Piezodorus guildinii ( Westwood) 431
8.4.2 Overwintering
Few studies have been conducted to determine the overwintering habits of Piezodorus guildinii in the
Americas. The most detailed studies have been conducted in South America, specifically Brazil and
Uruguay. In Brazil, studies were conducted in northern Paraná state in Londrina (S 23° - W 50°) where
five generations are completed per year. Three of the generations are completed on the soybean crop
during spring/summer months. The pest then moves to other legume plants such as lanceleaf crotalaria,
Crotalaria lanceolata E. Mey.; and pigeon pea, Cajanus cajan (L.), where it completes another genera-
tion. Finally, with the start of autumn and during the mild winter, the stink bug moves to indigo plants
where it may complete a fifth generation, depending on the severity of low temperatures (Panizzi 1997).
P. guildinii returns to soybean the following spring (Panizzi 1997). In cooler areas of southern Brazil, in
Rio Grande do Sul state, during fall/winter it is found on (but not reproducing on) alternate host plants
such as chickling pea, Vicia sativa L.; wild radish, Raphanus sativus L.; and white lupine, Lupinus
albus L. (Silva et al. 2006). In Passo Fundo (S 28°- W 52°), P. guildinii also might be found in a state of
reduced activity underneath crop residues and on the soil in areas with undisturbed vegetation (Antônio
R. Panizzi, unpublished data).
Further south in Uruguay at Colonia (S 34°- W 57°), Piezodorus guildinii has three generations per year
(Antônio R. Panizzi, personal communication). It reproduces on soybean and forage-cultivated legumes
such as alfalfa, Medicago sativa L.; red clover, Trifolium pratense L.; and bird’s-foot trefoil, Lotus cor-
niculatus L., during spring-summer. As temperatures drop, they move to trees [e.g., Pittosporum undu-
latum Ventenat (Pittosporaceae) and Ligustrum lucidum Aiton (Oleaceae)] and bamboo, Phyllostachys
sp. (Poaceae), looking for shelter. With the additional decrease in winter temperatures, adults move to
eucalyptus leaf litter, Eucalyptus spp., where they stay protected until the following spring (Zerbino
et al. 2016).
Zerbino et al. (2015) studied the temporal morphological and physiological changes of Piezodorus
guildinii that occurred in the field on different host plants through the year. As with laboratory studies
discussed above (Zerbino et al. 2014), they demonstrated that during autumn/winter adults accumulate
lipid reserves, both females and males showed undeveloped reproductive organs and smaller body size;
at this time, females showed darker coloration of the pronotum band and of the connexiva; these traits
indicated reproductive diapause (see Chapter 11 for discussion of diapause).
8.5 Host Plants
The plants associated with Piezodorus guildinii have been documented by Panizzi and Slansky (1985b)
for the Americas and Smaniotto and Panizzi (2015) for the Neotropics. This list, updated to include
all records found in the literature for the Americas, is summarized in Table 8.1 and includes 75 plant
species. The range of known hosts is smaller than that for Nezara viridula (see Table 7. 5 in Chapter 7),
although, as with N. viridula, most hosts for P. guildinii also are in the legume family (Fabaceae).
Indigofera spp. apparently are the most suitable hosts for P. guildinii (Panizzi and Slansky 1985a,
Panizzi 1992). Panizzi and Smith (1977) referred to Monte (1937) as originally reporting nymphs and
adults on Crotalaria spp. in Brazil. Quintanilla et al. (1967–1968) described P. guildinii morphology,
damage, and host plants in Argentina. Panizzi (1985b) identified and described the effects of non-crop
hosts on the biology of P. guildinii.
As discussed above, soybean is an important host for Piezodorus guildinii throughout the insect’s
range. In Argentina, Quintanilla et al. (1967–1968) also mentioned soybean as a host and referred to
other early reports on this bug’s distribution and host plants. Panizzi and Smith (1976a) and Heinrichs
(1976) reported that P. guildinii was abundant in Brazilian soybean, entering the crop in low numbers
from germination to flowering. When pods began to form, these insects began to increase in numbers
and populations peaked when the pods were nearing maturity.
Although Piezodorus guildinii is a serious pest of soybean, the crop apparently is a poor reproductive
host compared to preferred non-crop hosts. Females deposit as many as 37 egg masses on Indigo spp.
compared to an average of three masses on soybean (Panizzi et al. 2000b). Fraga and Ochoa (1972),