- Author: Ben Faber
Avocado fruit set is lousy up and down the coast this year. The trees were flowering in many places from January to June. They kept trying to set fruit, but nada. According to Daniel Swain at UCLA Weather West, this was the coldest winter on record without freeze and a long drizzly spring with little sun - cool days and night time temperatures. Cold day time temps mean poor pollinator activity. Honeybees just weren't working much. Then if pollen is transferred to the female stage flower, it takes 48 hours of above 50 deg F for fertilization - the deposition of pollen on the stigma and growth of the pollen tube down the style to the ovule. If the temp at night drops below 50, the process stops and the ovule never gets fertilized. So it doesn't matter if day time is warm and the pollinators are working, if it gets cold at night, the fertilization process stops.
So that's exactly what happened. Cool days for poor pollination and then cold nights for fertilization. It didn't matter how hard the tree flowered, it just wasn't the right weather. It didn't matter if you sprayed gibberellic acid. The weather was just not right for fruit set this tear.
And this should set off alternate bearing for next year if we have the right weather conditions. So you might think seriously about pruning because there could be a branch breaking crop set next spring – if the weather is right.
Interestingly,just as an observation it looks like GEM and Lamb Hass right next to Hass did set fruit just at the end of the flowering period. So there is some difference in varieties to weather conditions.
Image from American Museum of Natural History
The cool/moist weather has also created conditions for anthracnose and alternaria in fruit which causes problems for the consumer, but also caused early fruit drop and color change in the fruit on the tree. The trees just can't hold on to the fruit as one normally expects. It's a tough year for avocado growers. In the Central Valley all the stone fruit is late by almost a month. Apricots and cherries are just coming in season when they should have been available in late May.
Weird and Maybe we are going to have to get used to it.
Read more about the Basics of flowering
pollination - movement of male pollen to female stigma
fertilization - growth of pollen tube down to stimulate ovule
- Author: Deanne Meyer
This last week started with us waking up to learn of the 7.8 magnitude earthquake that rocked Turkey and Syria. Drone footage, satellite imagery, news reports all show the devastation. The World Health Organization estimates some 23 million people impacted by this natural disaster and the news outlets indicate more than 33,000 people dead. That doesn't count all the people who know those impacted. Our thoughts are with first responders, those in need of healing and those traumatized by the temblor. Many groups and organizations are on the ground to help including Californians. Californians know how long recovery can take and how lives change in an instant. Many in my family see earthquake disasters and are grateful to first responders from throughout the world. My great grandmother was married in 1903 and moved out of her family's home to live with her in-laws. The 1906 San Francisco earthquake (magnitude 7.9 estimate) and fire destroyed building, property and people. Because Grammy lived with her in-laws she survived and a few years later my grandmother and her sisters were born; decades later my mother, her brother and her three first cousins; my generation has 6 and the next generation has 4. I for one understand the value and importance of first responders and international help that came to San Francisco's aid in 1906 and I'm grateful to be able to help now.
How's our footprint doing? January was a busy month for hiring. Academics included: Eric Porse, Director California Institute Water Resources; Advisors [Ellie Andrews, Sonoma; Natalia Ott, Tehama; Justin Tanner, San Joaquin; Eddie Tanner, Humboldt; Tobias Oker, Kern; Haris Gilani, Riverside, and Ahmed Kayad, Intermountain REC. and Flavie Audoin, Central Sierra MCP]. It's exciting to have new Advisors from one end of California to the other! Two Project Scientists joined: Francisco Benitez, Berkeley Food Institute housed at Kearney and Alexis Zaragoza working with Vice President Humiston. There are also two new Staff Research Associates: Cristal Hernandez (Kern) and Nicole Dutch in Plumas/Sierra. Tim Nguyen joined the statewide IPM program as an applications programmer.
Great progress is being made toward the California Conservation Planning Partnership (C2P2) technical assistance agreementrollout meeting at the end of the month. You may remember previous discussions on this collaboration between ANR,CARCD (California Association of Conservation District), CDFA (California Department of Food and Agriculture), NRCS (Natural Resources Conservation Service) and Resource Conservation Districts. We provide service to the same people and this agreement helps all staff align with the responsibilities of their organization.
