Matthew Fidelibus
@viticulture.bsky.social
I am an Extension Specialist in the Department of Viticulture and Enology at UC Davis. I conduct applied viticulture research and extend the findings to industry. Also interested in plant science, horticulture, nature, and the environment.
Our 2-acre Sunpreme vineyard ended up filling 21.5 boxes with raisins. At most, a full box of raisins might weigh 1,000 pounds, so the vineyard probably made about 5 tons of raisins/acre, which is about 2.5 times more than a typical Thompson Seedless raisin vineyard.
October 2, 2025 at 11:57 PM
Our 2-acre Sunpreme vineyard ended up filling 21.5 boxes with raisins. At most, a full box of raisins might weigh 1,000 pounds, so the vineyard probably made about 5 tons of raisins/acre, which is about 2.5 times more than a typical Thompson Seedless raisin vineyard.
Last week our raisins were dry enough to pick but we didn't have the labor in place. Then we got nearly an inch of rain and now the raisins are wetter than they should be but with the possibility of more rain and cooler weather we decided to put what we had and finish drying
September 22, 2025 at 6:05 PM
Last week our raisins were dry enough to pick but we didn't have the labor in place. Then we got nearly an inch of rain and now the raisins are wetter than they should be but with the possibility of more rain and cooler weather we decided to put what we had and finish drying
"Natural" dry-on-vine raisin varieties offer unprecedented opportunities for mechanization but current varieties also have substantial preharvest fruit drop. This year we fumigated some clusters with 1-MCP, an ethylene action inhibitor, to explore the role of ethylene in these processes
June 26, 2025 at 9:08 PM
"Natural" dry-on-vine raisin varieties offer unprecedented opportunities for mechanization but current varieties also have substantial preharvest fruit drop. This year we fumigated some clusters with 1-MCP, an ethylene action inhibitor, to explore the role of ethylene in these processes
I am working with a grape variety that has a pre harvest fruit drop problem. The basal lateral arms of the cluster advise. We are going to try to measure arm retention force to better understand when the attachment begins to weaken. It's pretty strongly attached at the moment
June 19, 2025 at 9:19 PM
I am working with a grape variety that has a pre harvest fruit drop problem. The basal lateral arms of the cluster advise. We are going to try to measure arm retention force to better understand when the attachment begins to weaken. It's pretty strongly attached at the moment
Seems like something always happens when I am away for a few days
June 4, 2025 at 7:32 PM
Seems like something always happens when I am away for a few days
I gave a vineyard tour to a Food Systems class from Iowa State today and they gave me a #scotcheroo, which is evidently an #iowa delicacy.
May 23, 2025 at 6:14 PM
I gave a vineyard tour to a Food Systems class from Iowa State today and they gave me a #scotcheroo, which is evidently an #iowa delicacy.
Fruit is setting on the earliest varieties in the San Joaquin Valley. It's amazing how quickly the fruitlets start gaining size #grapes #viticulture
May 9, 2025 at 8:12 PM
Fruit is setting on the earliest varieties in the San Joaquin Valley. It's amazing how quickly the fruitlets start gaining size #grapes #viticulture
I noticed a western flower thrips larva peeking out from under the dried petals. Feeding activities cause scarring of the berries which can later lead to bunch rot. #grapevines #viticulture
April 27, 2025 at 7:37 PM
I noticed a western flower thrips larva peeking out from under the dried petals. Feeding activities cause scarring of the berries which can later lead to bunch rot. #grapevines #viticulture
Grapevines have rather plain flowers. Immature flowers have green colored petals that detach at the base of the flower and dry into pinkish-brown "caps" that usually fall off, exposing the anthers, stamens, stigma, and ovary.
April 27, 2025 at 7:35 PM
Grapevines have rather plain flowers. Immature flowers have green colored petals that detach at the base of the flower and dry into pinkish-brown "caps" that usually fall off, exposing the anthers, stamens, stigma, and ovary.
Early grapevine varieties in the South Central San Joaquin Valley are blooming now, maybe a few days to a week earlier than last year. Cool weather ahead could slow things down again though
April 25, 2025 at 4:00 PM
Early grapevine varieties in the South Central San Joaquin Valley are blooming now, maybe a few days to a week earlier than last year. Cool weather ahead could slow things down again though
The earliest clusters in the earliest varieties are getting close to bloom in Parlier, east-central San Joaquin Valley #grapes #viticulture
April 16, 2025 at 7:06 PM
The earliest clusters in the earliest varieties are getting close to bloom in Parlier, east-central San Joaquin Valley #grapes #viticulture
Grapevines in spring are just bursting with potential. With proper irrigation, fertilization, and pest management, we should have a good crop come fall.
