Agriculture Reference
In-Depth Information
Table 6.6.
Major diseases of
Annonas
.
Region or
country
Common name
Organism
Parts affected, symptoms
Anthracnose
Flowers, fruit, leaves,
dieback, seedling
damping off
Universal
Colletotrichum
gloeosporioides
(
Glomerella
)
Armillaria root
rot
Roots, base of trees,
decline
Australia
Armillaria
leuteobubalina
Bacterial wilt
Tree wilt
Australia
Pseudomonas
solanacearum
Black canker
(diplodia rot)
Leaf scorch, twig dieback
Universal
Botryodiplodia
theobromae
Black canker
Leaf scorch, twig dieback
Australia
Phomopsis
Purple blotch
Spots on immature fruit,
fruit drop, twig dieback
Australia
Phytophthora palmivora
Rust fungus
Leaves
Florida
Phakopsora cherimoliae
Fruit rot
Fruit
India
Glioclacium roseum
is the most serious in areas of high rainfall and atmospheric humidity and
during the wet season in dry areas (Alvarez-Garcia, 1949; Dhingra
et al.
,
1980). This disease causes twig dieback, defoliation and dropping of fl owers
and fruit. On mature fruit, the infection causes black lesions.
Black canker (
Phomopsis anonacearum
)
and diplodia rot (
Botryodiplodia
theobromae
)
occur mostly on neglected trees and cause similar symptoms of
purplish to black lesions, resulting in mummifi ed fruit. Marginal leaf scorch is
also caused by these two fungi and causes twig dieback. Diplodia rot has darker
internal discoloration and deeper, more extensive, corky rot in fruit. A fruit
and leaf spot is caused by a soil-borne fungus,
Cylindrocladium colhounii
,
which
can cause almost total loss of fruit during years of persistent heavy rains.
Symptoms begin with small, dark spots, primarily on the shoulders of the fruit,
which spread along the sides, enlarge, become dry and crack. Infection is skin
deep, but fruit becomes unmarketable. The control measures recommended
are good orchard maintenance with heavy mulching and lower-branch
pruning to prevent splashing of soil during heavy rainfall (Sanewski, 1991).
Bacterial wilt of atemoya is caused by
P. solanacearum
and is characterized
by rapid wilting and death of young trees and slow decline of old trees. There
is a general decline of vigour and defoliation on af ected limbs. Vascular
discoloration of woody tissues occurs in the roots and up to the trunk at
ground level. It has caused up to 70% tree death in 12 years in orchards using
A. squamosa
rootstocks in Queensland.
In sweetsop,
Phytophthora
blight (purple blotch) is caused by
Phytophthora
citrophthora
and
Phytophthora nicotianae
, which infest fruit and leaves, mainly
