The potential use of different predatory bug species in the biological control of<Emphasis Type="Italic"> Frankliniella occidentalis</Emphasis> (Pergande) (Thysanoptera: Thripidae)

In the present study, the suitability of different predatory bug species, such as Dicyphus tamaninii Wagner, Macrolophus pygmaeus (Rambur), Orius albidipennis Reuter, Orius majusculus Reuter and Orius sauteri Poppius, for the biological control of Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), were investigated. Development of the predatory bug species, their reproduction as well as their daily and total prey consumption over a 18-day period with F. occidentalis larvae or various stages of Tetranychus urticae Koch (Acari: Tetranychidae) individuals as prey species were studied during the experiments in the laboratory. In further experiments, the efficiency of D. tamaninii, M. pygmaeus, O. albidipennis and O. majusculus in controlling F. occidentalis under glasshouse conditions was investigated. Results showed that all the predators could develop under the experimental conditions with either F. occidentalis larvae or different stages of T. urticae as prey. When F. occidentalis larvae were offered as prey, the shortest duration of development was observed for O. albidipennis with a mean of 17.7 days, while D. tamaninii took the longest to develop with a mean of 36.3 days. With different stages of T. urticae as prey, the duration of development ranged from 19.3 days in O. albidipennis to 42.9 days in M. pygmaeus. Mean daily fecundity ranged from 0.8 eggs/female for O. majusculus to 2.2 eggs/female for O. sauteri with F. occidentalis larvae as prey and from 0.6, O. majusculus, to 2.3 eggs/female/day, O. sauteri, when different stages of T. urticae were offered as prey. Over the 18-day reproduction period, O. sauteri was the most fecund predatory species, laying a mean total of 31.6 and 31.3 eggs/female with F. occidentalis and T. urticae as prey, respectively. Daily consumption from F. occidentalis larvae ranged between 5.5 individuals consumed per day by O. majusculus and 29.1, by O. sauteri. When different stages of T. urticae were offered as prey, maximal consumption was observed in D. tamaninii with a mean of 29.0 individuals/day, while O. albidipennis consumed the least with an average of 8.1 preys/day. Over the 18-day prey consumption period, D. tamaninii consumed the highest mean number of 422.8 F. occidentalis larvae, while O. majusculus only consumed 98.8 larvae. Also, D. tamaninii had the maximum consumption of different stages of T. urticae with a mean of 522.4, while M. pygmaeus and O. albidipennis consumed the least, with an average of 146.1 and 146.0, respectively. The predatory bugs D. tamaninii, M. pygmaeus, O. albidipennis and O. majusculus significantly reduced the density of F. occidentalis on hybrids of Euphorbia milii, Serissa foetida and Saintpaulia ionantha in the glasshouse, which confirms their efficiency against this pest on different hosts under controlled climatic conditions.     

Biology and life table of the predacious mite,Agistemus exsertus Gonz. (Acari: Stigmaeidae)

The predacious mite,Agistemus exsertus Gonz. was reared on 4 types of animal egg diets (eggs ofTetranychus urticae Koch,Eutetranychus orientalis Klein,Brevipalpus pulcher [C. & F.] andBemisia tabaci [Genn.]). Life table parameters of each diet (net reproduction rate [Ro], mean generation time [T], intrinsic rate of increase [rm] and finite rate of increase [erm]) were determined. Eggs ofT. urticae were found to be preferred above other egg diets as food byA. exsertus and promoted a higher rate of oviposition. The intrinsic rate of increase was 0.15 individuals//day; the population multiplied 57.91 times in a generation time of 26.21 days. Rearing on eggs ofB. tabaci exhibited more attractive compared withB. pulcher. The average number of eggs consumed daily by female was 17, 12, 9 and 7 eggs ofT. urticae, E. orientalis, B. tabaci andB. pulcher respectively. In the sex ratio of the progeny, predator females fed inT. urticae andB. tabaci gave rise to more females.

