These native bees got strategy: how native bees deal with weather extremes.

All bees have the same goal: To create, protect and nourish their growing eggs, larvae and pupae.  Native bee species spend most of their life in their nest and they are small and elusive.  The mystery of it all makes it easy to suspect the worst but actually native bees indigenous to NY are possibly better equipped for these variable and extreme weather events than one might think.  To this end bee species have developed multiple ways to deal with variable and often extreme weather conditions like our recent late summer 2016 drought and wet and cold spring 2017.

Example of a moisture barrier (waxy film) in a ground nesting bee (Colletes); Photo credit: www.abundantnature.com

Some bee species line their nest with a waxy substance that has water repelling properties to the outside and moisture retention properties to the inside to prevent extra moisture from entering the nesting cell as well as preventing their brood from desiccating (see photo).  Extra moisture in nesting cells makes pollen provisions prone to fungal infection.

Another bee strategy is to produce quickly developing offspring that mature into workers and new reproductive females within the same season giving them multiple chances to lay and provision eggs each year.

And still other bee species stagger the development of their offspring by entire years so that they will emerge at a variety of times (same season, next season or delayed emergence for 2 or more seasons).

The latter strategy is common in desert regions where unpredictable drought conditions occur.   This delayed emergence is possible because bees diapause. Diapause is where the bee goes into a state of low metabolic activity during the winter months to conserve energy until the following season, very similar to a bear’s need to hibernate. It’s possible our NY bees utilize a similar delayed emergence strategy as desert bees to deal with the unpredictable wet spring and late summer drought conditions we can experience here in the northeast. Native bees are not opposed to hedging their bets and may have coined the term, “Don’t put all your eggs in one basket”.

While there is still much to learn about species response to extreme weather conditions in the northeast, research has repeatedly encountered bee nests in irrigated agricultural fields, leading us to believe many bees have the ability to deal with excess water. Reports on ground-nesting bee response to flood-like conditions is less predictable. While some bees can survive hurricane flooding, other bee populations have been decimated when the water table gets too high or river banks flood.

Preliminary analyses of Smartphone bee survey

Figure 1. Temperature at which bees exceed required minimum for adequate pollination of apple per 5 minute survey (> 60˚F)

We can’t yet determine how last years’ drought and the wet, cold ‘apple bloom’ weather impacted early Spring native bee population survival.  Our survey data from this wet Spring 2017 shows that most bees were not foraging at efficient proportions until the temperature was above 60˚F and sunny (Figure 1) and bumble bees and carpenter bees pulled the weight for most of the weather-affected orchards.  These are some of the few species that are known to fly in inclement weather.  Thankfully, many growers who were impacted by the wet weather conditions have reported that they received sufficient pollination for successful apple production this year.

Figure 2. Native bee and honey bee abundance depends on pesticide management program (2017).

Based on the App data that many of you submitted, IPM growers experienced slightly higher native bee counts in their orchards (Figure 2). Considering that the conventional orchards who submitted data were surrounded by 14% more forage habitat (p = 0.02; natural landscape and pollinator dependent crops) it’s possible this difference would have been greater.

In conclusion we will need to wait and see what next year brings. A poor foraging season one year can cause a dip in the population the following year, but bounce back after a few good foraging seasons.  To monitor native bee resilience, it will be even more important for all of you to use our Bee Survey app next apple bloom.

Reminder: Individual participant recommendations will be distributed in August!