Pollen dispensers (inserts) increase fruit set and yield in almonds under some commercial conditions
A Dag; S A Weinbaum; R W Thorp; D Eisikowitch
Most commercial almond cultivars are selfincompatible and flowering occurs in early spring when weather conditions are often unfavourable for pollinator flight. Thus, inadequate cross-pollination frequently limits almond yield. We evaluated the effect of pollen dispensers (inserts), fixed onto honey bee hives, on almond fruit set and yield in orchards differing in planting design, i.e. varying in the arrangement and proximity of the main cultivar and pollinizers. Pollen dispensers did not increase fruit-set percentage and yield in the 1 : 1 : 1 planting design in which (a), pollinizer rows were planted on either side of the main cultivar rows; and (b), bloom overlap was good between the pollinizers (cv. Carmel and Monterey) and the main cultivar Nonpareil. In contrast, pollen dispensers increased fruit-set percentage and yield in the 1 : 2 : 1 (one pollinizer row: two Nonpareil rows: one pollinizer row) planting design in which the branches of the two Nonpareil rows facing each other were more distant from effective pollinizers, and bloom overlap between Nonpareil and one of its pollinizers (Mission) was suboptimal. The increase in fruit set and yield, attributable to the use of pollen dispensers occurred primarily on Nonpareil branches facing the adjacent Nonpareil row. The impact of pollen dispensers was significant at 50 m but not at 150 m from the hive. Although pollen dispensers have been used for more than 60 years, this is the first large-scale study with replication, conducted under commercial conditions that demonstrates their benefit when cross-pollination is limited.