Establishing populations of ground-nesting native bees (Colletes) for orchard pollination services
The goal of this project is to improve native bee pollination services in Northeastern orchards. We
want to know if it is possible to establish and manage aggregations of ground nesting bees, especially Colletes species. If one of our proposed methods proves successful, other farmers will be able to copy the model. The new populations of bees on our farm could also serve as a source of bees for other fruit farms. We now propose to try three different methods to establish populations in three different orchard sites, two with sandy loam soil and one with silty loam soil. These methods will be 1) creating suitable ground nesting environment by removing vegetation from habitat patches around all three orchards, and bringing in sand to an area of the silty loam based orchard, to see if bees will move in naturally, 2) creating suitable ground nesting environments in both orchards and caging within the nesting area newly emerged and captured adult bees, 3) creating suitable ground nesting environments in both orchards and seeding them in the fall with bee pupae dug from other heavily populated areas that we know about.
Pollinator populations are in decline and fruit growers can no longer take their services for granted.
Relying solely on honeybees for pollination of spring flowering crops is risky due to hive rental supply issues and potential adverse weather during bloom. Native species, including Colletes inaequalis, have been shown to be effective orchard pollinators. Here in the Northeast, Colletes bees are some of the first to emerge in the spring and are well adapted to adverse conditions. They can form large aggregations of hundreds of bees nesting in sandy soils, yet they have not been managed for pollination services. Another type of native, ground nesting bee, the alkali bee (Nomia melanderi), is used for pollination of alfalfa in the western U.S. and farmers have become adept at creating nesting conditions for them. We propose to take a similar approach with Colletes.
In April 2017, we tried three different methods to establish a population of ground nesting bees on one farm as opposed to the three orchards planned. We were not able to find sufficient numbers of overwintering cocoons or adults to try our methods in three different orchards. From our experiences trying to source wild bees, we adapted our methods to depending on freshly caught adult bees from aggregation sites as an establishment strategy.
The three methods trialed at The Farm Between were:
1) created a suitable ground nesting environment by removing vegetation from a habitat patch
in an orchard and added 5 previously dug pupae from fall 2016, 2) created a vegetation free habitat patch and added 5 female and two male adults caged for 24 hours, 3) dug a pit and brought in sand to an area of a silty loam based orchard, then caged within the nesting area 20 female and 5 male newly emerged and captured adult bees along with floral resources for three days.
In November 2017, John spent 2 hours searching for pupae in the area where he had captured adults in the spring. None were found.
In 2018, from Mid April through May, all three new habitat sites were monitored for Colletes emergence.
The adult populations at our collecting sites were down in 2018, as only 6 adults (4 females and 2 males) were collected in 2, 3 hour sessions. This lack of bees made it impossible to carry out our plans to seed new habitat patches with adults. The 6 collected bees were brought back to The Farm Between and released.
A new 144 ft2 sand patch habitat was installed at LSF Orchard in Fletcher, VT in July 2018. We will try to collect more adults in 2019 with the goal of caging them on this new patch. We will monitor that along with the habitat patches at The Farm Between in 2019 for any nesting activity.
We won’t know if the establishments were successful until the spring of 2018 when adult bees emerge. The bees that were caged for 3 days showed signs of digging nesting holes in the sand provided. There was no clear evidence of bee activity in the other 2 trials. Not finding pupae in the fall in an area that was marked as an aggregation was discouraging. We will now focus on collecting newly emerged spring adults as a way to innoculate new orchards. We hope to collect enough bees in 2018 to try our 3 day caged adult method in 3 different orchards.
On May 5, 2018 one emergence hole and one adult Colletes female was observed it Site 1 (where the vegetation had been removed and 5 pupae buried the previous spring). After a few days the hole was no longer seen. Unfortunately that was the only nesting activity that we saw in 2018. We did see adults flying and visiting willow and apple flowers during bloom. However, we couldn’t determine where they were coming from. There was no clear nesting establishment in 2018.
In 2018, adult bees were increasingly difficult to collect. We will try to collect more in the Spring of 2019 and if successful cage them on new habitat patches. We will continue to monitor existing patches for nesting activity in 2019.
Champlain Orchards in Shelburne, VT is interested in establishing a habitat patch in 2019.
No conclusions until research observations are finished