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Pathogens
Table 89
Neodiprioll slI'ainei (Middleton), 343
Open releases and recoveries of predacious red wood ants against Swaine jack pine sawfly,
Neodiprion swainei (Middleton), in the St. Maurice river watershed in Quebec
Approximate
Status in 1981
Ant
species
Date of
release
number
released Recovery
Estimated
increase
Formica 1972 4 ()()() ()()() About 20 nests 15-fold
obscuripes Forel established (with
sexuals present)
1975 1 ()()() ()()() About 75 nests 20-fold
established (with
sexuals present)
F. lugubris Zett. 1973 1 ()()() ()()() Ten nests established
(with few sexuals)
1975 2 ()()() (added to previous ?
queens nests)
1976 5 ()()() (added to previous ?
queens nests)
Mcleod (1971) reported, in a preliminary analysis of the variation in cocoon survival
of N. swainei, that small animal predators accounted for about 47% of the mortality of
cocoons, and insect predators for about 16%. Mcleod (1974) also found that populations of
resident breeding birds in jack pine stands in Quebec varied little from 1964 to 1973, but
that the mole population showed a steady, statistically significant increase over the 9
years of sawfly infestation.
Tostowaryk (1971a) described in detail the life history and behaviour of Podisus
modestus (Dallas), a predacious pentatomid, which preys on N. swainei larvae as well as
on other defoliators. He gave details of the habits and abundance of the predator, and
also discussed the relationship between parasitism and predation of diprionid sawflies
(Tostowaryk 1971b). Experimental results of the functional response of P. modestus to
densities of N. swainei and N. pratti banksianae Rohwer (Tostowaryk 1971c) showed
that the response was two-fold: a domed curve when the sawfly larvae were active and
relatively large with respect to the size of the predator, and a negatively accelerated
curve when the sawfly larvae were freshly killed and relatively small with respect to the
predator's size. He also presented a list of coleopterous predators of N. swainei
(Tostowaryk 1972), and stated that it seemed these predators responded in a densityindependent
manner to the prey. Tostowaryk (1973) continued his observations on
carabids found in jack pine stands. He noted that the three most common species of
carabids preyed to a limited extent on cocoons of N. swainei.
A highly pathogenic strain of a Borrelina species of virus was studied (Smimoff 1961a,
Mcleod & Smimoff 1971) and a formulation suitable for aerial dispersion was developed
(Smimoff 1964). Aerial dispersion of the virus provided excellent control of the insect
(Smirnoff et al. 1962). The dosages used were 4.5 IIha and 3711ha, at a concentration of
2 x 1()6 polybedralml. Cold weather during and after treatment caused a reduction in
larval mortality, but because of trans-ovum and trans-ovarial transmission of the
disease from parent to progeny, there was a long-term control effect (Smimoff 1962).