Effects of Plastic Covers on Grape Microclimate and Quality
1. Effects of Plastic Covers on Canopy
Microenvironment and Fruit
Quality
Matthew Fidelibus
Viticulture & Enology
UC Davis
2. Justification and importance
• Table grapes are costly to produce
• Late-harvested fruit need rain protection
• Various plastic films provide rain shelter, but they may
allow heat and condensation to accumulate
• Characterizing performance of existing films will help
guide and assess the development of new films
3.
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7. Objective
• Determine how green and white-colored plastic
vine covers affect canopy microenvironment, and
yield, quality, and post-harvest spoilage of table
grapes.
8. Field study design and
layout
Green and white vine covers
were purchased from
commercial suppliers and
installed by a commercial
grower in ‘Redglobe’ (2011) and
‘Autumn King’ (2012) vineyards
Whole rows of vines were
covered with green or white
plastic, or remained uncovered,
in a randomized complete block
design replicated three times.
Covers were installed in
September, and kept in place till
harvest (November or October)
Environmental and fruit quality
data collected periodically
15. Plastic, time of day, and
condensation, Redglobe, 2011
Morning Afternoon
Plastic condensation (ml/cm2)
Green 0.026 a 0.020
White 0.017 b 0.016
16. Condensation at Different Positions
and Times of Day, Redglobe, 2011
Morning Afternoon
Position condensation (ml/cm2)
North 0.025 a 0.019 b
Central 0.032 a 0.028 a
South 0.009 b 0.008 c
17. Evaporative potential differed
among coverings and positions in
the canopy, Redglobe, 2011
Covering South Central North
Uncovered 6.47 6.18 A 6.85
Green 6.99 a 4.24 B b 6.92 a
White 7.12 a 3.27 B b 6.35 a
19. Percent clusters with rot, under
different covers, at different times
October 4 October 19
Rot incidence
Covering (% clusters with rot)
uncovered 7b 21
green 8b 21
white 14 a 19
Significance (P>F) 0.04 0.85
24. Summary of 2011 findings,
Redglobe
• Green plastic more transparent & less
reflective than white; increased peak canopy
temps by 5 C
• Greatest condensation in morning and under
vertical or north facing surfaces
• Both plastics reduced evaporative potential
and slightly delayed fruit maturity
• Maybe some protection from postharvest rot?
28. Fruit quality, Autumn King, 2012
• No treatment effects on berry weight, Brix,
pH, or TA
• No treatment effects on field assessment of
rot
• After 1 month post harvest storage, fruit from
uncovered vines had twice as much rot as
fruit from covered vines, regardless of plastic
color (40 vs 20% of clusters with some rot)
29. Overall summary
• Green plastic transmits more light than white,
resulting in higher peak temperatures
• Condensation worst in the morning, under top
& north-facing surfaces; variable differences
between plastics
• Both plastics reduce evaporative potential in
canopy but not fruit zone
• Both covers may slightly delay fruit maturation
• Covers appear to reduce post harvest rots
Temp range is 5 C (41 F) to 35 C (95 F). Difference among treatments in peak highs about 9 F.
Range 5 C (41 F) to 30 C (86 F). Date range is early-mid October
No sig difference in boxes picked overtime
Not significant, but numerical means of fruit from covered vines suggests half as much rot as from uncovered vines for about 30 days…Remember this…
Range about 41 to 95 F.
Range is 5 C (41 F) to 45 C (113 F). 5 C, about 10 F. Center temps are much hotter, especially for vines covered with green plastic.
Range is 5 C (41 F) to 35 C (95 F)
Short wavelengths of light pass through the plastic and heat the vine and trellis materials. Longer wavelengths emitted from the heated objects are trapped by the plastic. Effects on postharvest rot were variable and could use additional testing to verify