Positive results from experiments with photoselective shadecloth for color break and with plant growth-promoting bacteria for tree health were reported at a June 14 citrus under protective screen (CUPS) seminar. Presenter Arnold Schumann also gave an update on the generous fruit yields being generated in CUPS. Schumann is a University of Florida Institute of Food and Agricultural Sciences Citrus Research and Education Center (CREC) professor.
SHADECLOTH AND COLOR BREAK
Researchers experimented with colored photoselective shadecloth bags in an effort to improve color break. Results were:
- Black, blue and red bags increased peel blush on Ray Ruby grapefruit and the UF-914 (a combination of grapefruit and pumelo).
- Green bags have consistently produced the highest peel blush in the grapefruit and grapefruit hybrid varieties.
- Bag color had no impact on external peel color development of W. Murcott.
- Colored bags did not have an effect on internal juice color or quality.
PLANT GROWTH-PROMOTING BACTERIA
CREC researchers started using soil drench (drip) applications of the plant growth-promoting bacteria Bacillus velezensis and B. amyloliquefaciens in CUPS in February 2022. Results included:
- Tree growth and health have been visually boosted, and most varieties set more fruit this year following applications. The Early Pride variety set the most fruit to date.
- Spray applications of Double Nickel (B. amyloliquefaciens) were more effective than Kocide copper applications to control greasy spot and melanose on Ray Ruby grapefruit.
OTHER UPDATES
After 8.5 years of CUPS research at the CREC, 99.5% of trees remain free of HLB. Psyllids infested the trees during rescreening, but HLB spread was minimal, and psyllids were eliminated.
CUPS suffered moderate damage from three hurricanes from 2017 to 2022, but trees and fruit crops were undamaged. “The trees carried on like nothing happened,” Schumann said.
Over eight years, Ray Ruby grapefruit trees in the CUPS produced a cumulative 7,306 boxes per acre and brought $131,508 of revenue per acre at a price of $20 per box and a conservative 90% packout rate.
Schumann said the total CUPS revenue over eight years is equivalent to 49 years of conventional HLB-endemic grapefruit production at an average 267 boxes per acre, $20 per box price and 50% packout.
Read more about Schumann’s CUPS research here.
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