Prevention and Control of Common Olive Insects and Diseases

Bill Krueger, UC Cooperative Extension, Glenn County

Peacock Spot-Spilocaea oleaginea

Widespread worldwide

In all growing areas of the state

Peacock Spot symptoms

Spots 1/16 to ½ inch

Defoliation from Peacock Spot

Life Cycle

• Overwinters in margins of old lesions• Spores spread by wind and rain• Infections-fall winter-spring• Symptoms-spring and summer

Peacock Spot Variety Susceptibility

• Very susceptible -Blanqueta, Cornicabra,Empeltre,Mission, Picual

• Susceptible -Aglandou, Arbequina, Ascolano, Hojiblanca, Kalamata, Sevillano, Manzanillo, Pendolino, Picudo

• Resistant-Beauteillan, Cayon, Coratina, Leccino, Maurino, Moraiolo

• Very Resistant -Arbosana, Frantoio, Koroneiki

Cercospora Leaf SpotMycocentospora cladosporioides

• North Coast • Sooty mold like symptoms on underside of

leaf from sporulation• Yellowing and leaf drop – no spots• Life cycle similar to Peacock spot• Control measures are the same

Cultural Control

• Variety Susceptibility• Consider variety susceptibility• Cultural

– Contributors to disease• High humidity- heavy dew, fog, low lying areas• Dense canopies-low light• Excessive sprinkler irrigation

Control continued

• Copper sprays– Bordeaux, Fixed coppers

• Preventative applied before infection– Central Valley table varieties, post harvest

before significant rain, 1 to 2X– Coastal Areas ? Oil varieties?, post harvest

and spring– Consistent program important

Olive KnotPseudomonas syringae,pv.savastoni

Damage-girdle and kill twigs and some larger branches, reduce production

Life Cycle

• Bacteria survive in galls• Spread by wind and rain• Infect openings in tree

– Leaf scars, pruning wounds, freeze cracks• Infection-fall, winter, spring• Symptoms-late spring, summer

Freeze Injury

Hail Damage

Olive Knot Variety Susceptibility

• Very susceptible – Arbequina, Manzanillo, Picudo

• Suceptible – Empeltre, Sevillano, Hojiblanca, Koroneiki, Moraiolo, Pendolino, Picual

• Resistant – Ascolano, Blanqueta, Frantoio, Leccino, Mission

Average Rainfall by Month for Orland, California

0102030405060708090

100

Rai

nfal

l (m

m)

JAN. MAR. MAY JULY SEPT. NOV.

Wounded Limbs

Olive Knot Wound Study4 Wounds/tree

11 replicates 2-15-91 to 6-30-92 10 replicates 3-29-93 to 11-24-93

0

20

40

60

80

100

120

2/15

/199

1

3/22

/199

1

4/18

/199

1

5/25

/199

1

9/13

/199

1

11/2

3/19

91

12/3

/199

1

2/27

/199

2

4/6/

1992

6/30

/199

2

3/29

/199

3

5/3/

1993

5/21

/199

3

6/16

/199

3

7/26

/199

3

9/14

/199

3

10/1

5/19

93

11/2

4/19

93

Wounding Date

% In

fect

ion

Olive Knot Pruning Wound Study

Manzanillo Variety

0102030405060708090

100

% Infected (10 shoots)

Con

trol

5/22

- 0

5/20

- 2

5/18

- 4

5/15

- 7

5/13

- 9

5/11

- 11

5/8

- 14

Date / Days From Pruning to Inoculation 3.175 mm rain

Pruning Dates: 5-8-92 to 5-20-92

Inoculated 5-22-92

Cultural Control

• Variety susceptibility• Prune out during dry period (late spring)

– Reduces risk of freeze injury– Allows wounds to heal before infection period

Control-Continued

• Materials are at the same as Peacock Spot– Copper Sprays

• Timing-preventative• More sprays are better• Central Valley recommendation- 2 sprays,

fall and spring.• Spring spray is the most important

Verticillium WiltSoilborne fungusSurvive in the soil as microsclerotiaGrow into root and plug vascular tissue resulting in wiltInfections in cool moist soil in winterSymptoms in spring and summerMuch more prevalent in Southern San Joaquin Valley

Verticillium Wilt Variety Susceptibility

• Very Suceptible – Arbequina, Cornicabra, Hojiblanca, Picual, Picudo

• Susceptible – Kalamata, Leccino, Manzanillo, Mission, Moraiolo, Pendolino, Picholine

• Resistant – Aglandou, Ascolano, Koroneiki,

• Very Resistant – Empeltre, Frantoio

Control

• Site selection– Avoid that are known to have high levels of

Verticillium• sites that have previously grown susceptible hosts

• Solarization- inconsistant results• No resistant rootstock.

Black ScaleSaissetia oleae

• Soft Scale• One to two generations

(coast) generations per year

• Overwinter as 3rd instarnymph

• Mature spring summer• Lay eggs• Egg hatch May,

June,complete by July• Crawlers develop to 2nd

or 3rd instar by fall

Damage• Suck sap from

tree- honeydew• Suity mold• Reduces

photosynthesis and respiration

• Can reduce fruit bud formation, cause leaf drop and dieback

Black Scale Adult

Black Scale Crawlers

Pre-ovipositional-rubber stage

Cultural Control

• Pruning- Open airy canopy promotes heat mortality

• Most reliable control for Central Valley

Biological Control

Scutellistacyanea

Metaphycus helvolus

Control ants-deny access to tree

Cool environment is preferable

Treatment Thresholds

• May sample– Light population (0-1 per branch) no treatment– Moderate (1-4 per branch)- prune or prune

and spray– Heavy (4-10) Prune and Spray

Oil and/or Insecticide Treatment

• Crawler emergence (July 1) to Aug. 1– To prevent damage to subsequent crop

• Post Harvest– Until scale develops to rubber stage– Light to moderate populations

Armored Scales

• Olive, Oleander, Latania, Greedy and Red

• 2 to 3 generations per year• Damage-reduce yield and downgrade fruit

Olive Scale Paratoria Oleae

Scale on fruit-dark spots Adult female

Oleander Scale

Scale under covering-yellow

Green spots on dark fruit

Control

• Biological– Don’t disrupt– Promoted by open airy canopy

• Spray crawlers with oil and/or insecticide– Monitor for crawler emergence with 2 sided

sticky tape

Cribrate Weevil

Cribrate Weevil Damage

Cribrate Weevil Control

Block access to the tree