Biotic constraints cause major crop losses and, hence, food insecurity in sub-Saharan Africa. This study documented the popularity, production constraints, pests and diseases, farmers’ perceptions on the severity of biotic constraints and the impact of related crop losses on household food security for the key root, tuber and banana (RTB) crops (cassava, potato, sweetpotato and banana). Farmer interviews were conducted in 2014 covering 811 households in Rwanda and Burundi. Farmers were asked to list their RTB crop production constraints, name insect pests and diseases of RTB crops, estimate crop loss due to pests and diseases, and mention if their household experienced any form of food insecurity due to pests and diseases. Cutworms and late blight in potato, banana weevils and banana Xanthomonas wilt in banana, cassava whitefly and cassava mosaic disease in cassava, sweetpotato weevils, and sweetpotato virus disease in sweetpotato were the most predominant pests and diseases reported. Crop losses due to pests and diseases for sweetpotato, banana, potato and cassava were estimated at 26%, 29%, 33%, and 36%, respectively, in Rwanda and 37%, 48%, 38%, and 37% in Burundi. Pests and diseases reduce the profitability of RTB crops, threaten food security, and constitute a disincentive for investment. Sustainable and affordable integrated pest management packages need to be developed.

Misuse and poor handling of chemical pesticides in agriculture is hazardous to the health of farmers, consumers, and to the environment. We studied the pest and disease management practices and the type of pesticides used in four root, tuber, and banana (RTB) crops in Rwanda and Burundi through in-depth interviews with a total of 811 smallholder farmers. No chemical pesticides were used in banana in either Rwanda and Burundi, whereas the use of insecticides and fungicides in potato was quite frequent. Nearly all insecticides and about one third of the fungicides used are moderately hazardous. Personal protective equipment was used by less than a half of the interviewed farmers in both countries. Reported cases of death due to self- or accidental-poisoning among humans and domestic animals in the previous 12 months were substantial in both countries. Training of farmers and agrochemical retailers in safe use of pesticide and handling and, use of integrated pest management approaches to reduce pest and disease damage is recommended.

Banana Xanthomonas wilt was reported in Rwanda in 2005. The present study was conducted to determine the distribution and incidence of the disease and farmer knowledge of disease symptoms, modes of spread and control. A survey was conducted in Rwanda in 2009-2010 in 12 major banana-growing districts of the country. One hundred and eight banana growers were interviewed using a structured questionnaire. Farmers were asked about knowledge of disease symptoms, spread, control and use of control methods. They were also asked about their sources of information on Xanthomonas wilt. Direct field observations were made of the distribution and incidence of the disease as well. The proportion of fields with Xanthomonas wilt was highest in Rutsiro (89%) and lowest in Kayonza and Ruhango (11%). The disease was not found in Gakenke, Kicukiro or Ngoma. Within-farm incidence was highest in Rutsiro (average 36%) and lowest in Kayonza (1%). The awareness of disease symptoms ranged from 53% (discoloured fruit pulp) to 84% (wilting leaves). For modes of spread, the highest proportion of farmers (73%) was aware of the role of contaminated tools while the least known mode was spread via soil and water (24%). Some 72% of famers were aware of uprooting plants as a control measure. There were large differences between awareness and use of tool disinfection and destruction of infected plants as control measures. There is a need to develop user-friendly methods of disease control. The creation of awareness in newly affected and Xanthomonas wilt-free areas is advocated. Participatory approaches are encouraged as they may reduce the gap between knowledge and adoption of control measures.

Bacterial wilt (BW), caused by Ralstonia solanacearum species complex (RSSC), leads to substantial potato yield losses in Rwanda. Studies were conducted to (i) determine the molecular diversity of RSSC strains associated with BW of potato, (ii) generate a RSSC distribution map for epidemiological inferences, and (iii) test the pathogenicity of predominant RSSC phylotypes on six commercial potato cultivars. Surveys were conducted in 2018 and 2019, tubers from wilting potato plants were collected for pathogen isolation. DNA was extracted from 95 presumptive RSSC strain colonies. The pathogen was phylotyped by multiplex PCR and typed at sequevar level. Phylotype II sequevar 1 strains were then haplotyped using multilocus tandem repeat sequence typing (TRST) schemes. Pathogenicity of one phylotype II strain and two phylotype III strains were tested on cultivars Kinigi, Kirundo, Victoria, Kazeneza, Twihaze and Cruza. Two RSSC phylotypes were identified, phylotype II (95.79%, n = 91) and phylotype III (4.21%, n = 4). This is the first report of phylotype III strains from Rwanda. Phylotype II strains were identified as sequevar 1 and distributed across potato growing regions in the country. The TRST scheme identified 14 TRST haplotypes within the phylotype II sequevar 1 strains with moderate diversity index (HGDI = 0.55). Mapping of TRST haplotypes revealed that a single TRST ‘8-5-12-7-5’ haplotype plays an important epidemiological role in BW of potato in Rwanda. None of the cultivars had complete resistance to the tested phylotypes, level of susceptibility varied among cultivars. Cultivar Cruza, which is less susceptible to phylotype II and III strains, is recommended when planting potatoes in the fields with history of BW.

This paper evaluates the determinants of decision-making in relation to the production of four crops (banana, cassava, potato, and sweet potato). Understanding the division of labor and decision-making in crop management may lead to designing better interventions targeted at improving efficiency in smallholder agriculture. In 2014, the research team conducted a quantitative household survey with heads of households involving 261 women and 144 men in Burundi and 184 women and 222 men in Rwanda. Most of the decisions and labor provision during the production of both cash crops (potato and banana) and food crops (sweet potato and cassava) were done jointly by men and women in male-headed households. Higher values for ‘credit access’, ‘land size’, and ‘farming as the main occupation of the household head’ increased the frequency of joint decision-making in male-headed households. A decline in the amount of farm income reduced the participation of men as decision-makers. A reduction in total household income and proximity to the market was correlated with joint decision-making. Gender norms also contributed to the lower participation of women in both decision-making and labor provision in banana and potato cultivation. Although a large proportion of decisions were made jointly, women perceived that men participate more in decision-making processes within the household during the production of cash crops. Increased participation by women in decision-making will require an active and practical strategy which can encourage adjustments to existing traditional gender norms that recognize men as the main decision-makers at both the household and community levels.