Insect Pest Profile of Leaf Amaranth (Amaranthus hybridus L) and Prevention Herbivory Using Oil-Based Extracts of Alium sativum L, Xylopia aethiopica Dunal and Eucalyptus globolus L

Abstract

Pest profile of Amaranthus hybridus was recorded in a single organic agro-ecosystem in Southwestern Nigeria between November-December in 2016 and January-February 2017, during the dry season. Activities of different pests were monitored to identify those responsible for the most significant damage. Vegetable oil-based extracts of Alium sativum, Xylopia aethiopica and Eucalyptus globolus were prepared and applied on A. hybridus as protectants against herbivory by phytophagous insects and damage to foliage was assessed. Thereafter, the extracts were rated based on the mean percentage damage (MPD) recorded in different plots in relation to the treatments. A total of nine pests were recorded from three insect Orders namely, Orthoptera (62.5%), Coleoptera (12.5%) and Lepidoptera (25%) and they were grouped into Major, Minor or Occasional pests based on their activities. Two lepidopterans, Spoladea recurvalis and Psara basalis (Family: Crambidae) were responsible for the most significant damage. All the extracts reduced damage with a statistically significant difference (P<0.05) compared with the control. The MPD in X. aethiopica-, A. sativum- and E. globolus-treated plots and the control plots were 10.9%, 8%, 14% and 31.2% respectively when the amaranth was due for harvest in the first trial. The MPD to the amaranth in the treated plots during the second trial was between 13.6% and 16.3% when the harvest was due while the MPD in the control was 54.9%. The performances of E. globolus and X. aethiopica were comparable and they were relatively more effective in protecting A. hybridus against phytophagous pest attacks.