Spring Almond Disease Talk

David DollFarm Advisor

Merced CountyMarch 20th, 2012

Almond Foliar and Bloom Disease Control

Almond Bloom Diseases

Trees are susceptible to many fungi, blossoms are highly susceptible

Rainy conditions favor disease

Rainy periods occur during bloom!

Disease control is dependent upon:

Fungicide UsedTimingCoverage

Growers need to assess which diseases are present and select the fungicide

Rotation of fungicides is advised to reduce resistance


A typical bloom spray includes a spray at 5-20% bloom, and one at 80%- full bloom.

Persistent rainy conditions may require a third spray

- 10 days without protection


Three main diseases:1. Brown Rot Blossom Blight2. Shothole 3. Jacket Rot

Other diseases:Scab, Rust, and Anthracnose


Almost always sprayed for at least once – full bloom

Attacks anthers and pistils of opened flowers

Moves into and kills the spur, can move into shoot

Young fruit are also susceptible

All varieties are susceptible; Butte and Carmel are most susceptible

Brown Rot – Monilinia laxa

A conventional Butte orchard that missed a full bloom brown rot spray had over 50% blossom blight despite no rain!

Brown Rot or Bacterial Blast?

Early Spring Diseases

• 3 Main Disease:– Green Jacket Rot– Anthracnose– Shot Hole

• Tend to be more severe in wet weather

• Require retreatment of trees every 10-14 days if rain persists

• Once established, can become a re-occuring problem

Green Fruit/Jacket Rot

Caused by three fungi- Monilinia laxa- Botrytis cinerea- Sclerotinia sclerotiorium

Timing of infection is from flower opening to petal fall – symptoms are observed later

Cultivars that form tight clusters are most susceptible: Butte, Ne Plus, Carmel, Merced

Poor control with DMI’s (Bumper, Tilt, Quash,

etc.)!!!

Almond Anthracnose- Colletotrichum acutatum

Infected nuts show round, orangish, sunken lesions on the hull.

Symptoms may appear 3 weeks after petal fall;

Profuse gumming occurs as the infection progresses into the kernel.

Symptoms include spur and limb dieback.

Leaves on infected spurs develop marginal necrosis, beginning with water-soaked areas that fade in color; leaves die but remain attached to branches.

Control: Bloom to summer if wet

Almond Anthracnose- Colletotrichum acutatum

Shot Hole – Wilsonomyces carpophilus

Requires water for completion of lifecycle

Causes lesions on fruit and leaves; heavy fruit infection causes fruit drop

Around the first of May, the hull becomes resistant to the disease

Post-bloom fungicide applications (Petal Fall to 2-5 weeks after bloom)

Spots occur on leaves, fruit, twigs, and flowers;

Spots on young leaves usually fall out, leaving a hole (the shot hole); older leaves retain their lesions.

Fruit spots are small with purplish margins, slightly corky, and raised.


The fungus survives on infected twigs and as spores in healthy buds

Spores are moved by water to new sites; prolonged periods of wetness, either due to rain or sprinkler irrigation


Shot Hole or Herbicide Drift?

Shark herbicide drift on almond


Goal Drift on almond – note the yellow halo.


Paraquat on almond – note the distinctive dead lesion

Shot Hole!



Neither – Chemical Burn from a Spray Additive (Micro-nutrient).

Summer Diseases

• 3 Major Diseases Of Concern– Scab– Rust– Alternaria

• Becoming more of a problem with increased planting densities

• Documented cases of resistance formation

• Biggest concern to many almond growers

Gray-black, oil-like soft looking spots form on leaves, fruit, and twigs

Almond Scab - Cladosporium carpophilum

Young lesions are indistinct small yellow specks, best seen by holding a leaf up to the light.

Lesions usually are not visible until late spring or early summer.


The fungus survives in twig lesions, and spores are spread by wind or rain.

Scab is favored by prolonged wet spring weather


Severe scab infections can cause early defoliation

If left uncontrolled for several years, infected trees become weakened.

Control: Fungicides 2-5 weeks after petal fall

Time to when lesions begin sporulating


Late Season Scab Defoliation

Lingering Effects of Scab

Scab Control

• No History of Disease– Make an application 2-5

weeks post petal fall (PPF)– Consider chlorothalinil at

petal fall, 2 weeks PPF– Use of DMI or strobilurin – Micronized sulfur sprays

made monthly may help suppress, but not very effective

• History of Disease– Dormant application of

copper and oil, or chlorothalinil and oil

– Follow same spray program listed under the “no history”

Almond Rust - Tranzchelia discolor

Rust occurs sporadically throughout almond-growing areas in California.

It often is serious on young orchards where bloom sprays have not been applied.

Rust appears as small, yellow spots on the upper surface of leaves.

On the lower surface of the leaf these spots take on a rusty red appearance when the rust-colored spores produced in the lesions erupt through the surface.


Rust Management• In orchards with a history of rust, apply fungicides in late

spring and summer to control leaf infections. – 2-3 applications may be needed in orchards that have had severe

rust problems.

