No abstract

Integrated Pest and Pollinator Management (IPPM) advocates a pollinator-friendly approach to Integrated Pest Management (IPM), with emphasis on the need to protect pollinators from the harmful effects of chemical pesticides. However, in order to link the goals of IPM and pollinator management both more formally and comprehensively, we introduce here a unified decision metric, termed the joint Economic Impact Level (jEIL). The joint EIL integrates the use of economic injury levels, as well-established in IPM, with a proposed pollinator equivalent; the pollinator Economic Impact Level (PEIL). This joint metric can be used to weigh the cost and benefit of pest and pollinator management in a holistic sense – accounting for potential interactions, and remedial actions (such as the avoidance of pesticide use during flowering). However, especially where management priorities are unclear (when biocontrol and pollination services trade off; flower strips exacerbate pest injury; pests and pollinators show non-linear effects on yield); the joint EIL can be of particular value in identifying the most beneficial action. To render this decision metric actionable, we further introduce the concept of pest and pollinator Action Thresholds (ATpe and ATpo). We follow theoretical description of these metrics with a practical example for strawberry, to demonstrate calculation of a joint EIL in support of IPPM decision making. As a whole, the joint EIL provides a flexible framework for integrated decision making, in support of timely management action. This decision metric (supported by a forthcoming jEIL tool) could hence be of broad practical value for farmers, agricultural advisors, researchers, and commercial and governmental agencies.

Soil microorganisms and soil fauna may have a large impact on the tuber yield of potato crops. The interaction between root-lesion nematodes and the pathogenic fungus Rhizoctonia solani Kühn was studied on potato plants grown in pots under controlled conditions. In two similar experiments, different combinations of nematodes and fungal mycelium were added to the pots at three occasions; at planting, after 14 days, and after 28 days. The nematodes reduced root biomass and the combination of nematodes and R. solani resulted in reduced tuber yield in both experiments, but the interaction was not synergistic. In contrast, the number of stem canker lesions decreased in the presence of nematodes compared to treatments with R. solani only. The time of inoculation influenced the severity of both fungal and nematode damage. The nematode damage on tubers was less severe if the nematodes were added at 28 days, while the number of severe stem canker lesions increased if the fungus was added at 28 days. However, the time of nematode inoculation did not affect the incidence of fungal damage, hence the nematodes did not assist R. solani to infect the plant. Our results highlight the underestimated importance of root-lesion nematodes, not resulting in obvious above ground symptoms or misshaped tubers yet affecting the performance of other pathogens.

Aim Cadmium mitigation in crops is a worldwide concern. Selenium application has been suggested as a potential solution to reduce cadmium concentration in plants, but published results were contradictory. We analysed literature data with respect to the effect of selenium addition on cadmium uptake and elucidated processes possibly involved. Method A meta-analysis was performed on data collected from previously published studies presenting cadmium concentration in plants subjected to selenium treatments. Metaregression random models were run to test the impact of different factors. In addition, soil and crop inventory data exemplifying the natural variation of Cd and Se in soil were evaluated. Results The results highlighted a significant reduction of cadmium concentration in crops after selenium addition. The reduction was dose-dependent for crops growing under aerobic, but not for plants cultivated under anoxic conditions such as rice. This suggests that different process can be involved. Conclusion We demonstrated the potential of selenium fertilization to mitigate cadmium uptake and highlighted that for non-rice species, the main process seems to take place in the soil, while mechanisms in roots restricting uptake may be involved for all crops. The inventory data also indicated an impact of natural soil Se on Cd contents in crops.

The significance of nematodes for disease development caused by other soil-borne pathogens has been demonstrated in many crops throughout the world and specifically prevalent are interactions between plant-parasitic nematodes and species of plant pathogenic fungi. Here, the interaction between the fungus Rhizoctonia solani (AG2) and the migratory endoparasitic root-lesion nematode Pratylenchus penetrans was investigated on potato. The hypotheses were that the combination of R. solani and P. penetrans would result in more severe canker lesions, reduced quality of the tubers and lower tuber yield, and we also expected higher nematode levels to render more nematode damage. To test this, potato plants were grown in pots in two replicate experiments and the presence and/or abundance of the two pathogens were controlled. The first three hypotheses were rejected as (1) the tuber yield decreased when the fungus and nematode occurred together but not more than the sum of their separate effects, i.e. additive, (2) there was no effect of presence of nematodes on the incidence of stem canker, and (3) the quality of tubers was actually partly improved as the presence of the nematodes reduced the likelihood of elephant hide on the tubers in one of the experiments. As expected, there were more visible nematode damages with addition of more nematodes, but beyond that the different nematode levels rendered in most cases similar responses. To have knowledge about interactions between pathogens, as the one showed here, is essential for disease control through appropriate management methods.