Feldversuche zur Wirkung von Spinosad-, Neem- und B.t.t.- Präparaten auf die Regulierung des Kartoffelkäfers (Leptinotarsa decemlineata Say)

The Colorado potato beetle (CPB) is one of the most important pests on potatoes (Solanum tuberosum). In many areas, preventive measures are not sufficient enoughto prevent the damage caused by the CPB. Therefore insecticides such as neem and Bacillus thuringiensis v. tenebrionis (B.t.t.) have an important role in organic potato production in Germany. The new insecticide Spinosad was added to Council Regulations (EEC) No. 2092/91 on organic production in 2008. It is now possible to use Spinosad in organic agriculture in the EU. The active ingredient of Spinosad is obtained from the bacterium Saccharopolyspora spinosa through fermentation. Field studies compared three treatments to control CPB in 2008. 1: single Spinosad treatment (24 g/ha active ingredient (a.i.)) 2: first treatment B.t.t. (60 g/ha (a.i.)), second treatment (+4d) B.t.t. (100 g/ha a.i.) 3: first treatment neem (25 g/ha a.i.), second treatment (+4d) B.t.t. (100 g/ha a.i.). There was an average of 27 larvae per plant before the treatments. All treatments displayed nearly the same significant degree of effectiveness (78 % - 82 %) with regards to the damaged leaf area 25 days after treatment in comparison to the untreated control. The increment of the Spinosad treatment to untreated control was significant with more than 103 dt/ha

Potato Yield and Yield Components as Affected by Positive Selection During Several Generations of Seed Multiplication in Southwestern Uganda

Potato (Solanum tuberosum L.) is an important crop in Uganda but production is low. There is not a well-functioning official seed system and farmers use potato tubers from a previous harvest as seed. This study investigated how effectively the seed technology positive selection enhanced yield and underlying crop characteristics across multiple seasons, compared to the farmers’ selection method. Positive selection is selecting healthy plants during crop growth for harvesting seed potato tubers to be planted in the next season. Farmers’ selection involves selection of seed tubers from the bulk of the ware potato harvest. Positive selection was compared to farmers’ seed selection for up to three seasons in three field trials in different locations in southwestern Uganda using seed lots from different origins. Across all experiments, seasons and seed lots, yields were higher under positive selection than under farmers’ selection. The average yield increase resulting from positive selection was 12%, but yield increases were variable, ranging from − 5.7% to + 36.9%, and in the individual experiments often not significant. These yield increases were due to higher yields per plant, and mostly higher weights per tuber, whereas the numbers of tubers per plant were not significantly different. Experimentation and yield assessment were hampered by a varying number of plants that could not be harvested because plants had to be rogued from the experimental plots because of bacterial wilt (more frequent under farmers’ selection than under positive selection), plants disappeared from the experimental field and sometimes plants did not emerge. Nevertheless, adoption of positive selection should be encouraged due to a higher production and less virus infection of seed tubers in positive selected plants, resulting in a lower degeneration rate of potato seed tubers.</p

