Overcoming dormancy of pecan trees in mild winter conditions

This study aimed to determine chill accumulation to overcome endodormancy of pecan trees using the biological method. Cuttings of isolated nodes in different months and their exposure to natural chill under field conditions were used. The experiment was carried out using seven pecan cultivars: Barton, Mohawk, Jackson, Success, Desirable, Farley and Melhorada (Pitol 1), planted in orchards in the municipality of Canguçu, Rio Grande do Sul, Brazil. Every 30 days from June onwards, when 50% of leaves had fallen from trees (phenological stage 95), 20 cuttings per cultivar were collected in each period untill September. They were sterilized and sent to the phytotron for budbreak monitoring. Budbreak average time, time to reach 50% of budbreak and the final budbreak rate were evaluated. Average budbreak time of cultivars showed little variation along collection period. Chill requirement of pecan cultivars ranged from 51 to 369 chill hours (below 7.2 °C) to reach DD50. It was not possible to determine the chill requirement of the studied cultivars. The moment of cutting collection had little influence on average budbreak time and final budbreak rate.