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WINTER MOTH Operophtera brumata (L.) --
Lepidoptera, Geometridae (Contacts) ----- CLICK on Photo to enlarge &
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In the first few
years after its appearance in Nova Scotia, damage was evident in apple
orchards, shade trees and oak forests.
However, at this time hardwoods were not commercially exploited in the
Province and so the winter moth was not considered a serious pest (Embree
1971). Consequently it was possible
to initiate a biological control program rather than a program of insecticide
eradication. The general research
policy in the early 1950's was directed towards population dynamics of forest
insect populations and thus the biological control program was initiated in
1954 with a view to population studies of the host and introduced parasitoids. Prior to the
introduction of parasitoids from Europe, the winter moth fluctuated
erratically at high population densities.
These fluctuations resulted from the coincidence of hatching of the
overwintering eggs and bud burst in early spring (Embree 1965a,b). This same key mortality factor was also
found to be responsible for changes in population levels of winter moth in
Britain (Varley & Gradwell 1968). Three tachinid and
three ichneumonid parasitoids were obtained in sufficient quantity for
introduction into Nova Scotia from Europe.
The parasitoids were collected and shipped to Canada by staff of the
Belleville Laboratory and the CIBC and field releases were made during the
period 1954-62. These included
releases of over 22,000 individuals of the tachinid Cyzenis albicans
(Falk.) and a total of 2,261 individuals of the ichneumonid, Agrypon flaveolatum (Grav.), the only two species that became
established. C. albicans
is very fecund and oviposits microtype eggs around the edge of damaged
foliage where they are ingested by late-instar host larvae. The egg hatch in the midgut of the host
and the larvae bore through the gut wall to develop rapidly after the host
has pupated. The tachinid pupates and
overwinters within the host pupal case in the ground. The biology of A. flaveolatum
is similar but its oviposits directly into the host larvae and has larger
eggs and much lower fecundity. Following the
establishment of these two parasitoids, parasitism by C. albicans
increased rapidly to 50% in 1960 and life table data showed that a
considerable increase in prepupal mortality was responsible for the collapse
of the winter moth population in the main study site (Embree 1965a,b). Parasitism by A. flaveolatum
increased only following the initial decline of the host outbreak and while
it may have enhanced the depression of the winter moth density, population
models indicate that the efficiency of C.
albicans alone is sufficient
to account for successful biological control (Hassell 1980). However, a more recent analysis of the
life table data from Nova Scotia and Britain
(Roland, pers. comm.) indicates that the increased pupal mortality may
have arisen only indirectly from the introduction of C. albicans. Increased parasitism by C. albicans is closely followed by an increase in the
activity of soil predators, perhaps sustained on overwintering C. albicans puparia through late summer and early spring when
prey are generally scarcer. Thus
predation rather than parasitism may be more directly responsible for the
observed increase in winter moth pupal mortality. Recent unpublished work in British Columbia indicates that
staphylinid predators are especially important in regulation and that C. albicans puparia are avoided because they are too large
for the predators. More recently,
between 1976 and 1978, winter moth has been noted in Oregon, Washington and
British Columbia on various hardwood and fruit trees. Both C.
albicans and A. flaveolatum were relocated to these areas between 1979 and
1982 and recoveries were made in many regions (Kimberling et al. 1986). However, it is too early to determine the
success of these releases. But in
contrast to the earlier program in Nova Scotia, the western program has been
conducted at a time when research policy has moved away from population
dynamics toward practical application of pest control and thus no detailed
monitoring of the winter moth before and after parasitoid release has been
made. This program is
often considered a good example of biological control in which, in contrast
to earlier multiple introduction programs, selective introduction were
made. These led to the establishment
of a high host density specialist (Cyzenis),
with high fecundity to bring about the collapse of an outbreak, and a low
host density specialist (Agrypon),
that has good searching ability to maintain the collapsed population at a low
level of abundance. However, the main
reason for the release of a smaller number of parasitoid species was the
relatively meager size of collections in Europe, where winter moth abundance
was not high at the time. Thus the
only conscious selection process was of parasitoid species obtained in
sufficient quantity for meaningful release (Mesnil 1967), although once the
two established parasitoids were becoming effective in the early 1960's a
decision was made to curtail releases of other species (Embree 1966). The end results were the successful
establishment of two particularly suitable parasitoids and the program
provides one of the best examples of the detailed evaluation of a biological
control project. Also as was pointed
out in earlier sections, the development of a detailed model in England prior
to the importations tended to show very little regulatory impact by Cyzenis, which might have
precluded its importation into North America. For additional
detail on biological control effort and biology of host and natural enemies,
please also see the following (Silvestri 1941, McNay 1957, Graham 1958,
Maybee 1958, 1959; Embree 1960, 1966; Wylie 1960, Cuming 1961, McGugan &
Coppel 1962, Williamson 1962, 1963; Embree & Sisojevic 1965). REFERENCES: [Additional references may be found at: MELVYL
Library ] AliNiazee, M. T.
