Now that the gardening season is grinding down to a halt after a few hard frosts, it time to look forwards to another year. The summer of 2009 will be remembered for the widespread outbreak of late blight, Phytophora infestans and its devastating effect on the tomato (see The Summer without Tomatoes and companion video on this web site).
Hopefully the summer without tomatoes won’t repeat itself and we will have a summer with tomatoes in 2010. I still haven’t pulled out my unhappy looking plants; they are still trapped in their cages looking very sorry indeed. I will clean up the tomato patch after Halloween and will consider adding leaves that my landscaper friend Tom Martin dumps when he does his fall cleanups.
I’m also going to try to add a few dump truck loads of animal manure, cow or horse and work the leaves and manure into the soil. This combination should help those tomato plants obtain optimal performance next year. I tested the soil this spring, so I know its ph is 6.6 which is perfect for tomatoes. If you have not tested your soil do so this fall.
Soil testing mailers can be purchased through the University of Connecticut Soil Testing Lab, go to www.soiltest.uconn.edu for more information.
How can gardeners prevent late blight from surviving the winter?
Gardeners can take steps now and into the fall to prevent late blight from surviving the winter. As far as most plant pathologist determine at this time, there is only one mating type of Phytophora infestans in the Northeast. Dr. Kim Stoner of the Connecticut Agricultural Experiment Station writes “this is important because it means the pathogen cannot produce oospores able to survive away from living tissue. Because tomatoes don’t have any living tissue that survives the winter, all that needs to be done to infected tomato plants is cut them down and till them under.” Even seeds from the fruit that was infected will not carry the pathogen, so you can still use your own seeds to start next year’s crop.
Most gardeners have harvested potatoes by now. I harvested mine in late August when I noticed that the vines were beginning to exhibit late blight damage. I disposed of any diseased looking tubers and vines. Potatoes are more difficult to deal with than tomatoes because infected tubers can carry the pathogen in to the next spring if the tubers do not freeze or decay during the winter. For example, pathogens will survive if left several inches down in the soil at harvest or in a compost pile that does not fully decompose or freeze. It’s my feeling that it’s best to rid your garden of any infected debris and play it safe. Do not save seed form potato tubers to be planted next spring if you had late blight symptoms this year, the disease will be carried over in next year’s crop.
What can gardeners do next spring?
One step is to grow tomatoes (potatoes also) in well drained soil with good air drainage. Rotate the tomato crop away from the area where tomatoes and potatoes were grown this year. Plant them in another part of the garden. Grow these plants in highest sunlight areas and encourage ways to let more light and air circulation around the plants. Consider ways to improve the above points together with staking or caging tomatoes allowing for more rapid dry off time when plants become wet. Perhaps increase the distance between plants and even the rows all of which will improve air movement and keeping the plants dry.
Diversify the tomatoes you’re growing and use a mixture of cultivars. Plant some early, mid-season and late varieties to insure a good harvest. Consider the same technique with timing, planting some plants around Memorial Day and two to three weeks later. Equally important beside these cultural techniques select disease resistant tomato varieties for some of your tomato crop and use disease free seeds. Some tomato varieties that are being bred for resistance include Mountain Magic, Plum Regal and Legend. These are new varieties to the tomato market. Their availability may be problematic next year, we will have to wait and see.
In summary 2009 was a difficult growing season in Connecticut. Late blight became a major problem for farmers as well as home gardeners in relation to their tomato crops. Long periods of cool wet weather also contributed to the demise of many home gardens. Hopefully 2010 will be much better.