Studies on the efficacy of a new formulation of Uniconazole-P

Uniconazole-P is used in ‘Hass’ avocado production to stop vegetative shoot growth at the apex of indeterminate floral shoots to increase fruit set and yield and after pruning to maintain tree size, especially in high-density plantings. Uniconazole-P has the potential to reduce pruning costs, but also to reduce fruit size and increase fruit drop. Depending on crop load, reducing vegetative shoot growth in spring or summer could mitigate or initiate alternate bearing. In order to be approved by the California Department of Pesticide Registration (DPR), a new formulation of Uniconazole-P, which did not contain the restricted component, was developed for use in California. The objectives were to determine the effectiveness of the new formulation of Uniconazole-P applied at the suggested rate for Sunny in spring, summer, fall or winter to stop the growth of vegetative shoots at different stages of development (type 1 – shoots with zero to less than 6 mm of new growth, type 2 – shoots with 25 mm of new growth, and type 3 – shoots with advanced growth and red expanding leaves at the time of treatment) and to determine its effects on yield, including fruit size.