Studies on the biology of the leafhopper, Nzinga palmivora Wilson n.sp. (Homoptera: Cicadellidae: Typhlocybinae) in Ghana

Nzinga palmivora Wilson (Homoptera: Cicadellidae) is one of the homopterans suspected to be a putative vector of the lethal yellowing disease (Cape Saint Paul Wilt Disease)' of coconut palms in Ghana. The insect is under investigation in transmission trials under the Coconut Programme of the Oil Palm Research Institute. Because little is known about the insect, an experiment was set up to investigate its biology and its diurnal settlement activities to complement other work and for documentation. The study on the biology was carried out in breathing polyethylene sleeves at Agona Junction in the Western Region of Ghana. Ten coconut palms were randomly selected in the field and tagged. One lower frond of each selected palm was randomly selected and a breathing sleeve containing 10 adult leafhopper couples of unknown ages hanged on it. Each sleeve enclosed three frond leaflets which provided food source and support for the insects in the sleeve. Various aspects of the biology of the insects including adult survival in the sleeve, gestation period of the female insects, incubation period of the eggs and nymph development were then monitored. The diurnal settlement activities of the adult insects on palms were observed and recorded every 3h starting form 6 a.m. to 6 p.m. on the field on 10 randomly selected fronds of each of five selected coconut palms. The study was carried out on four Fridays in a month every quarter, i.e. March, June, September and December. Temperature and percentage relative humidity were also recorded at the same time on the field. Results showed that N. palmivora had gestation period of 19.13 ± 5.8 days, egg incubation period of 11.2 ± 1.0 days and nymph developmental time of 23 ± 1.5 days. There were five instars and mean of eggs per batch laid was 19.0 ± 5.8. The study on quarterly diurnal settlement activities indicated that most of the insects settled on the palms in the evening at about 6 p.m. when relative humidity was between 80 and 90 per cent and temperature 25-28 °C. N. palmivora settlement activities were generally low in June but very high in December.