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Zusammenfassung Die RaubmilbeAgistemus exsertus Gonz. wurde im Labor unter Fütterung mit veschiedenen Milben- und Insekteneiern (Tetranychus urticae, Eutetranychus orientalis, Brevipalpus pulcher, Bemisia tabaci) aufgezogen. Die life table-Parameter bei jeder Nahrung (Netto-Reproduktionsrate Ro, mittlere Generationsdauer T, Innere Zuwachsrate rm sowie Gesamt-Zuwachsrate erm) wurden bestimmt. Die Eier vonT. urticae wurden allen anderen Eiern vorgezogen und bewirkten die höchste Eiablege-Rate der Raubmilbe. Die innere Zuwachsrate betrug 0,15 Indiv.//Tag. Die Population nahm während der Generationszeit von 26,2 Tagen um das 57,9fache zu. Die Eier vonB. tabaci wurden jenen vonB. pulcher vorgezogen. Die durchschnittliche Zahl der täglich von einem Raubmilben-Weibchen verzehrten Eier betrug 17, 12, 9 und 7 Eier vonT. urticae, E. orientalis, B. tabaci undB. pulcher. Bezüglich des Weibchen-Anteils der Nachkommen brachten Raubmilben-Weibchen bei Fütterung mitT. urticae- undB. tabaci-Eiern die meisten Weibchen hervor.

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With one table     

Development and population growth of <Emphasis Type="Italic">Stephanitis pyri</Emphasis> (F.) (Heteroptera: Tingidae) at five temperatures

Pear lace bug, Stephanitis pyri (F.) (Heteroptera: Tingidae) is a pest of apple and pear trees and ornamental Rosaceae plants in Mediterranean countries and palearctic region. The aim of this study is to determine the effects of temperatures on S. pyri in the laboratory. Development and fecundity of S. pyri reared on apple leaves (Pyrus malus L.) were investigated at five constant temperatures (20, 23, 26, 29 and 32 ± 1°C) and a 16L:8D photoperiod. Longevity was determined to be 12.6 days at 32°C and 58.7 days at 20°C for females, and 9.7 and 37.7 days for males. Females laid 186.9 eggs per female with the highest number achieved during 28.5 days of oviposition period at 26°C. Female lifetime fecundity was reduced at 32°C (40.0 eggs per female). While the net reproductive rate (R ₀) was highest at 26°C, the intrinsic rate of natural increase (r _m ) was highest at both 26 and 32°C. The mean generation time (G) was estimated to be 27.2–78.4 days at 20 and 32°C, respectively. The longest development times for egg and total nymph stages were obtained as 22.0 and 24.9 days, respectively, at 20°C. S. pyri developed fastest from egg to egg in 24.3 days at 32°C. The lower developmental threshold (T ₀) was 9.7°C and the thermal constant (K) was 517.3 degree-days for S. pyri. Thus, S. pyri is calculated to have 3.8 theoretical generations in Tekirdag. The optimum developmental temperature for S. pyri was 26°C.     

Evaluation of resistance in 14 soybean genotypes to <Emphasis Type="Italic">Tetranychus urticae</Emphasis> (Acari: Tetranychidae)

The effect of 14 soybean genotypes (Sahar, Sari, Williams, Tellar, Hill, Clark, Tms, Dpx, Zane, 032, 033, L₁₇, Ks3494 and I27) on life history and fecundity of two-spotted spider mite (TSSM), Tetranychus urticae Koch, was investigated. All experiments were conducted at 28 ± 1°C, 65 ± 5% r.h. and a photoperiod of L16:D8 h. The highest development time was 8.41 and 8.78 days for male and female on I27, and the lowest value of this period was obtained on Sahar and Ks3494 for male and female, respectively (7.11 and 7.60 days, respectively). The TSSM fecundity varied from 33.62 to 153.82 eggs per female, which was minimum on 032 and maximum on L₁₇. The comparison of TSSM biological parameters on different soybean genotypes and cluster analysis of these parameters demonstrated that Ks3494, 032, Dpx and Sahar were the most resistant genotypes to this pest. An antibiosis process could be, at least in part, the cause of this variation. Knowledge of the extent of susceptibility or resistance of genotypes and biology of a pest on a crop are fundamental components of integrated pest management (IPM) programs for any crop. Implication of these observations in the control of TSSM on soybean is discussed.     

Zur Wirkung von Temperatur und Photoperiode auf die Entwicklung,Ernährung und Eiablage der Raubmilbe Amblyseius swirskii Ath.-Henr. (Acari,Gamasida, Phytoseiidae)

Amblyseius swirskii was reared on immature stages ofTetranychus urticae Koch, under 4 temperature and 3 photoperiod regimes. The raise of temperature produced more rapid development and reduced the adult longevity. The mite feeding capacity and fecundity were positively correlated with temperature. At a photoperiod of 16 h the predator developed quicker but it introduced a considerably lower prey consumption and fecundity.     

