Field Evaluations of Some New Avocado Rootstocks

In the last five years, we have increased this important field phase of our resistant rootstock program. Previously, clonal rootstocks were grown at our greenhouses at the university; but due to physical restraints (greenhouse facilities and personnel), the numbers of trees produced were relatively small. In 1984, we began to establish large plantings of rootstocks grafted with the Hass variety. With the assistance of Brokaw Nursery, we were able, during a single planting season, to plant approximately 2100 trees with 13 different grower cooperators located in the majority of the avocado growing counties. All of these trees were planted in commercial situations where root rot was present. The majority of the plantings were treated with Ridomil, at label rates, while a few were left untreated. A large number of the smaller plantings suffered from inadequate cultural care, so unfortunately did not yield any useful data. There were, however, two very successful plantings, including one very large planting; and we have chosen to present the preliminary data that they have provided.