Agriculture Reference
In-Depth Information
lay eggs; one or more generations occur per year based on the biology of individual
species.
More than 20 years of sampling the coccinellid community of KBS has revealed
a number of novel insights on the spatial and temporal patterns of insect pred-
ator responses to crop type and management practices. Our array of permanent
geo-located sites has allowed scaling of analyses from microhabitat to landscape,
and from individual weeks to seasonal to interannual change over two decades.
Moreover, the spatial-temporal design of our insect observation program has pro-
vided the ability to quantify several unanticipated events, including the arrival of
new herbivores and predators that, through long-range and local dispersal, entered
the KBS landscape.
Characterizing the Coccinellid Community
Maredia et al. (1992b) used a combination of sweep net, sticky trap, and visual
observations to characterize the occurrence and relative abundance of preda-
tory Coccinellidae at KBS LTER in 1989 and 1990. During that time period,
they recorded 12 native and 1 exotic species (Table 8.2). Subsequent sticky trap
sampling at the site has revealed the occurrence of one additional native species
(
Hippodamia glacialis
[Fab.]) and documented the arrival of three additional exotic
species (
Harmonia axyridis, Hippodamia variegata
[Goeze], and
Propylaea quatu-
ordecimpunctata
[L.]), bringing the total to 13 native and 4 exotic species by 2009.
Several native species have apparently declined in abundance since 1989-1990.
For example,
Adalia bipunctata
(L.),
Chilocorus stigma
(Say),
H. convergens
Guérin-Meneville, and
Hippodamia parenthesis
(Say), all reported as common in
1989-1990, became rare by 2009. In addition, several species that were listed as
occasionally observed in 1989-1990 fell below detectable levels by 2009, includ-
ing
Anatis labiculata
(Say),
Coccinella novemnotata
Herbst,
Hippodamia tredec-
impunctata tibialis
(Say), and
Hyperaspis undulata
(Say). Because Maredia et al.
(1992b) used multiple collection methods and subsequent sampling only used
sticky traps, it is uncertain if these represent true declines or sampling biases.
The exotic species
C. septempunctata
, which was intentionally released in
Michigan in 1985 for control of aphids (Maredia et al. 1992b) and rapidly became
a dominant species (Sirota 1990), was of particular interest to early LTER research-
ers. Maredia et al. (1992c) confirmed Sirota's (1990) observations that
C. septem-
punctata
was a univoltine (one generation per year) species in Michigan with peak
adult populations occurring in mid- to late June. Wheat and alfalfa were found to
be important early season habitats for
C. septempunctata
, likely because they con-
tained aphid prey prior to spring-planted annual crops like corn and soybean. Later
in the season,
C. septempunctata
dispersed throughout the landscape and was found
in all MCSE systems but particularly in the Early Successional and Poplar systems
that tended to have late season aphid infestations (Maredia et al. 1992b).
The LTER database also allows for coccinellid habitat preferences to be stud-
ied over longer periods of time, and examination of habitat use by nine species in
MCSE systems from 1989 to 2007 reveals distinct patterns (Fig. 8.3). With the
exception of
H. axyridis
, most species are found in greater abundance in one or
