You can use Neem oil and Pyrethrin. Both are effective and safe.
Hi Mate –
Grapes are susceptible to a large number of insect and disease pests. Select disease-tolerant cultivars when possible and utilize good sanitation practices. Monitor vines closely and if problems occur, treat early with organic pest solutions. For Japanese Beetles we recommend the following:
In the early morning or late evening, shake beetles from plants onto ground sheets and destroy.
Place pheromone traps around the perimeter of your property as adults emerge (May-July).
Spread beneficial nematodes on lawns or mulch around plants to kill immature stages. These microscopic, worm-like parasites actively hunt, penetrate and destroy grubs in the soil.
Milky Spore (Bacillus popilliae) is a naturally occurring host specific bacterium that attacks the destructive white grubs in turf. Apply 10 oz per 2,500 sq ft anytime of year when the ground is NOT frozen.
Surround WP (kaolin clay) forms a protective barrier film, which acts as a broad spectrum crop protectant for preventing damage from a large number of insect pests.
AzaMax contains azadirachtin, the key insecticidal ingredient found in neem oil. This concentrated spray is approved for organic use and offers multiple modes of action, making it virtually impossible for insect resistance to develop. Best of all, it’s non-toxic to honey bees and many other beneficial insects.
Safer® Grub Killer is an organic ready-to-use spray that is very effective against the larval stages of this pest. Easy to use, just attach the bottle to your garden hose and treat problem areas. Covers approximately 2000-4000 square feet and continues working for up to 7 days.
Hope it helps