Pest Management in Miombo Fruit Trees - Indigenous Fruit Trees in the Tropics: Domestication, Utilization and Commercialization - page 375

seen throughout the year on branches of Uapaca kirkiana (Parker, 1978).
However, the decomposition of wood starts in living trees.
On foliage, fungal infections give rise to leaf spots, shot-holes, blotch or
more extensive necrosis. Tar spot of leaves caused by Phaeochorella parinari is
common in Parinari species in Zambia (Parker, 1978) and Zimbabwe (Masuka
et al ., 1998). Leaf spot of Sclerocarya birrea caused by Alternaria longissima ,
Cochliobolus bicolor and Glomerella cingulata is common in Malawi (G. Meke,
unpublished results). In southern Malawi, Colletotrichum gloeosporioides ,
Alternaria obtecta and Phoma spp. caused leaf spots on Uapaca kirkiana (G.
Meke, unpublished results; G. Sileshi, unpublished results). Colletotrichum also
affects Annona species in Zimbabwe (Masuka et al ., 1998). A smaller leaf spot
of Uapaca kirkiana caused by Cercospora is common (Parker, 1978). Brown
leaf spot is very common on Uapaca kirkiana and almost all plants observed
had this symptom. Phoma sp., Fusarium pallidoroseum and Fusarium solani
have been isolated from infected Uapaca kirkiana plants but Fusarium species
are unlikely to be the causal agent of the leaf spot symptoms (G. Meke,
unpublished results). Widespread necrosis of older leaves of Uapaca kirkiana
has been linked to Pestalotiopsis versicolor. Pestalotiopsis fungi are mostly non-
pathogenic, and probably are opportunistic invaders of tissues damaged by
other agents (Parker, 1978).
Rust fungi heavily infect leaves of Flacourtia indica (G. Sileshi, unpublished
results). The powdery mildew ( Phyllactinia sp.) that attacks seedlings of
Sclerocarya birrea in the nursery also attacks saplings and mature trees in the
field. For instance, Phyllactinia guttata was observed on over 80% of plants,
with over 50% leaf infection in Malawi (G. Meke, unpublished results). Rusts
and powdery mildews are host-specific obligate parasites, and may cause
serious damage. It is necessary to study their ecology and biology to be able to
find the best way to keep infections under control.
Colletotrichum gloeosporioides has been reported to cause necrotic leaf
spot of Annona cherimola (Pennisi and Agosteo, 1994), leading to leaf fall. C.
gloeosporioides causes anthracnose in mango, and it affects leaves, flowers and
fruits. In India C. gloeosporioides also causes fruit rot of Ziziphus mauritiana
(Gupta and Madaan, 1977). C. gloeosporioides is an example of a fungus that
has spread worldwide and it is a highly variable species with many strains. This
fungus can spread between different tree species and can cause great losses.
Many tropical fruits are affected by the fungus, and other miombo fruit trees are
not likely to be exempt.
Sooty mould fungi can sometimes be found covering the surface of the leaf
and surrounding the petiole and shoot of Uapaca , Sclerocarya and Strychnos ,
especially those infested with aphids and scale insects (G. Sileshi, unpublished
results). However, sooty moulds are not parasitic. The presence of sooty
moulds is usually of rather minor importance to the health of the plant, but it
does indicate the presence of insects and may be a warning of a severe aphid
or scale problem. On the other hand, sooty mould of baobab ( Adansonia
digitata ), possibly caused by Antennulariella (or its Capnodendron state), has
been cited as a killing disease. Since the mid-1990s large numbers of baobab
trees in Zimbabwe have been reported to be dying. Affected trees exhibit a