Influence of host plant species of Bemisia tabaci (Genn.) (Hom., Aleyrodidae) on some of the biological and ecological characteristics of the entomophagous Serangium parcesetosum Sicard (Col., Coccinellidae)

The entomophagous Serangium parcesetosum Sicard (Col., Coccinellidae) is an effective predator of some whitefly species. However, information on the influence of the preys host plant species on its biological and ecological characteristics is still lacking in the literature. Therefore, the current study focuses on the possible influence of three greenhouse and two field host plant species of Bemisia tabaci (Genn.) (Hom., Aleyrodidae) on the number of eggs laid by S. parcesetosum. In addition, because of the economic importance and widespread planting of cucumber in greenhouses and cotton in the field, these plants were selected for further investigation into the development, mortality, longevity and reproduction of S. parcesetosum at a high temperature in the laboratory. Results showed that S. parcesetosum was able to lay eggs on all five host plant species of B. tabaci, whether greenhouse or field plants. However, among the three greenhouse plant species studied, S. parcesetosum females laid the highest number of eggs on cucumber followed by tomato and then sweet pepper. Of the two field plant species, significantly higher numbers of eggs were laid on tobacco than on cotton. S. parcesetosum could develop either on cucumber or on cotton as preferable host plant species for B. tabaci. There were significant differences in mean developmental duration of larval instars of the same sex between both host plant species; the duration was significantly shorter on cucumber than on cotton. There were no significant differences for mean total developmental duration from egg to adult emergence between both host plant species within the same sex; females showed a mean of 15.9 days and males of 15.1 days on cucumber, while on cotton the means were 17.2 days for females and 16.2 days for males. Total mortality percentage of S. parcesetosum during development from egg to adult stage was lower on cucumber than on cotton, 20.6 and 23.8%, respectively. Longevity of S. parcesetosum varied according to host plant species and sex with a mean of 63.4 days for females and 50.3 days for males on cucumber, and 92.4 days for females and 52.5 days for males on cotton. On cucumber, mean period of oviposition of S. parcesetosum was significantly longer than on cotton. Mean total fecundity was significantly higher on cucumber than on cotton, with means of 97.7 and 31.0 eggs/female, respectively.     

Factors influencing the parasitism of codling moth eggs by Trichogramma cacoeciae March. and T. principium Sug. et Sor. (Hymen. Trichogrammatidae)

Non-choice laboratory experiments were conducted to evaluate the influence of host acceptance, previous rearing host, host age and the contact time between parasitoids and host on the efficacy of Trichogramma cacoeciae Marchal and T. principum Sug. et Sor. against the codling moth Cydia pomonella. The tendency of T. cacoeciae and T. principum females to attack the codling moth was similar to E. kuehniella, and it was not affected by the previous rearing host. T. cacoeciae showed a greater preference for codling moth eggs than T. principum. A high mean number of emerged F₁ progeny was observed when both parasitoids were sequentially reared on codling moths. Codling moth acceptance, the number of parasitized eggs and the number of emerged progeny were higher when younger codling moth eggs were offered. The tendency of female parasitoids to oviposit remained unchanged when the contact time with the host was prolonged. When the contact time was increased, the number of parasitized eggs and emerged offspring was higher. The results showed that the codling moth fertility (egg hatch) was reduced when younger eggs were offered and when the contact time with the parasitoids was increased. T. cacoeciae was more efficient in reducing codling moth fertility. The current study provided essential information necessary to increase the efficiency of T. cacoeciae and T. principum against the codling moth.     

Effect of food,light and host instar on the egg load of the synovigenic endoparasitoid <Emphasis Type="Italic">Venturia canescens</Emphasis> (Hymenoptera: Ichneumonidae)

Laboratory experiments investigated the effect of host instar, light and food on the number of mature eggs in ovaries (egg load) of the synovigenic parasitoid Venturia canescens (Grav.) (Hymenoptera: Ichneumonidae). The wasps that developed from third or fifth instar larvae of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) were exposed to food (honey) or had no food, had access to water or not, and were reared at the photoperiod 16:8 h light:dark or in continuous darkness at 25 ± 1°C, and 60–70% relative humidity. After death, the parasitoids were dissected to remove the reproductive systems, and mature eggs in ovaries were counted. A three-way ANOVA for egg number with host instar, food and light as factors revealed that egg load varied significantly. In addition, some interactions among the three factors were also found to be significant. The maximum average number (215.80 ± 8.51) of mature eggs was found when the parasitoids developed from third instar larvae, were exposed to continuous darkness and fed with honey. In conclusion, host instar, food supplement and photoperiod could have potential for improving biological control efficacy in stores. However, further studies determining the effect of these factors on egg laying behavior and fecundity should be done.     

