1. Can I do something to avoid the tomato blight (early and/or late season) and what should I do if my tomatoes (or potatoes) are infected?
For tomatoes, try growing blight resistant varieties and space plants 30" to 36" apart for good air circulation. Destroy infected plants ASAP to limit spread of the disease which needs living tissue to survive - plants should go into trash bags and taken to a land fill - not the compost pile. Organic treatment requires that a copper fungicide be applied before the disease appears and every 5-7 days in persistent wet weather.
Each year, plant breeders come out with varieties that are more resilient to blight. Of the varieties we grow, we recommend Juliet and San Marzano Gigante III. They both seem to have naturally occuring resistance to the disease.
For potatoes, try planting potatoes in hills, rather than trenches for better air flow around foliage, and cut off infected leaves on a hot, dry day before the blight moves to the stem. Wait 2 or 3 weeks to dig tubers to reduce the chance for spores in the soil from infected foliage and in potentially nicked tubers. Also, make sure that you are buying potato seed that is certified disease free and comes from a reputable source.
Thanks to Ann Hazelrigg, Plant Pathologist, UVM Extension, above adapted from "2011- Late Blight Reappears in Vermont".
Websites: www.hort.cornell.edu/lateblight for disease ID and webinar. www.uvm.edu/mastergardener to submit samples for LB confirmation www.nevegetabl.org for info on fungicides labeled for late blight control