Q.Leather Jackets
My grass has died off over the winter. My neighbor has told me that I have leatherjackets in the soil, confirmed by digging up patches and fishing them wriggling about. Now, I have been looking at nemasys leatherjacket killer. It says that the leatherjackets start to pupate in May and June, so is there any point in treating them now? Can I go ahead and reseed/turf the garden and then treat it in August/September when they begin to hatch again? I need some grass!!!

Here is a link that will help you.
https://www.gardeningknowhow.com/plant-problems/pests/insects/crane-flies-and-lawn-damage.htm