Discolored berries are another example of crops affected by intense summer heat
This close-up on two blackberries shows the white-to-tan drupelets that can develop in hot, dry weather. Courtesy UC Integrated Pest Management
Add another crop to our list of heat victims this summer: Blackberries.
Throughout the Sacramento region, blackberries are developing odd white or tan discoloration. The little drupelets – the juicy sacs that make up the berry – turn white or tan. It’s not just cosmetic; they generally don’t taste so good either. Often, the discolored drupelet withers to nothing but a dried seed.
I noticed these weird drupelets on my own Baby Cakes blackberries as well as the wild blackberries that grow near our home. Was it the heat?
Thanks to Farmer Fred Hoffman (and UC research), we know why: Excess UV radiation. (And yes, that’s related to the heat.)
Hoffman, host of “Garden Basics with Farmer Fred” podcast, solved this mystery in response to an Oroville listener who saw her berries go from pink to tan to yuck.
In his column, Hoffman recapped heat-related problems with other crops such as tomatoes.
“And now, you can add blackberries to the list of crops that develop problems when it gets too sunny, too hot, dry and windy, especially because of extended heatwaves. The problem is known as White Drupelet Disorder (WDD),” Hoffman wrote.
It’s not just a matter of adding shade; the berry plants need humidity.
According to the UC Integrated Pest Management Guidelines for Caneberries:
"White drupelet is a tan-to-white discoloration of one to many drupelets on the fruit. Most often, white drupelets will appear when there has been an abrupt increase in temperature accompanied by a drop in humidity; it is especially pronounced when there is wind. ...
“While white drupelets may seem to be directly caused by weather, they are actually caused by ultra-violet (UV) radiation,” note the UC experts. “Weather conditions modulate this by the effect they have on penetration of UV radiation into the fruit. Cool, humid air scatters and absorbs UV radiation, while hot dry air has the opposite effect and allows more direct UV rays to reach the fruit.
“The movement of humidity away from the canopy by wind only heightens the effect of hot dry air. Additionally, as humidity is moved away from the plant canopy, more UV rays penetrate the canopy and damage fruit that may not even have been exposed to the sun. Fruit inside of the canopy is not acclimatized to UV radiation and is subsequently more susceptible when it reaches them.”
How do you combat WDD? Make your own fog.
“Some growers of caneberries in the Willamette Valley of Oregon, where rapid changes from a normally mild climate to temperatures up to and above 100 degrees occur through the summer, use overhead irrigation to minimize fruit loss to white drupelet,” say the researchers. “This is not merely to mist the fruit; instead, large amounts of water are applied to thoroughly wet the canopy and maintain cool temperatures and high canopy humidity for as long as possible. Sprinkling is not done too late in the evening to allow fruit to dry before nightfall.”
Learn more here: https://ipm.ucanr.edu/agriculture/caneberries/white-drupelet/#gsc.tab=0
Hoffman also cited other university researchers. As other berry-growing regions get hotter and drier, WDD will only become a bigger problem.
Meanwhile, Hoffman offered tips for berry success in his “Beyond the Garden Basics” segment, plus reasons why taking time to smell the roses (and other aromatic plants) really is good for you in his Friday podcast, “Stressed? Your Garden Can Help.” (And who isn't this summer?)
Find Hoffman’s podcasts and more here: https://gardenbasics.net/.
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Garden Checklist for week of Nov. 3
November still offers good weather for fall planting:
* If you haven't already, it's time to clean up the remains of summer. Pull faded annuals and vegetables. Prune dead or broken branches from trees.
* Now is the best time to plant most trees and shrubs. This gives them plenty of time for root development before spring growth. They also benefit from fall and winter rains.
* Set out cool-weather annuals such as pansies and snapdragons.
* Lettuce, cabbage and broccoli also can be planted now.
* Plant garlic and onions.
* Keep planting bulbs to spread out your spring bloom. Some possible suggestions: daffodils, crocuses, hyacinths, tulips, anemones and scillas.
* This is also a good time to seed wildflowers and plant such spring bloomers as sweet pea, sweet alyssum and bachelor buttons.
* Rake and compost leaves, but dispose of any diseased plant material. For example, if peach and nectarine trees showed signs of leaf curl this year, clean up under trees and dispose of those leaves instead of composting.
* Save dry stalks and seedpods from poppies and coneflowers for fall bouquets and holiday decorating.
* For holiday blooms indoors, plant paperwhite narcissus bulbs now. Fill a shallow bowl or dish with 2 inches of rocks or pebbles. Place bulbs in the dish with the root end nestled in the rocks. Add water until it just touches the bottom of the bulbs. Place the dish in a sunny window. Add water as needed.
* Give your azaleas, gardenias and camellias a boost with chelated iron.
* For larger blooms, pinch off some camellia buds.
* Prune non-flowering trees and shrubs while dormant.
* To help prevent leaf curl, apply a copper fungicide spray to peach and nectarine trees after they lose their leaves this month. Leaf curl, which shows up in the spring, is caused by a fungus that winters as spores on the limbs and around the tree in fallen leaves. Sprays are most effective now.
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