Untersuchungen über die Eiparasiten (Hym.: Chalcidoidea) der rotgelben Kiefern-BuschhornblattwespeNeodiprion sertifer Geoff. (Hym.: Diprionidae)

IV. Summary 1. Four or five species of egg parasites ofNeodiprion sertifer have been found in central Europe.2.Dipriocampe diprioni is a primary parasite which overwinters as a first instar larva within the host's egg, The larvae complete feeding in early spring and enter an obligatory diapause which lasts until July–August. Under the influence of the parasite, the egg shell of the host turns brownish. The adults emerge from mid-August onward. The univoltine parasite is thus well synchronized with its major host,N. sertifer.3. A second species, or form, ofDipriocampe has been found, the taxonomic status of which is still unresolved. It is here referred to asDipriocampe sp. forma ignorata. Although not yet separable fromD. diprioni morphologically, its biology is quite different. The larvae mature before the winter and the adults emerge in April–May of the following year, being dependent on alternate hosts. This form is exceedingly rare in lowland areas but possibly common at high altitudes. It remains to be seen whether it is a separate species or a polymorphic, non-diapausing form ofD. diprioni. Host eggs attacked byDipriocampe sp.forma ignorata turn blackish.4. Two species ofAchrysocharella have been found,A. ruforum andA. ovulorum. In lowland areas,Achrysocharella spp. attack the eggs ofN. sertifer in a hyperparasitic capacity, developing at the expense of the larvae and pupae ofDipriocampe spp. or of larvae and pupae of their own kind. There are two or three such hyperparasitic generations during the summer, the last entering hibernation before the new eggs ofN. sertifer make their appearance, thus failing to attack them in a primary capacity.In mountainous areas, where the eggs ofN. sertifer appear earlier,Achrysocharella spp. pass the first generation as primary parasites in the sawfly eggs, and the second (summer) generation as hyperparasites of larvae and pupae ofDipriocampe spp. or of larvae and pupae of their own kind.5.Tetrastichus oophagus has been associated with the eggs ofN. sertifer in a few cases only, but has been more common as a parasite of the eggs ofDiprion pini.6. The importance of the egg parasites ofN. sertifer has to date been underestimated. Egg parasitism is apparently density-dependent and can reach high values during, and immediately after, the break-down of the sawfly populations.     

Effect of adult nutrition and insect density on the performance of spotted stem borer, <Emphasis Type="Italic">Chilo partellus</Emphasis> in laboratory cultures

The spotted stem borer, Chilo partellus (Swinhoe) (Lepidoptera: Crambidae) is being successfully reared on artificial diets for screening programmes. Besides quality characteristics of the diet, rearing density and adult nutrition have significant implications on the successful mass multiplication of lepidopterans. The performance of C. partellus moths was assessed on different adult diets (water and sugar solution) and compared with unfed adults. Further, three pairing densities, viz. 2, 5 and 8 pairs/oviposition jar (1177.5 cm³) were compared for their effect on C. partellus longevity and fecundity. In another experiment, different larval densities (100, 150 and 200 neonate larvae/diet jar) were evaluated for their effect on the larval survival. Water-fed moths (both males and females) lived longer (7.32 and 7.26 days, respectively) and showed higher fecundity (307.17 eggs) than the sugar-fed or unfed moths. The latter, however, showed better egg hatchability (76.55%) than the water- or sugar-fed moths (60.45 and 50.59%, respectively). The longevity (5.67 days) and fecundity (258.46 eggs) were significantly greater at pairing density of 2 pairs/jar. The larval survival was higher (58.50%) at rearing density of 100 larvae/jar. The neonate larval release into diet jars was compared with conventional egg release and both modes were no different with respect to larval survival.     

