Agriculture Reference
In-Depth Information
and this affects their potential importance as both insect and weed seed preda-
tors (Clark et al. 1997, Menalled et al. 2007). Similarly, some natural enemies
appear to have innate preferences for specific crop types (e.g., C. maculata in
corn), which influence their ability to provide predation services to other parts
of the agricultural landscape. Spatial configuration of different crops within a
local area also influences the distribution of insect predators, with coccinellids
showing predictable patterns of movement from one crop to another throughout
the season.
Taken as a whole, these findings suggest that at the farm scale growers have
significant capabilities to manage their local landscape to promote more effective
pest control services (Bianchi et al. 2006, Landis et al. 2000). However, landscape
context also matters. Though landscape management is beyond the control of most
farmers, except those with exceptionally large land holdings, it determines the
regional pool of natural enemies that are present to move through individual fields
(Gardiner et al. 2009a) and has critical implications for pest suppression (Gardiner
et  al. 2009b) and even crop profitability (Landis et  al. 2008). Finally, the arrival
of new exotic organisms has been a regular occurrence at KBS (Fig. 8.5) and has
resulted in major shifts in plant productivity (Kosola et  al. 2001), plant defense
(Kosola et al. 2006), native insect communities (Colunga-Garcia and Gage 1998),
and pest management (Costamagna and Landis 2006, 2007, Costamagna et  al.
2007a, Costamagna et al. 2008).
Much remains to be learned about arthropod biodiversity and pest suppression
in agricultural landscapes. Continuing studies at KBS LTER focus on understand-
ing the role of transient generalist predators in regulating population levels of key
herbivores (Woltz and Landis 2013) and the impact of landscape structure and key-
stone invaders such as R. cathartica in shaping these interactions. One of the most
important forces poised to affect future agricultural landscapes is the creation of
cellulosic biofuel cropping systems (Robertson et al. 2008). Future research at KBS
LTER and elsewhere is needed to reveal how habitat type affects pest suppression
services, and could provide a strong rationale for increasing landscape diversity via
biofuel crop choice (Meehan et al. 2011).
In conclusion, arthropod predators and parasitoids play critical roles in regu-
lating herbivore abundance and damage in agricultural systems. Likewise, there
is evidence that arthropod seed predators may also influence weed population
dynamics in row-crop systems. Work at KBS LTER has elucidated the relative
influence of crop management and farm- and landscape-scale spatial heterogene-
ity on the ability of arthropod natural enemies to provide pest suppression ser-
vices and thus reduce grower reliance on chemical pesticides. Case studies of
carabid beetles, coccinellids, and soybean aphids illustrate a dynamic agricultural
landscape where the arrival of exotic organisms—both herbivores and natural
enemies—has had a major impact on insect dynamics and ecosystem performance.
Moreover, they suggest that pest suppression services are influenced by features
of both the crop production system and the broader landscape in which the crop is
grown. Collectively, KBS LTER studies suggest that there is significant potential
to understand and even design future agroecosystems to take better advantage of
pest suppression services.
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