Q.Radish
The radishes I planted some 4 weeks ago has something that is eating the tops of the bulbs. Can you please enlighten me?

Certified GKH Gardening Expert
If the damage is to the roots (bulb) themselves, this article may find helpful: https://www.gardeningknowhow.com/edible/vegetables/cabbage/control-cabbage-maggot.htm
As for foliage damage, there are several kinds of caterpillars that feed on the leaf tops. The standard treatment for almost any caterpillar is Bacillus thuringiensis, also known as Bt. You can also try neem oil. This is usually effective on those kinds of pests, as well as many others.