Influence of Nitrogen Fertilisation on Red Spider Mites (Oligonychus coffeae
Nietner) and Overhead Volatile Organic Compounds in Tea (Camellia sinensis)

P. Okinda Owuor; Jenipher A. Odak; Lawrence O.A. Mang’uro; Francis N. Wachira; Evelyne Cheramgoi

doi:10.20425/ijts.v13i01-02.9985

P. Okinda Owuor Maseno University, Department of Chemistry, P.O. Box 333, 40105 Maseno, Kenya
Jenipher A. Odak Maseno University, Department of Chemistry, P.O. Box 333, 40105 Maseno, Kenya
Lawrence O.A. Mang’uro Maseno University, Department of Chemistry, P.O. Box 333, 40105 Maseno, Kenya
Francis N. Wachira Tea Research Institute, Kenya Agricultural and Livestock Research Organization, P.O. Box 820, 20200 Kericho, Kenya
Evelyne Cheramgoi South Eastern Kenya University, P.O. Box 170, 90200, Kitui, Kenya

DOI: https://doi.org/10.20425/ijts.v13i01-02.9985

Keywords: Tea, overhead volatile organic compounds, mites, nitrogen fertiliser

Abstract

Nitrogen fertilisation influences tea yields, quality and pests infestation levels. Red spider mites reduce tea production in western Kenya during prolonged droughts. Nitrogen fertiliser use maybe an agronomic practice that may influence infestation levels by mites. Overhead volatile compounds (OVOCs) composition also influences infestations of tea by mites. Influence of nitrogenous fertiliser rates on red spider mite infestations and OVOCS levels was determined. Mites populations varied (pd less than 0.05) with nitrogenous fertiliser rates. High infestations were at 0 and 300 kg N/ha/year, and sharp decline between 150 and 225 kg N/ha/year. Green leaf volatiles increased while some aromatic and terpenoid compounds decreased with increasing nitrogenous fertiliser rates. Significant (pd less than 0.05) direct linear regressions between 1-penten-3-ol, 3-penten- 2-ol, E-2-hexenal, Z-3-hexenyl acetate and inverse relationship between 2-phenyl ethanol, ethyl benzene, -methyl styrene, longifolene and ß-cedrene and nitrogenous fertiliser rates were observed. Most aromatic and terpenoid compounds, which are repellents of mites, were highest between 150 and 225 kg N/ha/year where infestations by mites were lowest. The recommended fertiliser rates of 100 to 225 kg N/ha/year in Kenya also produce most repellents of mites, protecting tea plants against infestations. Use of recommended nitrogen rates can protect tea from infestations by mites.

Influence of Nitrogen Fertilisation on Red Spider Mites (Oligonychus coffeae Nietner) and Overhead Volatile Organic Compounds in Tea (Camellia sinensis)

Abstract