Overwintering of Piezodorus guildinii (Heteroptera, Pentatomidae) Populations.

Piezodorus guildinii (Westwood) is a soybean pest that causes significant economic losses in the Americas. The variability of overwintering (diapause) traits was evaluated in populations of the Southwest (SW) (33°55'-34°17'S, 57°13'-57°46'W) during 2-year period (2011-2013) and of the Northwest (NW) (32°01'-33°02'S, 57°50'-57°24'W) during 1-year period (2014-2015) Regions of Uruguay. Samples were taken from different plant species (cultivated legumes, wild shrubs, and trees) and from overwintering sites (leaf litter and bark). Alfalfa, Medicago sativa L. was the main host, with a collection period of 10-11 months in the SW and 12 months in the NW. Cluster analysis for each sex was carried out to group the months according to the similarity in diapause traits of populations (body size, body lipid content, immature reproductive organs, and clear type of pronotum band and connexivum in females). Female diapause in the SW was longer (beginning of autumn to end of winter) than that in the NW (mid-autumn to mid-winter). Male diapause was longer (mid-autumn to mid-winter) in SW1 (1st year) than in SW2 (2nd year) and NW (late-autumn to mid-winter). In both regions, male diapause was shorter than female. Differences were associated with maximum temperature at daylight hours ≤ 12.1, being necessary maximum temperatures below 23.8 °C for females and 19.2 °C for males to initiate diapause.

Performance of Nymph and Adult of Piezodorus guildinii (Westwood) (Hemiptera: Pentatomidae) Feeding on Cultivated Legumes.

Performance of nymphs and adults of Piezodorus guildinii (Westwood) feeding on different cultivated legumes was studied under controlled laboratory conditions (25 ± 1°C, 80 ± 10% RH, 14 h of photophase) on soybean immature pod (SIP; R5.5-R6), birdsfoot trefoil immature pod (BTIP), alfalfa immature pod (AIP), and red clover flower with immature seeds (RCF). Food had significant effects on the life history of P. guildinii. The major differences in nymph survivorship were observed at second and third instars, with similar survivorship on SIP and AIP as hosts and higher than that recorded on BTIP and RCF. Total nymph mortality was much greater on BTIP (87.6%) than on SIP (32.6%) and AIP (54.2%); all nymphs died on RCF. Food did not affect nymph development time (about 20 days). Adult longevity was highest and lowest on AIP and RCF (62 and 32 days), respectively. Percentage of ovipositing females was highest (≈ 80%) on SIP and AIP, and intermediate on BTIP (52.2%); no females reproduced on RCF. Fecundity on SIP and AIP was similar (≈ 9 egg masses/female; and ≈ 141 eggs/female) and twice as higher than on BTIP (4.1 egg masses/female; and 60.2 eggs/female). Egg fertility (58%) did not vary with food sources. Adults fed on SIP and AIP gained weight during 43 days, remained unaltered on BTIP, and decreased on RCF. Data obtained indicated that SIP and AIP are suitable food sources, and emphasize the importance of alfalfa as a host plant of P. guildinii in Uruguay.