New Pest Response Guidelines - aphis - US Department of Agriculture

outbreaks of Dendrolimus spp. can make these forests less attractive,
negatively impacting tourism (Davis et al., 2008).
Pest Information
Dendrolimus pini
PTL is a serious pest of coniferous forests in Europe and Asia where it causes
extensive defoliation to pine trees during periods of outbreaks. Outbreaks can
cover thousands of hectares and last for as long as nine years in areas where
Scots pine (Pinus sylvestris), the moth’s primary host, is the dominant forest
species (Malyshev, 1997; Sierpinska, 1998; Varley, 1949). In forests in Poland,
where Scots pine covers an estimated 70% of the total forested areas, outbreaks
have been reported since the late nineteen century. Between 1946 and 1995
these outbreaks have resulted in extensive aerial treatments of 233,000 ha to
control PTL (Sierpinska, 1998). During severe outbreaks, pine trees can be
completely defoliated. Trees with more than 90% defoliation will die after the
second or third year of the outbreak and those that survive after several years
of infestation will show a significant reduction in growth and thus, wood
production (Csoka, 1991; Gedminas, 2003; Sliwa and Cichowski, 1975). Sliwa
and Cichowski (1975) estimated that defoliated trees that regenerated foliage
showed a 60% reduction in height growth, 30% reduction in diameter growth
and 30% reduction in wood volume.
Outbreaks have also been reported in Germany and Russia. In Germany, more
than 100,000 ha of forest were affected in the period between 1994 to1995.
Insecticide applications to control the moth covered an estimated 105,000 ha
between 2004 and 2006 (Moeller and Engelmann, 2008). In Russia, the area of
pine stands completely killed by PTL between 1990 and 2001 was 116,000 ha
(Mozolevskaya et al., 2002b).
Dendrolimus punctatus
MPC is a serious defoliator of pine plantations in Southeast Asia, particularly
damaging in southern China and Vietnam where it feeds on P. massoniana and
P. merkusii in silvicultural settings (Ying, 1986b) . Outbreaks can rapidly lead
to high deforestation, resulting in more than 50% deforestation of affected
areas (Billings, 1991). The severity and impact of infestations can variable
depending on the many factors listed in the relevant sections above (including,
e.g., environmental factors, generation times, host plant species and density).
12/2012-01 Dendrolimus Pine Moths 2-39