apple blossoms at night

Arkansas study shows nocturnal pollinators have similar pollinating potential as diurnal pollinators

In *All, Agricultural Systems, Pollinator Week by AgIsAmerica

The study overseen by Ashley Dowling, professor of entomology for the Arkansas Agricultural Experiment Station, was among the first to examine nocturnal pollination in agriculture and the first recorded study on night pollinators for apples. Robertson said apples were chosen because they are a primary food crop in the United States. Dowling said the night pollinator study was important because it provides scientific data on night observations, which have been neglected in agriculture. It could also help save declining numbers of night pollinators, Dowling added. Night pollinators could be at work on many other food crops as well, Robertson said.

In the spring of 2016 when Robertson was working on a study to make insect traps more efficient, he noticed he was catching more moths during the period of fruit bloom. He soon began investigating the impact of nocturnal pollinators on apple trees for his doctoral thesis. The field observations took place during 2017 and 2018 with four treatments: closed, with apple blossoms bagged day and night; open, with no bags; diurnal, with blossoms bagged at night to only allow daytime pollinator access; and nocturnal, blossoms bagged during the day to allow only nighttime access.

Each day during bloom when weather allowed, Robertson was in the orchard at sunrise and sunset to take bags off some branches and put them on others. After bloom was over, Robertson and his colleagues counted fruit set and seed set. Seed set is the number of seeds produced in a single fruit and represents the number of ovaries that were fertilized by pollen granules. In this way, seed set is a direct proxy of the level of pollination.

The researchers also looked to see if at least one flower per cluster had set fruit. Numbers of set fruit were observed two weeks after all bags had been removed. Because of changes in research design in 2017 and 2018, data from each year was analyzed separately. Apples were harvested in late July in 2017 and in early June in 2018, before full development but late enough that seeds could easily be counted. Harvested fruit were bisected laterally to expose seeds, and the number of seeds from each apple was counted. Seed set was used to compare levels of pollination among treatments.

Source: National Impacts Database


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