"Using worm tea on your plants and soil will help you prevent pests and disease. You should apply your worm tea in the morning or late afternoon for best results."
http://www.pollardwo...e_worm_tea.html
"What is worm castings tea?
Worm castings tea is the liquid plant food that is extracted from worm castings. Worm castings tea is an effective plant watering additive or foliar spray. Worm castings tea, when used as a spray on foliage, replenishes natural microbes that protect plant surfaces from disease. Worm castings tea will help plants grow strong and resist disease. Many commercial orchards and vineyards have found castings tea effective in both curing and preventing plant disease."
http://organicwormbl...om/products.htm
"Regular use of Worm Tea will prevent outbreaks of pests, but when a new plant brings an infestation into the growing area, we increase the concentration to 20:1."
http://www.orchidsam...nstructions.htm
"Worm castings tea, when used as a spray on foliage, replenishes natural microbes that protect plant surfaces from disease. "
It is a wide practice to use it to prevent disease and pests.