Agriculture Reference
In-Depth Information
3.
B
IOLOGY AND
E
COLOGY
a. Number of Molts (Instars)
In a study carried out in the greenhouse (ambient temperature and
humidity) to determine the growth and development of pea aphids on various
legumes, the number of molts did not vary between legume species (faba bean
also called broad bean, field pea, lentil and grass pea) (Wale et al., 2000). The
study also indicated that in northwestern Ethiopia, under experimental
conditions, the pea aphid undergoes up to three molts. This indicates the
number of nymphal stages. The nymphal period lasted between nine and 11
days and did not vary among legumes. It appears that the warm episodes in the
area speed up maturity of pea aphids. Similar findings were reported elsewhere
(Sharma et al., 1976).
b. Adult Longevity and Fecundity
Lifespan.
The lifespan of the pea aphid, from birth to death, was
significantly longer on lentil than on other crops (Wale et al., 2000). Pea
aphids lived for about a month on lentil, with their lifespan ranging from 27 to
41. Pea aphid lifespan was 20.1 days on faba bean, 22.7 on field pea, 34.9 on
lentil and 24.6 on grass pea. Extended reproductive and post-reproductive
period of pea aphid on lentil resulted in longer lifespan. The shortest lifespan
was recorded on faba bean with a mean of about 20 and a range of 15- to 26
days (Table 1).
Survival curve.
Slightly more pea aphids survived on field pea for the first
10 days of adult life after which more aphids survived on lentil than all other
crops (Wale et al., 2000). The shortest survival duration of all ages of the
aphid was recorded on faba bean. Aphids survived on this host for 17 days.
Pea aphids survived less on faba bean and better on lentils and field pea.
Adult life history.
Significantly higher reproductive period, post-
reproductive period and longevity of pea aphids were recorded on lentil than
on other crops (Wale et al., 2000). This is in agreement with lifespan and
survival curves mentioned above (Table 1).
