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

Abstract

Potato cyst nematodes (PCN) are the most economically important nematode pests of potato. Early harvesting is part of a preventive management approach for very early potato varieties. In Belgium, tubers are harvested before 20 June because it is assumed that no cyst formation occurs by that date. However, this assumption might not be valid any more because of climate change, the availability of new cultivars (with new traits), and the increasing prevalence of Globodera pallida. Therefore, pot, microplot and field trials were conducted to study the life cycle of PCN in early potato-growing conditions. The development of populations of G. pallida on three potato cultivars, Eersteling (susceptible to PCN), Premiere (resistant to G. rostochiensis) and Ambassador (partially resistant to G. pallida) and that of G. rostochiensis on cv. Eersteling was monitored in the growth chamber with simulation of field temperatures of the season. On cvs Eersteling and Premiere, second-stage juveniles (J2), males, females and cysts of G. pallida populations were found 28, 56, 63 and 77 days after infestation with cysts (DAI), respectively. The number of degree days (DD) for G. pallida to complete its life cycle using a base temperature of 4 degrees C was calculated 450 DD4. On cv. Ambassador, females of G. pallida were never observed. J2, males, females and cysts of G. rostochiensis were detected 42, 70, 70 and 84 DAI, respectively. This species needed 398 DD6 at a base temperature of 6 degrees C to complete its life cycle. Observations in two fields and in microplots under prevailing weather conditions in 2013 revealed that cysts of G. pallida and G. rostochiensis were formed on June 12, when the accumulated degree days were 463 DD4 and 401 DD6, respectively. Our observations show that both species of Globodera develop earlier than was assumed based on previous data. Therefore, harvesting based on the accumulated heat above the basal development temperature required by PCN species can replace the set harvest date

Climate change is predicted to alter the current pest status of Globodera pallida and G. rostochiensis in the United Kingdom

“…They emerge through the cortex onto the root surface and continue to grow on main crop potatoes in the United Kingdom from June onwards. For example, first emergence of females onto the root surface occurred in Southern England in late June, 55 days after planting in early May (Whitehead, ) and mid‐June for early planted potatoes in Belgium (Ebrahimi, Viaene, Demeulemeester, & Moens, ).…”

“…A partial second generation has been observed for some populations of G. rostochiensis in the United Kingdom (Evans, 1969;Jones, 1950) and Italy (Greco, Brandonisio, Tirro, & de Marinis, 1988). Potatoes are grown widely in England and Scotland with planting of main crops from mid-April and harvest up to early October (Daccache et al, 2012;Gregory & Marshall, 2012 (Whitehead, 1992) and mid-June for early planted potatoes in Belgium (Ebrahimi, Viaene, Demeulemeester, & Moens, 2014).…”

Population dynamics of the potato cyst nematode, Globodera pallida, in relation to temperature, potato cultivar and nematicide application

“…The temperatures at Harper Adams were higher than at East Lothian during three of the periods between soil samplings and were particularly high during the final harvest period (average 16.9 compared to 12.9 °C). Assuming a base temperature of 4 °C for G. pallida (Ebrahimi et al ., ), there were 1511 and 1804 DD at the East Lothian site and Harper Adams sites respectively. A t ‐test confirmed significant differences in the soil temperature between the sites ( P < 0.001).…”

“…Ebrahimi et al . () estimated the degree day requirement for G. pallida of 450 DD with a 4 °C base temperature. There were 1511 DD and 1842 DD at the East Lothian and Harper Adams sites respectively, both sufficient for two generations to be completed.…”

“…In the last century, global temperatures have been increasing due to climate change and the effect of this trend on crop losses due to plant pests and diseases, including soil dwelling organisms such as PCN, is of concern (Ellenby & Smith, ; Stanton & Sartori, ; Munir et al ., ; Ebrahimi et al ., ; Jones et al ., ; Skelsey et al ., ). Recently Jones et al .…”