Banana pests and diseases spread to higher altitudes due to increasing temperature over the last 20 years

Abstract

In this study, we established changes in minimum and maximum temperature over the past 20 years, and how these changes a r e likely to affect the status of key banana pests and black Sigatoka disease in main banana cropping systems. A survey was conducted at elevations of 1200, 1400, 1600 and 1800 m above sea level in 13 sites previously used in 1 9 9 2 / 1993. Mean monthly minimum and maximum temperatures at different elevations were computed between 1991 and 2013 and used to determine the temperature change. Data was collected on weevil damage, nematode populations and black Sigatoka severity. Changes in weevil damage, nematode population densities and black Sigatoka severity were determined. Pearson's correlation analysis was used to establish relationship between minimum and maximum temperature change, changes in weevil damage, black Sigatoka severity and nematode population densities at different elevations. Results show that minimum temperatures in sites above 1400 masl increased by 1°C over the 20 years. Key banana pests and black Sigatoka disease were observed at elevations where they had not occurred before. Change in black Sigatoka disease, Rhadopholus similis, Helicotylenchus multicinctus and Meloidogyne spp. positively correlated with change in both temperature but change in banana weevil's damages positively correlated with maximum temperature.

Distribution of Pseudocercospora species causing Sigatoka leaf diseases of banana in Uganda and Tanzania

“…Occurrence of the pathogen in all surveyed areas suggests the presence of an environment conducive to P. fijiensis infection and development, the presence of susceptible cultivars and an adequate source of inoculum. Previous reports of P. fijiensis presence at high altitudes have been made in Uganda (Erima et al , ), Colombia (Belalcázar, ), where the pathogen was detected at 1600 m a.s.l. 10 years post‐incursion, and in Costa Rica, where P. fijiensis was observed to have expanded from 900 to 1500 m a.s.l.…”

“…The change in temperature over the past 20 years might have contributed to the displacement of P. musae in Uganda and Tanzania. Erima et al () reported that minimum temperatures in the high‐altitude areas in Uganda (>1400 m a.s.l.) have increased by more than 1 °C over the last two decades.…”

“…In Africa, black Sigatoka is most prevalent at mid‐altitude areas below 1350 m a.s.l., and was previously not found above this altitude (Tushemereirwe et al , ; Mouliom‐Pefoura et al , ; Johanson et al , ). However, the adaptation range of P. fijiensis has gradually expanded to higher and cooler altitudes (Mouliom‐Pefoura et al , ; Erima et al , ). The changing climate (i.e.…”

“…Studies of Sigatoka leaf diseases in the African Great Lakes region were last conducted in Uganda in 2012 (Erima et al , ). The study documented the presence or absence of Sigatoka (Tushemereirwe et al , ; Johanson et al , ; Erima et al , ), without recording disease severity. There are no recent studies to document incidence and severity of Sigatoka in Tanzania.…”

Banana pest risk assessment along banana trade axes running from low to high altitude sites, in the Eastern DR Congo and in Burundi

“…In 1941, M. musicola was also reported in Cameroon, West Africa, about 2,400 km away (Stover, 1962). BLS prevalence has been reported to be high at hot and humid lower altitude sites (Erima et al, 2017). The fact that no BLS was observed in lowland zones (<1200 m) along the Mwenga axis in eastern DR Congo can be explained by the short lifespan of plantains caused by poor suckering and weevil damage.…”