This document discusses several common pecan nut diseases, including pecan scab, pecan casebearer, bacterial leaf scorch, sooty mold, anthracnose, downy spot, shuck and kernel rot, powdery mildew, vein spot, crown gall, and zonate leaf spot. It provides details on the symptoms caused by each disease, such as lesions on leaves and fruit, holes in nutlets, necrotic leaf tissue, rotting of fruit, fungal growth on leaves and spots, and premature leaf drop. Managing these diseases requires identifying their symptoms and controlling any insect vectors through integrated pest management practices.

2. Pecan nut Diseases
A
Lecture To ToT trainees ( FFS)
By
Mr. Allah Dad Khan
Provincial Coordinator IPM KPK
MINFAL Pakistan

3. Pecan Nut Scab
 Small, rough or velvety olive green to black spots on leaves, green twigs or fruit;
lesions may coalesce to form large dark areas with an irregular shape; leaflets may
drop from plant if they are infected at the base of the petiole; lesions on young leaves
may dry out and crack, resulting in a "shot hole" appearance as the leaves expand;
lesions on shucks are virtually identical to those on the leaves ; severe infection of fruit
can cause fruit to stop developing

4. Scab
Scab lesions on pecan
foliage
Scab symptoms on pecan
shucks

5. Scab
Scab symptoms on pecan
shucks
Scab symptoms on pecan
shucks

6. Pecan nut casebearer Acrobasis nuxvorella
Symptoms
 Holes in nutlets at base
which usually is
associated with black
frass that protrudes from
the hole; frass and
damaged nutlets are held
together by silken thread;
adult insect is a small,
light gray moth; larvae are
initially white with a brown
head and mature to olive
or jade green

7. Bacterial leaf scorch Xylella fastidiosa
Symptoms
Bacterial leaf scorch
symptoms on pecan
 Tan to brown necrotic
lesions with distinct dark
brown line separating the
diseased tissue from
healthy; lesions occur on
leaf margin or apex; entire
leaves becoming necrotic;
leaflets may drop from
tree; symptoms may be
confined to one limb or
scattered throughout
canopy

8. Bacterial leaf scorch
Bacterial leaf scorch
symptoms on pecan
Bacterial leaf scorch
symptoms on pecan

9. Bacterial leaf scorch
Bacterial leaf scorch
symptoms on pecan
Bacterial leaf scorch
symptoms on pecan

10. Sooty Mold
Symptoms Figure 27. Sooty mold.
 Sooty mold is a conspicuous black,
sooty fungus found on leaves
(Figure 27) and nuts of pecans.
This fungus is not pathogenic on
plants and can easily be removed
by rubbing with a clean cloth. It
grows on honeydew produced by
insects. The direct damage to
plants is minimal; however, severe
infestations will reduce the amount
of light reaching the leaf surface,
thus reducing the production of
carbohydrates in the tree.
Controlling aphids and other
honeydew-producing insects
should help to control sooty mold.

11. Anthracnose Colletotrichum gloeosporoides
Symptoms
 Shiny, dark brown
sunken lesions on
green fruit which may
coalesce to cover the
whole fruit; may be pink
colored fungal masses
on lesions during wet
weather; yield may be
reduced

12. Downy spot Pseudocercosporella caryigena
Symptoms
 Circular, pale yellow spots
on lower surface of
leaves; spots may be
covered with fuzzy white
growth during wet; lesions
develop through leaves
and become visible on
upper leaf surface; lesions
on upper leaf surface
yellow-brown; leaflets may
drop from tree; nut yield
may be reduced die to
defoliation

13. Shuck and kernel rot Phytophthora cactorum
Symptoms
 Rotting fruit with rot
starting at stem end of
fruit; dark brown rot with
light brown margin
spreading to cover
entire fruit; kernels have
a dark seed coat and
bitter taste.

14. Powdery mildew Phyllactinia guttata
Symptoms
 Small, powdery white
spots on leaves and
fruit; spots spread to
cover entire leaf; small
black fungal fruiting
bodies may be visible in
the white growth; young
leaflets may crinkle as
they mature

15. Vein spot Gnomonia nerviseda
Symptoms
 Dark brown to black
lesions associated with
vascular tissues e.g.
along leaf veins or leaf
midribs; leaves may fall
from trees

16. Crown Gall
Symptoms

Crown gall is a disease that results in
round to irregular swollen tumors or
galls, usually found at or near the soil
line on the trunk or roots. Infected trees
show a lack of vigor, foliage lacks
normal green color, and occasionally
the tree may die. To prevent crown gall,
plant disease-free trees. For individuals
with a small pecan nursery, it is
important not to locate a nursery in an
area where crown gall has been
observed previously. As a preventative
control measure, it would be advisable
to treat the seed with Galltrol-A before
planting

17. Crown Gall

18. Zonate leaf spot Grovesinia pyramidalis
Symptoms
Zonate leaf spot lesions on pecan
leaflet
 Lesions with concentric
rings on leaves which are
tan to light brown on the
leaf underside and gray-
brown on the upper leaf
surface; a crystalline
substance may be present
on the surface of the
lesion; infected leaves dry
out by late summer and
drop from the tree
prematurely; defoliation

19. Zonate leaf spot
Zonate leaf spot symptoms on
pecan leaf
Close-up of zonate leaf spot
lesions on pecan leaflet