Organic Treatment for Blight

Thanks to the Landreth Seed Co. for the following info:

This is a ‘heads-up’. It is not meant to alarm or frighten. The intent is to educate and inform.

During the 2012 gardening season, blight is going to be a problem. Early season, mid season and late season blight are going to be a problem for tomatoes and potatoes and possibly eggplants. The moisture that inundated the United States east coast with Hurricane Irene and tropical storm Lee and the extraordinarily mild winter have combined to create an unusually comfortable environment for the proliferation of blight spores.

Blight is a fungus transmitted by spores which can lay dormant in soil and be carried by the wind as much as 50 miles in a day. Under ideal conditions spores can germinate in ½ hour. The last great outbreak was in 2009, but 2012 may also be a record year.

For those of you who intend to grow tomato, potato or eggplant plants, you MUST take precautions early even if you are organic gardeners. Landreth suggests that you use copper fungicide, a fungicide approved for organic farming. Use the powder form of copper fungicide. Copper fungicide is sold at most garden centers. Dust the soil where you are going to plant your tomatoes, potatoes and eggplants and till the dust into the soil. On the day you plant your seedlings, dust the seedlings, and repeat this dusting every two weeks, for two more dustings.

If you observe signs of blight later in the season, (a spotting of the lower leaves and stems), dust the plants immediately and repeat the dusting in 5-7 days. Copper fungicide is very effective. If you follow the suggested protocols your plants will probably be okay. If you do nothing, or if you wait until late July or August to address this issue, you may lose your entire potato, tomato or eggplant crop.

Unfortunately, we did not know to take the above precautionary measures at the beginning of our gardening season, but it now appears that we may have late blight hitting our potatoes.  A few of the plant stems have rotted and collapsed, so we removed them from the garden and destroyed them.  We then dug to see what, if any, potatoes may have been formed on the diseased plants.  Our gold potato plant yielded only two small (1-2") tubors, while our red potato plant yielded a few small tubors, and eight very small (less than 1") tubors.  Many of the remaining plants are showing signs of blight -- brown spots on their leaves, and major wilting, so we will begin dusting with copper dust fungicide.

Photo of Late Blight on Potato:  plantdiagnostics.umd.edu/_media/client/diagnostics/fullsize/late_blight_potato_l.jpg

For more info on Late Blight:  www.ag.ndsu.edu/extplantpath/plant-pest-alerts/potato-tomato-late-blight-start-monitoring-early

For info on using copper dust to control early or late blight, or other plant diseases, go to www.bonide.com/lbonide/backlabels/l771.pdf

You may find the Landreth Seed Co. at:  www.landrethseeds.com/