Some days ago we mowed down a plot of peonies which was heavily infected with (strawberry)leaf nematodes (aphelenchoides fragariae). It’s one of only a few problems with peonies that regularly occur here, the other being botrytis and, less common, phytophthora. The plants will no doubt experience a setback, but it is hoped the pest can be controlled this way. Spraying during the season doesn’t seem to work is our experience. Before the onset of growth the fungicide/nematicide fluopyram (sold as ‘Luna’ here) can keep it under control more or less we found (from limited experience though). There’s a new biological pesticide on the market here which will be trialled as well for comparison. Results are for next year of course.

The damage from leaf nematodes can be alarmingly large in only a few years’ time. Some 90% of flowers lost on infected plants is not unusual. There is difference in susceptibility between varieties (and soil, sandy soil being most susceptible, clay less so): Coral Sunset and Old Faithful are two of the most prone ones. But in fact I know of no resistant/tolerant varieties within the herbaceous group, if there is an infected plant in the midst of a field with different cultivars, you’ll see a circle of infected plants around it soon, no matter what varieties grow there. The tree peonies have never shown any such damage, but again, this is from limited experience as only few tree peonies grow here. Intersectionals seem better able to withstand them as well.