The rice leafroller Cnaphalocrocis exigua (Butler) in the only species of the rice leaf folder/roller complex in Fiji. It is one of the major rice pests in the country, its pest status being exacerbrated by the cultivation of high-yielding varieties with minimal pest resistance. Detailed studies on the biology of the moth, in particular on the development, emergence, mating and flight behaviour, effect of adult nutrition on fecundity, egg hatchability and longevity, effect of larval nutrition on larval survival, pupation, pupal weight, pupal eclosion, and fecundity, egg hatchability and longevity of resultant adults, parasitism, and population ecology of C. exigua were carried out in Fiji from 1985 to 1987, and from June to August 1990. This study showed that there are several parasitoids of C. exigua in Fiji, and of those the egg and larval parasitoids Trichogramma sp. and Trathala flavo-orbitalis (Cameron) respectively are significant biotic mortality factors. Their impact as natural suppressors of C. exigua in fields of high yielding rice varieties was, however, inadequate to prevent C. exigua reaching damaging levels. Since C. exigua responds strongly to rice varietal differences, plant nitrogen status, and seasonal factors, is suspected to utilise pheromones during mating, and has numerous biocontrol agents in South East Asia and the Philippines, it appears to be an excellent candidate for an integrated pest management (IPM) program in Fiji. Before IPM strategies can be formulated, however, further investigations on rice varietal resistance, exploitation of exotic parasitoids and pathogens, and detailed studies on the possible presence of sex pheromones need to be conducted. / Doctor of Philosophy (PhD)

Thesis (Ph. D.)--University of Chicago, Dept. of Economics, June 1999. / Includes bibliographical references. Also available on the Internet.

There is growing interest in learning the impacts of agricultural technologies especially in developing economies. Economic analysis may entail assessment of employment and time allocation effects of new technologies. An issue of importance in South Asia is the impacts of technological change on a specific type of occupation: rural non-farm activities. In order to fully understand these effects, the research must integrate gender differences and determine if the results would be similar irrespective of gender. This paper particularly looks at the effects of HYV adoption on time allocation and labor force participation of men and women in non-farm activities. In estimating the effects of HYV adoption on non-farm labor supply, information on the dependent variable, supply of non-farm labor (or the number of days worked while engaged in non-farm labor), is not available for individuals who do not participate in non-farm labor. Hence sample selection or self-selection of individuals occurs. A feasible approach to the problem of sample selection is the use of Heckman's Two Stage Selection Correction Model. Income functions were estimated for males and females while correcting for the sample selection of non-farm wage earners. An enhanced understanding of the conceptual links among HYV adoption, non-farm labor supply, and gender issues is achieved by discussing the Farm Household Model. The constrained maximization which is drawn from the Farm Household Model would bring about demand functions and reduced form functions for adoption and labor supply. The reduced-form equations are estimated at the individual level for the following: adoption of HYV technology in rice cultivation, and non-farm labor supply of both adult males and females. Regression results are presented for both Ordinary least squares (OLS) and Tobit estimates. HYV adoption and non-farm labor supply of men and women are influenced by several factors in Bangladesh. The household characteristics assumed to potentially determine technology adoption and non-farm labor decisions are the following: non-farm wages per month of the males and females, farm size, asset value, ratio of yield per decimal land of high-yielding to traditional variety of rice, HYV yield, local variety yield, and the ratio of variance of yield per decimal land of HYV to traditional or local varieties. The empirical findings suggest that the decision to adopt HYV technology is determined primarily by farm size, value of total assets of the household, ratio of yield per decimal of land of high-yielding to traditional variety of rice, and the ratio of variance of yield per decimal of land of high-yielding to traditional variety of rice. A larger farm size or land owned in decimal unit increases the non-farm labor supply of females, but not of men. HYV yield is significant and positive, while the local variety yield is significant and negative. This means that higher HYV yields increase the supply of non-farm labor of women, while higher local or traditional yields lower women's supply of non-farm labor. / Master of Science

