The key gap in blight vs mildew comes down to what happens to your plant tissue. Blight kills tissue fast and turns it brown or black right away. Mildew grows on living tissue as a visible coating without killing cells at first in most cases you'll see.
I dealt with both diseases in the same summer a few years back in my beds. My tomatoes caught late blight and the leaves turned brown and died in just days. The mildew crept across my squash leaves so slowly that the plants kept making fruit for weeks before it got too bad to ignore.
Blight symptoms show up as dead or dying tissue that changes color fast on your plants. Early blight on tomatoes creates brown spots with rings that look like targets on the leaves. Late blight spreads wet patches that turn black and crispy. Your affected leaves can't come back once blight kills the cells.
Mildew on plants appears as fuzzy or powdery growth sitting on top of your leaf surfaces. Powdery mildew looks like someone dusted your leaves with white powder from a shaker. Downy mildew grows gray or purple fuzz on leaf bottoms. The tissue under it stays alive at first while the fungus feeds on your plant.
This fungal disease comparison matters for how you respond to each problem in your garden. Blighted tissue is dead and won't bounce back no matter what you spray on it. Remove it right away to slow the spread through your beds. Tissue with mildew might still produce if you catch and treat it early enough.
Blight spreads faster and kills your plants quicker than most mildew will ever do. Late blight can destroy a tomato plant in less than a week under wet conditions. Powdery mildew takes weeks or months to harm a strong plant in your garden. Both need your attention but blight demands faster action.
Sprays work better on mildew than blight in most cases you'll face at home. Spraying mildew early can stop it from spreading across your squash or cucumbers. Blight moves so fast that sprays often can't keep up once symptoms appear on your plants. Stopping blight before it starts matters more than trying to cure it.
Weather favors each disease in different ways in your garden beds. Blight loves cool, wet weather that keeps your leaves damp for hours at a time. Powdery mildew does better in warm, dry air with cool nights instead. Knowing which weather favors each helps you watch for trouble at the right times each season.
Look at where damage shows up on your plants for more clues about what you have. Blight often starts at the bottom where soil splashes up on lower leaves. Mildew tends to show up in shaded, crowded spots where air doesn't move well. Both can spread to cover whole plants if you don't catch them early in your beds.
I now remove blighted leaves the moment I spot them and spray mildew when it first appears. This two-track plan works much better than treating both the same way would. Knowing the gap saves me from wasted effort and lost harvests each growing season in my garden beds.
Read the full article: How to Identify Plant Diseases Like a Pro