Prey consumption preferences of<Emphasis Type="Italic"> Serangium parcesetosum</Emphasis> Sicard (Col., Coccinelidae) for different prey stages,species and parasitized prey

Serangium parcesetosum Sicard (Col., Coccinellidae) is considered one of the important predators of whiteflies. However, knowledge about its preferences for different prey stages, species and parasitized prey is still lacking in the literature. The present work investigated the preferences of S. parcesetosum for different stages of B. tabaci, different prey species and B. tabaci parasitized by Encarsia formosa Gahan (Hym., Aphelinidae) by prey consumption at different temperatures in the laboratory. Results showed that L₂ and L₄ predatory instars of S. parcesetosum preferred puparia to nymphs and eggs of Bemisia tabaci (Genn.) (Hom., Aleyrodidae). The mean daily prey consumption was 5.1–9.0, 4.5–6.2 and 3.6–4.3 by L₂ and 6.4–9.7, 5.5–8.5 and 2.5–7.5 by L₄ for puparia, nymphs and eggs, respectively. Adult females, however, indicated a significantly greater preference for both puparia and nymphs, consuming a daily mean of 6.4–7.5 puparia and 5.1–6.7 nymphs, but only 3.0–4.7 eggs. At 18 and 30 °C, all S. parcesetosum stages tested significantly preferred B. tabaci and Trialeurodes vaporariorum Westwood (Hom., Aleyrodidae) over the other three prey species offered. At both temperatures, all predatory stages preferred B. tabaci to T. vaporariorum, the L₂ instar at 18 °C, showing significantly more preference for B. tabaci than T. vaporariorum. In contrast, very few individuals were consumed from Aphis gossypii Glover (Hom., Aphididae), Frankliniella occidentalis (Pergande) (Thys., Thripidae) and Tetranychus urticae Koch (Acari, Tetranychidae). At 18 °C, a daily mean of 7.5–8.0, 6.6–9.0 and 6.7–8.1 B. tabaci as well as 5.3–6.4, 5.4–7.8 and 5.6–6.3 T. vaporariorum was consumed by L_2, L₄ and adult females, respectively, while at 30 °C, L₂, L₄ and adult females consumed a mean of 9.3, 8.8–9.7 and 8.3–9.7 B. tabaci/day as well as 8.3–9.0, 7.8–9.1 and 5.5–8.4 T. vaporariorum/day, respectively. S. parcesetosum L₂ and L₄ instars as well as adult females and males at both studied temperatures showed a significant tendency to avoid B. tabaci puparia after 5 days of parasitism by E. formosa and preferred to feed on unparasitized whiteflies. At 18 °C, the mean daily consumption was 8.7 and 0.2 (L₂), 11.1 and 0.6 (L₄), 12.1 and 1.0 () as well as 10.5 and 0.2 (), while at 30 °C the means were 15.9 and 0.5 (L₂), 19.8 and 1.0 (L₄), 18.9 and 1.2 () as well as 17.4 and 0.6 () from unparasitized and parasitized B. tabaci puparia, respectively.This paper is gratefully dedicated to Prof. Dr. W Schwenke on his 83rd birthday, 22 March 2004     

Über die Wirkung der Photoperiode auf den Schlüpfrhythmus der Falter vonSpodoptera littoralis Boisd. (Lep., Noctuidae)

Effect of photoperiod on emergence rhythm of adult Spodoptera littoralis Bolsd. (Lep., Noctuidae) Adult emergence ofSpodoptera littoralis Boisd. from pupae, reared since the egg stage at different photoperiodic conditions was studied. The photoperiods tested were: 8 hours light and 16 hours darkness (8L:16D), 10L:14D, 12L:12D, 16L:8D together with continuous light (24L:0D) and complete darkness (0L:24D), In the shortest day-length (8L:16D) all adults emerged at night, while in the longest one (16L:8D) 40%) only emerged during the dark period of the day. In the intermediate photoperiods, the percentage of the light-emerging moths increased with the prolongation of the photophase, thus at the photoperiods of 10L:14D, 12L:12D and 14L:10D such percentages were 9, 13 and 28 respectively. In cases where insects were reared in continuous light (24L:0D) or complete darkness (0L:24D), emergence took place at random and the rhythmicity disappeared. By transferring newly formed pupae, reared in complete darkness, to photoperiod of 12L:12D, adults emerged mainly during the dark phase (90%). On the other hand, when pupae reared in 12L:12D were transferred to complete darkness emergence took place at random (arrhythmic emergence). This indicates that the pupal stage is the sensitive one to phase regulation and not the larval stage.     

