Neem Oil: Update from Garden Remedies Page
I did use neem oil as anti fungal and for pest control. I think it helped, but you must under take other measures. First, for fungus, especially blackspot on roses the best help is to remove old mulch, debris from plant and any old leaves or twigs from around rose in the spring and replace with completely new, fresh mulch. Also try spraying ground arond roses before mulching after clean up with mycorrhizal fungus. This may help give rose plant a fighting chance against fugus and critters. As for insects, spraying at the right time makes a big difference. If you want to keep squash bugs from killing plants or japanese beetles from eat all of your roses and raspberries spray while eggs are laid in late May early June. The neem oli covers eggs and keeps larvae from hatching. Also, look for adult bugs to catch and kill preventing them from laying eggs. Planting geraniums (pelagorums) seems to help with Japanese beetles.