April 4, 2025 at 8:09 PM
Grapevines in spring are just bursting with potential. With proper irrigation, fertilization, and pest management, we should have a good crop come fall.
Sunpreme raisin grapes are in the rapid growth phase and will pick up steam this week with the warmer weather
March 24, 2025 at 4:41 PM
Sunpreme raisin grapes are in the rapid growth phase and will pick up steam this week with the warmer weather
A paper I wrote with Kaan Kurtural in 2021 is currently the most read paper in the American Journal of Enology and Viticulture
March 6, 2025 at 1:32 AM
A paper I wrote with Kaan Kurtural in 2021 is currently the most read paper in the American Journal of Enology and Viticulture
Getting close to what I would call "bud break" of Sunpreme at Parlier. About the same as last year, probably.
February 24, 2025 at 8:53 PM
Getting close to what I would call "bud break" of Sunpreme at Parlier. About the same as last year, probably.
A few buds are breaking on Sunpreme raisin grapes at the UC Kearney Ag Center in Parlier, central CA
February 18, 2025 at 10:16 PM
A few buds are breaking on Sunpreme raisin grapes at the UC Kearney Ag Center in Parlier, central CA
Winter weather has been very mild so far in the San Joaquin Valley to the point where a few live leaves can still be found on mature vines and some young vines are still slowly producing young leaves
January 10, 2025 at 7:39 PM
Winter weather has been very mild so far in the San Joaquin Valley to the point where a few live leaves can still be found on mature vines and some young vines are still slowly producing young leaves
Most growers in the San Joaquin Valley have started pruning. I will probably start next week, as I need to collect pruning weights and am hoping the rest of the leaves will fall by then.
December 2, 2024 at 8:12 PM
Most growers in the San Joaquin Valley have started pruning. I will probably start next week, as I need to collect pruning weights and am hoping the rest of the leaves will fall by then.
The pattern of fall color in grapevine leaves provides insight into plant health. A distinct red leaf margin indicates Mg deficiency, deeply colored blade & veins with girdled petiole from threecornered alfalfa hopper, & burgundy blade tissue between green veins, indicates grapevine leafroll virus.
November 20, 2024 at 10:23 PM
The pattern of fall color in grapevine leaves provides insight into plant health. A distinct red leaf margin indicates Mg deficiency, deeply colored blade & veins with girdled petiole from threecornered alfalfa hopper, & burgundy blade tissue between green veins, indicates grapevine leafroll virus.
I would like to start collecting pruning weights, but there are still too many leaves. Hopefully the colder and stormier weather predicted for this weekend will clear things up
November 18, 2024 at 10:26 PM
I would like to start collecting pruning weights, but there are still too many leaves. Hopefully the colder and stormier weather predicted for this weekend will clear things up
We've been seeing more carpenter worms in San Joaquin Valley vineyards. The larvae bore into trunks and vine mealybugs find refuge in the holes. For more info: www.mdpi.com/2075-4450/12...
February 21, 2024 at 10:27 PM
We've been seeing more carpenter worms in San Joaquin Valley vineyards. The larvae bore into trunks and vine mealybugs find refuge in the holes. For more info: www.mdpi.com/2075-4450/12...
Magnesium deficiency in Allison table grapes
October 14, 2023 at 2:40 PM
Magnesium deficiency in Allison table grapes
Preharvest application of jasmonates and/or ethylene stimulate abscission of certain grape varieties. We're testing these hormones as harvest aids and as means to improve the quality and shelf life of destemmed table grapes. Compare untreated vs treated after 2 wks storage
October 11, 2023 at 8:44 PM
Preharvest application of jasmonates and/or ethylene stimulate abscission of certain grape varieties. We're testing these hormones as harvest aids and as means to improve the quality and shelf life of destemmed table grapes. Compare untreated vs treated after 2 wks storage
This has been a tough season for California grape growers as cool weather, high humidity, and rain have delayed ripening and reduced yield and quality, especially in the South San Joaquin valley. Now rain is forecast for this weekend, which is once again bad timing, especially for raisin growers.
September 27, 2023 at 9:08 PM
This has been a tough season for California grape growers as cool weather, high humidity, and rain have delayed ripening and reduced yield and quality, especially in the South San Joaquin valley. Now rain is forecast for this weekend, which is once again bad timing, especially for raisin growers.