Tools for nematode management
1. Cultivation of nematode-resistant catch crops
By cultivating resistant catch crops, you can prevent the development of high nematode populations in close sugarbeet crop rotations You can even reduce existing high population densities with catch crops. Effective plants available for this purpose include a variety of resistant yellow mustards and fodder radishes.
Reducing the nematode population by shifting the sex ratio toward the male population. Females require about 40 times more food during their development than males to complete their development.
- In the case of susceptible host plants, the male-female ratio is almost 1:1;
- in resistant plants it is 100:1
To control nematodes effectively, you should keep in mind that:
- Only resistant fodder radish and mustard varieties will reduce the population density;
- all other varieties of these species contribute to multiplication
- Pay attention to optimal seedbed preparation!
- Hatching stimulus can only be triggered when the nematodes have intensive contact with the roots
- A very dry or very cool autumn limits the reduction of the nematode population
2. Cultivation of rapeseed and sugarbeet in crop rotation
When you want to cultivate rapeseed in a crop rotation, there are some challenges to be mastered, since both rapeseed and beets can increase nematode counts.
However, cultivation of winter rapeseed usually has a more limited potential for propagation of Heterodera schachtii, since:
- Winger rapeseed is sown in autumn with decreasing soil temperatures.
- The development cycle of the beet cyst nematode cannot be completed before winter
- The nematodes also have a low development rate in spring because of the low soil temperatures
- The larvae have only fine roots available during infection
- With the beginning of flowering, rapeseed root growth is greatly reduced, and hence so is the hatching stimulus of the nematodes
Cultivation of summer rapeseed and dealing with volunteer rapeseed present greater challenges.
The rapeseed that emerges in spring or summer experiences its taproot growth with increasing or already high soil temperatures and encounters simultaneously high nematode activity.
Thus, the volunteer rapeseed of winter rapeseed can lead to very great multiplication of nematodes!
Prevent nematode multiplication by:
- Precise and well-timed control of volunteer rapeseed
- Stubble management or herbicide application after reaching a heat sum of 250°C
- By killing off this rapeseed, the multiplication cycle is broken, and nematode reduction can even be achieved
In rapeseed-beet crop rotations, you should not cultivate either nematode-resistant fodder radish or yellow mustard, since both catch crops belong to the family of cruciferous vegetables and family and facilitate the plant disease, clubroot.
3. Variety selection
Effect of variety selection on nematode infestation several years ago
Economic damage threshold for nematode-resistant sugarbeet varieties:
- Approx. 1,200 eggs + larvae/100 g soil
- Approx. 500 eggs + larvae/100 g soil
These thresholds are set lower in light, non-irrigated soils and somewhat higher in very good soils with appropriate additional water supply.
Effect of variety selection on nematode infestation today
The smaller the difference in performance between susceptible and tolerant varieties in the absence of infestation, the lower the damage thresholds should be.
If sugarbeets have been grown on the fields for decades and if the crop rotation periods show a trend toward becoming narrower, there is a scientifically confirmed risk to yields from beet cyst nematodes. This can be minimized by the cultivation of nematode-tolerant varieties .
With the availability of more nematode-tolerant varieties with performance comparable to the simply tolerant varieties, the former damage thresholds have lost their significance.