Abundance of Two Generalist Insect Pests of Cassava (Manihot esculenta Crantz) as Influenced by NPK Fertilization

Abstract

The influence of NPK fertilizer on the population of two generalist pests, grasshopper (Zonocerus variegatus) and termites (Isoptera spp.) on some cassava varieties (Manihot esculenta Crantz), was investigated in a field trial carried out at Teaching and Research Farm of Department of Crop science, University of Nigeria, Nsukka. The treatments comprised all possible combinations of four rates of fertilizer application (0 kg/ha, 200 kg/ha, 400 kg/ha and 600 kg/ha), four improved cassava varieties (‘TMS 01-1368’, ‘TME 419’, ‘TMS 98-05-50’, ‘TMS 05 10’) and three modes of fertilizer application (Single, Split and Split-split) arranged in a factorial experiment and laid out in a randomized complete block design (RCBD). There were three replications of each treatment. Data were collected on Z. variegatus and termite incidences. In each season, incidence of Z. variegatus on cassava showed significant (p<0.05) difference among varieties. Varieties ‘TMS 01-1368’, ‘TMS 05 10,’ and ‘TMS 98-05-05,’ were significantly (p<0.05) more susceptible to the pest compared to variety ‘TME 419’. Incidence of termites on cassava differed significantly (p<0.05) among varieties in the late season and variety TMS 05 10’ was more susceptible to this pest than other varieties. Rates of NPK fertilizer had significant (p<0.05) influence on Z. variegatus incidence only. Application of various NPK fertilizer rates increased the incidence of Z. variegatus on the varieties compared to plots without fertilizer (0 kg/ha). The abundance of Z. variegatus in cassava field was influenced by fertilization and variety while termites were influenced by variety.

Keywords

• Cassava; generalist pests; incidence; insect-plant interaction; NPK