What else is happening within ANR? The biweekly meetings with the Vice Chancellors for Research continue with discussions to incorporate the UC data policy into local policy. Specifically, we need to ensure data are protected when academics transfer, leave or retire. As a reminder, all data associated with research projects are the property of the Regents of the University of California. Also happening at this time of year is our Directors of State wide Programs and Institutes are working on the budget call for 2023/2024. These are due later in February and go to Program Council for discussion in April.
Winter rains may or may not be done. Yet, we're at that time of year when millions of workers invade California: bees! Often, almost every healthy beehive in the country is in California as we prepare for a big bloom. I remember reading there's a new technology that made the top 10 at the World Ag Expo related to hive management. Maybe I'll get a chance to see it in the week ahead. May the weather be warm enough for the bees to be buzzing around and doing their job as buds bloom. Bees teach us that the mighty are mighty because of what they do and not because of their size.
- Author: Ben Faber
Microbes multiply in heat,
Changing nectar,
Upsetting bees
Bumblebees pollinate many of our favorite foods, but their own diet is being upset by climate change, according to a new UC Riverside study.
Bombus impatiens, aka the common eastern bumblebee, served as taste tester for this experiment.
There's a sweet spot where floral nectar that bees eat has just the right balance of microbes like bacteria and yeast in it. Hotter weather can upset the balance, endangering the bees' health and potentially, our own.
A new study in the journal Microbial Ecology examines the effects of these nectar composition changes on an American bumblebee. Without bumblebees, who perform a type of pollination that honeybees do not, it would be difficult to mass produce food crops like tomatoes, blueberries, peppers, or potatoes.
“Micro changes in floral nectar may alter the way bees forage and look for food, affecting their health and in turn, potentially affecting human health, by reducing the availability of fresh foods,” said UCR entomologist and study lead Kaleigh Russell.
Bumblebees do enjoy nectar with some microbes in it, but too much of a good thing can deter them, Russell said.
With even a small increase in temperature, microbes' metabolism speeds up, causing them to reproduce more and eat up a higher percentage of the sugars in the nectar. “Less sugar means the nectar could be less palatable for our pollinators,” Russell said.
To test the bumblebees' taste preferences, Russell made nectar in a laboratory. Some was sterile and some contained microbes, and she grew both at a lower and a higher temperature.
The lower temperature, 80.6 degrees Fahrenheit, represents the average springtime high for Riverside in 2017. The higher temperature, 89.6 F, corresponds with what the predicted average temperature will be at the end of the century due to climate change.
Nectar from wild mustard, abundant in Southern California, was collected for this experimental taste test.
A clear preference for some level of microbes was evident even when the nectar contained less sugar. However, the bees only went for this less sugary nectar containing a moderate amount of microbes at the cooler temperature. They did not prefer the nectar with too many microbes, as well as the nectar with no microbes at all.
It isn't yet clear why the bees have such specific preferences. Russell speculates that bacteria or yeast may help bees digest sugars in the nectar. Another theory is that the microbes produce secondary metabolites that aid in bee health.
What is clear is that it isn't likely that an increase in average temperatures will have a positive effect on bumblebees.
“We could see shifts in the locations of bee communities, since they leave when they can't find the food they like or need,” Russell said. “We might also see a decline in overall pollinator populations.”
For concerned readers with gardens, Russell recommends growing native plants that have not been treated with insecticide. “That's the best thing someone could do right now to help bumblebees,” she said.
- Author: Kathy Keatley Garvey
Hey, wait, take me with you!
No, leave me alone! Let me go!
Have you ever seen insects struggling to free themselves from the reproductive chamber of a milkweed blossom?
Instead of producing loose pollen grains, milkweeds produce pollinia, a waxy, sticky packet of golden pollen grains originating from a single anther. When bees and other insects forage for nectar in the "nectar troughs," where the pollinia are, they emerge with wishbone-shaped pollinia on their feet or other body parts. That is, if they emerge at all. Sometimes they die there; the reproductive chamber becomes a floral death trap.
What may seem like nature's appalling act of cruelty is actually a unique case of floral pollination, the transfer of pollina from one blossom to another.
