BIESBROCK, J. A.;BOHLOOL, B. B.;MARX, D. H., 1974: Study of mycorrhizae by means of fluorescent antibody. Can. J. Microbiol. 20, 137-139. ZoLLFRANK, U., 1986: Inimunhistochemischer Nachweis von Armillaria sp. und Heterobasidion annosum an infizierten Fichten. Doctoral thesis. Technical University of Munich. ZOLLFRANK, U.; HoCK, B., 1987: Infection of Norway spruce by Armillaria under defined conditions. Submitted to Eur. AbstractSoil baiting techniques identified the presence of five fungal genera capable of causing pre-and postemergent damping-off in two eucalypt species [Eucalyptus obliqua (messmate stringybark) and E. radiata (narrow leaf peppermint)] under laboratory conditions. Post-emergent damping-off of these eucalypts in the field was primarily caused by five Pythium species, two Fusarium species and Cylindrocarpoyi destructans Zins. Although these losses were of small consequence in the total number of post-emergent deaths, most eucalypt seeds were not observed to germinate, perhaps due to pre-emergent damping-off caused by the above fungal genera.Receipt of ms.: 12. 8. J986

During tree disease surveys between February 1996 and March 1998 in highland forests of Kenya, leaves of Prunus africana (Hook f.) Kalkman collected from regeneration wildings in natural forests and seedlings raised in nurseries were found to be consistently heavily infected with a leaf spot and shot-hole disease caused by Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. in Penz., anamorph of Glomerella cingulata (Stoneman) Spauld. & H. Schrenk. The pathogen was identified by sectioning sub-epidermal acervuli on the leaf and also by plating infected tissue segments on 2% malt extract agar. The cultural and conidial morphologies were characteristic of C. gloeosporioides. The isolate is maintained at Kenya Forestry Research Institute (KEFRI) culture collection (No. 069-63) and identity ascertained by the International Mycological Institute (IMI) (ref. W5794). To confirm pathogenicity, leaves of 3-month-old seedlings of P. africana were sprayed to run-off with a conidial suspension adjusted to 105 conidia per ml or sterile water as a control. Following inoculation, the seedlings were covered with transparent plastic bags for 48 h and kept in a glasshouse at 23 ± 3°C under natural light conditions and relative humidity of 80%. Leafspot symptoms similar to those found on leaves of wildings in natural forests and nursery seedlings were evident on the inoculated leaves within 3 weeks. Five weeks later the necrotic spots on the leaves measured 2 to 6 mm in diameter. The spots were circular or irregular usually surrounded by a zone paler than the healthy tissue. Later the centers of the spots fell, leaving clean shotholes. C. gloeosporioides was consistently reisolated from all inoculated plants. When infection was severe, the pathogen caused premature leaf fall and die-back of the leader shoot. P. africana, formerly known as Pygeum africanum, is a widespread tree species in moist tropical Africa and produces durable timber; extracts from its bark are used for the treatment of prostrate gland disorders. This is the first report of which we are aware of C. gloeosporioides emerging as an important pathogen of P. africana. Reference: (1) M. H. Tsingalia. Afr. J. Ecol. 27: 207, 1989.

Prunus africana, formerly known as Pygeum africanum, is widely distributed in moist, tropical Africa and produces durable timber. Extracts from its bark are used in treatment of prostate disorders. Powdery mildew was observed on nursery-grown seedlings of P. africana in Kenya (Nyeri, Kiambu, and Kericho districts) in the dry seasons of 1998, 1999, and 2000. White ectotrophic mycelial growth was observed on leaves. The fungus caused stunting, distortion of leaves, surface necrosis of invaded tissues, and general decline in growth of seedlings that led to premature leaf fall and death. Invaded leaflets wilted and dropped, leaving behind a bare stem. The primary mycelium was hyaline, with no secondary brown mycelium. The conidial state was conspicuous, with conidia produced in chains. Appressoria were unlobed and nipple shaped. Conidiophores were straight and three-celled, measuring 75 to 112 μm. Conidiophore foot cells were topped by a longer cell and one or two shorter cells measuring 35 to 77 μm. Conidia had fibrosin bodies, were ovoid, and measured 27 to 30 × 17 to 18 μm. The fungus was identified by the International Mycological Institute IMI (W6496) as Podosphaera leucotricha (Ellis & Everh.) E. S. Salmon. Infected leaves of P. africana were deposited at the East African Herbarium, National Museums of Kenya (Accession No. KM-KEFRI/446/2001). Pathogenicity was confirmed by inoculating seedlings of P. africana by gently pressing infected leaves with abundant sporulation onto healthy leaves. The plants were then incubated under moist conditions for 48 h and thereafter maintained in a glasshouse. After 15 days, powdery mildew symptoms developed on seedlings. Examination of leaves confirmed that they were infected with Podosphaera leucotricha. Uninoculated control plants were free of powdery mildew. To our knowlege, this is the first report of Podosphaera leucotricha as a pathogen of P. africana. Reference: 1. H. J. Boesewinkel. Bot. Rev. 46:167, 1980.

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