Different diseases of olive

1. By Muhammad Usman Arshad
(Internee at Barani Agriculture
Research Institute, Chakwal)

2. Olive
Introduction:
The olive, known by the botanical name Olean
Europaea, meaning "European olive", is a species of
small tree in the family Oleaceae.
The olive tree, Olea Europaea, is an evergreen tree or
shrub native, to the Mediterranean, Asia and Africa.
 It is short, squat and rarely exceeds 8-15 m in height.

3. The silvery green leaves are oblong, measuring 4-10 cm
(1.6-3.9 inch) long and 1-3 cm (0.39-1.18 inch) wide.
The fruit is a small drupe 1-2.5 cm (0.39-0.98 inch)
long, thinner-fleshed and smaller in wild plants than
in orchard cultivars.
Olives are harvested in the green to purple stage.

4. Diseases of Olive
 Botryospaeria Blight
 Mycocentrospora
 Olive Knot
 Peacock Spot
 Phytophthora Root & Crown Root
 Verticillium Wilt
 Armillaria Root Rot
http://ipm.ucanr.edu/PMG/selectnewpest.olives.html

5. Botryosphaeria Blight
 PATHOGEN: BOTRYOSPHAERIA DOTHIDEA
 SYMPTOMS AND SIGNS
 The pathogen enters through wounds or tissue infected,
invades the branch, forming an elliptical canker.
 This canker can girdle and subsequently kill small
shoots and branches.

6.  Sources of inoculum for this disease are rachises,
shoots, and petioles killed by B. dothidea during the
previous growing season.
 Cankers can also provide inoculum for as long as 6
years.
 Cankers caused by the genus Botryosphaeria can
colonize the vascular tissue very fast, it is critical to
manage the disease properly.

7. Management
 Proper orchard sanitation, pruning, and irrigation
management can be helpful in managing this diseases.
 The best approach to reduce both the disease level and
production of inoculum within olive orchards is a
combination of proper orchard sanitation, pruning,
and irrigation management.
http://ipm.ucanr.edu/PMG/r583100511.html

8. Mycocentrospora
 Pathogen: Mycocentrospora cladosporioides
 SYMPTOMS AND SIGNS
 It causes the leaves to appear slightly chlorotic
(yellowing—some varieties show more chlorosis than
others). The undersides of some leaves become
discoloured

9.  High temperatures restrict spore germination and growth,
thus the disease is inactive during the warm, dry summers.
 MANAGEMENT
 In cool, wet areas, apply preventive treatments to olive trees
after harvest, but before winter rains begin and again in
spring, if rainy weather persists.
http://ipm.ucanr.edu/PMG/r583100411.html

10. Olive Knot
 Pathogen: Pseudomonas savastanoi
 SYMPTOMS AND SIGNS
 Olive knot appears as rough galls or swellings about 0.5
to 2 inches in diameter on twigs, branches, trunks,
roots, leaves, or peduncles (fruit stems).

11.  Olive knot can girdle and kill trees if infections occur
on the trunks of young trees.
 They are readily spread by water at all times of the
year. Bacteria survive in galls and as epiphytes on
leaves and twigs.

12.  MANAGEMENT
 It is also helpful to carefully prune during the dry season
(July to August) to remove galls on twigs and branches.
 Leaf scars are susceptible when fresh, time treatment to
protect as many leaf scars as possible.
 Harvest occurs in fall or winter when rain is likely.

13. Peacock Spot
 Pathogen: Spilocaea oleaginea
 SYMPTOMS AND SIGNS
 Peacock spot appears on leaves as sooty blotches that
develop into black, circular spots about 0.1 to 0.5 inch
(2.5–12 mm) in diameter.
 The optimum temperature is 58oF to 75oF.

14.  Twig death may occur as a result of defoliation.
 The margins of lesions enlarge in fall, and a new crop of
spores develops there.
 New infections are associated with rainfall and mostly
occur during fall and winter.

15.  MANAGEMENT
 If olive trees exhibit peacock spot leaf symptoms, it is
important to treat for it yearly.
 Apply a preventive treatment in late October before
winter rains begin, and again in the spring if wet
weather persists.

16. Phytophthora Root and Crown Rot
 Pathogen: Phytophthora citricola
 SYMPTOMS AND SIGNS
 The bark of the root crown turns dark
as the infection spreads.
 It requires free moisture in the soil to
produce and disperse swimming
zoospores.

17.  The pathogen can live independently in the soil and
survive long periods of dryness as oospores.
 MANAGEMENT
 Careful soil water management is the best foundation
for control of Phytophthora root and crown rot.
 Plant trees on berms, shorten irrigation times, and
improve soil water penetration and drainage.

18. Verticillium Wilt
 Pathogen: Verticillium dahliae
 SYMPTOMS AND SIGNS
 Symptoms of Verticillium wilt appear when leaves on
one or more branches of the tree suddenly wilt early in
the growing season.
 Darkening of xylem tissue, a key symptom for
distinguishing.

19.  The fungus survives from season to season in the soil
and probably in the roots of infected trees.
 Some trees recover naturally from an initial infection,
but others may die.
 This mostly depends on the strain of the fungus
(defoliating or non-defoliating), the resistance of the
cultivar, and the amount of inoculum in the soil.

20.  MANAGEMENT
 Inoculum levels can be reduced before planting by
flooding the fields during summer, growing several
seasons of grass cover crops.
 After trees have been planted, there is no reliable
method of control.
 Post plant soil solarization has provided inconsistent
control in established plantings.

21.  Soil Solarization
 Beginning in late spring, cover the surface of an entire
block with transparent plastic that has a UV-inhibitor
additive.
 Leave the plastic on throughout the summer and as long
as practical. Inferior plastic will break down and render
the treatment ineffective.
 Solarization gives inconsistent results when used in
replant spots.

22. Armillaria Root Rot
 Pathogen: Armillaria mellea
 SYMPTOMS AND SIGNS
 Infected trees have slowly thinning canopies and appear
weak.
 This symptom often develops first on one side of the tree and
then progresses over several years to involve the whole tree.

23.  Roots infected with Armillaria mellea have white to
yellowish fan-shaped mycelial mats between the bark
and the wood.

24.  MANAGEMENT
 Armillaria root rot is most likely to be present in soils
where oak trees previously grew.
 No olive rootstocks are known to be resistant, and
infected trees cannot be cured.

25.  Although the research has not been conducted
on olive in this regard but there are some
techniques that can be applied such as-
 Remove soil from around the base of the tree to a
depth of 9-12 inches.
 Leave the trunk exposed and keep the upper roots and
crown area as dry as possible.

26.  During winter, provide drainage if necessary so that rain
doesn't collect in the hole.
 Recheck the hole every few years to make sure it has not
filled in with leaves, soil, and other matter; the hole must
be kept open and the crown and upper roots exposed.
http://ipm.ucanr.edu/PMG/r583100211.htm