Showing 2 results for Population Fluctuation.
H. Masjedian, H. Seyedoleslami,
Volume 6, Issue 4 (1-2003)
Abstract
Pistachio oyster shell scale is one of the important pests of pistachio in Iran whose females are reported to exist in two or three forms, each form developing on a specific part of the pistachio tree. In this study, abundance of the pest is investigated on leaves and branches for different ages, two heights and four cardinal directions of tree crown. Paralelly seasonal population fluctuations of three forms were studied on leaves, and one-and two-year-old branches separately.
This insect overwintered as female mostly on one and two-year-old branches. It had two separable periods of activity, through the season. In the first period, eggs mostly hatched in April and crawlers mostly settled on leaves, fruits and newly grown twigs but rarely on older branches.These populations are male and female. In the second period, eggs mostly hatched in June, and crawlers settled mostly on leaves and one and two-year-old branches, but all individuals settled on leaves are males and those on branches are females. Population density is significantly higher on upper surface of leaves than on the lower surface. Analysis of variance showed that only significant differences existed in densities observed between trees in both generations, and also between two heights of tree crown for populations settled on wood. Two predatory species from Cybocephalidae and Coccinellidae, one ectoparasitoid from Aphelinidae and two endoparasitoids from Encyrtidae were collected as natural enemies of this pest in Isfahan.
S. S. Modarres Najafabadi, H. Akbari Moghaddam, G. Gholamian,
Volume 8, Issue 4 (1-2005)
Abstract
Four different species of aphids belonging to the Aphididae family in four genera were collected and identified in Rape-seed fields in Sistan region during 2000-2001. Among them, Brevicoryne brassicae (Cabbage aphid) was the dominant species with an abundance of about 89% in area. The population fluctuation of Brevicoryne brassicae was studied simultaneously on fields in Sistan region (Zahak research station and her around fields). The research was conducted on a half hectare of each farm. Thirty leaves from each field at week intervals were randomly picked up and the aphids were collected and identified at the species level. The Brevicoryne brassicae had a peak of activity in early mid March to April at temperature and R.H. ranging between 22-28ºC and 45-65 R.H., respectively. Controlled conditions indicated that the Brevicoryne brassicae has a life cycle of 6-7 days and adult female longevity is 20-31 days (25±2 ºC and 75±5 R.H.). Rearing study also revealed that this species has the ability to reproduce up to 18-98 nymphs under laboratory conditions and an apterous female gives birth to 22-93 nymphs in her life time. Samplings for recognition of predators and parasitoids were also taken at 3-day intervals. Natural enemies in fields during the two years were identified to be 5 coccinellid (Col:Coccinellidae), 4 syrphid(Dip:Syrphidae) and 2 chrysopid species (Neu:Chrysopidae). Also in Hymenoptera, 2 parasitoids (Hym: Aphidiidae & Pteromalidae) were determined.
