Shimon Steinberg

Competition between two parasites of the Florida red scale in Israel.

ABSTRACT. 1. During the last decade, the endoparasitic wasp Pteroptrix smithi (Compere) has gradually replaced the ectoparasitic wasp Aphytis holoxanthus DeBach on the Florida red scale, Chrysomphalus aonidum (L.), on citrus in Israel. The studies reported herein were aimed at elucidating some of the mechanisms of this process.

Evaluation of the parasitoid Copidosoma koehleri for biological control of the potato tuber moth, Phthorimaea operculella, in Israeli potato fields

Abstract The potato tuber moth Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae) is a major agricultural pest of solaneceous crops in warm countries worldwide. The encyrtid polyembryonic parasitoid Copidosoma koehleri (Blanchard) has been successfully introduced for biological control of the moth in potato fields in South Africa and Australia; however, augmentative releases of the parasitoid in trial plots and in commercial potato fields in Israel did not reduce pest populations or infestation levels more than chemical treatment. Copidosoma koehleri accounted for 4–5% of parasitism on tuber moth caterpillars, while most parasitism was due to local species of larval parasitoids. The abundance and composition of local parasitoids did not differ between C. koehleri release plots and conventionally treated control plots. These findings can be interpreted as failure of the introduced parasitoids to survive and locate their hosts, or as mortality of C. koehleri within hosts in the field. Sentinel hosts, placed in trial plots and collected after 24 h, were rarely parasitised by C. koehleri, supporting the first interpretation. To test the second hypothesis, hosts parasitised by C. koehleri were placed in field plots for a week, collected, and reared out in the laboratory. The emergence rates of C. koehleri from these hosts resembled those of lab-reared controls, suggesting that mortality within hosts in the field is not a major cause of C. koehleris poor biocontrol performance.

Diapause induction in the codling moth, Cydia pomonella: effect of prediapause temperatures

The effect of four prediapause temperatures (18, 22, 26 and 30 °C) on the photoperiodic response of the codling moth, Cydia pomonella (L.), was studied under controlled conditions. The highest rates of diapause were recorded, for all day‐lengths, at temperatures of 22 and 26 °C while relatively lower rates of diapause were elicited at 18 and 30 °C. The same trend was demonstrated by projecting the values of the critical photoperiod which induces 50% diapause (= CPhP50) over the prediapause temperature. The change in diapause incidence as a function of photoperiod, at all prediapause temperatures, exhibited a response characteristic of long‐day insects, i.e. high rates of diapause at short days (12–13.5 h) and a decrease in diapause incidence at long days (14–15 h). The results for temperatures 22, 26 and 30 °C support the view that lower prediapause temperatures enhance diapause induction, at a given photoperiod, while higher temperatures tend to avert or diminish the process. On the other hand, the low rates of diapause obtained at 18 °C contradict this view. Nevertheless, high correlation was found between the laboratory evidence and field data, indicating the adaptability of the Israeli codling moth to subtropical climate.

Biological control of the Florida red scale, Chrysomphalus aonidum, in Israel by two parasite species: current status in the coastal plain.

For the last 20 years there has been a trend of dynamic change in the relative composition of the parasite complex of the Florida red scale,Chrysomphalus aonidum (L.), in Israel —Aphytis holoxanthus DeBach (an ectoparasite) being gradually replaced byPteroptrix smithi (Compere) (an endoparasite). Monthly sampling of fruits and leaves in citrus groves located along the coastal plain in Israel indicated that the Florida red scale is effectively controlled by its parasites. The two parasite species coexist in the citrus groves,P. smithi generally being the dominant species. Parasitism byA. holoxanthus is relatively low during autumn and winter, increasing gradually during the spring and reaching a peak between May and August. Parasitism byP. smithi remains relatively high throughout the year.

Control of the Tomato Leafminer, Tuta absoluta (Lepidoptera: Gelechiidae), in Open-Field Tomatoes by Indigenous Natural Enemies Occurring in Israel

Abstract The tomato leafminer, Tuta absoluta (Meyrick), had established in Israel by 2010, attacking both open-field tomatoes and greenhouse crops. We searched for its natural enemies in open-field tomatoes, and tried to determine their potential for controlling this pest. We surveyed the local natural enemies in open tomato fields and measured their impact on pest populations in an unsprayed field. We assessed the suppressive ability of the dominant hemip-teran predator, Nesidiocoris tenuis Reuter, against T. absoluta under controlled laboratory conditions and evaluated the impact of its augmentation on T. absoluta control in open-field tomatoes. We found five natural enemy species: the predator, N. tenuis, two braconids, and two eulophids. Predation accounted for 64.5 ± 9.2% (mean ± SE) of T. absoluta larval mortality, whereas parasitism accounted for 20.9 ± 7.5%. Together, they eliminated the pest population at tomato harvest time. Under controlled conditions, predation by N. tenuis rose from 58 to 72% with increased density of T. absoluta, suggesting positive density dependence. The reduction of T. absoluta (83%) by N. tenuis was higher than that of Bemisia tabaci (32%), suggesting a preference of N. tenuis for T. absoluta. Augmentation of N. tenuis was as effective as conventional treatment insecticide treatment, and plant damage was low and did not seem to affect yield. Results indicate that reduced pesticide use enables indigenous natural enemies, particularly N. tenuis, to successfully control T. absoluta and prevent crop damage in open-field tomatoes.