"Milkweed flowers bloom in umbels which are clusters of individual flowers on stems that emerge from a common point," explains Eric Eldredge in an article published by the U.S. Department of Agriculture's Natural Resources Conservation Service. "Flowers of different species of milkweed differ in size, color, and fragrance, but all produce their pollen in waxy sacs called pollinia. The pollinia are located in two anther pouches adjacent to vertical stigmatic slits of the flowers. Pairs of adjacent pollinia are connected to each other by translator arms from a clamp located in the middle, called the corpusculum (Bookman, 1981). The complete structure is called a pollinarium."
"Insects that visit a flower to drink nectar struggle to grasp the slippery surfaces and may accidentally slip their leg, tarsus, mouthpart, or other appendage into the opening at the bottom of the stigmatic slit. This slit is formed by guide rails, which are lined with bristles that prevent the insect moving its appendage any direction but up. The top of the slit leads into the opening of the corpusculum, which has hard, sharp inside edges that taper together at the top. The corpusculum clamps firmly to the insect by pinching onto the insect's appendage. In its struggles to escape, if the insect is large enough, it can withdraw the paired pollinia from the anther pouches and fly away."
We've seen dead honey bees trapped in the milkweed blossoms while other bees forage around their carcasses. And then we've seen the frantic struggles (below). Fortunately this bee in the first three photos escaped. Another bee did not.
- Author: Ben Faber
Rae Olsson rachel.olsson@wsu.edu 509-335-4846
PULLMAN, Wash. - A tiny bee imposter, the syrphid fly, may be a big help to some gardens and farms, new research from Washington State University shows.
An observational study in Western Washington found that out of more than 2,400 pollinator visits to flowers at urban and rural farms about 35% of were made by flies--most of which were the black-and-yellow-striped syrphid flies, also called hover flies. For a few plants, including peas, kale and lilies, flies were the only pollinators observed. Overall, bees were still the most common, accounting for about 61% of floral visits, but the rest were made by other insects and spiders.
"We found that there really were a dramatic number of pollinators visiting flowers that were not bees," said Rae Olsson, a WSU post-doctoral fellow and lead author of the study published in Food Webs. "The majority of the non-bee pollinators were flies, and most of those were syrphid flies which is a group that commonly mimics bees."
Syrphid flies' bee-like colors probably help them avoid predators who are afraid of getting stung, but they are true flies with two wings as opposed to bees which have four. The flies might have additional benefits for plants, Olsson added, since as juveniles they eat pests like aphids. As adults, they consume nectar and visit flowers so have the potential to move pollen the same way that bees do, though it is less intentional than bees who collect pollen to feed their young.
For the study, the researchers surveyed plants and pollinating insects and spiders on 19 rural farms and 17 urban farms and gardens along the Interstate 5 corridor in Western Washington. They conducted surveys six separate times over two years. In addition to the visits by bees and syrphid flies, they also catalogued more rare visits by other arthropods including wasps, lacewings, spiders, butterflies, dragonflies, beetles and ants--all with visits of less than 4%.
Olsson first noticed the many different non-bee pollinators while working on a bee-survey project led by Elias Bloom, a recent WSU doctoral graduate. The results of this study underscore the need for researchers as well as gardeners and farmers to pay more attention to alternative pollinators, Olsson said, and hoped that similar studies would be conducted in other regions of the country.
"Bee populations are declining, and we are trying to help them, but there's room at the table for all the pollinators," Olsson said. "There are a lot of conservation and monitoring efforts for bees, but that doesn't extend to some of the other pollinators. I think people will be surprised to find that there are a lot more different types of pollinating insects - all we really need to do is to start paying a little more attention to them."
The study also noted pollinator differences between rural and urban spaces. Observations sites in urban areas showed a greater diversity of pollinators corresponding with the wider range of plants grown in city gardens and smaller-sized farms. Rural farms with their larger fields of plants had a greater abundance.
For every grower, urban or rural, who is interested in increasing the number and diversity of pollinators visiting their fields or gardens, Olsson recommended increasing the variety of flowering plants.
Making sure that something is flowering all throughout the season, even if on the edge of a field, will support the biodiversity of pollinators because their different life stages happen at different times of the year.
"Some pollinators like certain butterflies and moths are only present in a pollinating form for a small period of time," Olsson said. "They may only live for a few days as adults, so when they emerge and are ready to pollinate, it's good to make sure that you have something for them to eat."
Read On: https://news.wsu.edu/2021/06/22/bee-impersonating-flies-show-pollinator-potential/
Photo: Not a bee, a hover fly or syrphid fly