By Jonathan Mitschele
In late July 2017 I discovered that my potato plants were not doing well. Leaves were yellowing and the plants were not growing as expected. Suspecting some sort of blight, I sent photos to Eric Sideman at MOFGA. He thought the problem was potato leafhoppers and referred me to a MOFGA pest report. Potato leafhoppers (PLH) are tiny buggers that suck juices from the host plant and inject a toxin that clogs the vascular system of the plant and kills it. The only insecticide approved for organic production is pyrethrum, but you must treat before you see the symptoms; once symptoms appear, it is too late. For me last year, it was too late. Looking at my potato plants very carefully, I could see that Eric was right. The little beasties were there!
Last year was my first encounter with PLH in more than 30 years of gardening, but suspecting it was not my last, I decided this year to protect my potatoes from PLH with floating row covers. I guessed that row covers would also be effective against Colorado potato beetles, an annual problem for me. With potato beetles in mind, I also planted in late June, a few weeks later than in past years, to avoid the early summer rush of those pests.
I plant potatoes in 50-foot-long shallow furrows that I make with a triangular hoe. I spread compost in the furrows, then place seed potatoes a foot apart on top of the compost, cover with more compost, and pull enough soil over each furrow to cover all. When each furrow is complete, I lay out a soaker hose along its length, securing it with ground staples.
When the first leaves appeared above ground, I spread lightweight row cover over each furrow, securing the fabric with ground staples. To hill furrows, I removed staples from one side and pulled the fabric aside, then replaced the row cover when I was done. I hilled each furrow twice, first when plants were 6 inches high and again when they had grown another 6 inches. I left the row covers on until the plants bloomed, by which time they needed more room than the row covers allowed. During dry spells in the growing season, I watered each row for two to four hours weekly, using a water timer.
When I removed the row covers, I saw no evidence of PLH or potato beetles. Plants were healthy and happy and remained so. Eventually potato beetles, but not PLH, did appear, but they never caused significant damage.
I planted about 45 pounds of seed potatoes; my harvest totaled about 350 pounds, and the potatoes were scab free – my best crop ever by far! Row covers are not cheap, but with care they can be reused for two or more years, so I think they are a worthwhile investment.