The thematic session on Crop Biotic Stresses on Friday 7 October, 2011 touched upon various research into crop production and crop management methods. While the results were also unique, the discussions at Tropentag focused their interest on the improvement of methodologies. The impacts of crop management. The session looked at the effects of Chlorpyrifos in Costa Rica and how they are having a negative impact on the children in the area. The exposure came from the use of Chlorpyrifos-bags used in banana and plantain Plantations. We were also introduced to the research through a microarray analysis of gene expression induced in tomato leaves. The genes were compared between treated/untreated/diseased/healthy tomato plants and observed for activation of plant resistance. Interestingly enough, someone in the crowd commented on the research and arrived at opposite results having done the same research. The debate was left up in the air… to be continued during the following coffee break. Fellow presenters listening to their colleague's presentation. Africa stricken with Striga! Two presentations applied unique methods for analyzing Strigas in Africa. While one looked at the geographic distribution in different climate conditions, the other presentation looked at Striga on a molecular level for Biocontrol agents. Distribution graphs showed that climate envelope models were able to accurately predict Striga distribution in western Africa under different scenarios with results that were as expected. It showed that climate data can effectively pinpoint where Striga will grow. However comments suggested that further research would need to include more information on crop management, soils, and vegetation in relation to Striga. The presentation on a molecular analysis confirmed the applicability of a developed qPCR protocol to assay the fate of Fusarium oxysporum under controlled incubation conditions. This highlighted the growth of Striga in different soil types, possibly suggesting further collaborative research into Striga with the previous presentation. The Striga weed growing in crop fields. Mono-cropping vs. Mixed cropping. Within this session, we again note the continuation of a common discussion throughout Tropentag 2011: the possible benefits/disadvantages of mono-cropping and mixed cropping techniques. We were introduced to the effect of different biofumigants with mixed cropping of pea and oat. Possibilities were suggested to minimize these negative impacts by reducing soil borne pathogens through cultural cropping methods. Generally most presentations suggest mixed cropping methods as a solution to issues of food-security and crop management. They also address risks of mixed cropping such as stress on the soil and nutrients. A significant number of presentations ended with the question whether land equivalent ratios were used when comparing mono-cropping and mixed cropping as this was often something that was not done. Does mixed cropping really improve the yield per unit of land, and have the stresses on plant and soil been taken into account?