Effect of soybean cultivar on life history parameters of <Emphasis Type="Italic">Tetranychus urticae</Emphasis> Koch (Acari: Tetranychidae)

The two-spotted spider mite, Tetranychus urticae Koch, is a very polyphagous pest with a worldwide distribution. In order to appraise population growth parameters of this pest, samples of two-spotted spider mites were taken from soybean (Glycine max) fields of Moghan region, Iran in June 2007 and are reared on bean plants var. Derakhshan (Phaseolus vulgaris) in a growth chamber. The life table parameters of this pest were calculated on three commercial soybean cultivars (Zane, Hach, and L17) and one hybrid (Hob × Will) at 25 ± 1°C, 60 ± 10%RH, and 16 h photophase. The developmental times of immature stages varied from 9.69 on Hach to 9.82 days on L17, whereas the immature survival was 57–79% on Hach and Hob × Will, respectively. On average, there were 65.5, 40.8, 38.8 and 34 eggs produced per female on L17, Hach, Hob × Will and Zane, respectively. The intrinsic rate of natural increase (r _m ) for T. urticae on Hob × Will was the highest, whereas the values for r _m ranged from 0.211 (females/female/day) on Zane to 0.292 on Hob × Will. Also, jackknife values of other life table parameters such as net reproductive rate (R ₀), generation times (T), doubling time (DT), and finite rate of increase (λ) on these cultivars were estimated. Overall, the two-spotted spider mite indicated a better performance on Hob × Will than on the other soybean cultivars.     

Potential fecundity of the bamboo gall maker,Aiolomorphus rhopaloides (Hymenoptera: Eurytomidae), and its inquiline,Diomorus aiolomorphi (Hymenoptera: Torymidae), in relation to gall size and body size

I examined the adult potential fecundity of the bamboo gall maker,Aiolomorphus rhopaloides Walker (Hymenoptera: Eurytomidae), and its inquiline,Diomorus aiolomorphi Kamijo (Hymenoptera: Torymidae) by dissection just after emergence, and at death after rearing. Emerging females ofA. rhopaloides hadca. 80 mature eggs in their ovaries. The number of eggs at emergence and after death at rearing was not significantly different. However, emerging females ofD. aiolomorphi had no eggs in their ovaries but hadca 20 eggs at death after rearing. These results suggest thatA. rhopaloides is pro-ovigenic andD. aiolomorphi is synovigenic. Female body sizes of both species were positively correlated with the size of galls from which each emerged. Number of eggs in each species was also correlated with female body size, suggesting that gall size might be a good predictor of potential fecundity. This study was supported in part by a Grant-in-Aid for scientific Research (No. 11460068) from the Ministry of Education, Science, Sports, and Culture, Japan.     

Zur Massenvermehrung des Schlehenspinners,Orgyia antiqua (L.) 1971/72 in Bayern

Summary On an outbreak of Orgyia antiqua L. (Lepid., Lymantriidae) at Memmingen, Bavaria, 1972.The number of larvae ofO. antiqua on pine trees at Memmingen reached its high level during autumn 1971. About 350 ha mainly the old trees were infested. The number of egg masses per stem was more than 42 in max. with an average of 205 eggs per egg mass (n = 40). The percentage of hatching was found to be 74,5%. The rest of the eggs was mainly parasitized byTelenomus dalmanni (Ratz.). The pest had only one generation. The old larvae were infected with a virus disease and a great part of pupae was killed by fungi. These two diseases were the main factors in regulating the population ofO. antiqua.     

Host-tree conditions affecting the oviposition activities of the woodwasp,Sirex nitobei Matsumura (hymenoptera: Siricidae)

Experiments were conducted to elucidate how the oviposition activities ofSirex nitobei Matsumura could be affected by different conditions of the host trees, using logs from felled healthy trees and the dead and living trees ofPinus densiflora Sieb. et Zucc. According to days elapsed after tree-felling, the proportions of oviposition defined as the proportion of eggs laid to the potential fecundity of a female during her lifetime, could be divided arbitrarily into three groups. The proportions of oviposition on the logs within 0–3 days after felling,i.e fresh logs, varied greatly from log to log, and about half of female adults showed proportions of oviposition under 50% (mean ±SD: 39±32%). However, all the females that oviposited on the logs 4–24 days after felling,i.e. intermediate logs, invariably showed proportions of oviposition over 50% (88±1.5%). On the other hand, proportions of oviposition in most of the females that oviposited on the logs over 25 days after felling,i.e. old logs, were less than 50% (26±17%). The proportions of oviposition were significantly different between intermediate logs and old logs. The mean proportion of oviposition on living trees and that for dead trees were 45 and 58%, respectively. Thus,S. nitobei in the field would exhibit its preference for weakened trees ofP. densiflora as oviposition sites, as it did for the logs 4–24 days after felling in this study.     

