Models for spring migration of two aphid species Sitobion avenae (F.) and Rhopalosiphum padi (L.) infesting cereals in areas where they are entirely holocyclic

1 Cereals can be attacked severely by the grain aphid, Sitobion avenae (F.), and the bird cherry‐oat aphid, Rhopalosiphum padi (L.). The time of migration from winter hosts in spring is important regarding input to decision support systems concerning insecticide treatment of aphids. 2 The present study aimed to construct two separate migration models, which could be used immediately for advisors and farmers but also be part of a decision support system for the chemical control of aphids in winter wheat and spring barley. 3 Winter wheat (Triticum sativum Lam.) and spring barley (Hordeum vulgare L.) fields were monitored from 1991–2005 for the occurrence of grain aphids and bird cherry‐oat aphids, and the data were used to construct migration models. 4 The models were constructed based on all 9 years data and subsequently validated by using all 9 years data, excluding 1 year at a time. 5 The migration model for the grain aphid producing the best forecast was obtained with migration date M (number of days from 1 June), degree‐days (DD) of April (T_a) and DD of May (T_m), with the model being M= 265.0 ? 10.2 log_e(T_a) ? 35.1 log_e(T_m). 6 The migration model for the bird cherry‐oat aphid producing the best forecast was obtained with migration date M (number of days from 15 May), DD of April (T_a) and DD from 1–15 May (T_m1), with the model being M= 294.4 ? 34.7 log_e(T_a) ? 22.5 log_e(T_m1). 7 The models only worked well in areas where the grain aphid and the bird cherry‐oat aphid are entirely holocyclic.