Latest Survey Data
- Rust Issues: Stem rust is a constraint to wheat production.
- Ug99 Status: Three variants of Ug99 have been detected in Tanzania – Races: TTKSK (Ug99), TTTSK (Sr36 variant of Ug99) and TTKST (Sr24 variant of Ug99). All three races were first detected in 2009.
Situation Updates:
A paper by Hale, Mamuya and Singh (2013) has just been published in Plant Disease which confirms and documents the presence of three Sr31 virulent races of stem rust in Tanzania. The three races – TTKSK, TTKST, TTTSK – are all members of the Ug99 race group and all three races are previously known from neighbouring Kenya. This study confirms and details the initial findings posted in April 2011. All samples described in the study were collected in 2009, although there are some indications that Sr31 virulence may have been present in Tanzania since at least 2006. The authors recommend that future surveys and systematic race monitoring efforts should be undertaken in Tanzania.
Three variants in the Ug99 lineage have been confirmed in stem rust samples collected in Tanzania during August 2009 by a team of Tanzanian and international scientists. Races confirmed by the USDA-ARS Cereal Disease Laboratory, St. Paul, MN, USA were; TTKSK (Ug99), TTKST (Sr24 variant of Ug99) and TTTSK (Sr36 variant of Ug99). Races TTKSK and TTTSK were present in samples from the Hanang, and Ngorongoro areas, whilst race TTKST was present in the Karatu and Monduli areas (Lowe et al forthcoming). All three races have been present in neighbouring Kenya since 2001, 2006, and 2007 respectively. Given the close proximity of wheat areas in Kenya and Uganda known to be infected by stem rust Ug99, and observed regional wind patterns, the results from Tanzania are not unexpected. No crop damage was observed in Tanzania in 2009 due to stem rust. A combination of effective chemical control and early senescence due to drought resulted in the majority of wheat fields surveyed being rust-free apart from a few isolated infected plants. These confirmed results support previous findings which indicate the expected and continued regional spread of Ug99 variants out of Kenya.
Additional reports of wheat stem rust were received from several African countries. In August, wheat stem rust was reported to be widespread in Tanzania. Wheat growing areas in Northern provinces and the Southern highlands both reported the presence of wheat stem rust. In South Africa, wheat stem rust was reported to be widespread in the Southern and Eastern Cape regions during Sept-Oct. One 160 ha field reportedly suffered complete yield loss to stem rust. In Zambia, trace amounts of wheat stem rust were found on 3 breeding lines at Golden Valley Research Station in late October. In all countries, the identity of stem rust races present remains unknown.
In Yemen, reports were received indicating higher incidence of wheat stem rust, compared to 2008, in highland areas during October. No race information is currently available.