pdf, 57.71Mb - Entomological Society of Canada

Releases and Recoveries
Tipilia pailldosa Mcigen. 87
fllivipennis De Geer. T. viltala Meigen. T. sllbnodicornis Zetterstedt. T. monlillm Egger.
and T.maxima Poda (Rennie & Sutherland 1920. Chiswell 1956, Coulson 1962, Alma
1975) as well as from T. pailldosa. It has been reared from only T. pailldosa in British
Columbia.
A phorid, Megaselia pailldosa (Wood), was found in T. pa/udosa by Coggins (1970) and
by Carl (1972). It is rare in Europe and requires damp conditions.
Many insecticides tested for the control of leatherjackets were effective. but only
diazinon. chlorfenvinphos, and parathion were registered. Diazinon is used primarily on
home and public lawns and the other two are used on pastures. Except in the more recent
infestations at Nanaimo, Pon Alberni, Prince Rupen, and Victoria. there is very little
need for chemical control. If these infestations follow the pattern of those in the lower
Fraser Valley. populations will decline and chemical controls will no longer be needed.
The B-exotoxin of Bacillus thuringiensis Berliner and the DD-136 nematode of
Neoplectana carpocapsae Weiser were investigated by Lam & Webster (1972) as possible
controls for T. pailldosa. Both B-exotoxin and DD-136 were successful in killing
leatherjackets in the laboratory, but the experimental evidence suggests that the heavy
application required to achieve high mortality would not be practical for control of T.
paludosa in the field.
Carter (1973a. 1973b) showed that Tipula iridescent virus (TIV) can be transmitted
when healthy larvae feed on a TIV-infected larva. Field trials by Caner (1978) showed
that TIV can be introduced into field populations of T. paludosa but with low efficiency.
In 1968. 331 adult S. geniculata were received from the Commonwealth Institute of
Biological Control (CIBC). Switzerland. from which 565 adults were reared and released
near Cloverdale. British Columbia. Between 1971 and 1975 an additional 7000 S.
geniculata received from the CIBC or reared at the Vancouver Research Station were
released in the lower Fraser Valley. A technique for breeding S. geniculata was developed
by Carl (1972). Leatherjackets were inoculated with larvae dissected from fieldcollected
or laboratory-reared gravid females of S. geniculata. The first recovery was in
1972 when 4 flies were reared from puparia attached to a leatherjacket cadaver. Counts
of leatherjackets and parasitism were taken from January to August at Cloverdale from
1974 to 1977 and at Ladner from 1975 to 1979. Parasitism was never very high. At
Cloverdale. the highest parasitism recorded for the first generation (December to
March) was 4.3% with an average of 1.6%, and for the second generation (June and July)
the highest parasitism recorded was 5.1 % in 1974 and for the 4 years parasitism averaged
2.4%. At Ladner during 5 years the highest parasitism was 3.3% for the winter generation
with an average of2.3%. and for the second generation the highest parasitism recorded was
6% with an average of 2.8%. As in Europe. the percent parasitism determined for the
second generation was based on low numbers of the host because of the marked
decrease in the larval population late in the season.
In 1973. 100 S. geniculata adults were air expressed to Newfoundland; 79 survived
and were released. In 1974. 600 were sent and released. None has yet been recovered.
Megaselia pa/udosa was found in some of the leatherjackets received at the Vancouver
laboratory from CIBC. Switzerland. It was reared for several generations but the
colony died and the parasitoid was never released.
Tipll/a iridescent virus-infected larvae were released near Ladner in 1975 but the virus
has not been found in any larvae examined from this area.