No abstract

Studies were conducted to determine the utility of overseeding endophyte enhanced varieties of perennial ryegrass, Lolium perenne L., into existing stands of Kentucky bluegrass, Poa pratensis L., to manage bluegrass billbug, Sphenophorus parvulus Gyllenhal, larval populations and their damage. Two commercial varieties of endophyte enhanced perennial ryegrass (Repell II and Triple Play) were overseeded at two different rates in the field. S. parvulus larval populations, their damage, and turfgrass composition were monitored over the course of 3 yr. Significantly fewer larvae were found in plots overseeded with Repell II, whereas Triple Play had no significant effect on larval population density. Endophyte infection was confirmed in approximately 58% of all Repell II shoots, whereas only approximately 31% of Triple Play shoots were infected. Regression analysis, using a segmented model, demonstrated that larval populations declined as the proportion of endophyte-infected perennial ryegrass increased. However, no additional reductions in larval population density were achieved in stands containing >40% endophyte-infected perennial ryegrass. Visual damage varied with cultivar, seeding rate, and year, but generally decreased as the proportion of endophyte-infected perennial ryegrass increased. Although seeding rate had an initial effect on turfgrass composition, these differences were not detected after the first year of the study. Results indicate overseeding existing stands of Kentucky bluegrass with endophytic varieties of perennial ryegrass can reduce S. parvulus larval populations and their damage. However, plant genetic characteristics (i.e., different cultivars) may be overriding determinants of many aspects of plant performance including establishment, tolerance to insect feeding, and expression of endophyte-mediated resistance.

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4n attempt was made to suppress Rn incipient spruc-budworm outbreak in the Lower St. Lawrence region of Quebec througli rhe acrial application of DDT. Operations began in 1960 and continued in 1961 and 1961 when they finally mct with succcss. Failure to achierc success earlier was due parrly to the exceptionally favoural)le survival conditions for the insect in 1960, and partly to the inadvertent omission of a small infested area from the program in 1961. T h e operations grearlv reduccd spruce bud~cform populations each year in the outbreak area, whilc the action of natural control factors. including pnrasitcs and predators increased. The col!apsc of tllc outbrcak was the result of the combined effects of the chenlical treatments and of natural control factors.

No abstract