Synergism between biological control and sterile insect technique: Can commercial mass production of biocontrol agents and sterile insects be integrated within the same industrial entity?

Abstract The integration of commercial facilities for mass production of beneficial arthropods (Bio-Bee) and sterile insects (Bio-Fly) within the same industrial entity in Israel has proven successful. The synergism between the two companies has resulted in the integration of nuclear techniques and the use of biocontrol agents in area-wide integrated pest management programmes.

Diapause induction in the codling moth, Cydia pomonella: effect of larval diet

The effect of larval diet on diapause induction in the Israeli strain of the codling moth, Cydia pomonella (L.), was studied in a field trial using intact apple fruits of two varieties: ‘Ana’ (early‐ripening, in the end of June) and ‘Granny Smith’ (late‐ripening, in October). Diapause incidence increased as fruit age (determined as days from fruit‐set) progressed. These results corroborate former studies on other strains of the codling moth, where excised fruits were used.

Diapause induction in field populations of the codling moth,Cydia Pomonella, in Northern Israel

Diapause induction in field populations of the codling moth,Cydia pomonella L., was studied for three consecutive seasons (1984–86) in two commercial apple orchards in Upper Galilee. One orchard was located in the Hula Valley and the other in the high mountain region. The onset of diapause sometimes occurred during increasing day-length, before the summer solstice. This phenomenon represents a small proportion of the population which is probably genetically univoltine. The critical photoperiod which induces 50% diapause (= CPhP50) varied up to 5 days within the valley region, up to 6 days within the mountain region, and up to 7 days between the two regions. The trend of this variation was consistent: the CPhP50 of the valley poulation preceded that of the mountain on both ‘Jonathan’ and ‘Granny Smith’ apple varieties and, within each location, the CPhP50 on the early-ripening ‘Jonathan’ preceded that of the late-ripening ‘Granny Smith’. The higher prediapause temperatures of the Hula Valley caused earlier diapause induction as compared with the lower temperatures of the mountain region. Immature fruits delayed diapause induction in comparison with mature ones.

Development of an economic rearing and transport system for an arid-adapted strain of the predatory mite, Neoseiulus californicus, for spider mite control

Neoseiulus californicus (McGregor) is a relatively effective phytoseiid predator against spider mites reported from the Americas (North and South), Africa, the Mediterranean basin, and Japan. This study was a collaborative effort to identify and mass-rear a strain of N. californicus that is more efficacious under arid conditions than the standard commercial strain from California (USA). N. californicus strains were collected in arid areas worldwide. Discriminant analysis performed with 30 morphological variables allowed for their separation. The performance of these strains under arid conditions and on selected host plants was evaluated in laboratory and semi-field trials. Development and survival of eggs and juveniles differed among strains and humidities. Female performance (survival, oviposition) was influenced by strain but not by humidity. The Californian reference strain was superior to all others, when considering both adaptation to dry conditions and power of population increase at low humidities. Whole potted plant trials (cucumber, strawberry, and pepper) confirmed this result. Field trials were conducted to compare this new product to the standard commercial strain of Phytoseiulus persimilis Athias-Henriot. To identify possible influence of symbiotic bacteria on strains of N. californicus general primers for the 16S rDNA gene were used in a PCR. Among other bacteria, a Spiroplasma, closely related to the one found in various arthropods, was detected in two strains, and it was further characterized. No influence on the hosts developmental time, fecundity, and sex ratio could be detected. To provide this product at an affordable cost for European growers an economic rearing and delivery system for N. californicus was developed and its marketing potential in Europe and neighboring countries was estimated.

Contagious sterility in the parasitoid wasp Eretmocerus mundus (Hymenoptera: Aphelinidae)

Abstract The parasitoid wasp Eretmocerus mundus (Hymenoptera: Aphelinidae) is used commercially to control the sweet potato whitefly Bemisia tabaci (Homoptera: Aleyrodidae). Recently, a rapid deterioration of E. mundus populations has been documented under mass-rearing conditions. We found that deteriorating cultures consist of increasing proportions of sterile individuals, up to 90% within 6 months. Microscopic examination revealed that the gonads of wasps from both sexes are severely underdeveloped. Preliminary screening for potential pathogen candidates by means of polymerase chain reaction and denaturating-gradient gel electrophoresis did not provide any indication of possible causative agents.