Hemipteran bugs associated with pistachio trees and notes on major species

Assessment of Toxicity Risk of Selected Insecticides Used in Pistachio Ecosystem on Two Egg Parasitoids (Hymenoptera: Scelionidae) of Stink Bugs (Hemiptera: Pentatomidae)

Psix saccharicola (Mani) and Trissolcus semistriatus (Nees) are the most abundant eggs parasitoids of the stink bug, Acrosternum arabicum Wagner, in pistachio orchards and have the potential to contribute to their suppression. However, treatment of orchards with broad-spectrum insecticides may greatly reduce populations of these beneficial natural enemies. Therefore, we conducted risk assessments and evaluated sublethal impacts of two insecticides routinely used in pistachio orchards: the organophosphate fenitrothion and a formulated mixture of the neonicotinoid thiamethoxam and the pyrethroid lambda-cyhalothrin on parasitism success, emergence and sex ratio of P. saccharicola and T. semistriatus. Based on the values of their risk quotients (RQ), which are derived from toxicity data, the two insecticide products would be classified as slightly-to-moderately toxic although an alternative metric, the safety factor (SF), showed them to be highly risky. Assessments of sublethal effects on adult wasps showed that insecticide exposure significantly reduced their ability to successfully parasitize stink bug eggs, and exposure of adult females reduced the emergence, survival, and proportion of females of their progeny, which could disrupt biological control for an extended period of time. Analysis of the decreased emergence and parasitism for P. saccharicola and T. semistriatus in accordance with the standards of the International Organization for Biological Control (IOBC) indicate that fenitrothion is slightly harmful to both parasitoid species whereas the mixture of thiamethoxam + lambda-cyhalothrin is moderately harmful. These findings will be useful for integrating insecticides and egg parasitoids into a comprehensive integrated pest management program for managing stink bugs populations in pistachio orchards.

Effect of Cold Storage on Biological Traits of Psix saccharicola (Hymenoptera: Platygastridae), an Egg Parasitoid of Acrosternum arabicum (Hemiptera: Pentatomidae)

Psix saccharicola (Mani) (Hymenoptera: Platygastridae) is a solitary egg parasitoid of the pistachio green stink bug, Acrosternum arabicum (Wagner) (Hemiptera: Pentatomidae), which is one of the most important pests of pistachio in Iran. Augmentation of P. saccharicola field populations using mass-reared individuals may provide an alternative to conventional pesticide use for pistachio green stink bug control. Cold storage is an important component of mass-rearing protocols for optimum timing of host egg parasitization and potentially extended storage of P. saccharicola pupae prior to adult emergence. The impact of cold storage on A. arabicum eggs for various time intervals at 4.0°C was investigated. Results indicated that host eggs stored at 4.0°C for up to 60 d could be exploited by P. sacchricola, whereas no offspring were produced when eggs were stored for 120 d. The emergence rates of the F1 and F2 generations declined with increased host egg storage time. Both sex ratio and survival rate of the F2 generation decreased as the refrigeration time of host eggs increased. The impact of cold storage on P. saccharicola pupae was evaluated. Reared pupae of P. saccharicola were held for 1 wk at three temperatures and compared with a control (27 ± 1°C). Psix saccharicola pupae were tolerant to cold storage at 8 and 12°C. Cold storage adversely affected mean adult emergence at 4°C, which decreased following low temperature exposure. Furthermore, mean percentage survivorship was unaffected by storage at low temperatures in the F1 generation, but was reduced at 4°C. The sex ratio of the F1 generation became more male-biased when held at lower storage temperatures. The highest female proportion was observed at 12°C.

Biological Characteristic of Brachynema germari (Hemiptera: Pentatomidae): Comparative Study of Composite and Natural Diet

This research was conducted to develop a composite diet and compare its effects on developmental time, fecundity, survival rate, and life table parameters of pistachio green stink bug, Brachynema germari Kolenati (Hemiptera: Pentatomidae) with a natural diet. The biological parameters of this pest were investigated using two-sex, age-stage life table theory on both composite and natural diets (25 ± 1°C, 50 ± 10% relative humidity, and a photoperiod of 16:8 [L:D] h). Based on the preliminary studies, the combination of the green beans ( Phaseolus vulgaris L.), sunflower seeds ( Helianthus annuus L.), and wild rue capsules ( Peganum harmala L.) was introduced into a composite diet. There was no significant difference between the longevity of each stage on diet treatments, but the mean fecundity of female fed on composite diet was about 196.48 ± 12.02 (eggs), which indicated a significant decrease than the fecundity of female fed on the natural diet (265.81 ± 11.67 eggs; P  = 0.05, t -test). Also, main parameters of life table ( r , R 0 , T , and λ) for composite and natural diets were about 0.0863 ± 0.0031 d -1 , 89.03 ± 13.33 eggs, 51.987 ± 0.536 d, and 1.091 ± 0.0034 d -1 and 0.1023 ± 0.003 d -1 , 128.75 ± 17.56 eggs, 47.454 ± 0.439 d, and 1.1077 ± 0.0037 d -1 , respectively. There was a significant difference between these four parameters on both diets. Despite a significant decrease in fecundity with using composite diets, this diet can satisfy our needs now and the laboratory rearing of pistachio green stink bug did not stop over the year in the absence of host weeds and insect did not diapause.

Enzyme Activity, Cold Hardiness, and Supercooling Point in Developmental Stages of Acrosternum arabicum (Hemiptera: Pentatomidae)

Several species of pentatomid bugs feed on pistachio fruits in Iran. Acrosternum arabicum Wagner (Hemiptera: Pentatomidae) is one of the most important pests of pistachio in Rafsanjan, Iran. This study was carried out to investigate the carbohydrase activities, supercooling points, and cold hardiness profiles of different developmental stages of A. arabicum under laboratory conditions. The midgut amylolytic of A. arabicum showed an optimal pH at 7.0. The highest amylolytic activity was found in the female adults (35.41 ± 0.90 nmol/min/gut). The mean amylolytic activity measured in first instar nymph was 6.75 ± 0.54 nmol/min/gut. Midgut α- and β-glucosidase showed an optimal activity at pH 5 and 7, respectively. These activities increased from first (83 ± 5 and 54 ± 5 nmol/min, respectively) to fifth (881 ± 17 and 237 ± 14 nmol/min, respectively) instar nymphs. The enzyme activities increased in the adults. Midgut α- and β-galactosidase showed an optimal activity at pH 5. α- and β-galactosidase activities were low in the first instar nymphs (73 ± 5 and 21 ± 3 nmol/min, respectively). The level of α- and β-galactosidase activities in the female adults (533 ± 18 and 246 ± 6 nmol/min, respectively) was higher than the nymphs. The lowest super cooling points (-19 and -18.2 °C, respectively) and the highest cold hardiness (22 and 18% following 24 h exposure at - 20 °C, respectively) were recorded for the eggs and adult females.