Hoary Squash Bees - Peponapis pruinosa

[OldGreenVulture]

Hoary Squash Bees - Peponapis pruinosa.



Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Apidae
Genus: Peponapis
Species: Peponapis pruinosa Say, 1837

Peponapis pruinosa is a species of solitary bee in the tribe Eucerini, the long-horned bees. Its common name is eastern cucurbit bee. It may be called the squash bee, but this name can also apply to other species in its genus, as well as the other squash bee genus, Xenoglossa. This bee occurs in North America from the East Coast of the United States to the West Coast and into Mexico. It is an oligolege, specializing on a few host plants, the squashes and gourds of genus Cucurbita. Its range expanded as human agriculture spread throughout North America and squash plants became more abundant and widespread. It may also have spread naturally as the range of its favored wild host plant Cucurbita foetidissima expanded.

This bee is 11 to 14 millimeters long and 4 to 5.5 millimeters wide at the abdomen. It is black with whitish bands on the abdomen and it is coated in yellowish hairs.

This bee relies on wild and cultivated squashes, pumpkins, gourds, and related plants. It may occasionally obtain nectar from other types of plants, but the female will only use Cucurbit pollen to provision her young. Females dig a nest in the ground near its host plants. The nests are known to reach depths of 46 centimeters, but the offspring are usually placed at shallower depths. The bee seems to favor irrigated soils and soils cleared by fire. It may also nest in lawns. The bee will sometimes plug the nest just below the surface, and it may place a tumulus at the entrance. Nest building activity often occurs later in the day, as mornings are usually spent foraging. The squash flower opens early in the morning and closes before noon, and the bee's activity pattern is tied to the flower's cycle. The male bee spends most all of his time in and around flowers, foraging and mating in the open flowers and sleeping inside the closed flowers after noon. The females live in and around the flowers until nesting season, when they live in and maintain one or more nests. The young pupate in late June and early July.

This species is an important pollinator of cultivated crops of squash, pumpkins, and related plants. A squash field with a healthy population of squash bees can be completely pollinated with no need for the introduction of honeybees. This ground-nesting bee often spends its entire life in an irrigated crop field, and there it can face a number of hazards, such as tillage and pesticides. The Common Eastern Bumblebee Bombus impatiens has also been found to be a good pollinator of squash, pumpkins in particular.

From Carnivora.

carnivora.net/hoary-squash-bees-peponapis-pruinosa-t6934.html

[OldGreenVulture]

Wild ground-nesting bees might be exposed to lethal levels of neonics in soil.

by University of Guelph



A female squash bee. Credit: University of Guelph

In a first-ever study investigating the risk of neonicotinoid insecticides to ground-nesting bees, University of Guelph researchers have discovered at least one species is being exposed to lethal levels of the chemicals in the soil.

Examining the presence of these commonly used pesticides in soil is important given the majority of bee species in Canada make their nests in the ground.

This study focused on hoary squash bees, which feed almost exclusively on the nectar and pollen of squash, pumpkin and gourd flowers.

Researchers found that the likelihood that squash bees are being chronically exposed to lethal doses of a key neonicotinoid, clothianidin, in soil was 36 per cent or higher in squash fields.

That means 36 per cent of the population is probably encountering lethal doses, which is well above the acceptable threshold of 5 per cent, in which 95 per cent of the bees would survive exposure.

"These findings are applicable to many other wild bee species in Canada that nest on or near farms," said U of G School of Environmental Sciences professor, Nigel Raine, who holds the Rebanks Family Chair in Pollinator Conservation and worked on the study with Ph.D. student and lead author Susan Chan.

"We don't yet know what effect these pesticides are having on squash bee numbers because wild bees are not yet tracked the same way that honeybee populations are monitored. But we do know that many other wild bee species nest and forage in crop fields, which is why these findings are so concerning."

Published in Scientific Reports, the study began with Chan collecting soil samples from 18 commercial squash fields in Ontario. Pesticide residue information from these samples and a second government dataset from field crops was used by Chan and colleagues Prof. Ryan Prosser, School of Environmental Sciences, and Dr. Jose Rodríguez-Gil to assess the risk to ground-nesting squash bees.

