Impact of Drought on Tree FruitKathryn Carter, Fruit (Tree fruit and Grape) Specialist,

OMAFRA

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Background

• 2016 was a record breaking dry year for Niagara and many other parts of the province.

• Climate change may result in more extreme weather.

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Jan Feb Mar April May June July August Sept Oct Nov Dec

Precipitation

normal preciptation

Precipitation in Vineland 2016 vs normal precipitation (Environment Canada, 2016)

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Post harvest (PH) irrigation

• Peach-during bud differentiation to avoid doubling.

• Apricot- to avoid bud drop.• Cherries- bud differentiation to prevent

spur fruit.

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Drought can impact fruit trees in several different ways

• Tree establishment/growth• Fruit• Roots• Nutrition• Winter hardiness• Next years crop

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Drought impact on Tree Establishment

• Tree growth/Mortality• Defoliation, gumming.• Photosynthesis• Rootstocks vary in

susceptibilty to drought. • High density need more

water.• Training system

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Drought and Tree growth

• mid or late season drought has less impact on tree growth.

• -’ve effect on seasonal trunk radial growth• -’ve effect on shoot basal diameters, leaf

size, shoot length

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• Fruit doubling

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Impact of drought on Fruit

• Deep suture disorder

Effect of irrigation on fruit size, quality and skin colouration for O’Henry Peach,

Lopez et al, 2010

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Parameters No thinning (583 fruits treefull irrigation non irrigated

Fruit Weight (g) 105.5 a 75.0bFruit Diameter (mm) 60.4a 55.5bDry matter Concentration (%) 16.8b 18.7aFirmness (N) 17.7b 21.5a

Titratable acidity (g malic acid 1-1) 4.9b 6.3a

Soluble solids concentration (%) 12.5b 15.4a

Skin colourMost exposed to light hue 42.3a 45.1aLeast exposed to light hue 50.7a 63.1b

Impact of drought on Fruit

• DMC may decrease fruit juiciness• No research linking hi DMC to peach

quality (mango),

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Impact of Drought on Fruit

• Early vs late maturing• Increase in fruit drop• Mod. stress advances

fruit maturity, • Severe stress delays

maturity (5-10 days).• Split pits

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Impact of Deficit irrigation on Fruit

• No impact on internal browning or mealiness in peaches.

• Fruit shrivelling less in deficit irrigation than optimum or excess irrigation.

• Increase SSC in deficit irrigation.

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Impact of drought on Roots

• Roots less sensitive then shoot/fruit growth.

• Reduced root growth.• Roots formed in the

upper 1.5 ft of the soil.

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Impact of drought on nutrition

• no direct effect on N of Ph, • increased magnesium and

manganese,• Decreased Ca and K,• reduced photosynthesis

and respiration, • Apply boron to plums

especially after a severe drought.

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Drought impact on Winter Injury (WI)

• Tree mortality from WI and diseases • -’ve impact on plant phenology, growth

and photosynthesis• Decrease in root carbon reserves- bud-

break mortality (peach, cherry)

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Next years crop

• Decrease in pollen viability, • Decrease in root

carbohydrate content,• Decreased yields in

apricots, nectarines peaches, plums and pears

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Drought impact on next years crop

• Mod. drought had little effect on next years crop in peaches, pears and cherries.

• Trees under severe stress could take up to 2 years to recover.

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Impact of irrigation regimes on return bloom and fruit set

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Irrigation treatment

No. flowers/40 cm

Fruit set/40 cm percent fruit set

Wet 4.35 2.29 52.6medium 4.74 2.3 48.5dry 6.16 3.99 64.9

LSD (p=0.05) 1.18 1 13.7

Larson and DeJong, 1988

Impact of drought on return bloom

• Other studies show an inhibition of flowering

• Variation due to crop, timing or severity of the stress.

• Stress from June on has less impact on next years crop.

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Minimizing impact of drought

• Irrigation• Thinning fruit-some or all• pruning• Managing weeds

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Irrigation

• Irrigate during cell division (bloom-30 days after)

• Cell expansion (2-4 weeks before harvest)

• Sod can compete for moisture.

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Effect of fruit thinning on fruit size and quality under drought conditions

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Parameters full irrigation No irrigation

No thinning commercial thinning heavy thinning no thinningcommercial thinning heavy thinning

FW (g) 105.5b 144.8a 154.1a 75b 77.1b 99.2a

FD (mm) 60.4b 66.7a 68.2a 55.5b 55.8b 59.4a

DMC (%) 16.8 15.7 16.7 18.7b 20.7a 19.3b

FF (N) 17.4 16.2 15.9 21.5b 31a 26.8a

TA (gma1-1) 4.9 4.7 4.9 6.3b 6.9 6.9a

SSC 12.5ab 12.2b 12.9a 15.4b 17.2 16.1b

Skin colur

most exposed to light hue 42.3 40.6 41.1 45.1b 54.6a 46.1b

least exposed to light hue 50.8 47.7 50.9 63 67.7 64.6

Lopez et al, 2010

Impact of fruit thinning on effects of drought

• Thinning fruit can increase fruit size for trees in drought.

• Thinning does not impact DMC• Impact of DMC on fruit quality in peach?• High DMC linked to quality traits in mango• Increase in DMC may cause lack of fruit

juiciness in peach.

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Impact of Pruning on drought stressed trees

Lopez et al, 2004

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Drought and Experimental pruning

Drought and commercial pruning

Wat

er s

tatu

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Managing weeds and insects

• Manage weeds to reduce competition for moisture.

• Control of defoliating insect pests and diseases to enhance photosynthesis.

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Conclusion

• Drought impacts tree growth, yields, fruit quality and survival of fruit trees.

• The impact depends on the severity and length of drought.

• Monitor the crop this year for impact from last years dry weather.

• Irrigate

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Thank you!

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