Influence of spatial arrangements in maize/solanum potato intercrops on incidence of potato aphids and leaf hoppers in Uganda

A study to investigate the effect of intercropping maize (Zea mays L.) and potato (Solanum tuberosum L.) on the incidence of potato aphids and leafhoppers was conducted at Namulonge in Uganda during the two growing seasons of 1995. Three potato varieties and one maize variety were intercropped in six spatial arrangements; sole crops, 2:1, 2:2, 1:1, 1:2 potato: maize row arrangements and one additive mixture. Aphids and leafhopper infestations in the different spatial arrangements were similar at early stages but differed significantly later probably because increase in maize height with time and the associated effects had negative effects on pest establishment. Least aphid and leafhopper infestation were observed in the additive mixture. There was no significant influence of spatial arrangement on tuber damage although that tendency was for more damage in plots with high potato concentration. High relative humidity negatively affected aphids but not leafhoppers. Key Words: Additive mixtures, Myzus persicae, relative humidity, Solanum tuberosum, Zea mays (African Crop Science Journal 2001 9(1): 175-184

Epidemiology and population dynamics of Phytophthora infestans in Sub-Saharan Africa: Progress and constraints

Global estimates of losses attributed to plant diseases are approximated at 24.8 million dollars, of this amount 3.4 million dollars has been recorded for potato. Of the potato diseases, late blight (Phytophthora infestans) is the most significant constraint in tropical Africa. Variation in losses of potato caused by late blight have been documented in several countries, and has shown that yield losses can range from 30 to 75% on susceptible varieties. In terms of disease cycle, the sources of primary inoculum have not been adequately investigated, however, the continuos cropping of potato and tomato ensures inoculum presence year-around in tropical Africa. Data on the low incidence of tuber blight and the lack of evidence for potato seed-borne infection suggests that tuber blight is not a significant source of primary inoculum in the tropics. Population studies of P. infestans in Sub-Saharan Africa (SSA) have been conducted primarily on isolates from Uganda, Kenya and S. Africa. Mating type tests with A1 tester isolates coupled with DNA analysis revealed that the fungal isolates from Uganda, Kenya and S. Afirca are of A1 mating type (US 1 clonal lineage). Variation and lack of consistency in oospore production (10 % selfing, 24 % mating, & 15 % non-oospore producers) have been detected among the isolates from Uganda and Kenya. Similarly, variability in metalaxyl sensitivity, has been detected among these isolates. Fungicide and variety reaction studies conducted in Uganda, Kenya and Ethiopia suggests that significant late blight control can be achieved when the protectant fungicide, Dithane (a.i mancozeb) is applied on a scheduled basis. On-farm research also indicates that three timely applications of a protectant or a protectant fungicide alternated with systemic fungicide can be effective for late blight management. Results of in-vitro tuber blight development and host-specificity studies imply that isolates from potato are more virulent than isolates from tomato. Studies are underway to quantify general resistance of potato varieties as well as to monitor the significance of fungal population deviations in the region. Decision support systems are in the process of being developed to optimize fungicide application and variety resistance for late blight management. Key Words: Phytophthora infestans, fungal population, fungicide sensitivity, epidemiology, yield loss, tropical Africa (African Crop Science Journal 2001 9(1): 185-194

What is the cost of integration? Evidence from an integrated health and agriculture project to improve nutrition outcomes in Western Kenya

Sweetpotato Action for Security and Health in Africa ProjectIntegrated nutrition and agricultural interventions have the potential to improve the efficiency and effectiveness of investments in food security and nutrition. This article aimed to estimate the costs of an integrated agriculture and health intervention (Mama SASHA) focused on the promotion of orange-fleshed sweet potato (OFSP) production and consumption in Western Kenya. Programme activities included nutrition education and distribution of vouchers for OFSP vines during antenatal care and postnatal care (PNC) visits. We used expenditures and activity-based costing to estimate the financial costs during programme implementation (2011–13). Cost data were collected from monthly expense reports and interviews with staff members from all implementing organizations. Financial costs totalled US$507 809 for the project period. Recruiting and retaining women over the duration of their pregnancy and postpartum period required significant resources. Mama SASHA reached 3281 pregnant women at a cost of US$155 per beneficiary. Including both pregnant women and infants who attended PNC services with their mothers, the cost was US$110 per beneficiary. Joint planning, co-ordination and training across sectors drove 27% of programme costs. This study found that the average cost per beneficiary to implement an integrated agriculture, health and nutrition programme was substantial. Planning and implementing less intensive integrated interventions may be possible, and economies of scale may reduce overall costs. Empirical estimates of costs by components are critical for future planning and scaling up of integrated programmes

Detoxification of Corn Antimicrobial Compounds as the Basis for Isolating Fusarium verticillioides and Some Other Fusarium Species from Corn

The preformed antimicrobial compounds produced by maize, 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3-one and its desmethoxy derivative 2,4-dihydroxy-2H-1,4-benzoxazin-3-one, are highly reactive benzoxazinoids that quickly degrade to the antimicrobials 6-methoxy-2-benzoxazolinone (MBOA) and 2-benzoxazolinone (BOA), respectively. Fusarium verticillioides (= F. moniliforme) is highly tolerant to MBOA and BOA and can actively transform these compounds to nontoxic metabolites. Eleven of 29 Fusarium species had some level of tolerance to MBOA and BOA; the most tolerant, in decreasing order, were F. verticillioides, F. subglutinans, F. cerealis (= F. crookwellense), and F. graminearum. The difference in tolerance among species was due to their ability to detoxify the antimicrobials. The limited number of species having tolerance suggested the potential utility of these compounds as biologically active agents for inclusion within a semiselective isolation medium. By replacing the pentachloronitrobenzene in Nash-Snyder medium with 1.0 mg of BOA per ml, we developed a medium that resulted in superior frequencies of isolation of F. verticillioides from corn while effectively suppressing competing fungi. Since the BOA medium provided consistent, quantitative results with reduced in vitro and taxonomic efforts, it should prove useful for surveys of F. verticillioides infection in field samples