PHYTOTOXICITY INVESTIGATIONS OF MINERAL-OIL AND DIAZNON SPRAYS APPLIED TO KIWIFRUIT IN WINTER SPRING FOR ARMORED SCALE CONTROL

The effect of 1, 2, or 4% mineral oil (Mobil Superior 663 97%) sprays plus technical grade diazinon (24 g a.i./100 litres) applied to kiwifr uit vines at various times from 35 days before to 25 days after budbre ak, was investigated in orchards at Kerikeri, Te Kauwhata, and Motueka , New Zealand. There was no significant effect on budbreak, flowers, f ruit, and yield parameters on treated vines compared with unsprayed vi nes at Te Kauwhata and Motueka. At Kerikeri the 4% mineral oil-diazino n treatment caused phytotoxic damage to 25% of canes from an August ap plication, 3% of canes from a September application, and no damage fro m an October application after budbreak. Damaged canes typically had 2 -5 terminal buds which were dead. No damage was found at the 1 and 2% rates. At Kerikeri fruit numbers and yield of the mineral oil-diazinon treated vines were significantly reduced compared to untreated vines. After adjusting for differences in cane numbers per vine, yield losse s ranged from 13 to 17% for the 1-4% rates.