Observations on Globodera pallida and G. rostochiensis on early potatoes

Abstract

SUMMARY Observations in south Wales during 1971–78 on population changes in the cyst nematodes G. pallida (Stone)‐Behrens Pal and G. rostochiensis(Woil.) Behrens Rol on early potatoes grown in concrete‐bounded microplots confirmed that populations can be controlled by early harvesting. When potatoes were planted on 11 Match, harvesting 83 days later led to a decline in the population density of G. pallida in every year except 1976, which was exceptionally warm. The best estimate of the rate of decline was 55 per cent per annum. Harvesting after 91 days resulted in population densities otily slightly less than harvesting after 103 or 120 days, when population densities fluctuated around an equilibrium of 120 eggs/g soil. Sitnilarly, when plots infested with G. rostochiensis were harvested after 83 days, population densities declined. Harvesting after 91 days resulted in fluctuations about an equilibrium of 7 eggs/g soil and after 103 and 120 days around an equilibrium of 120 eggs/g. Females of G. pallida developed faster and produced eggs sooner than those of G. rostochiensis over the spring temperature range. Therefore, early harvesting would favour G. pallida and, if done routinely, would lead to the selection of this species and the replacetnent of G. rostochiensis. Harvesting a fixed number of days after planting would probably give satisfactory population control in most years, but harvesting on the basis of accumulated temperature above a known basal development temperature would probably be better, especially in years in which, the temperature departs appreciably from the average.

Comparison of the in-soil hatching responses of Globodera rostochiensis and G. pallida in the presence and absence of the host potato crop cv. British Queen

“…In this scenario, 10 4 tubers (i.e., one tuber per m 2 ) would be sufficient to cover the entire field. The timing of the removal of the trap crop is critical in preventing PCN multiplication (Whitehead, 1997); in our experiment hatching had largely been completed 54 days after plant emergence (by the 24 May) and the plants could have been safely destroyed without any carryover of newly formed PCN cysts as, in Western Europe, it takes approximately 83-91 days for either PCN species to complete their life cycle (Webley & Jones, 1981).…”

Construction and preliminary evaluation of a simulation model of the population dynamics of the potato cystnematode Globodera pallida

“…As described by Mugniery (1978b) and Webley and Jones (1981), harvesting early (90 days after planting) results in a considerable decrease in multiplication rate and equilibrium density, provided the initial density is below 100 eggslg soil.…”

“…At densities below this threshold, damage could be limited by combinations of other methods, e.g. · resistant cultivars, tolerant cultivars (Trudgill and Cotes, 1983a), crop rotation and the appropriate selection of non-host crops, natural enemies (Goswamy and Rumpenhorst, 1978;J atala et al, 1979;Kerry, 1980;Franco et al, 1981), treatment of the soil with root extract or tree bark (Hoestra and Harshagen, 1981), or early harvesting (Grainger, 1962;Van den Brande and d'Herde, 1964;Mugniery, 1978a,b;1982;Webley and Jones, 1981;Hoestra, 1983). Clearly, to optimize the use of these very diverse methods it is necessary to be able to predict their consequences.…”

Observations on the life cycle of potato cyst nematodes, Globodera rostochiensis and G. pallida, on early potato cultivars

“…It has also been shown that the two PCN species are notice ably different in their behaviour and life cycle (Den Nijs & Lock, 1992). Compared with G. rostochiensis, G. pallida has a lower optimum temperature for hatching (Franco, 1979) and its females develop faster and produce eggs ear lier at lower temperatures (Webley & Jones, 1981). The latter authors also observed a significant population de cline of both species after an early harvest of early pota toes.…”