Q.Neem Oil as fungicide against white rot?
Can I use Neem Oil as a fungicide against white rot
in my garlic and other types of onion –
if so when/how is best.

Certified GKH Gardening Expert
There is little that can be done to thwart fungus in garlic. Here also are tips for fungal infections in onions:
https://www.gardeningknowhow.com/edible/herbs/garlic/common-garlic-problems.htm
https://www.gardeningknowhow.com/edible/vegetables/onion/treating-onion-fusarium-rot.htm
https://www.gardeningknowhow.com/edible/vegetables/onion/controlling-downy-mildew-on-onions.htm
https://www.gardeningknowhow.com/edible/vegetables/onion/managing-mushy-rot-in-onions.htm