NOTULAE ENTOMOLOGICAE - Helda

s. EKIIOI.M, THE l'KA MOTII (l.ASl'EYRESIA NIGRICANA STEI'II.)
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2B 30 3 7 11 15 19 23 27 31 4 8
July August September
l'igure 3. Tiine at which full-grown larvae abandoned the pods in the years
1959, 1961 and 1962. A = time of harvest, B = time when frost killed the
plants and larvae. Development in 1962 was about one month later than normal.
In 1959, 1961 and 1962, analyses were carried out of Pea IMoth larva infestation
of the pods at different periods of the summer (figure 3). On August
10, 1959, about 50 per cent of the larvae were already out of the pods; by the
end of the same month nearly all the larvae had emerged. During the late
summer of 1962, when development was retarded by about one month
compared with normal summers, few larvae were found in the pods counted
on August 10; on September 1, at most 20—25 per cent of the pods were
injured and a considerable proportion of the larvae were quite young. At this
same time only 2 per cent of the larvae had left the pods. For comparison, it
may be mentioned that on the Gaspé coast in Canada, in 1936, the first fullgrown
larvae abandoned the pods during the third week of August, yet occasional
larvae were found in the pods as late as October (BAKER 1937).
Fluctuations between different broods
The first literature record concerning the Pea IVIoth as a pest in Finland
dates from 1899 (REUTER 1900). As long ago as the nineteentens numerous
observations were carried out in different parts of the country. During the
years in question (1911 — 1962), collection of records concerning the Pea Moth
was confined to information obtained from farmers and gardeners. Thus the
data can only be used for studying large fluctuations in this species. In the
years 1912 — 1913 the moth was very common in Sweden, and 15—75 per cent
of the pods were damaged (TULLGREN 1917). In Finland, the species was very
harmful in the years 1914—1915 (HUKKINEN" 1925), and on several occasions
the damage averaged 70—80 per cent (LIN'N'AXIEMI 1916 and 1921).
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