|
Member Articles
|
Maize Diseases: Reflection on the 2004/2005 season |
|
|
|
Rikus Kloppers: PANNAR research services, P.O.Box 19, Greytown 3250 We are heading for a record harvest in the 2004/2005 maize season. It is an unwritten rule that a good season for a crop is also a favourable season for plant diseases. This was no exception and has provided its share of problems in the form of leaf diseases earlier in the season, followed by the stem rots, and later the cob rots and associated grading problems which are now beginning to crop up with harvesting. The presence of disease must not been seen in isolation – leaf diseases that occurred earlier in the season can lead to an increase in the root, stem and cob diseases later in the season. The impact of maize diseases is generally greater with the ultra-short season hybrids. This is as a result of a combination of factorssuch as their inherent susceptibility to the majority of diseases and the high plant populationsthat provide a favourable microclimate for diseases. In addition, the shorter growingseason provides little chance for corrective action and recovery, and control is often toolate or less effective. |
|
Read more...
|
|
|
Researching black foot disease in South African vineyards and grapevine nurseries |
|
|
|
 Francois Halleen1, Paul H. Fourie2 & Pedro W. Crous3
1 Plant Protection Division, ARC Infruitec-Nietvoorbij, Stellenbosch. E-mail:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
2 Department of Plant Pathology, University of Stellenbosch, Matieland
3 Centraalbureau voor Schimmelcultures, Utrecht, The Netherlands
Cylindrocarpon spp. which cause black foot disease of grapevine, were
recently found to be associated with declining grapevines in South
Africa. Results obtained from the diagnostic service at ARC
Infruitec-Nietvoorbij showed that Cylindrocarpon spp. were isolated
from 52%, 22% and 29% of diseased vines during the 1999/2002, 2002/2003
and 2003/2004 seasons, respectively. However, it was unclear how
and where these infections occurred as very little information was
available regarding the aetiology and epidemiology of these
fungi. Diseased plants display an array of decline
symptoms. In vineyards, the first visible symptoms are usually
delayed budding or absence of budding (Fig. 1).
|
|
Read more...
|
|
|
A collaborative project to better understand Siricid-Fungal symbioses |
|
|
|
|
Bernard Slippers1, 2, Rimvis Vasiliauskas2, Brett Hurley1, Jan Stenlid2 and Michael J Wingfield1
1 Tree Protection Co-operative Programme, Forestry and Agricultural
Biotechnology Institute, University of Pretoria, Pretoria, South Africa
2 Department of Forest Mycology and Pathology, Swedish University of Agricultural Biotechnology Institute, Uppsala, Sweden
The Forestry and Agricultural Biotechnology Institute, University of
Pretoria and the Department of Forest Mycology and Pathology, Swedish
University of Agricultural Biotechnology Institute, Uppsala, Sweden are
collaborating on a study of the Siricid-Fungal symbiosis, and its
parasites. This project aims to address questions in two general areas,
namely (a) the evolution and biology of mutualistic symbiosis and (b)
the monitoring and control of wood inhabiting pests and pathogens that
threaten biodiversity and forest production in introduced and native
environments.
|
|
Read more...
|
|
|
Collaborating Within Africa: Searching For Forest Pathogens |
|
|
|
|
Knowledge of forest/tree fungi on the African continent is very
limited, particularly those of indigenous African tree species. In the
earlier part of the previous Century, up to around 1960, some research
was conducted into diseases of plantation tree species, but during the
course of the last 40 years very few publications relating to this
field has appeared from Africa, particularly countries north of South
Africa. Information concerning macro-fungi has been more consistently
published in several excellent publications, but there remains a
tremendous shortage of information pertaining to tree related fungi
from Africa. We need only attend any international congress to note the
lack of information from Africa in phylogenetic trees and other
studies. |
|
Read more...
|
|
|
A Protocol To Quantify Spray Deposits In Grape Bunches |
|
|
|
Introduction
Various studies revealed that
Botrytis cinerea, the causal pathogen of Botrytis bunch rot, is mostly
associated with rachises, laterals, pedicels and berry bases, and not
with berry skins as previously conceived (Holz et al., 2003). Provided
that sufficient coverage of inner bunch parts was achieved, laboratory
studies have shown that fungicides almost completely reduce the amount
infection and symptom expression of B. cinerea at all growth stages.
The same efficacy was, however, not achieved with the same fungicides
when using conventional spraying methods in vineyards (Van Rooi &
Holz, 2003). |
|
Read more...
|
|
|
Black pod rot of groundnut (Arachis hypogaea) caused by Chalara elegans |
|
|
|
|
Fig. 1. Chalara elegans (Thielaviopsis basicola), the causal agent of black pod rot of groundnut.
A.J. Cilliers
ARC Grain Crops Institute Potchefstroom
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
Peanut (Arachis hypogaea L.) is an important
protein crop planted on approximately 150 000 ha in South Africa. The
groundnut pods, being borne underground, are particularly susceptible
to various soilborne fungal pathogens, including the black hull fungus Chalara elegans
Nag Raj & Kendrick (Fig. 1). Black pod rot or black hull (Fig. 2)
results in severe pod and kernel damage of groundnut in South Africa
(10,13), and was first isolated from groundnuts in this country by
Jooste in 1979 (7). In South Africa the disease is observed mainly on
pods of groundnuts plants, but may also occur on the roots (10). The
disease reduces both yield and kernel quality thereby reducing the
value of groundnut consignments (16). |
|
Read more...
|
|
| | << Start < Prev 1 2 Next > End >>
| | Results 17 - 26 of 26 |
|
|
Home 
