Invasive Stink Bugs and Related Species (Pentatomoidea)

318 Invasive Stink Bugs and Related Species (Pentatomoidea)

Research efforts to determine when to treat soybeans with insecticides for Megacopta cribraria are
ongoing and represent critical and needed information for managing this invasive species in the crop.
Current recommendations are to interrupt development of each generation in soybeans with insecticide
applications targeting the immature stages of this bug (Greene 2015, Roberts et al. 2015). Insecticide
use is recommended when immatures are detected in sweep-net samples at approximately one nymph
per sweep, regardless of instar. The critical time to protect soybeans from losses due to M. cribraria
appears to be the time of pod and seed development, suggesting that producers should probably consider
soybean growth stage as well as presence of nymphs when making control decisions (Seiter et al. 2016).
Seiter et al. (2015a) and Blount et al. (2017) found that a single insecticide application timed to coincide
with the presence of nymphs, particularly during the critical growth stages, prevented soybean yield
losses. Sweep-net samples should be taken from all areas of the field (edges and middle) to represent the
entire field, taking care not to bias sampling along border rows where populations build up initially. As
an alternative to sweep-net sampling, visual inspections of insect density down in the canopy may suf-
fice (Greene et al. 2012). If immature bugs are easily and repeatedly found on petioles and main stems
using canopy observations, treatment likely is warranted (Table 5.3). This type of observational/visual
sampling for these bugs also could help define and exploit differential colonization of border and interior
areas of fields by the pest.
In addition to insecticidal control, management of Megacopta cribraria is aided by several other fac-
tors. A study by Del Pozo-Valdivia et al. (2016) in North Carolina and South Carolina found that early
planted soybeans tended to have more bugs in untreated plots than did later planted soybeans, so planting
later may help manage this bug. The authors also noted that later planted soybeans tend to experience
more drought conditions and larger numbers of defoliators, so later plantings may not be a management
option. The type of tillage impacts numbers of bugs with increased oviposition and up to four times as
many bugs in conventional till versus no till or reduced till plots (Tillman et al. 2016, Del Pozo-Valdivia
et al. 2017). Host plant resistance also has some potential. Bray et al (2016) identified six soybean lines as
sources of resistance and they characterized the type of resistance as antibiosis. Fritz et al. (2016) evalu-
ated 44 genotypes of soybean were evaluated over two growing seasons in NC and a number of these
exhibited lower numbers of M. cribraria and reduced yield loss.

5.6.3 Biological Control Agent for Kudzu

Kudzu originally was introduced into the United States as an ornamental vine in the late 1800s and
widely planted for forage and erosion control in the early to mid-1900s (Britton et al. 2002). It is a fast-
growing vine that smothers all other vegetation and limits the production of pine trees, reduces plant
biodiversity, damages power transmission lines, and can cause derailments along rail lines (Lindgren et
al. 2013). The loss of productive forest land has been estimated at 48 to 84 dollars per acre/year, with lost
production costs of up to US $588 million/year and control costs for power companies estimated at US
$1.5 million/year (Britton et al. 2002, Hanula et al. 2012). Clearly the economic impact of kudzu on the
United States economy is significant.
There has been only one study evaluating the impact of Megacopta cribraria on kudzu in the south-
eastern United States. Zhang et al. (2012) compared biomass of kudzu in plots that were exposed to the
invasive bugs with plots from which bugs were excluded by biweekly insecticide applications. The plots

TABLE 5.3

Current Sampling Methods and Treatment Thresholds for Megacopta cribraria

in Soybeans in Georgia and South Carolina

Sampling Method Minimum Observations Threshold

Sweep net

(15-inch diameter)

At least ten 10-sweep samples

representing entire field^1

1 nymph/sweep

Canopy observation

(visual)

At least ten observation spots

representing entire field^1

Nymphs easily found on petioles,

main stems, or leaves

(^1) Samples should be taken from multiple stops across the field and not just field borders.