Variation of grasshopper abundance in light and heavy rain periods, significant for effective pest control measures
Abstract
Varying abundance of grasshoppers relative to light and heavy rain periods, significant for effective pest control measures was investigated on Oilpalm trees in experimental field 54, located in Nigerian Institute for Oilpalm
Research (NIFOR), Edo State, Nigeria. The survey was conducted on a twice-a-week interval using systematic random sampling technique, within a period of four months during the early rains in the month of April through the month of heavy rains in July. Grasshoppers of interest: Zonocerus variegatus, Catantops spissus spissus and Cyrtacanthacris aeruginosa were recorded on oilpalm fronds 17 and 25. Being a pre-requisite for an effective and well planned timing for subsequent control program for these leaf feeding pests of oilpalm trees in the region, the survey was done to
establish a baseline data on occurrence of the grasshoppers relative to the various climatic parameters used. Meteorological data (mean monthly temperature, monthly total rainfall and mean monthly relative humidity) were
collected from Meteorological unit in NIFOR. Zonocerus variegatus had the highest mean monthly occurrence all through the period of survey (7.75±0.32, 12.97±0.55, 14.48±0.60 and 14.71±0.29 for April, May, June and July respectively) relative to the climatic parameters. No clear second position was occupied by either of the other grasshoppers, as Cyrtacanthacris aeruginosa occupied it in April (6.38±0.80) and June (11.85±0.91) and Catantops spissus spissus in May (10.14±0.80) and July (12.63±0.34). The grasshopper population correlated positively
(r=+0.753, and +0.807) with rainfall and relative humidity respectively, revealing their population abundance andreduction with the parameters. A strong mean negative correlation (-0.718) also existed between them and
environmental temperature. This study has revealed the higher occurrence of Zonocerus variegatus more than the other grasshopper species surveyed during this period and the sensitivity of the surveyed grasshoppers’ occurrence to their ambient weather conditions in this region.
Research (NIFOR), Edo State, Nigeria. The survey was conducted on a twice-a-week interval using systematic random sampling technique, within a period of four months during the early rains in the month of April through the month of heavy rains in July. Grasshoppers of interest: Zonocerus variegatus, Catantops spissus spissus and Cyrtacanthacris aeruginosa were recorded on oilpalm fronds 17 and 25. Being a pre-requisite for an effective and well planned timing for subsequent control program for these leaf feeding pests of oilpalm trees in the region, the survey was done to
establish a baseline data on occurrence of the grasshoppers relative to the various climatic parameters used. Meteorological data (mean monthly temperature, monthly total rainfall and mean monthly relative humidity) were
collected from Meteorological unit in NIFOR. Zonocerus variegatus had the highest mean monthly occurrence all through the period of survey (7.75±0.32, 12.97±0.55, 14.48±0.60 and 14.71±0.29 for April, May, June and July respectively) relative to the climatic parameters. No clear second position was occupied by either of the other grasshoppers, as Cyrtacanthacris aeruginosa occupied it in April (6.38±0.80) and June (11.85±0.91) and Catantops spissus spissus in May (10.14±0.80) and July (12.63±0.34). The grasshopper population correlated positively
(r=+0.753, and +0.807) with rainfall and relative humidity respectively, revealing their population abundance andreduction with the parameters. A strong mean negative correlation (-0.718) also existed between them and
environmental temperature. This study has revealed the higher occurrence of Zonocerus variegatus more than the other grasshopper species surveyed during this period and the sensitivity of the surveyed grasshoppers’ occurrence to their ambient weather conditions in this region.
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