Title : Insect pest population dynamics of lowland rice in the forest belt of Ghana
Abstract:
Ghana is striving to be self-sufficient in rice and acreages cultivated to rice are rapidly expanding. Rice intensification, like most monocultures, has increased pest outbreaks as being experienced in some rice growing areas. Insect pest populations over rice growth cycle were monitored over 2 years in 108 rice fields in 9 key rice growing communities in Ashanti Region. Insect pests were sampled using sweep net, and direct observation along transect from nursery to physiological maturity stage. Deadheart rice plants were counted as indirect incidence of stem borers. Samples of rice deadhearts with live larvae were also incubated in the laboratory until moth emergence. A total of 29 insect pest species were identified, of which 13 were considered major pests. The major insect pests were the stem borers Chilo zacconius, Scirpophaga sp, Maliarpha separatella, Nymphula sp., Diopsis thoracica; leave beetles Chnootriba similis, Xanthadalia sp., Lema sp., Chaetocnema sp., Dicladispa viridicyanea and sucking bugs Leptocorisa sp, Riptortus sp. Aspavia armigera. The leafhoppers Nephotettix modulates, Cofana spectra, Cofana unimaculata were prevalent but were not considered major pest because no rice leafhopper burn associated with them was recorded. They could however be important in fields where yellow mottle virus disease was recorded, since they and leaf beetles are vectors. Population densities of all the major pests, except Riptortus sp., peaked at the tillering/stem elongation stages. Although rice leaf beetles occurred in all surveyed areas, species distribution differed among locations. Nymphula sp. seems to be endemic in some locations, as these areas recorded consistently high incidence especially under flood conditions. The mean incidence of deadheart was 8.2 % while leaf damage by caseworm and leaf beetles was 11.42 % incidence and 2.3 severity. Major insect pests and population build up at different growth stages of rice in the study area is understood and can form basis for the development of IPM package for rice production.
Audience Takeaway:
- Overview of suite of insect pest incidence at different growth stages of rice.
- Observation offers basis for the design of integrated pest management plan for smallholder rice farmers.
- Outlines the primary insect pests of importance, which makes it easier for pest managers to prioritize. Thus, in this ecological zone, management should focus on stem borers and leaf feeding beetles (which are major vectors of rice yellow mottled virus)
- Training of farmers on proper identification of these pests will help early detection and reporting of any new invasive alien pest.
