We had a fantastic turnout on Saturday and we are very thankful to all of the helpers. Everyone worked hard and there were just enough people. All the field tomatoes are out of the field and under a very large plastic tarp! The potato field and the greenhouse tomatoes are much safer now. Saturday was an interesting day of plant disease identification. At first glance all the tomato plants we pulled out looked beautiful and lush, but then, there it was, the slightest hint of the blight blown in from the wind. It was slightly torturous to pull those beautiful plants so early, but we know what the future holds if the infection is left unchecked. We felt that the safest policy for our farm, as well for our impact on other farms and gardens, was to be very pro-active and get rid of the plants before the disease was rampant.
Late blight is usually quite controllable from growing season to growing season if proper precautions are taken. Evangeline and I worked at a farm in 2003 where late blight was rampant in the field tomatoes in the early fall. The field was disgustng and there was an astronomical amount of blight, but the next year was a blight free year. Late blight occurs every year, but typically towards the end of the season. As one Cornell Professor wrote, "It normally occurs sporadically."(Ha Ha very punny). This year with the spread of box store tomato plants in more backyards than ever before the blight has spread in record proportions. Buy local!
What we know at this point is that blight favors 70 degree weather and cloudy conditions (sound familiar?) It can sail in the wind unchecked for miles on a cloudy days. Conversely, if the sun is out, UV rays destroy the spores quickly in midair. This ability to travel very quickly in the air is the main reason that late blight is able to spread so quickly. It does not thrive above 90 degrees (our greenhouse temperatures). It reproduces every 3 to 7 days, producing 100,000 to 300,000 spores with each reproduction. Without a host it dies within two weeks. Overwintering has typically occurred in large cull potato piles from commercial fields. Cornell recommends placing infected garden plants in a plastic bag out in full sun for a week to sterilize the material. Farms like ours are recommended to do the same (but on a larger scale) or till the plants into the soil.
On the bright side, roughly half of our yearly tomato yields come from the greenhouse. So far there is no sign of blight in there, so we'll keep our fingers crossed. Maybe we'll have tomatoes out of the greenhouse for the rest of the season. We caught the blight very early in the potatoes and acted quickly, so hopefully we've preserved most of that crop. Time will tell. And, we've said it before and we'll say if again THANK YOU to all of our members. This kind of crop damage can break a farm (especially in it's start up years) and we are so thankful to all of you for sharing in the risk of farming.
So! We hope that this helps everyone understand late blight a bit more.
Here's some basic recommendations:
1. Eat your potato skins, or put the peelings in the garbage, not the compost.
2. If you are growing potatoes or tomatoes, make sure that you can identify the disease so that you can get rid of the plants if they become infected (to protect other growers). Set aside a pair of garden shoes that you only wear in the garden and wash