Agriculture Reference
In-Depth Information
seedbank (Gross et al. 2015, Chapter 7 in this volume) to better understand the role
of insects in shaping weed community dynamics. Also, new invasive insects have
been studied as they entered KBS, including herbivores such as the gypsy moth
(
Lymnatria dispar
L.; Parry 2000, Kosola et al. 2001, Agrawal et al. 2002, Kosola
et al. 2006), the soybean aphid (
Aphis glycines
Matsumura; Noma and Brewer
2007, 2008), and the exotic predaceous coccinellids
C. septempunctata
(Maredia
et al. 1992b) and
Harmonia axyridis
Pallas, the multicolored Asian ladybird bee-
tle (Colunga-Garcia and Gage 1998). In the remainder of this chapter, we pres-
ent three case studies focusing on carabids, coccinellids, and the soybean aphid.
Together, these examples encompass the breadth of insect studies conducted on
site and illustrate some of the key lessons to be drawn from this long-term effort.
Carabids in the KBS Landscape
Ground-dwelling beetles in the family Carabidae are a diverse and frequently stud-
ied taxon. With over 2500 species in North America, they inhabit nearly all ter-
restrial ecosystems and perform a variety of ecological functions as herbivores,
carnivores, and omnivores. In agricultural ecosystems, carabids are best known as
predators of insects, gastropods, and other invertebrates. However, many carabid
species are omnivorous and some species feed mainly on seeds (granivores). In
row-crop systems, carabids can thus provide significant pest suppression by con-
suming insect pests and weed seeds in the soil seed bank.
Carabid Response to Habitat
Clark et al. (1997) first characterized the carabid communities of KBS LTER in the
5th and 6th years following MCSE establishment in 1989. They recorded 18 species,
but 4 predatory species dominated and comprised 87% of the total catch. Pronounced
differences in carabid communities occurred between the annual and perennial plant
systems and between the Conventional and No-till systems. Management practices
influenced habitat characteristics and served to structure the carabid communities
in particular ways. For example, annual crop habitats contained significantly more
Poecilus lucoblandus
(Say) and
Agonum placidum
(Say), while the No-till and
perennial crop systems favored
Cyclotrachelus sodalis
(Leconte).
Overall, Clark et al. (1997) concluded that no single system or habitat could be
characterized as favoring carabid communities as a whole; rather, some systems
and practices (e.g., tillage) favor particular species and disfavor others. Because
carabids were frequently associated with feeding on crop insect pests, Clark et al.
suggested there is potential for managing for selected carabid communities to
enhance pest suppression.
Carabids and Weed Seed Predation
Weed seedbanks can build over time and present a significant challenge for agro-
nomic management of annual row crops. Menalled et al. (2001) observed that the
