Vertical distribution and tissue selection of Helicoverpa zea (Lepidoptera: Noctuidae) adult oviposition and neonates on soybean with an indeterminate or determinate growth habit.

Helicoverpa zea (Boddie) is a polyphagous pest that can cause serious damage to crops, including soybeans (Glycine max L.). In soybeans with both determinate and indeterminate growth habits, H. zea larvae are more commonly found on leaves compared to blooms, stems, and pods. Past research demonstrated that H. zea adults tend to oviposit near the upper part of the plant canopy in soybeans with a determinate growth habit. However, ovipositional selection on soybeans with an indeterminate growth habit is unknown. We hypothesized that H. zea would oviposit more uniformly throughout the canopy on indeterminate soybean growth habits due to more diffuse reproductive tissue. We planted field and greenhouse experiments with varieties sharing a similar relative maturity (2 maturity group [MG] 5.2 varieties and 2 MG 5.4/5.5 varieties) but with different growth habits. To test oviposition selection, adult H. zea females were allowed to oviposit under field and caged conditions. We counted the number of H. zea eggs and neonates on each plant tissue type from each of 3 equal parts in the plant canopy: upper, middle, and lower. In both experiments, eggs and neonates were most common on leaves at the top of the plant regardless of soybean growth habit. Consequently, ovipositional selection is likely independent of reproductive tissue availability, and patterns of oviposition through the canopy are similar in growth habits. An improved understanding of H. zea ecology in soybeans relative to indeterminate growth habits may improve recommendations for managing this significant pest of soybean.

Helicoverpa zea Boddie (Lepidoptera: Noctuidae) pupal success and adult eclosion across variable soil type and moisture.

Helicoverpa zea Boddie (Lepidoptera: Noctuidae) is an important pest in many crops in the southern United States. Upon reaching the final larval instar, H. zea quests for a pupation site in the soil. Pupae are vulnerable to mortality since their movement is limited. Soil type and moisture can influence H. zea emergence, but the interaction of these factors has not been demonstrated. We compared sandy and clay soils in greenhouse and laboratory experiments. In the first experiment, we evaluated the preference of larvae to choose either sandy or clay soil for pupation. In a second experiment, we set the sandy soils at different moisture levels and observed prepupae pupation preference in a choice scenario. In a third experiment, we observed prepupae pupation in different moisture levels in a no-choice scenario. In a 4th experiment, we evaluated adult emergence following pupation when we increased moisture or kept it constant. In a final experiment, we evaluated pupation behavior in sandy or clay soils with a webcam and a glass arena. We found that larvae preferred to pupate in sandy soils over clay soils and that pupal success was highest at intermediate moisture levels. In addition, elevated soil moisture levels did not impact the emergence of H. zea between sandy or clay soil. Finally, H. zea did not take longer to burrow in either sandy or clay soil, but the tunnels of the pupal burrow were larger in sandy soil compared to clay soil. Our results clarify H. zea behavior across soil moisture and soil type.

Stink Bugs Nymph and Adult Biology and Adult Preference on Cultivated Crop Plants in the Southern Brazilian Neotropics.

Laboratory studies were conducted with Dichelops furcatus (F.), Euschistus heros (F.), and Nezara viridula (L.) (Heteroptera: Pentatomidae) aiming to evaluate nymph and adult biology and adult preference for immature reproductive structures of the cultivated plants, soybean, Glycine max (L.) Merrill (Fabaceae), wheat, Triticum aestivum L. (Poaceae), and canola, Brassica napus L. var. oleifera (Brassicaceae). Considering the survivorship for D. furcatus nymphs, it was greater on soybean and wheat, for E. heros nymphs it was greater on soybean compared to canola and wheat, and for N. viridula nymphs the survivorship was greater on soybean and canola. Dichelops furcatus nymphs developed faster on soybean and wheat, and E. heros and N. viridula nymphs developed faster on soybean and canola. Body weight at adult emergency for D. furcatus was greater on soybean and wheat, and for E. heros and N. viridula, it was greater on soybean. Adult survivorship and longevity were similar on soybean/wheat/canola for D. furcatus and N. viridula, and greater on soybean for E. heros. Reproduction and weight gain of adults were greater on soybean and wheat for D. furcatus, and on soybean for E. heros; N. viridula reproduced only on soybean and tended to gain greater body weight in this food source. As expected, soybean considering its superior nutritional quality was, in general, the best food. These laboratory studies coupled with field observations allow to conclude that the sequence of soybean/wheat/canola crops in the area studied forms a 'green bridge' that favor stink bug populations abundance in southern Brazilian neotropics.

Development of Dichelops furcatus (Hemiptera: Heteroptera: Pentatomidae) Reared on Spring Cereals Versus Soybean.

The performance and preferences of the stink bug, Dichelops furcatus (F.), for spring cereals (wheat, rye, triticale, oat, and barley) were compared in the laboratory to their preferred host crop, soybean pods. Nymphs took significantly less time to reach adulthood on soybean pods compared to those fed seed heads of the five spring cereals tested. Wheat and rye yielded the longest developmental times, while nymphs fed triticale, oat, or barley developed faster, but still not as fast as those reared on soybean pods. On all foods ≥78% of nymphs reached adulthood. Adult body weight was significantly greater on soybean pods than on any of the spring cereals, and adults increased in body weight on all food sources tested. Fecundity was significantly greater for females fed soybean pods than those reared on the cereals. Egg viability was ≥66.9% except for bugs fed triticale (31.4%). In general, adult D. furcatus preferred soybean pods to seed heads of spring cereals, with wheat being preferred over the other spring cereals.