Research carried out in several countries has concluded that high yielding varieties (HYV) of rice have tremendous potential compared to traditional rice varieties in alleviating poverty. On the other hand, it is argued that despite increase in yields, high yielding varieties do not benefit the poor farmers because of high costs associated with input acquisition and other operational costs. To further understand the issues related to production and economics of HYV, this study was carried out with its primary objective to assess the profitability of smallholder rice production in Mangol, Bilene district in southern Mozambique. Out of a total population of eighty farmers, sixty farmers participated in this research. Two groups of farmers, one using traditional rice varieties and the other using high yielding varieties were surveyed. The study consisted of field observations; yield measurements and interviews of the farmers using a semi-structured questionnaire. Gross margins were calculated for both traditional input users (TIU) and modem input users (MIU). Results show that an average farmer using high yielding varieties produces 4.4 tons of rice per ha, corresponding to a gross margin of 4 238 000,00 MZM. The highest yield obtained with high yielding varieties was 7.3 tons of rice per ha, producing a gross margin of 10 038 000,00 MZM. On the other hand, an average TIU farmer produces 2.5 tons per ha, realising a gross margin of 3 483 125, 00 MZM. The maximum yield attainable using traditional inputs is 2.9 tons per ha, producing a gross margin of 4 283 125, 00 MZM. The results also show that the lowest yield obtained by farmers using modern inputs was 3.1 tons per ha, producing gross margins of 1 638 000,00 MZM while the lowest attainable when using traditional inputs is 1.7 tons producing gross margins of 1 913 125,00 MZM. The main conclusion of this study was that HYV are more profitable than traditional varieties, both in financial terms, to individual farmer and in economic terms, to the society as a whole. However, due to high production costs, farmers producing HYV must attain yield levels not less than 3.4 tons per ha as yields below that level make little financial incentives and does not motivate farmers to shift from traditional varieties to modern varieties. In order to ensure high yields, farmers must be assisted to carefully implement the recommended agronomic practices because the adoption of high yielding varieties does not ensure profitable yields if the other agronomic and management practices are not observed during the production process. The study also assessed the contribution of agricultural support services such as input supply, credit and extension, on the adoption of new technologies and it was concluded that when agricultural support services are available, farmers can successfully adopt recommended technologies. / Dissertation (M Inst Agrar (Agricultural Economics))--University of Pretoria, 2006. / Agricultural Economics, Extension and Rural Development / unrestricted

Thesis (M.Sc. Agriculture (Agronomy) -- University of Limpopo, 2019 / Erratic rainfall and insect infestation are some of the factors that limit cowpea production in Limpopo (Asiwe, 2009). Improved cowpea varieties available for dryland production in Limpopo do not meet the farmer’s needs. Specific trait crosses are needed to be made with adapted varieties for the purpose of developing high yielding, pest tolerant and adapted varieties. Varieties with desired specific traits were planted in isolation plots for outcrossing by insects. F1 lines derived from parental lines that were half sib seeds were harvested and planted as F2, and seeds obtained from F2 generation were used to develop F3 segregating population at University of Limpopo Experiential Farm, Syferkuil, and planted along with parents. This F3 generation forms the current evaluation on which this report is based. Data collected included; aphid severity (measured on a 9-point scale), number of days to 90 % maturity, grain yield, 100 seed weight and number of genotypes selected for advancement. Results showed significant variation among progeny over parents therefore expressing transgressive segregation. Genotypes derived from pedigree TX08-30-5 were five while pedigree IT98K-205-8 and IT97K-499-35 had four genotypes each that expressed early maturity (80-90 days) which are desirable for evading drought. Twenty-three genotypes from pedigree GEC and three from pedigree IT97K-499-35 obtained grain yield (>101 g/plot and >161 g/plot) that was better than their parents. Only one genotype derived from pedigree TX08-30-1 expressed high resistance to aphids better than the parent with a mean aphid score range of 1-2. Four genotypes from pedigree TX08-30-5 obtained bigger 100 seed weight (>18.6 g) compared to parent. These progeny also proved to be high yielders as they expressed heterosis for all yield attributes than their parents. Eighty-two genotypes were selected for advancement. Significant variations were observed among progeny giving opportunity to make selections. In most cases, genotypes outperformed their parents which indicate positive heterosis. The 82 promising genotypes selected will be advanced for further selections from multi location testing for stability and adaptation.