The effects of soil amendments on the viability of potato cyst nematodes (Globodera rostochiensis and G. pallida)

The potato cyst nematodes (PCN) Globodera rostochiensis and G. pallida are considered the most economically important nematode pests of potato. Their success is due, in part, to their ability to survive for years in the absence of host plants. The goals of this study were: (1) to evaluate the effects of soil amendments on the survival of PCN, and (2) to compare 3 methods of viability assessment. Seven soil amendments (pig slurry, cattle slurry, farmyard manure, chitin, nitrogen fertilizer, wood chip compost and a combination of wood chip compost and biochar) were mixed with a sandy soil and added to 2-liter-pots. Non-amended soil was used as a control. Batches of 21 cysts of G. rostochiensis or G. pallida were placed in retrievable bags and added to the soil in each pot. Pots were left outside, exposed to prevailing weather conditions, in a randomized design with 4 replicates. The viability of the cysts content was determined at 8, 12 and 16 weeks after inoculation (1) by visual assessment of the viability of eggs and juveniles using a microscope, (2) by measuring the trehalose content of the eggs, and (3) by determining the hatching percentage of eggs in cysts. The three methods showed that the exposure of cysts to nitrogen fertilizer and pig slurry for 16 weeks caused a reduction (P<0.001) in the viability of eggs of PCN. Negative effects of pig slurry on cyst survival were already visible after 8 weeks exposure for G. pallida. The other amendments had no significant effects on survival of both Globodera species compared with non-amended control. The trehalose method and the visual assessment identified more (P<0.001) viable eggs than the hatching test.

Key words- survival, manure, trehalose, hatching.