pdf, 57.71Mb - Entomological Society of Canada

Pest Status
Table 39
Chapter 35
Euphorbia esula-virgata complex, Leafy
Spurge and E. cyparissias L., Cypress
Spurge (Euphorbiaceae)
P. HARRIS
Leafy and cypress spurge. Euphorbia esu/a'I'irgala complex and E. cypar/ss/as
L.. are herbaceous perennials of European origin that have become problem species in
parts of North America. Leafy spurge is particularly serious on the Canadian prairies
and the north central United States. while cypress spurge is most prevalent in Ontario
and Quebec. Both spurges are unpalatable to most grazing animals except sheep and
displace other herbaceous vegetation. In two leafy spurge stands investigated in Sas·
katchewan in 1981. there was 65-72% less grass within the stand than just outside it.
Cypress spurge on a thin limestone soil at Braeside. Ontario. comprised 56% of the
herbaceous vegetation in a dry year and 26% in a wet year (Table 39). Cypress spurge is
Density of Hy/es euphorbiae (L.) larvae, dry weight of E. cyparissias L. and total
herbaceous vegetation at Braeside. Ontario.
Year No. H. euphorbiae Dry weight of Dry weight of all
larvae/m 1 E. cyparissias glml vegetationlm l
1968
6.8 x 10-)
1969 1.75 x 10- 1
56.6 216.0
1970 0.4 44.7 79.2
1971 1.0 73.1 147.1
1972 0.3 91.9 213.1
1974 0.6
1975 2.3
1976 0.4
also of concern as extremely small amounts of its latex are intensely irritating to the
eyes. The provincial and most municipal governments of the Canadian prairies have an
active programme for the control of leafy spurge. For example in the early 1950s,
Saskatchewan spent around $100 OOO/year against persistent perennial weeds and by 1979
the amount had risen to $150 OOO/year, with leafy spurge being the main target. The sum
covers the cost of treatment on provincial and municipal lands and roadsides but only
the cost of the chemical on private lands. Thus the actual cost of controlling leafy spurge
was considerably higher. In Manitoba in 1981. $38649 was spent on leafy spurge control
by the provincial government of which $32 890 represented the cost of the chemical (E.
Johnson. 1982. personal communication). In Saskatchewan in 1982, the full cost was
$640Iha of spurge treated as the infestations are scattered or on rough terrain.
In the first twenty years of the control programme in Saskatchewan the chemicals
used were soil stcrilants such as sodium chlorate and various borates either alone or in
combination with other herbicides. These were both expensive and ecologically un-
159