Life-history parameters and population dynamics of Ericaphis fimbriata (Hemiptera: Aphididae) on blueberry, Vaccinium corymbosum

Development rate and age-specific fecundity and Survival of Ericaphis fimbriata (Richards) virginoparae were determined during the spring Oil Young leaves of blueberry, Vaccinium corymboswn L., as functions of temperature. The same traits were measured during the summer and the autumn on both young and mature leaves at 21.2 degrees C. The temperature threshold for development was 4.1 +/- 0.5 degrees C (SE). For apterae, development time from birth to adult was 157.7 +/- 5.9 day-degrees (dd). Proportional lengths of instars I-IV were 0. 16, 0.14, 0.34, and 0.36, respectively. Adult life was 434.5 +/- 17.5 dd and proportional lengths of the prereproductive, reproductive, and post-reproductive periods were 0.05, 0.74, and 0.21, respectively. Mean fecundity was 23.6 +/- 1.0 nymphs per female. Mean Survival was 602.9 +/- 14.6 dd, and more than 80% of apterae survived the peak reproductive period. Alate fecundity was 16.5 +/- 3.2 nymphs per female and alate survival was 460.9 +/- 47.5 dd. Leaf type and season of measurement had significant effects on development time and fecundity: development time was 158.2 dd (+4.9 upper asymmetric SE) on young V corymbosum 'Duke' leaves in the spring but 312.4 dd (-16.9 lower asymmetric SE) on mature 'Bluecrop' leaves, the dominant leaf type, from a commercial field in the summer. Fecundity for the respective leaf types and seasons was 16.7 (-1.6) and 1.4 (+0.5) nymphs per female. From summer to autumn, development time increased on young 'Duke' and 'Bluecrop' leaves but decreased oil mature 'Bluecrop' leaves, fecundity decreased on young 'Duke' and 'Bluecrop' leaves but remained at low levels oil mature 'Bluecrop' leaves. A simulation model showed that seasonal changes in development time and fecundity were capable of reducing population growth rates to near zero depending on aphid distribution with respect to young and mature leaves. The results support a combined bottom-up and top-down view of aphid population regulation and suggest that control efforts should focus on the spring. when the population growth rate is maximal.