Effect of timing of diseased plant cutting, altitude and banana cultivar on efficacy of singly removing Xanthomonas wilt infected banana plants

The single diseased stem removal (SDSR) technology (i.e. timely cutting of diseased banana plants) is an important Xanthomonas wilt (XW) control method being promoted in XW-endemic zones of east/central Africa. Proper SDSR application leads to quick field recovery. However, its efficacy on farms has been variable. For example, delayed cutting of diseased stems/plants is postulated to increase Xcm inoculum buildup and risk of infection in other physically attached shoots, while larger suckers were thought to be less reliant on the mother plants for nutrients and water thus being less susceptible than small suckers. Previous SDSR evaluations took place at mid-high altitudes dominated by east African highland bananas whereas low-lying altitudes especially dominated by ABB types exist, and this site and type is more prone to insect-mediated XW infections. This study hence determined effects of: i) timing of cutting symptomatic plants on recovery of mats, ii) size of attached suckers at infection on their susceptibility to infection, and iii) the efficacy of SDSR at an ABB banana dominated low altitude site. XW incidence in suckers increased with a delay in cutting of symptomatic mother plants, with lowest incidence (0.27%) observed when symptomatic plants were immediately cut upon symptom expression and highest (1.61%) when plants decayed in situ. The larger maiden (32.1% diseased shoots) and sword suckers (22.2%) were significantly more susceptible than the small peepers (7.4%). XW incubation period was shorter for the maiden suckers (4.5 to 6.2 months) compared to 8.9–11.3 months for sword suckers and 11.3 months for peepers. Immediate cutting of plants after first visible symptoms should be recommended to farmers, while additional studies to understand the low susceptibility of small peepers would be warranted. SDSR was observed to be as effective at the ABB banana dominated low altitude sites as previously reported for highland bananas and environments.