Prevalence and distribution of plant parasitic nematodes associated with sweet potato: A case study of Kirinyaga County in Kenya

Abstract

A survey of plant parasitic nematodes (PPNs) associated with sweet potato (Ipomoea batatas) was carried out in three agro-ecological zones of Kirinyaga County in Kenya. Samples of rhizosphere soil and sweet potato tubers were collected for PPN extraction and morphometric characterization. Seven genera were morphologically identified (Meloidogyne, Pratylenchus, Helicotylenchulus, Scutellonema, Rotylenchulus, Heterodera and Aporcelaimellus). There were differences in the shapes and sizes of the mature PPN females and the diameter ranged from 204.3 μm to 437.3 μm. Meloidogyne had the highest prevalence (25%) and distribution (0.161), followed by Pratylenchus with a prevalence and distribution of 23% and 0.151, respectively. Farmers’ perceptions were captured using a semi-structured questionnaire. Overall, sweet potato farming was mainly practiced under mixed cropping (70.11%), small-scale (60.11%) and subsistence (55.17%). A higher proportion of the respondents (49.43%) sourced sweet potato vines from their own farms. The main control strategies applied for PPN were insecticides (55.59%), nematicides (11.49%) and concoctions (5.75%). Of all the respondents, 29.89% could not recognize symptoms of nematode infection. The distribution was significantly (p < 0.05) different among agro-ecological zones, with UM3 (upper midlands) showing the highest prevalence of 31. In conclusion, the differences in shapes and sizes of the mature females extracted from PPNs reveal a high level of morphological diversity. However, morphological characterization should be integrated with molecular methods for proper identification of PPNs. Awareness-raising among farmers about the best practices for proper management of PPN is necessary.