G.1 Riceland preparation with oxen, Africa
G.2 Riceland preparation with water buffaloes, Philippines
G.3 Deep ploughing by tractor, Malaysia
G.4 Aerial infrared photograph of a riceland system, Texas, USA
G.5 Rice harvesting equipment, Texas, USA
G.6 Equipment tire racks in rice field, Texas, USA
G.7 Aerial photograph of riceland study site, Texas, USA
G.8 Colour infrared photograph of levees and tire tracks, Texas USA
G.9 Oviposition features in ricelands, Texas, USA
Credit individual slides:
Food and Agriculture Organization of the United Nations
G.1, G.2, G.3
Professor Jim K. Olson. Texas A&M University
G.4, G.5, G.6, G.7, G.8, G.9
Slide G.1 Riceland preparation with oxen, Africa
Slide G.2 Riceland preparation with water buffaloes, Philippines
Traditional methods of land preparation for irrigated lowland rice still employ animal power, such as the oxen in the African example (G.1) and the carabao - water buffalo - in the Philippines (G.2). Vector-borne disease issues include water bodies used by cattle, human-livestock-vector contact patterns, livestock in the domestic environment and the potential for zooprophylaxis (all covered in section H).
Slide G.3 Deep ploughing by tractor, Malaysia
In many rice growing areas, the past two or three decades have seen a dramatic displacement of draught animals by tractors, as illustrated in this slide from Malaysia. Such mechanization makes it practical and economic to put marginal lands under cultivation. The ensuing ecological changes and the creation of monocultures (habitat simplification) can have far-reaching consequences for the health status of local communities. Farm mechanization will also change peoples lifestyles, possibly increasing the mobility of migrant and seasonal labour. In relation to rice cultivation, mechanization is likely to be associated with increased areas under flooding and more vector breeding opportunities. The introduction of upland or dry rice varieties will, on the other hand, reduce such risks. The recent trend of broadcasting rather than transplanting rice (in countries were manual labour is becoming too expensive) is also likely to have a beneficial effect with respect to vector-borne disease risks.
Slide G.4 Aerial infrared photograph of a riceland system, Texas, USA
In a study to explore the potential of aerial colour infra-red photography to survey the oviposition sites of floodwater mosquitoes, a series of pictures was made, supported by ground truthing. This study was carried out by the Entomology department of Texas A&M University, as part of the USDA funded Riceland Mosquito Management Programme. The cropping pattern, and several natural and man-made features are clearly visible.
The remote sensing technique was also tested and proved effective in pinpointing rice fields in California that produce high numbers of Anopheles freeborni (a potential malaria vector; malaria is, however, not endemic in California). In extensive, uniform agro-ecosystems, this method would support a focused and, therefore, more efficient vector control effort.
Slide G.5 Rice harvesting equipment, Texas, USA
Slide G.6 Equipment tire racks in rice field, Texas, USA
One of the important features of rice production systems in the southern USA is the impact of machinery, such as this harvesting equipment (G.5). The tire tracks left in the moist soil will provide ideal conditions for oviposition by Psorophora columbiae, the floodwater mosquito. It is estimated that these conditions account for between 1.7 and 2.9 million P. columbiae eggs per hectare in recently harvested rice fields.
P. columbiae transmits a number of viruses, most important of which is the Western Equine Encephalitis (WEE) virus.
Slide G.7 Aerial photograph of riceland study site, Texas, USA
This oblique aerial photograph of the riceland study site gives additional information concerning micro relief and vegetation.
Slide G.8 Colour infrared photograph of levees and tire tracks, Texas USA
This colour infrared photograph of levees and tire tracks in a recently harvested field is an impressive example of the density of features conducive to the breeding of Psorophora species under modern conditions of cultivation.
Slide G.9 Oviposition features in ricelands, Texas, USA
A list of oviposition features in ricelands, Texas, USA