Distribution and fixed-precision sampling plans for diamondback moth (Lepidoptera: Plutellidae), on winter-spring cabbage.

The diamondback moth (Plutella xylostella L.) is the most destructive insect pest on cabbage (Brassica oleracea var. capitata L.). Infestation by this pest usually results in the indiscriminate use of insecticides by farmers due to a lack of sampling plans for this pest. Sampling plans for P. xylostella management decisions on winter-spring cabbage in the Eastern Cape Province of South Africa were developed, through population monitoring that comprised weekly counts of immature stages of P. xylostella on 60 plants for 11 wk each during the winter and spring seasons. The mean density-variance relationship was used to describe the distribution of the pest, and number of infested plants was used to develop a fixed-precision sampling plan. All plant growth stages preceding maturation were vulnerable to P. xylostella damage resulting in yield losses. A high aggregation of P. xylostella on cabbage was observed in spring than in winter. The average sample number to estimate P. xylostella density within a 15% standard error of the mean was 35 plants. Furthermore, the estimated plant proportion action threshold (AT) was 51% with density action thresholds of 0.50 and 0.80 for spring and winter, respectively. Fitting P. xylostella cumulative counts in the winter and spring sampling plans resulted in 100% and 45% reduction in insecticide treatments. The similarity of sample size and ATs between both seasons provides evidence that a single sampling plan is practical for all cabbage growing seasons. The similarity of the estimated ATs to those acceptable in established integrated pest management programs indicates reliability.

Factors influencing rice production in the south-eastern belt of Ghana.

Ghana has great potential to produce rice for local consumption, however, the average rice produced barely meets half of the country's consumption needs. Focus group discussions (FGDs) and surveys were held within the coastal lowland rice production belt in Ghana. The FGDs were held at Okyereko and Afife followed by surveys in the two communities in addition to Dawenya and Ashaiman. The objectives were to assess the production challenges faced by farmers in the four communities and determine the rice traits preferred by the farmers. Twenty farmers were involved in each of the FGDs while 227 respondents were selected through convenient sampling for the interviews. Sixty-nine percent of respondent farmers were male, 53% were above 50 years while 44% had varied levels of education. Farmers preferences mainly related to marketable traits such as aroma (87%), taste (83%) and yield potential (78%). There was special preference for Jasmine 85 (62.8%) and Togo Marshal l (25%), an indication of the high adoption of aromatic rice varieties in the study areas. Challenges such as securing credit, input supplies, soil salinity and ageing work force were matters of grave concern to respondent farmers. Given the importance of rice cultivation in the study areas to Ghana's quest to achieve self-sufficiency in rice, targeted and coordinated support from relevant governmental and non-governmental organizations is needed to sustain a higher level of production in the study areas.