A comparison of the effects of the nematodes Radopholus similis and Pratylenchus goodeyi on growth, root health and yield of an East African highland cooking banana (Musa AAA-group)

Abstract

The effects of Radopholus similis and Pratylenchus goodeyi on growth, root health and yield of the East African highland cooking banana cultivar Mbwazirume (Musa AAA-group) were compared at Mbarara, Uganda, at 1430 m above sea level. In 3-year-old mats infected only with P. goodeyi, functional root length and functional root density of suckers detached from recently-harvested plants were 40 and 45%, respectively, greater in mulched mats and 120 and 108%, respectively, greater in non-mulched/bare mats compared to mats infected with both P. goodeyi and R. similis. In mats infected with both P. goodeyi and R. similis, dead root length, dead root density and percentage necrosis of functional roots of the suckers were about 30% greater in mulched mats and about 40 – 50% greater in non-mulched/ bare mats compared to mats infected only with P. goodeyi. In the non- mulched/bare mats, the bunch weight of plants infected with P. goodeyi and R. similis was reduced on average by 6 kg or 30% compared with plants without R. similis, while 60% of the plants infected with both P. goodeyi and R. similis toppled, a percentage three times greater compared to plants infected only with P. goodeyi. In the mulched mats, 25% of the plants infected with both P. goodeyi and R. similis toppled, a percentage four times greater compared to plants infected only with P. goodeyi. Thus, R. similis is probably more virulent than P. goodeyi in the banana-growing areas of southwestern Uganda. However, the results also indicate that under poor management P. goodeyi alone can cause considerable damage. The presence of R. similis resulted in a reduction in the number of standing leaves. More open leaf canopies may have led to higher soil temperatures due to direct sunlight and this could have influenced the nematode population composition in favour of R. similis, resulting in turn in an increase in root damage. This cycle was most pronounced in the non-mulched/bare mats. Mulching appeared to reduce the population densities and the damaging effects of R. similis. Mulched mats had a lower soil temperature compared to non-mulched/ bare mats, which may have slowed R. similis reproduction and feeding activity and reduced root damage.