Piezodorus guildinii ( Westwood) 439
soybean and on forage legumes: Telenomus podisi, Trissolcus basalis ( Wol la ston), Trissolcus brochy-
menae (Ashmead), Trissolcus urichi (Crawford), and Trissolcus teretis (Johnson), with T. podisi most
common. In Argentina, Cingolani et al. (2014) reported T. podisi, T. basalis, and T. urichi as egg para-
sitoids of P. guildinii on soybean and alfalfa fields, but they did not occur on egg masses collected from
red clover. In the United States on soybean, T. podisi also is the most common egg parasitoid of stink
bugs (Yeargan 1979, Orr et al. 1986, Koppel et al. 2009). These studies were conducted before P. guildi-
nii became an important pest of soybeans in the United States (Temple et al. 2013a). However, at this
time, T. podisi, T. basalis, and Gryon sp. have been shown to parasitize eggs of P. guildinii in Florida
(Buschman and Whitcomb 1980, Temerak and Whitcomb 1984).
Tachinid flies also have been reported as parasitoids of Piezodorus guildinii, though they do not appear
to have the impact of egg parasitoids (Panizzi and Smith 1976b). In Brazil, Panizzi and Smith (1976b)
recovered low levels of Eutrichopodopsis nitens (Blanchard) from the bugs on soybean. In Florida, also
on soybean, Trichopoda pennipes (F.) and Euthera tentatrix Loew have been reported from P. guildinii
(Buschman and Whitcomb 1980, Panizzi and Slansky 1985c, McPherson and McPherson 2000).
Entomogenous nematodes have been utilized as insect biological control agents (Smart 1995), and some
research has examined the susceptibility of stink bugs to these natural enemies. Nezara viridula has been
reported as being susceptible to Steinernematidae under laboratory conditions (Wassink and Poinar 1984)
and has been found infested with Pentatomimermis spp. in Russia and India (Rubtsov 1977, Bhatnagar
et al. 1985). Field-level nematode infections of Hexamermis spp. have been found in Chinavia hilaris
in Louisiana (Kamminga et al. 2012) and Hexamermis or Mermis spp. have been found in Piezodorus
guildinii in Louisiana (Kamminga et al. 2012) and Uruguay (Ribeiro and Castiglioni 2009). Although
nematode populations can be found infesting stink bugs (Esquivel 2011), infections are rare and do not
appear to reduce field populations of stink bugs. A survey in Louisiana of parasitoids infesting N. viridula
in soybean and clover indicated that only about 2% were infected with nematodes (Fuxa et al. 2000).
Predators have received little attention in biological control efforts, but native predatory species may be
important in various cropping systems. Tillman et al. (2015) analyzed the gut contents of various predators
collected from soybean and cotton fields in Georgia for the presence of DNA from Piezodorus guildinii.
The following species tested positive: Geocoris spp. (Geocoridae); Orius insidiosus (Say) (Anthocoridae);
Hippodamia convergens Guérin-Méneville, Harmonia axyridis ( Pa l las), Scymnus sp. (Coccinellidae);
Solenopsis invicta Buren (Formicidae); Mecaphesa asperata (Hentz) (Thomisidae); and Oxyopes salticus
(Hentz) (Oxyopidae).
8.7.4 Chemical Control
Chemical control is the primary management tactic used to manage Piezodorus guildinii in soybean (Temple
et al. 2013b). Prior to P. guildinii becoming a soybean pest in the United States, it was relatively easy to manage
stink bugs with low to medium rates of pyrethroids or organophosphates (Willrich et al. 2000). Unfortunately,
P. guildinii is less sensitive to commonly used insecticides in comparison to other stink bug species (Temple
et al. 2013b). Therefore, farmers spray more frequently to manage P. guildinii infestations (Davis et al. 2011).
The average number of insecticide applications in Louisiana soybean has increased from one to two per sea-
son to three to five per season (Temple et al. 2013b). Likewise, increased insecticide applications to soybean
have been reported in Texas due to an increase in P. guildinii abundance (Vyavhare et al. 2014).
Baur et al. (2010) reported baseline toxicity data for Louisiana populations of Piezodorus guildinii to sev-
eral insecticides including acephate, cypermethrin, and methamidophos in glass vial bioassays. This work
also demonstrated initial field efficacy data for control of P. guildinii in soybean, but made no direct com-
parisons to other stink bugs. Control of P. guildinii with all insecticides was estimated at approximately 50
to 80% in those field tested. Temple et al. (2013b) conducted insecticide field efficacy experiments comparing
Nezara viridula and P. guildinii control. They found that labeled rates of pyrethroids provided 94% and 75%
control, organophosphates 90% and 85% control, and neonicotinoids 78% and 63% control, for N. viridula
and P. guildinii, respectively (Temple et al. 2013b). P. guildinii was four to eight-fold less susceptible to
pyrethroids and two to eight-fold less susceptible to organophosphates than N. viridula (Temple et al. 2013b).
In South American soybean, chemical control of stink bugs also has increased in recent years. The fre-
quency of application has increased from one to two applications per season to four to five applications. In most