The research comes as Health Canada places new limits on the use of three key neonicotinoids, including clothianidin, while it decides whether to impose a full phase-out of these pesticides. Neonics have been linked to concerns about honeybee colony health, with research showing these bees can ingest dangerous amounts through nectar or pollen.

"Current risk assessments for insecticide impacts on pollinators revolve around honeybees, a species that rarely comes into contact with soil," said Raine. "However, the majority of bee species live most of their life in soil, so risks of pesticide exposure from soil should be a major factor in these important regulatory decisions."

"Until now, no one has examined the risk to bees from neonics in soil despite the fact these pesticides are applied directly to seeds planted into the ground, or sprayed directly onto soil at planting, and can persist for months after application," said Chan.

"Only about 20 per cent of the neonicotinoid insecticide applied to coated seeds is actually taken up into the crop plant; the rest stays in the soil and can remain there into subsequent seasons."

Squash bees are at particular risk because they prefer the already-tilled soil of agricultural fields for their elaborate underground homes. And as they build their nests, they move about 300 times their own body weight worth of soil.

Since the bees don't eat soil, it's difficult to know exactly how much pesticide residue enters the bees. But the researchers calculated that even if they are conservative and assume only 25 per cent of the clothianidin enters the bee, the risk of lethal exposure in pumpkin or squash crops is 11 per cent—still above the widely accepted threshold of 5 per cent.

The team also examined the exposure risk in field crops, since many ground-nesting bee species live near corn and soybean fields, which use neonics as well. They found that 58 per cent of ground-nesting bees would be exposed to a lethal dose of clothianidin while building their nests even if only 25 per cent of the clothianidin in the soil enters the bee.

"Pumpkin and squash farmers face a dilemma in that they want to protect pollinators, such as the squash bee, because they are vital to crop production, but at the same time need to protect their crops from pests," said Chan.

"New approaches are needed that allow farmers to control pests and protect pollinators simultaneously. My advice to farmers is if you find an aggregation of squash bees nesting on your farm, protect these key pollinators from exposure to neonicotinoids by either not using them at all, or at least not using them near the aggregation. Creating pesticide-free places to nest will help your population of squash bees to grow over time."

phys.org/news/2019-08-wild-grou ... ethal.html
Journal Reference:
D. Susan Willis Chan et al, Assessment of risk to hoary squash bees (Peponapis pruinosa) and other ground-nesting bees from systemic insecticides in agricultural soil, Scientific Reports (2019). DOI: 10.1038/s41598-019-47805-1

Abstract
Using the hoary squash bee (Peponapis pruinosa) as a model, we provide the first probabilistic risk assessment of exposure to systemic insecticides in soil for ground-nesting bees. To assess risk in acute and chronic exposure scenarios in Cucurbita and field crops, concentrations of clothianidin, thiamethoxam and imidacloprid (neonicotinoids) and chlorantraniliprole (anthranilic diamide) in cropped soil were plotted to produce an environmental exposure distribution for each insecticide. The probability of exceedance of several exposure endpoints (LC50s) was compared to an acceptable risk threshold (5%). In Cucurbita crops, under acute exposure, risk to hoary squash bees was below 5% for honey bee LC50s for all residues evaluated but exceeded 5% for clothianidin and imidacloprid using a solitary bee LC50. For Cucurbita crops in the chronic exposure scenario, exposure risks for clothianidin and imidacloprid exceeded 5% for all endpoints, and exposure risk for chlorantraniliprole was below 5% for all endpoints. In field crops, risk to ground-nesting bees was high from clothianidin in all exposure scenarios and high for thiamethoxam and imidacloprid under chronic exposure scenarios. Risk assessments for ground-nesting bees should include exposure impacts from pesticides in soil and could use the hoary squash bee as an ecotoxicology model.

www.nature.com/articles/s41598-019-47805-1

From Carnivora.

carnivora.net/hoary-squash-bees-peponapis-pruinosa-t6934.html