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 (Ta) and DD of May (Tm), with the model being M= 265.0 − 10.2 loge(Ta) − 35.1 loge(Tm).
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 (Ta) and DD from 1–15 May (Tm1), with the model being M= 294.4 − 34.7 loge(Ta) − 22.5 loge(Tm1).
7 The models only worked well in areas where the grain aphid and the bird cherry-oat aphid are entirely holocyclic.