Understanding seed potato selection practices in Uganda

Potato (Solanum tuberosum L.) is an important crop for food security and cash income for&nbsp; smallholder farmers in Uganda. However, the national mean potato yield has been in decline to less than 5 Mg ha-1 in 2016. Low productivity of potato might be associated with poor and diverse adoption of innovative crop management practices. Smallholder farmers in Uganda commonly use seed potato tubers from the informal sector, especially by seed recycling over several generations. Therefore, seed tubers are highly degenerated with viruses and other diseases, resulting in poor yield and quality of the produce. Over one cycle of multiplication, the degeneration management by positive seed selection was found to be efficient in reducing virus diseases compared with the farmers&rsquo; method of selection. The aim of this thesis was to provide novel information regarding understanding positive seed selection by investigating it across multiple cycles of multiplication with an interdisciplinary approach. To identify potato farms that are homogeneous in uptake of innovations (use of fertilizer, organic input, fungicides, pesticides, seed selection methods, seed renewal by using quality declared seed, and sole cropping), a farm typology was used and socio-economic characteristics, access to agricultural extension services, memberships of farmers&rsquo; groups, yield levels of potato and economic return rates were assessed. A farm household survey (n=270) was carried out and principal component analysis and cluster analysis were used to identify types of farms differing in adoption of innovations. Four farm types were identified that demonstrated significant differences in uptake of innovation practices; these differences in uptake were associated with small but significant differences in yield and further in land ownership, availability of labourers and cash, economic return, and access to knowledge. The farm type with relatively high frequencies of using organic input, fungicide input, pesticide input, seed plot technology or positive selection, quality declared seed and sole cropping achieved highest potato productivity; the farm type with relatively frequent use of fungicide input and no use of pesticides was associated with the lowest potato yield. To assess to what extent positive selection over several seasons can reduce incidences of six different viruses in seed lots of different starting quality, multi-seasonal trials were carried out in three locations, with five seed lots from four sources and three cultivars. Detection of viruses was based on DAS-ELISA and Luminex xMAP technology. Results showed fluctuations in some viruses over seasons, with lower Potato leafroll virus (PLRV) and Potato virus X (PVX) incidences in lots from positive selection compared with lots from farmers&rsquo; selection. Some seed lots were initially highly infected with Potato virus S (PVS) and Potato virus M (PVM) and showed no reduction in virus incidence through positive selection. In general, little infection with Potato virus Y (PVY) and Potato virus A (PVA) was found. To investigate how effectively positive selection enhances yield and underlying crop characteristics, positive selection was compared with farmers&rsquo; seed selection for up to three seasons in three field trials at different locations. Across all experiments, seasons and seed lots, yields were higher under positive selection than under farmers&rsquo; selection. The average yield increase resulting from positive selection was 12%, but yield increases were variable, ranging from &ndash;5.7% to +36.9%, and in the individual experiments often not significant. These yield increases were associated with higher yields per plant, and mostly higher weights per tuber, whereas the numbers of tubers per plant were not significantly different. Experimentation and yield assessment were hampered by a varying number of plants that could not be harvested because plants had to be rogued from the experimental plots because of bacterial wilt (more frequent under farmers&rsquo; selection than under positive selection), plants disappeared from the experimental field and sometimes plants did not emerge. To evaluate costs and benefits of positive selection in order to assess its feasibility and affordability, data from the smallholder farms in the four farm types were used for an economic analysis. It showed that farms that already adopted positive selection, invested on average 1.2 extra days (i.e. 2.7 extra labourer days) per acre in positive selection, with an average of 4.0% extra labour costs. A scenario study among the non-adopters of positive selection, assuming a 10% extra yield by carrying out positive selection, showed that a marginal rate of return of adopting positive selection of far above 100% was achieved in every farm type. Gross and net benefit varied because of different yield increases and different selling prices of potatoes in the different farm types, indicating that some farm households benefitted more than others. The present study shows that positive selection does fit in the current seed system for smallholder farmers and has the capacity to increase yield and reduce viruses with visible symptoms compared to farmers&rsquo; selection. Positive selection being part of the informal and integrated seed sector will help improve seed quality and seed health in farmers&rsquo; networks

A farm typology for adoption of innovations in potato production in southwestern Uganda

In Uganda, low productivity of potato might be associated with poor and diverse adoption of innovative crop management practices. This paper aims to identify the potato farm typologies in southwestern Uganda, i.e., collections of farms that are homogeneous in uptake of innovations (use of fertilizer, organic input, fungicides, pesticides, seed selection methods, seed refreshment by using quality declared seed, and sole cropping), and to analyse these typologies based on socio-economic characteristics, access to agricultural extension services, memberships of farmers\u27 groups, yield levels of potato and return rates. A farm household survey (n = 270) was carried out and principal component analysis and cluster analysis were used to identify types of farms differing in adoption of innovations. Four farm types were identified that demonstrated significant differences in uptake of innovation practices; despite the small differences in yield among farm types, differences in uptake were associated with significant differences in the yield and further in land ownership, availability of laborers and cash, economical return, and access to knowledge. The farm type with relatively high frequencies of using organic input, fungicide input, pesticide input, seed plot technology or positive selection, quality declared seed, and sole cropping achieved highest potato productivity; the farm type with relatively frequent use of fungicide input and no use of pesticides was associated with the lowest potato yield. The findings emphasize associations between innovation uptake and farm characteristics. Opportunities for improvement through extension services and shared knowledge can achieve wider adoption, enhance potato productivity and increase income for smallholder farmers

Impact of Positive Selection on Incidence of Different Viruses During Multiple Generations of Potato Seed Tubers in Uganda

Smallholder farmers in Uganda commonly use seed potato tubers from the informal sector, especially by seed recycling over several generations. Therefore, seed tubers are highly degenerated with viruses and other pathogens, resulting in poor yield and quality of the produce. Over one cycle of multiplication, degeneration management by positive seed selection was found to be efficient in reducing virus diseases compared with the farmers’ method of selection. The objective of this study was to assess to what extent positive selection over several seasons can reduce six different virus incidences in seed lots of different starting quality in southwestern Uganda. Multi-seasonal trials were carried out in three locations, with five seed lots from four sources and three cultivars. Detection of viruses was based on DAS-ELISA and Luminex xMAP technology. Analysis was carried out with analysis of variance (ANOVA) on angular-transformed percentages of virus incidence. Results showed fluctuations in some viruses over seasons with lower Potato leafroll virus (PLRV) and Potato virus X (PVX) incidences in lots from positive selection compared with lots from farmers’ selection. In contrast, some seed lots were initially highly infected with Potato virus S (PVS) and Potato virus M (PVM) and showed no reduction in virus incidence through positive selection. In general, little infection with Potato virus Y (PVY) and Potato virus A (PVA) was found. Based on these results, it is recommended that smallholder farmers are trained in positive selection to opt for less virus-infected plants and tubers, thus increasing potato production