The predatory bug Orius strigicollis shows a preference for egg-laying sites based on plant topography

Background Oviposition site selection is an important factor in determining the success of insect populations. Orius spp. are widely used in the biological control of a wide range of soft-bodied insect pests such as thrips, aphids, and mites. Orius strigicollis (Heteroptera: Anthocoridae) is the dominant Orius species in southern China; however, what factor drives its selection of an oviposition site after mating currently remains unknown. Methods Here, kidney bean pods (KBPs) were chosen as the oviposition substrate, and choice and nonchoice experiments were conducted to determine the preferences concerning oviposition sites on the KBPs of O. strigicollis. The mechanism of oviposition behavior was revealed through observation and measurement of oviposition action, the egg hatching rate, and the oviposition time. Results We found that O. strigicollis preferred the seams of the pods for oviposition, especially the seams at the tips of the KBPs. Choice and nonchoice experiments showed that females did not lay eggs when the KBP tail parts were unavailable. The rates of egg hatching on different KBP parts were not significantly different, but the time required for females to lay eggs on the tip seam was significantly lower. Decreased oviposition time is achieved on the tip seam because the insect can exploit support points found there and gain leverage for insertion of the ovipositor. Discussion The preferences for oviposition sites of O. strigicollis are significantly influenced by the topography of the KBP surface. Revealing such behavior and mechanisms will provide an important scientific basis for the mass rearing of predatory bugs.

Establishment of a Faba Bean Banker Plant System with Predator Orius strigicollis for the Control of Thrips Dendrothrips minowai on Tea Plants under Laboratory Conditions

The stick tea thrip Dendrothrips minowai (Priesner) (Thysanoptera: Thripidae) is a destructive pest in tea plantations in south and southwest China. To control this pest, a non-crop banker plant system was developed using a polyphagous predator Orius strigicollis (Poppius) (Heteroptera: Anthocoridae) with the black bean aphid Aphis fabae (Scopoli) (Hemiptera: Aphididae) as an alternative prey and the faba bean Vicia faba as the banker plant to support the predator in targeting the pest. The fitness of A. fabae on tea plants and faba bean was evaluated to determine its host specificity. Moreover, the control efficacy of the banker plant system on D. minowai on tea plants was tested in the laboratory and compared with that of direct release of O. strigicollis. The experiments showed that faba bean was an excellent non-crop host for A. fabae because, while the aphid population increased quickly on faba bean, it could only survive for up to 9 days on tea plants. Compared with direct release of O. strigicollis, lower densities of pest were observed when introducing the banker plant system. Our results indicate that this banker plant system has the potential to be implemented in the field to improve the control of the pest thrips.

THE POTENTIAL OF THREE LARVAL PREDATORS AGAINST FALL ARMYWORM SPODOPTERA FRUGIPERDA (LEPIDPTERA: NOCTUIDAE) UNDER THE LABORATORY CONDITION

Most cereal crops are often damaged by lepidopterous insects. Of recent, fall armyworm, S. frugiperda (J.E. Smith) has resulted into yield and economic loss in many African and Asian countries. This reduces farmers’ income drastically and to overcome this damage, pesticides have been used which are not also environmentally friendly. Experiments were set up to collect data on the potential of three larval predators Orius strigicollis, Micromus angulatus, and Podisus maculiventris against S. frugiperda. The consumption of S. frugiperda larvae by three predators had highly significant effects (P≤0.05) on first, fourth, and sixth instars. No significant difference was reported between M. angulatus and O. strigicollis on second, third and fifth larval instars of S. frugiperda. O. strigicollis consumed more first larval instar (6.2±0.71) of S. frugiperda than M. angulatus (4.9±1.07) and P. maculiventris (4.2±0.74). However, P. maculiventris consumed more second to sixth larval instars of S. frugiperda than other two predators (O. strigicollis and M. angulatus). The predator P. maculiventris is recommended for controlling S. frugiperda in their second to sixth larval instars while O. strigicollis in the first larval instar. It can be also concluded that fourth larval instars of S. frugiperda is more suitable for its control using predator P. maculiventris as compared to other larval instars. This study therefore recommends predator Podisus maculiventris to be used in control of S. frugiperda under laboratory conditions.

Determination of fitness traits of Orius strigicollis Poppius (Hemiptera: Anthocoridae) on Pectinophora gossypiella (Lepidoptera: Gelechiidae) using two-sex life table analysis

Background Pink bollworm (Pectinophora gossypiella) is a destructive insect pest of cotton crops in China and globally, which is actively predated on by Orius strigicollis. Studies on the fitness or survival of O. strigicollis fed on P. gossypiella at different temperatures have not been reported. The fitness of O. strigicollis may be well explained using two-sex life table parameters. Thus, the present study provides important insights for the effective biocontrol of P. gossypiella. Methodology Considering the importance of fitness parameters and biocontrol, the present study explores the feeding potential and age-stage, two-sex life table traits of O. strigicollis on P. gossypiella eggs at different temperatures (24, 28 and 32 °C) in the laboratory. Results The intrinsic rate of increase (r) was higher at 28 °C (0.14 d−1) than at 24 °C (0.0052 d−1) and 32 °C (0.12 d−1). Similarly, the net reproductive rate (R0) was higher at 28 °C (17.63 offspring) than at 24 °C (1.13 offspring) and 32 °C (10.23 offspring). This concluded that the maximum feeding potential and growth capacity of O. strigicollis could be attained at 28 °C when fed on P. gossypiella eggs. O. strigicollis adults preferred to feed on P. gossypiella eggs compared with first instar larvae. Based on these results, the present study suggests that O. strigicollis represents a promising biological control agent against P. gossypiella eggs in cotton fields.