management Tips from Top Tomato Producers” for ideas.