1986. The European winter moth
as a pest of filberts: Damage and chemical control. J. Ent. Soc. British Columbia 83: 6-12. Croft, B. A. & M. T. AliNiazee. 1999. Biological
control in deciduous tree fruit crops.
In: Bellows, T. S.
& T. W. Fisher (eds.), Handbook of
Biological Control: Principles and
Applications. Academic Press, San
Diego, New York. 1046 p. Cuming, F. G. 1961. The distribution, life history and
economic importance of the winter moth, Operophtera
brumata (L.) (Lepidoptera:
Geometridae) in Nova Scotia. Canad.
Ent. 93: 135-42. Embree, D. G. 1960. Observations on the spread of Cyzenis albicans, an introduced parasite of the winter moth, Operophtera brumata (L.) in Nova
Scotia. Canad. Ent. 92: 862-64. Embree, D. G. 1965a. The bionomics and population density of Cyzenis albicans (Fall.) (Tachinidae: Diptera) in Nova
Scotia. Canad. Ent. 97: 631-39. Embree, D. G. 1965b. The population dynamics of the winter moth
in Nova Scotia: 1954-62. Mem. Ent.
Soc. Canad. No. 46. 57
p. Embree, D. G. 1966. The role of introduced parasites in the
control of the winter moth in Nova Scotia.
Canad. Ent. 98: 1159-68. Embree, D. G. 1971. The biological control of winter moth in
Canada by introduced parasites. p.
217-26. In: C. B. Huffaker
(ed.), Biological Control. Plenum
Press, New York. 511 p. Embree, D. G. & P. Sisojevic. 1965. The bionomics and
population density of Cyzenis
albicans (Fall.)
(Tachinidae: Diptera) in Nova Scotia.
Canad. Ent. 97: 631-39. Graham, A. R. 1958. Recoveries of introduced species of
parasites of the winter moth, Operophtera
brumata (L.) in Nova
Scotia. Canad. Ent. 90: 595-96. Hassell, M. P. 1969. A population model for the interaction
between Cyzenis albicans (Fall.) (Tachinidae)
and Operophtera brumata (L.) (Geometridae) at
Wytham, Berkshire. J. Anim.
Ecol. 38: 567-76. Hassell, M. P. 1980. Foraging strategies, population models and
biological control: a case
study. J. Anim.
Ecol. 49: 603-28. Kimberling, D. N., J. C. Miller & R. L. Penrose. 1986.
Distribution and parasitism of winter moth, Operophtera brumata
(Lepidoptera: Geometridae), in western Oregon. Environ. Ent. 15: 1042-46. MacNay, C. G. 1957. Summary of parasite and predator
liberations in Canada in 1957. Canad.
Insect Pest Rev. 35: 291-98. Maybee, G. E. 1958. Summary of parasite and predator
liberations in Canada and of insect shipments from Canada in 1958. Canad. Insect Pest Rev. 36: 300-13. McGugan, B. M. & H. C. Coppel. 1962. A review of the
biological control attempts against insects and weeds in Canada. Pt. II. Biological control of forest insects,
1910-1958. Commonwealth Inst. Biol.
Control Tech. Commun. 2: 35-127. Mesnil, L. P. 1967. History of a success in biological
control: the winter moth project in
Canada. Tech. Bull. Comm. Inst. Biol.
Contr. 8: 1-6. Silvestri, F. 1941. Contribuzioni
alla conoscenze degli insetti dannosi e dei loro simbionti. VI.
La falena brumale o la brumale (Operophtera
brumata L.). Bol. Lab. Ent. Agric., Portici 5: 61-119. Varley, A. C. & G. R. Gradwell. 1968. Population models
for the winter moth, p. 132-42. In: T. R. E. Southwood (ed.), Insect Abundance. Symp. Royal Ent. Soc. London 4. Williamson, G. D.
1962. Summary of parasite and
predator liberations in Canada and of insect shipments from Canada in
1962. Canad. Insect Pest Rev.
40: 147-58. Williamson, G. D.
1963. Summary of parasite and
predator liberations in Canada and insect shipments from Canada in 1963. Canad. Insect Pest Rev. 41:
137-51. Wylie, H. G. 1960. Insect parasites of the winter moth, Operophtera brumata (L.) in Western
Europe. Entomophaga 5: 111-29. |
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