none Dynamics of the asparagus aphid, Brachycorynella asparagi (Mordvilko), were studied in two mature asparagus fields and one immature field for a minimum of two seasons. Numbers of B. asparagi were low early in the spring and increased to a peak in late June or July or in September to early October. No midseason peak was observed. Fields with an early summer peak had a midsummer low point and usually a late summer peak. Decline of aphid numbers in the fall coincided with egg laying that started during the last week of September when day length was about 12 h. Reproduction; Reproductive behaviour; Life cycle and development; Development; Evolution; Variation; Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Host parasite relationships; Ecology; Abiotic factors; Physical factors; Light; Land and freshwater zones; Nearctic region; North America; USA Diaeretiella rapae (Braconidae); Hemipteran hosts; Brachycorynella asparagi, host density relationship; Prevalence; Brachycorynella asparagi (Hemiptera), host density relation; USA; Washington; South central; Prevalence in hemipteran host Brachycorynella asparagi (Aphidoidea); Breeding season; Oviposition phenology, photoperiod relationship; Oviposition; Phenology & population dynamics relationship; Hatching; Phenology, temperature & plant host relationships; Seasonal races; Winged form production; Hymenopteran parasites; Diaeretiella rapae, population density relationship; Plant hosts; Asparagus officinalis (asparagus); Phenology & population dynamics on undisturbed hosts; Prevalence; Diaeretiella rapae (Hymenoptera) density relationship; Population dynamics; Undisturbed plant host; Climate and weather; Rainfall, abundance relations, plant host; Photoperiod; Oviposition phenology relationship; Temperature; Hatching phenology & population dynamics relationship; Washington; South central; Phenology & population dynamics on plant host