In 2002, similar symptoms were observed in a cashew field of the Newala District, Mtwara, Tanzania (Sijaona et al. The disease was first observed in 2000 in a cashew field at Itoculo, Monapo District, Nampula in Mozambique, where it was confused with anthracnose. However, further observation and monitoring have indicated that the disease can also attack flowers and cashew apples. The disease was originally called “cashew leaf and nut blight disease” because of the pathogen’s ability to infect and show symptoms both on cashew leaves and nuts. Investigations of the disease, including pathogen identification in collaboration between the Naliendele Agricultural Research Institute (NARI) and Commonwealth Agricultural Bureaux International (CABI), identified the pathogen at the genus level as a Cryptosporiopsis sp. Similarly, recent cashew attacks by Fusarium oxysporum represent yet another alarming challenge for cashew producers (Tibuhwa and Shomari 2016).Ĭashew Leaf and Nut Blight Disease (CLNBD) continues to be a serious destructive disease of cashews often causing substantial yield losses. 2002) have been considered as the major challenges in cashew nut production. Diseases such as powdery mildew, blight, anthracnose, dieback (Nene and Sijaona 2017 Sijaona 2013), black mould, angular leaf spot and gummosis (Freire et al. However, like other crops, many different diseases can affect cashew at different stages of its growth (Freire et al. In Tanzania, cashew is the topmost cash crop, contributing significantly to the foreign exchange earnings (BOT 2016) and is a source of income for more than 500,000 households (NARI 2018). Plant disease epidemics are associated with weather patterns and climatic parameters, and each disease can be affected differently by weather parameters (Burt 2002). Direct yearly agricultural production losses associated with biotic stress have been estimated to be between 20 and 40% (James 1998 Oerke 2006 Oerke et al. These diseases can be caused by biotic factors such as fungi, bacteria, viruses, and mycoplasmas or abiotic factors including light, heat, cold, drought, excessive precipitation, pH, nutrition, chemical, and mechanical injury (Manners 1993). Plant diseases continue to be one of the major constraints to agricultural production (Palmgren et al. This would help timely initiation of appropriate management strategies. Findings from this study, particularly the association of rainfall and temperature on disease epidemics, can be used as tools for forewarning incidences of CLNBD. Thus, it appears that for the blight pathogen to initiate and complete its infection processes, a continuous wet period of at least 8 h is required. This study also established that symptoms for blight disease on cashew leaves appear 8 h post exposure to continuous wet periods. Cashew trees in Mtwara District recorded higher blight disease incidence as compared to the rest of the studied areas. Blight incidence was significantly higher ( p < 0.001) during the rainy season (range: 11.7 to 36.6%) compared to the dry season (1.4 to 11.5%). However, temperature was negatively associated with disease incidence and a unit increase of 1 ☌ in temperature caused a 21.56% decline in disease incidence (e = –0.2428, p < 0. Rainfall was positively associated with CLNBD and a unit increase of 1 mm in rainfall caused a 2 percent increase in the percentage of disease incidence (e = + 0.01995, p < 0.011). Poisson regression analysis indicated a significant association between rainfall and temperature with CLNBD incidence (df = 3, Chi Pr < 0.001). We conducted a study to assess the association between weather variables, particularly rainfall and temperature, on cashew leaf and nut blight disease (CLNBD) outbreaks and establish a minimum wetness duration period for initiation and development of the disease. is a devastating disease of cashew crop resulting in a significant reduction of nut production. Cashew leaf and nut blight disease caused by Cryptosporiopsis spp. Cashew ( Anacardium occidentale L.) which is an important cash crop in Tanzania, is susceptible to various abiotic and biotic stresses.
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