Efficacy assessment of some<Emphasis Type="Italic"> Trichogramma</Emphasis> species (Hymenoptera: Trichogrammatidae) in controlling the potato tuber moth<Emphasis Type="Italic"> Phthorimaea operculella</Emphasis> Zell. (Lepidoptera: Gelechiidae)

Laboratory studies were conducted to assess several life-history characteristics of three Trichogramma species—T. cacoeciae, T. evanescens, and T. principium—reared on potato tuber moth eggs. The effects of host age, parasitoid age, and different temperatures on the mean number of parasitized eggs and the percentage of emerged progeny were determined. The age of both Trichogramma and host eggs significantly affected the number of eggs parasitized by the wasps, but did not affect the percentage of parasitoids emerging from parasitized eggs. No intraspecific differences for potato tuber moth eggs were found among the tested Trichogramma species. However, T. principium proved to be more effective than T. cacoeciae and T. evanescens in parasitizing host eggs at high temperatures (>33 °C). Trichogramma significantly decreased the number of potato tuber moth F₁ emerged progeny when they were released with moths in small cages either over potatoes or potato seedlings.     

Cannibalism and interspecific predation of the phytoseiid mite,<Emphasis Type="Italic"> Amblyseius swirskii</Emphasis>

A laboratory study revealed that females of the phytoseiid mite, Amblyseius swirskii Athias-Henriot, fed on protonymphs of their own species or of other predatory mites i.e. Agistemus exsertus Gonzales and Euseius scutalis Athias-Henriot exhibited a marked decline in their fecundity and a shortening in their longevity. Moreover, the rate of predation was also reduced. When A. swirskii females were fed on nymphs of the two-spotted spider mite Tetranychus urticae Koch after having been fed previously on protonymphs of either A. swirskii or A. exsertus increases in the rates of oviposition and consumption were observed, although these rates were lower than those of conspecific females reared continuously on the two-spotted spider mite only.     

Trichogramma evanescens West. (Hym., Trichogrammatidae) as an egg parasitoid of Grape MothLobesia botrana (Den. & Schiff.) (Lep., Tortricidae)

The adaptation of the primary internal parasitoid,Trichogramma evanescens (Westw.), as an egg parasitoid ofLobesia botrana (Den. & Schiff.) was the first report in Alexandria region, Egypt. The life-span of this parasitoid on eggs ofL. botrana andSitotroga cerealella Ol. was investigated. The duration from egg to adult, longevity of adult stage, sex-ratio and total life cycle each of the two hosts were recorded. The ovipositional periods of mated females ofT. evanescens on egg ofL. botrana at 27±2c^o and 75±2% R.H. were studied. Also, percentages of parasitism byT. evanescens ranged from 22%–64% on the eggs ofL. botrana. Therefore, this parasitoid was very efficient as a biocontrol agent against the most serious grape pestL. botrana in Egypt.     

Effects of repeated and delayed exposure to codling moth eggs on reproduction of Trichogramma cacoeciae and T. principium (Hymenoptera: Trichogrammatidae) females

Laboratory experiments were conducted to evaluate the influence of repeated and delayed exposure to fresh codling moth eggs on the parasitism of Trichogramma cacoeciae Marchal and T. principium Sug. et Sor. The percentage survival of T. cacoeciae and T. principium females significantly declined as the number of exposure times increased (or as the females became older). The highest mean number of parasitized eggs and F₁ progeny were recorded during the first day of exposure, after which they declined. However, the percentage mortality of parasitized eggs of T. cacoeciae and T. principium was negatively correlated with repeated exposure. When the exposure of T. cacoeciae and T. principium females to host eggs was delayed for 3 days after emergence, the percentage of oviposited females was not affected; however, the mean number of parasitized eggs, F₁ individuals and the percentage mortality declined significantly. The current study provided essential information necessary to determine the optimal timing of parasitoid releases to increase the efficiency of T. cacoeciae and T. principium against codling moth.