D. J. Boethel

Delayed Maturity Associated with Southern Green Stink Bug (Heteroptera: Pentatomidae) Injury at Various Soybean Phenological Stages

Abstract Delayed maturity in soybean, Glycine max (L.) Merr., occurred in response to infestation by southern green stink bug, Nezara viridula (L.), in 4 yr of field studies. Maturity delays followed stink bug infestation that occurred only during the pod set and filling stages (R3–R5.5), and infestations at R3–4 and R5 resulted in delayed maturity more consistently than did infestation at R5.5. Infestation levels of six stink bugs per 0.3 m of row for 7–14 d generally were required to delay soybean maturity. The greatest impact on seed yield and quality parameters followed stink bug infestations that occurred during R3–R5.5, which corresponded closely with the periods of infestation that resulted in delayed maturity. If both delayed maturity and yield reduction are considered, the pod elongation through late pod filling stages were most critical for protecting soybeans from southern green stink bugs.

Arthropod populations in early soybean production systems in the mid-South.

Abstract We compared the severity of insect problems in early and conventional soybean, Glycine max (L.) Merrill, production systems in the mid-South. The conventional soybean production system (cultivars in maturity groups V–VII planted in May) experienced significantly higher populations of late-season defoliators than the early soybean production system (cultivars in maturity group IV planted in April). However, the early soybean production system harbored significantly larger populations of southern green stink bug, Nezara viridula (L.) and threecornered alfalfa hopper, Spissistilus festinus (Say). Predators were significantly more abundant in the early soybean production system compared with the conventional soybean production system, early in the growing season. Late in the growing season, predator populations were lower in both productions systems and differences between the two systems were not significant. The results from the current study illustrated the benefits of early-planted early-maturing cultivars (early soybean production system) in avoiding lepidopterous and coleopterous defoliators that occur late in the growing season. However, our data also indicate that arthropod management will be essential in the early soybean production system because widespread use of this system will result in an abundance of suitable hosts for early-season pests.

Effects of Diflubenzuron on Pseudoplusia includens (Lepidoptera: Noctuidae) and its Parasitoid Copidosoma floridanum (Hymenoptera: Encyrtidae)

Abstract The insect growth regulator (IGR), diflubenzuron (Dimilin 2L), was evaluated for its effect on development of Copidosoma floridanum (Ashmead) and its host, Pseudoplusia includens (Walker), when applied at 0.035 kg ai/ha to soybean, Glycine max (L.), a rate used in preventive programs for control of velvetbean caterpillar, Anticarsia gemmatalis Hübner. Parasitized and nonparasitized soybean looper larvae were fed either diflubenzuron-treated or nontreated foliage. The feeding period of parasitized larvae was 1.7 and 1.8 d longer on diflubenzuron-treated and nontreated foliage, respectively, than that of nonparasitized larvae. Pupation period of C. floridanum and soybean looper was not significantly influenced by diflubenzuron. Although parasitized soybean looper fed both foliage treatments experienced 100% mortality, nonparasitized soybean looper fed nontreated foliage was 23.2% and nonparasitized soybean looper fed diflubenzuron-treated foliage was 12.2%. Parasitized soybean looper fed nontreated foliage consumed 19.2% more leaf area than nonparasitized larvae fed nontreated foliage, whereas parasitized soybean looper fed diflubenzuron-treated foliage consumed 21.2% more leaf area than nonparasitized larvae on the same foliage. There was no significant difference in number of parasitoids emerging from host mummies among treatments; however, there was a positive correlation between leaf area consumed and adult parasitoids per mummy. Diflubenzuron does not appear to produce deleterious effects in C. floridanum or its host, soybean looper, at the current rate used for management of other lepidopteran pests.

Interactions Among the Soybean Looper (Lepidoptera: Noctuidae), Threecornered Alfalfa Hopper (Homoptera Membracidae), Stem Canker, and Red Crown Rot in Soybean

Field experiments in 1988–1990 determined the (1) effects of defoliation by Pseudoplusia includens (Walker) (soybean looper) or basal stem girdling by Spissistilus festinus (Say) (threecornered alfalfa hopper) on soybean stem canker severity and (2) effects of the soybean looper defoliation on red crown rot incidence. Compared to ungirdled plants, stem canker severity was increased while stem length, stem diameter, and yield were reduced for girdled plants. Stem canker severity, number of perithecia, yield, stem length, and stem diameter were reduced on defoliated soybean, compared to undefoliated soybean. Red crown rot incidence, perithecial production, and yields were reduced on defoliated soybean compared to undefoliated soybean. This suggests different types of insect injury may either increase or decrease the severity of soybean diseases.

Leaf residue compartmentalization and efficacy of permethrin applied to soybean.

Permethrin (EC, 0.084 kg AI/ha) was applied to soybean by backpack sprayer and eight determinations of leaf residue compartmentalization and insect mortality were made during the 27 days following ...

FECUNDITY AND EGG HATCHABILITY OF TWOSPOTTED SPIDER MITE, TETRANYCHUS URTICAE KOCH (ACARI: TETRANYCHIDAE) REARED ON NINE SOYBEAN GENOTYPES

Nine genotypes of soybean, Glycine max (L.) Merrill, were tested for their effect on fecundity and egg hatchability of twospotted spider mites, Tetranychus urticae Koch. Fecundity of both virgin an...

Multiple pest complexes on soybean: influences of threecornered alfalfa hopper injury on pod and stem blight and stem anthracnose diseases and seed vigour.

Abstract Girdles on soybean, Glycine max (L.) Merr., stems caused by the threecornered alfalfa hopper (TCAH), Spissistilus festinus (Say), were examined with regard to their effects on Phomopsis sojae Leh. and Colletotrichum truncatum (Schw.) Andrus and Moore, causal fungi for pod and stem blight and stem anthracnose, respectively. Presence of basal stem girdles had no effect on disease incidence for either pathogen. Effects of girdles were most evident on disease severity. C. truncatum disease severity ratings were significantly greater on girdled than on non-girdled stems of cvs Hartz 5171 (group V) and Bragg (group VII). C. truncatum was not observed on stems of cv. Centennial (group VI). Ratings for P. sojae were significantly greater on girdled than on non-girdled stems only for cv. Centennial, in the absence of C. truncatum . Production of diseased plant debris as a result of girdle-induced death of soybean stems occurred as much as four weeks earlier than on non-girdled stems. High TCAH populations reduced germination and vigour of soybean seeds but did not influence 100-seed weight or colonization by seedborne fungi.

Persistence of Diflubenzuron on Soybean Leaves

Diflubenzuron [Dimilin™, N-[{(4-chlorophenyl)amino}carbonyl]-2-6-difluorobenzamide] is an insect growth regulator that is highly effective and provides residual control (up to 54 days) against velv...