EFFECTS OF COMBINED APPLICATIONS OF AMMONIUM THIOSULFATE AND FUNGICIDES ON FRUIT LOAD AND BLOSSOM BLIGHT AND THEIR PHYTOTOXICITY TO PEACH-TREES

Timing of bloom sprays of ammonium thiosulphate (ATS) for foliar ferti lization and fruit thinning, and of fungicides for disease control, is critical in peach production. Initial observations in commercial orch ards indicated that ATS and fungicides, when applied as tank mixes, co uld cause burn of blossoms and shoots, but not when applied separately . Nine fungicides, alone and in combination with ATS, were evaluated o n single tree plots in 1993 and five representative treatments were re peated in 1994 under commercial orchard conditions. Treatments were ap plied by hand-gun from a 100 litre sprayer in 1993 and by air-blast sp rayer in 1994. In 1993, fruit number per tree was affected only by ATS and the numbers of blossom blight cankers per tree only by fungicide, with no interaction between ATS and fungicides. There were however so me ATS x fungicide interaction regarding phytotoxicity to blossom and one-year old shoots, but the damage to the latter was slight. In 1994 blossom blight did not occur and there was no evidence of phytotoxicit y to shoots or blossoms. Fruit number was not affected by any treatmen t.