RESUMEN

The stink bugs Acrosternum arabicum Wagner and Brachynema germari Kolenati (Hemiptera: Pentatomidae) damage developing pistachio nuts in Iran. Ooencyrtus egeria Huang and Noyes (Hymenoptera: Encyrtidae) parasitizes eggs of both species, alternating between them seasonally. We compared the biological and life history attributes of O. egeria reared for 3 generations on each host species with those that had been transferred to the alternate host for 2 generations. We also tested female responses to host egg density. Eggs of B. germari were parasitized at higher rates and yielded faster wasp development, heavier female progeny with greater fecundity, and a more female-biased sex ratio, than eggs of A. arabicum. Rearing on A. arabicum did not diminish wasp fitness on B. germari, and the F1 progeny of wasps switched to A. arabicum inherited some beneficial parental effects from rearing on B. germari. Regardless of host species, females parasitized fewer eggs in 8 h as density increased from 10 to 30 eggs, but progeny sex ratio (% female) increased. The anomalous response to host density appears to arise from a combination of behavioral and egg load constraints. Females mature only 10-12 eggs per day. Carefully inspect egg clusters before selecting the most suitable eggs for oviposition, a more time-consuming process for large clusters. Our results indicate that rearing O. egeria on eggs of A. arabicum, which are more convenient and cost-effective to produce than those of B. germari, will not diminish its performance on B. germari following augmentative release, beyond a slight reduction in female fecundity.

RESUMEN

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.

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Pistacia vera L. is one of the most important horticultural crops in Iran. The stink bugs Acrosternum arabicum and Brachynema germari are two of the key pests that cause significant direct and indirect damage on Pistacia vera. Egg parasitoids have been considered as potential biological control agents of pistachio green stink bugs. Among them, Trissolcus semistriatus and Psix saccharicola are the most abundant and efficient parasitoid for A. arabicum in pistachio orchards. In this study, we assessed lethal and sublethal effects of two commonly used insecticide products (fenitrothion and a binary mixture of lambda-cyhalothrin + thiamethoxam) on these two parasitoid wasps under laboratory conditions. The median lethal concentration (LC50) values for fenitrothion and thiamethoxam + lambda-cyhalothrin in P. saccharicola and T. semistriatus were estimated as 1.03, 0.48 and 0.87, 0.98 mg a.i./liter, respectively. In terms of sublethal effects, insecticide treatments altered the type of functional response from type III to type II in T. semistriatus. However, P. saccharicola exhibited a type II functional to density of A. arabicum for all treatments, although attack rates were lower for insecticide-exposed wasps while handling times increased. Our results show that sublethal effects of insecticides further reduce the efficacy of biological control agents. Effective integrated pest management programs should avoid antagonistic interactions between chemical and biological control methods. The results of this study provide useful information to develop comprehensive integrated pest management programs for stink bugs in pistachio orchards.

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Laboratory studies were conducted to determine the effect of two prey species, Agonoscena pistaciae Burckhardt and Lauterer (Hemiptera: Aphalaridae) and Aphis gossypii Glover (Hemiptera: Aphididae) on the biology, reproduction, and food consumption indices of Coccinella septempunctata L. (Coleoptera: Coccinellidae). Both species of prey were readily consumed by C. septempunctata larvae and adults. The predator was able to successfully utilize the psylla prey for larval development, but failed to lay eggs when fed this prey. However, A. gossypii fully supported both development and reproduction of C. septempunctata. Dry mass of ingested food was similar on both diets for each larval instar. However, the dry mass gained during each stadium for C. septempunctata was significantly greater with A. gossypii prey. The aphid diet was superior to the psylla diet in terms of food conversion efficiency as larvae consumed aphids more efficiently than psyllas, regardless of the higher consumption index on the psylla prey. Our results confirm that the study of prey suitability for larvae and adult stages of predatory lady beetles should be studied separately.

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BACKGROUND: Knowledge of the nutritional ecology of predatory coccinellids is important for the selection of efficient biocontrol agents. We examined five species common in pistachio orchards and determined their nutritional indices when fed on the key psylla pest of the system, Agonoscena pistaciae, in contrast to an alternative prey common on herbaceous plants in orchards, Aphis gossypii. RESULTS: Feeding experiments revealed that Oenopia conglobata contaminata and Adalia bipunctata may be more efficient as biocontrol agents for A. pistaciae than for A. gossypii, as A. bipunctata had a high efficiency of conversion of ingested food and a high relative growth rate and O. conglobata contaminata had a high consumption index on psylla prey. In contrast, the nutritional indices of Coccinella undecimpunctata aegyptica, Hippodamia variegata and Exochomus nigripennis suggest that A. gossypii was a more suitable host food. CONCLUSION: Where both the psyllids and the aphids occur in pistachio orchards, especially under conditions of unlimited access to A. gossypii, C. undecimpunctata aegyptica, H. variegata and E. nigripennis may prefer to move from psylla-infested leaves of pistachio trees and travel to and stay on weeds to feed on A. gossypii. The value of using nutritional ecology as a means of understanding and predicting biocontrol outcomes and selecting better candidates for mass rearing is discussed. © 2018 Society of Chemical Industry.

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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.

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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.