The influence of landscape patterns on ecological processes is generally ac
knowledged, but often difficult to quantify. The objective of our study was
to quantify the relation of jack pine budworm (Choristoneura pinus pinus)
population levels to both the abundance of jack pine (Pinus banksiana) and
of jack pine stand edges in the landscape. The 450000 ha Pine Barrens regio
n, located in northwestern Wisconsin, USA, experienced a severe jack pine b
udworm outbreak from 1990 to 1995. We calculated landscape indices on a lan
dcover map derived from Landsat TM satellite imagery. Landscape indices wer
e calculated on circular buffers (0.5; 0.75, 1, 1.5, and 2.5 km radius) cen
tered on 143 budworm population sampling points for which annual budworm co
unts were available. Edge density was normalized for the proportion of jack
pine in the landscape using random maps as a standard. Correlations betwee
n landscape patterns and budworm populations varied over time: proportion o
f jack pine showed strongest positive correlation with budworm population l
evels up to the peak of the outbreak (1993). Edge density exhibited positiv
e correlation up to the peak of the outbreak, but negative correlation in t
he subsequent years as the outbreak declined. This may suggest that pollen-
bearing male cones. which are more abundant along edges, support higher bud
worm populations in the initial phase of the outbreak, but stronger predati
on on budworm along edges subsequently reduces populations. We provide insi
ght into previously inconclusive results on the relation of jack pine budwo
rm population density to jack pine stand edges. The effects of landscape pa
tterns, such as edge density, may vary not only in magnitude, but also in d
irection, being positive and negative during different phases of an insect
outbreak. Therefore, caution should be taken in relating landscape patterns
to process at either a single scale or point in time.