I found a bunch of my leaves look like this picture. These plants are pretty close to harvest, like 2-3 weeks. Does that white powder look like mold? Whats the best way to prevent that, and will it kill other plants?
This is an outdoor grow btw.
That goes by the name of powdery white mildew. It is a problem. There are many threads on the topic so you should look some up for more info.
If it isn’t too bad and only effects a small area, the normal treatment is a regular spraying of diluted hydrogen peroxide. If the problem is bad you will be tempted to use a higher concentration of hydrogen peroxide, but it can burn the pistils and kill off the buds.
If it is only on one plant you should isolate it from others, but treat all of them with a hydrogen peroxide spray. Cut off as much as you can. Increasing circulation will reduce chance of it happening in the future.
There are some sprays that you can buy specifically for pwm, but you’ll have trouble finding something that you can use this close to harvest.