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FIELD STUDIES ON THE INFLUENCE OF WEATHER CONDITIONS ON EGG‐LAYING BY THE CABBAGE ROOT FLY, ERIOISCHIA BRASSICAE BCHÉ. I
Author(s) -
MILES MARY
Publication year - 1953
Publication title -
annals of applied biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.677
H-Index - 80
eISSN - 1744-7348
pISSN - 0003-4746
DOI - 10.1111/j.1744-7348.1953.tb01109.x
Subject(s) - biology , zoology , infestation , horticulture , ecology
The duration and intensity of egg‐laying by the spring generation of Erioischia brussicue Bché has been studied by removing daily the soil around the stems of cabbage plants on an observation plot. In 1952, eggs were first found on 22 April; the peak period of egg‐laying lasted from 30 April to 22 May, and in the last week of May the rate of egg‐laying declined rapidly. In the peak period the rate of egg‐laying was 5–46 eggs per day per plant with a mean rate of 23 eggs per day per plant. The spring infestation on observed plants was 258–817 eggs with a mean of 533 eggs per plant. Variation in the daily rate of egg‐laying was associated with weather conditions. Warm sunny weather induced heavy egg‐laying but in cool, wet and windy weather fewer eggs were laid. A summer peak of egg‐laying associated with the second generation of E. brassicae occurred in late June and early July. Attack in summer was less intense than in spring, a total of 1298 eggs being recorded for the summer peak period (24 June‐14 July) compared with 5796 eggs during a similar period (30 April‐20 May) in spring. Observations on the numbers of flies that emerged from alternate plants on the observation plot showed that the low rate of egg‐laying in summer was not the result of a lack of adults. Consideration of biotic and climatic factors suggested that while high temperatures and long periods of sunlight stimulated the summer flies to great activity the environment provided little food to sustain them, and in consequence they did not survive to complete oviposition. The puparia were collected from the undisturbed alternate plants in order to obtain information on the numbers of E. brassicae that reached maturity. It was estimated that 5–6% of the eggs reached the pupal stage; approximately two‐thirds of the puparia gave rise to flies and one‐third were parasitized. About 9% of the puparia remained viable in the soil to give rise to the following spring generation, about 90% having given rise to flies in the year in which they were formed.