Non-cultivated areas are resting, overwintering, feeding, and/or reproducing habitats for insects, and also places from where crop areas are colonized; thus, they are essential for understanding the biological control programs in agroecosystems. We developed a simulation model for a non-cultivated area of Buenos Aires province (Argentina), and we analyzed the control of Nezara viridula achieved by the action of two parasitoids: the oophagous Trissolcus basalis and the tachinid Trichopoda giacomellii, which attack older nymphs and adults. The model is a discrete time, deterministic, phenomenological, spatially homogeneous with a 1-week time interval simulation model, based on the age-structure and/or stage-structure of N. viridula and its two parasitoids. The host–parasitoid interactions were combined with a degree-day model affecting development times of T. giacomellii pupae and T. basalis pre-imaginal stages. The simultaneous attack of both parasitoid species enables the persistence of the system at low host densities, mediated by the functional response of the parasitoids, identified as population regulation factors. However, if only one parasitoid exists (i.e., only T. basalis or only T. giacomellii) the interaction N. viridula–parasitoid persisted but at higher density of N. viridula. These results explain the successful biological control of N. viridula after the introduction of T. basalis in the 1980s, when T. giacomellii was the only parasitoid present, unable to control N. viridula. Our model shows an indirect competition when both parasitoids are present: the attack of one of them diminished the potential number of hosts available to the other parasitoid species. In the field this interaction is obscured by the hibernation period which acted as a reset mechanism affecting the density and age/stage structure of all three populations. Our model was supported by field observations, and never exhibited the extinction of any of the parasitoids from the interaction.

Methyl parathion or Penncap M (an encapsulated methyl parathion) are used extensively throughout the United States for controlling stink bug pests in soybeans, Glycine Max (L.) Merrill. However, this insecticide is highly toxic to mammals, birds, and non-target arthropods, and thus is less environmentally sound than other insecticides. For environmental and human health considerations, investigating alternative insecticides for control is desired. For this investigation, research based on field experimental data from Florida, Georgia, and Louisiana during the 1988 and 1989 growing seasons were employed. Results indicate that alternative, currently available, and less toxic insecticides may reduce producer costs, increase yield, and improve soybean quality. These alternative insecticides include Scout (tralomethrin), Karate (lambda-cyhalothrin), Orthene (acephate), and Baythroid (cyfluthrin). In terms of improved profits these alternative insecticides may dominate methyl parathion or encapsulated methyl parathion.

Stink bugs (Heteroptera: Pentatomidae), including Nezara viridula (L.), Euschistus servus (Say), and Chinavia hilaris (Say), are economic pests in farmscapes where they move within and between closely associated crop and non-crop habitats. Thus, field edges in these farmscapes include not only crop-to-crop interfaces but also those edges adjoining non-crop habitats. We examined the influence of field edges on colonization of stink bugs in southeastern USA farmscapes composed of typical combinations of corn, peanut, and cotton. For E. servus and N. viridula, egg-to-adult development and presence of both sexes on all crops indicated that the crops served as reproductive plants. Adult C. hilaris were rarely found on corn and on crops associated with it, and they were present mainly in cotton in peanut–cotton farmscapes. Mature crop height was significantly higher for corn than for cotton and significantly higher for cotton over peanut, and an edge effect in dispersal of stink bugs into a crop was detected up to 4.6, 8.2, and 14.6 m from the crop-to-crop interface in corn, cotton, and peanut, respectively. These results suggest that stink bug dispersal into a crop decreases as crop height increases. The first stink bug-infested crop at the crop-to-crop interface was the most significant contributor of colonizing stink bugs to an adjacent crop. An edge effect in dispersal of stink bug adults was detected in corn next to non-woodlands and woodlands and in cotton adjacent to woodlands. Edge effects were never detected in side edges of peanut. Overall, our results indicate that both plant height and host plant suitability can influence edge-mediated dispersal of stink bugs at field edges.

Trissolcus basalis has been used as a biological control agent of its main host, Nezara viridula, in many countries. However, estimations of its functional and numerical responses in the field are lacking. We estimated the density of N. viridula eggs, the proportion of parasitized N. viridula eggs, and the number of T. basalis adults/trap in the field. We transformed relative parasitoid density to an absolute density, and estimated the parasitoid's attack rate, a, and the mutual interference parameter, m, in two ways: following Arditi & Akçakaya (1990) and using the Holling–Hassell–Varley model with two iterative techniques. The attack rate estimated by both methods were a=1.097 and a=0.767, respectively. Parameter m varied less between methods: m=0.563 and m=0.586, respectively, and when used to calculate the number of parasitized N. viridula eggs per m2, differences with the observed values were not significant. The numerical response of T. basalis was affected by the sex allocation of their progeny and the proportion of adult parasitoids trapped decreased with field parasitoid population density. Theoretical models show that 0<m<1 is a stabilizing factor and previous re-analysis of field data showed a mean m value of 0.8. The Holling–Hassell–Varley model leads to a flexible description of the functional response allowing to predict acceptable weekly host parasitism. The pre-imaginal parasitoid survival and the change in sex ratio as a function of parasitoid density adequately describe the numerical functional response of the parasitoid.

The effects of increasing population densities of the cowpea pod-sucking bugs (PSB) Riptortus dentipes, Mirperus jaculus, Anoplocnemis curvipes and Nezara viridula were studied in caged potted cowpea (Vigna unguiculata) plants with infestation levels from 0 (control) to 12 adult bugs per cage. Generally, there was an increase in damage to cowpea (measured as damage to pods and seeds) with increasing in insect density. There was also a highly significant correlation between the number of infesting adult bugs and damage to pods and seeds, and a significant negative correlation between bug numbers and cowpea yield. The results suggest that control measures should be initiated at: 4 bugs (fourth instar and above) per 10 plants for R. dentipes and M. jaculus; 2 bugs per 10 plants for A. curvipes and 6 bugs per 10 plants for N. viridula at podding stage.

Studies were carried out on the neonatal development of Riptortus dentipes (Fabricius) and Nezara viridula (Linnaeus) on pods of cowpea Vigna unguiculata (L.) Walp (var. VITA-3) and soybean Glycine max (L.) Merrill (TG× 536–02D). Both crops sustained nymphal development and adult reproduction of R. dentipes. Nymphal duration was 20.7 days on cowpea and 21.3 days on soybean; mean adult weight was 56.3 mg (male) and 58.3 mg (female) on cowpea and 55.8 mg (male) and 57.6 mg (female) on soybean. Adults preferred soybean to cowpea for egg laying though a substantially higher number of eggs was laid on the mesh walls of the cages indicating the somewhat suboptimal nature of both plant substrates. The nymphal period for TV. viridula was 24.4 days on cowpea and 25.4 days on soybean, and the mean adult weight for males was 139.0 mg while that for females 186.0 mg on cowpea. On soybean, the mean adult weight was 127.3 mg for males and 176.9 mg for females. Soybean leaves were preferred for oviposition. The concept of host plant suitability to the various stages of these insects with respect to host switches between cowpea and soybean.

Experiments on artificial infestation of soybean with pod-sucking bugs showed that Riptortus dentipes caused more damage to the plant than did Nezara viridula. The density of four insects per plant used was high enough to significantly damage the plant. The reproductive developmental stages of the plant defined as R3, R4 and R5 were sensitive to the pod-sucking bugs studied. Plots infested with R. dentipes adults suffered 72% pod damage compared to 44% pod damage in plots infested with N. viridula. Riptortus dentipes significantly affected the physiology of the plant and reduced grain yield and grain quality. The results also showed that there is potential for biocontrol of pod-sucking bugs.