• To be effective, fungicide must be applied before rust symptoms are visible.

• To prevent the rust inoculum from increasing in late fall, apply zinc sulfate (20-40 lb/acre) in late October to early November to hasten leaf fall

• Fungicide Control: 5 weeks after petal fall on, • My recommendation: Severe issue - Micronized sulfur once

a month from May through July, Moderate issue - Strobilurin with May Spray


Alternaria Leaf Blight

• Being found more frequently within orchards

• Causes complete defoliation

• Dense Plantings, orchards with high humidities have issues

• Strobilurin resistant populations exist within California

• Lesions have distinct bulls-eye, zonate look

• Sprays start 5 weeks post petal fall and continue through May and June

• Rotations are essential

Alternaria Leaf Blight

Hull Rot of Almond Monilinia fructicola, Rhizopus stolonifer

• Infection of the inside of the hull

• Doesn’t occur until after the almond has split

• High vigor increases the number of strikes


Most Moderately LeastNonpareil Price Fritz

Butte Sonora CarmelWinters Aldrich Monterey

Wood ColonyPadre

Mission

Varietal Susceptibility

Drip Fan Jet

TreatmentsA= N 125lb/acB= N 200lb/acC= N 275lb/acD= N 350lb/ac

b

a

a a

b

b

aa

Green line represents mean

Effect of N fertilization on Hull Rot-N Source UAN 32

• Application of water stress at hull-split initiation– Achieve water stress

of -14 bars using SWP– Resume irrigation – Around a 50%

reduction in water applied during the first week of hull split

Effect of RDI on Hull Rot 2003

17.7

2.2

0

5

10

15

20

Strik

es p

er tr

ess

Control

RDI


• Reduce fertilization if too high– Leaf Value 2.2-2.5%

• Reduce irrigation at onset of hull split

• Application of fungicides timed to when the hull is <0.25” split.


Fungicide Rotation: Why?

A

B

Fungicide Rotation: Why?

• Rotate through different group numbers

• Never use same number back to back

• Provided on fungicide label

Fungicide Rotation: How?

Fungicide Rotation: How?

Further Resources

• UC IPM Website• Almond Doctor Blog• Local Extension

Office• Chemical PCA

Fungicides for Brown Rottiming: pink bud-full bloom-petal fall

• Topsin/Benlate high risk (1) Benzimidazole• Pristine medium (11/7) Strobilurin/Boscalid• Rovral low risk (2) Dicarboximide• Vangard high risk (9) Anilinopyrimidine• Scala high risk (9) Anilinopyrimidine

• Abound high risk (11) Strobilurin• Rally/Laredo high risk (3) Demethylation• Elevate high risk (17) Hydroxyanilide• Flint / Gem high risk (11) Strobilurin• Bravo/Echo low risk (M5) Aromatic hydrocarbon• Captan low risk (M4) Phthalamide• Ziram/Maneb low risk (M3) Carbamate

Fungicides for Shot Holetiming:petal fall till 2-5 weeks after bloom

• Pristine (11/7) medium Strobilurin/Boscalid• Captan (M4) low risk Phthalamide• Ziram (M3) low risk Carbamate• Rovral (2) low risk Dicarboximide• Bravo/Echo (M5) low risk Aromatic nitrile• Abound (11) high risk Strobilurin• Flint (11) high risk Strobilurin• Gem (11) high risk Strobilurin

• Vangard (9) high risk Anilinopyrimidine• Scala (9) high risk Anilinopyrimidine• Laredo (3) high risk DMI-Triazole

Fungicides for Scabtiming 2-5 weeks after petal fall

• Pristine (11/7) medium Strobilurin/Boscalid• Flint / Gem (11) high risk Strobilurin• Abound (11) high risk Strobilurin

• Captan (M4) low risk Phthalamide• Ziram (M3) low risk Carbamate• Bravo/Echo (M5) low risk Aromatic nitrile• Topsin (1) high risk Benzimidazole

• Maneb (M3) low risk Carbamate• Lime Sulfur low risk

Fungicides for Rusttiming: 5 weeks after petal fall on

• Pristine (11/7) medium Strobilurin/Boscalid• Flint / Gem (11) high risk Strobilurin• Abound (11) high risk Strobilurin• Maneb (M3) low risk Carbamate

• Sulfur low risk Inorganic• Rovral (2) low risk Dicarboximide

Fungicides for Anthracnosetiming: bloom to summer if wet

• Pristine (11/7) medium Strobilurin/Boscalid• Flint/Gem (11)high risk Strobilurin• Abound (11) high risk Strobilurin

• Captan (M4) low risk Phthalamide• Ziram (M3) low risk Carbamate• Bravo/Echo (M5) low risk Aromatic nitrile

• Maneb (M3) low risk Carbamate• Rally/Laredo(3) high risk DMI-Triazole

Spring Almond Disease Talk

Documents

Transcript of Spring Almond Disease Talk