agronomy Review Coffee Leaf Rust (Hemileia vastatrix) in Kenya—A Review Elijah Gichuru *, Getrude Alwora, James Gimase and Cecilia Kathurima   Citation: Gichuru, E.; Alwora, G.; Gimase, J.; Kathurima, C. Coffee Leaf Rust (Hemileia vastatrix) in Kenya—A Review. Agronomy 2021, 11, 2590. https://doi.org/10.3390/ agronomy11122590 Academic Editor: Pedro Talhinhas Received: 8 October 2021 Accepted: 30 November 2021 Published: 20 December 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Coffee Research Institute, Kenya Agricultural and Livestock Research Organization, Ruiru P.O. Box 4-00232, Kenya; alworahgetrude@gmail.com (G.A.); jgimase@gmail.com (J.G.); cwkathurima@yahoo.com (C.K.) * Correspondence: ekgichuru@gmail.com or elijah.gichuru@kalro.org Abstract: Coffee is one of the most important cash crops and beverages in the world. Production of coffee is limited by many factors, which include insect pests and diseases, among others. One of the most devastating coffee diseases in many coffee-producing countries is Coffee Leaf Rust caused by the fungus Hemileia vastatrix. Kenya is a coffee-producing country and has conducted studies to understand and manage the disease. Management strategies for the disease include the development and use of fungicide spray programs, cultural control practices, breeding resistant coffee varieties, and biological control agents. This paper reviews the status of the disease and management options applied in Kenya. Keywords: coffee; Kenya; Coffee Leaf Rust; races 1. Introduction Coffee is an important crop and beverage in the world, creating incomes for over 125 million people. In terms of commerce, it is the second most traded commodity after oil [1]. Coffee is a tropical crop mainly grown in Southern America, Africa, Asia, and parts of Oceania primarily by smallholder farmers. In Africa, coffee is produced in Eastern, Central, and West Africa, with Ethiopia being the largest producer. It is also the origin of Arabica coffee (Coffea arabica) which is the main species produced in the world. Kenya produces Arabica coffee and is currently the fifth largest producer in Africa, down from being the second-largest producer in the 1980s [2–4]. Coffee in Kenya is produced in 32 counties by 800,000 smallholder farms and 6000 estates [2,5]. On the global scale, coffee production has been on a decline over the last two decades as compared to consumption which has been on a steady increase over the same period [1,6,7]. The recent decline has mainly been attributed to the Coffee Leaf Rust, Hemilleia vastatrix Berk. and Br. (CLR) outbreak that hit most coffee-producing countries in 2008–2011 [8–11]. Other challenges facing coffee production include climate change, insect pests, other coffee diseases, volatile prices, soil fertility management, competition from other enterprises, aging farmers, and high costs of production [4]. Coffee Leaf Rust is a major disease of Arabica coffee, causing significant economic losses and has been reported in over fifty (50) coffee-growing countries [12]. The disease can cause yield losses in excess of 75% where outbreaks are severe [13] due to loss of foliage by up to 100% and loss of berries by up to 70% [14]. The disease cause losses of one to two billion US dollars annually [15]. Since 1976 when the disease was observed in Central America, the worst was the recent epidemic affecting all countries in the region, during which a 53% incidence was experienced. The first case of CLR in Kenya was reported in 1912, though records indicate that it was noticed in 1861 near Lake Victoria (western Kenya) on wild coffee [16]. This indicated that the pathogen was infecting other Coffea species before the introduction of Arabica coffee in Kenya. Coffee in Kenya is mainly grown in two regions, the East of Rift Valley (areas around Mount Kenya, the Aberdare ranges, and Machakos) and West of Rift Valley (Kisii highlands, Agronomy 2021, 11, 2590. https://doi.org/10.3390/agronomy11122590 https://www.mdpi.com/journal/agronomy