Phenological Behavior of Guava Trees (Psidium guajava']java L.) under Different Climatic Conditions of Mexico

Guava (Psidium guajava L.) is an important fruit crop in Mexico. There are around 23 thousand hectares producing 300 thousand tons per year. Given the topographic conditions under which guava trees are grown, it is possible to find guava orchards in a wide altitudinal range. Altitude has an important influence on their phenological behavior, mainly due to temperature differences. The objective of the present work was to study the phenological development of guava trees and their relationships with ambient temperature at three locations of Mexico having different climatic conditions. The present study was carried out during the growth cycle of 2011. Guava trees were established previously at the following locations: 1) Santiago, Ixcuintla, Nayarit (hot-sub humid); 2) Huanusco, Zacatecas (semi hot-semi dry) and 3) Temascaltepec, Mexico (temperate to semi cool-sub humid). Annual mean temperature fluctuates from 25 to 18 degrees C at the hottest and coolest sites, respectively. Phenological development of guava trees was greatly influenced by temperature conditions (elevation) at each location. Duration from pruning to flowering (P-F) ranged from 60 to 115 days, whereas the period from flowering to beginning of harvest (F-BH) varied from 100 to 180 days at Santiago Ixcuintla and Temascaltepec, respectively. Phenology of guava trees at Huanusco was intermediate between the other two locations. Although a great variation on the number of days for the phenological development among locations was observed, accumulated heat units were similar for all sites. Guava trees require about 800 to 850 and from 1,950 to 2,000 heat units for stages P-F and F-BH, respectively. Heat units were calculated using the residual method with a threshold temperature of 9.0 degrees C. Thus, phenological development of guava could be predicted more accurately using heat units accumulation rather than counting calendar days.