Cryptorhynchus lapathi (L.) (Coleoptera: Curculionidae)
Poplar-and-willow borer larvae burrow into stems of all ages of poplar; their galleries weaken the bole and limbs of infested plants, causing them to break when stressed by high winds. There are no chemicals available to professional integrated pest management (IPM) personnel to control this pest. Professionals need to be able to identify the pest species, avoid using infested cutting for propagation, use properly timed harvest, and recommend long-term management strategies to minimize losses to poplar-and-willow borer infestations.
There are two main taxonomic orders of insects that are the primary wood-boring pests of hybrid poplars in eastern Oregon and eastern Washington. They are Lepidoptera, or moths, and Coleoptera, or beetles. Lepidoptera species are discussed in greater detail in the publication on western poplar clearwing moth (Brown et al. 2006).
The main wood-boring beetles that attack hybrid poplars fall into three families. Buprestidae (Figure 1) or metallic wood-boring beetles, Cerambycidae (Figure 2) or long-horned borers, and Curculionidae, which comprise weevils and bark beetles. Curculionidae is one of the largest families of insects with 20 subfamilies. Within hybrid poplars grown in eastern Oregon and eastern Washington there are four weevil pests: Cryptorhynchus lapathi L., the poplar-and-willow borer, is in the subfamily Cryptorhynchinae (Anderson 2008), Polydrusus impressifrons and Otiorhynchus ovatus belong in the broad-nosed weevil subfamily Entiminae, and finally the bark beetle subfamily Scolytinae is represented by Xyleborinus saxeseni (Ratzeburg), commonly known as the fruit-tree pinhole borer.
Long-horned borers, family Cerambycidae (Coleoptera), are common pests of poplars. Dramatically colored black and white cottonwood borer adults, Plectrodera scalator F. (Cerambycidae), are some of the larger beetles found in the US east of the Rocky Mountains (Solomon 1995). Oberea schaumii LeConte and O. delongi Knull (Cerambycidae) are both cottonwood twig borers found in the southeastern US (Furniss and Carolin 1977; Ostry et al. 1988). Saperda calcarata Say is a major pest of poplar and aspen east of the Rocky Mountains (Roe 2001) and S. inornata is a borer of aspen and poplar in the Lake States (Nord et al. 1972).
The primary hosts of C. lapathi are poplar and willow (Furniss 1972), hence the common name, but C. lapathi can successfully breed in alder and birch (Smith and Stott 1964; Garbutt and Harris 1994). Among Populus species there are differences in C. lapathi susceptibility among species (Cadahia 1965; Dafauce 1976; Morris 1981; Abebe and Hart 1990; Mattson et al. 2001; Johnson and Johnson 2003; Broberg and Borden 2005; Broberg et al. 2005). Understanding tolerance and/or resistance will be important when managers and breeders choose production clones (Painter 1951; Smith 1989; Larsson 2002).