Selection of suitable trichogramma strains to control the codling mothCydia pomonella and the two summer fruit tortrix mothsAdoxophyes orana,Pandemis heparana [Lep.: Tortricidae]

Simple laboratory methods to select candidateTrichogramma strains for use in biological control were tried. 17 strains were screened for their suitability against the codling mothCydia pomonella L. as well as the 2 summer fruit tortrix mothsAdoxophyes orana F.R. andPandemis heparana Schiff. In one set of experiments, the capacity ofTrichogramma to parasitize each of these target pests was examined, in another set, the preference ofTrichogramma to contact and parasitize the target pests compared to the standard mass rearing hostSitotroga cerealella was assessed in choice experiments. A strain ofTrichogramma dendrolimi from the People's Republic of China was found to have the highest fecundity with all the 4 hosts tested. In choice experiments, however, this strain was shown to have a near equal preference between the target tortrix pestsC. pomonella, A. orana and the replacement hostS. cerealella. 11 localTrichogramma strains collected from fruit orchards and vineyards in different locations in the Federal Republic of Germany were reared separately. Four of these local strains, one identified asT. embryophagum, showed clear preference to the tortrix pestsC. pomonella andA. orana compared toS. cerealella. The preference of one of these strains was particularly strong and amounted to a near total rejection ofS. cerealella eggs in the presence of any of the 2 tortrix pests. The remaining 12 strains had weaker parasitization capacity and/or less preference to the target pests. Four of the strains tested in these experiments, includingT. dendrolimi andT. embryophagum, were mass reared and released in apple orchards between 1984 and 1986. The results of these field experiments are planned to be published in this journal. Mit Unterstützung der Deutschen Forschungsgemeinschaft.     

Releases of Trichogramma platneri (Hymenoptera: Trichogrammatidae) in Apple Orchards under a Sterile Codling Moth Release Program

Based on the premise that augmented host numbers may help multiply and support parasitoid populations, the egg parasitoid Trichogramma platneri Nargarkatti was released in apple orchards which were participating in a sterile codling moth, Cydia pomonella (L.), release program. Nonviable eggs resulting from matings involving at least one sterile codling moth partner can be successfully parasitized by T. platneri. Grain moth-reared, as well as codling moth-reared, T. platneri were released either in the spring or in the spring and summer oviposition period(s) of wild codling moth. Sentinel codling moth eggs were hung weekly, for 3-day periods, from May until September to determine fluctuations in T. platneri populations both during and between releases. Low numbers of wild or nonviable codling moth eggs or other susceptible host eggs resulted in sufficient eggs to maintain low spring- or summer-introduced T. platneri populations. T. platneri reduced codling moth damage in trees in which the Trichogramma were released.     

Parasitism of the apple maggot,Rhagoletis pomonella,infesting hawthorns in Washington

Five species of larval parasitoids were reared fromRhagoletis pomonella (Walsh) infested fruit of hawthorn,Crataegus, collected from several locations in southwest Washington over a four year period. A braconid,Biosteres melleus (Gahan), parasitized larvae infesting fruits of a native hawthorn species,Crataegus douglasii Lindl. Another braconid,Opius downesi Gahan, emerged exclusively fromR. pomonella pupae reared from fruits of an introduced species of hawthorn,Crataegus monogyna Jacq. A pteromalid,Pteromalus sp., and two eulophids,Tetrastichus spp., attackedR. pomonella larvae infesting fruits of both hawthorn species. No parasitoids emerged from a total of 4385 pupae reared from apple. Percent parasitism ofR. pomonella was higher inC. monogyna compared toC. douglasii fruits. The highest average levels of parasitism ofR. pomonella inC. monogyna andC. douglasii fruits were 90% and 23% respectively. The kinds of parasitoids, their relative abundances and timing of parasitization on the two hawthorns was related to differences in fruit ripening patterns and its effect on the development ofR. pomonella on these two hosts. Parasitization ofR. pomonella byTetrastichus spp. is a new host record. The detection of these species andPteromalus sp. in southwest Washington are the first records of ectoparasitoids attacking this tephritid.     

Two new species ofTrichogramma [Hym.: Trichogrammatidae] from the U.S.A.

Two new species ofTrichogramma from the U.S.A. are described.T. parkeri sp. n., a morphologically distinct species, was reared from an egg ofHeliothis zea (Boddie), whileT. platneri sp. n. which is morphologically indistinguishable fromT. minutum Riley, was reared from eggs ofCydia pomonella (L.). Reproductive incompatibility ofT. platneri andT. minutum is discussed.     

The size of the female and quality assessment of mass-rearedTrichogramma spp.

The relationship between the index of female's size, hind tibia length (HTL), and selected fitness parameters used in quality assessment of mass-rearedTrichogramma spp. (Hymenoptera, Trichogrammatidae) was investigated. The studied fitness parameters were: the number of mature eggs present in the ovaries of females 0–2 hours, as well as 1, 2 and 3 days old, lifetime fecundity, fecundity during a 24 h period, longevity in the presence and absence of the factitious host (Ephestia kuehniella Zeller) and locomotor activity. The relationship between HTL and fitness parameters was analysed in 7 strains ofTrichogramma spp. (Trichogramma dendrolimi Matsumura,T. evanecens Westwood,T. maidis Pinturea et Voegelé andT. ostriniae Pang et Chen) using linear correlation. No significant relationship was found between HTL and egg complement, fecundity, longevity and locomotor activity. The results indicate that HTL used as an index of female's size is not suitable for quality assessment ofTrichogramma reared onE. kuehnieIla.     

Trichogramma platneri (Hym.: Trichogrammatidae): Host choices between viable and nonviable codling moth,Cydia pomonella,and three-lined leafroller,Pandemis limitata (Lep.: Tortricidae) eggs

In laboratory host-preference studies,Trichogramma platneri Nagarkatti (Hym.: Trichogrammatidae) females, reared on viable codling moth,Cydia pomonella (L.) (Lep.: Tortricidae) eggs, parasitized significantly more viable than nonviable codling moth eggs produced by cobalt 60 irradiated adults. This ovipositional preference was maintained when competition increased per host egg. Similarly, one, three and fiveT. platneri females consistently oviposited more eggs into viable versus nonviable host eggs. A single femaleT. platneri parasitized a similar number of viableC. pomonella and three-lined leafroller,Pandemis limitata (Robinson) (Lep.: Tortricidae) eggs. However, as the number of females per host eggs increased, a significantly larger number of codling moth versus leafroller eggs were parasitized. One, three and fiveTrichogramma females parasitized significantly moreP. limitata versus nonviableC. pomonella eggs. NonviableC. pomonella eggs deflated to less than 25% of their original volume in four and ten days when held under dry and humid conditions respectively. The blackened prepupal stage of the parasitoid generally occurred in the nonviableC. pomonella eggs four days post-parasitization whereas the parasitized viable eggs blackened zero to one day earlier. Incubation under dry or humid conditions did not appear to influence the number of parasitized eggs that were able to blacken and show evidence of parasitism. Summerland Research Centre Contribution No. 938.     

Possible mechanisms of the difference in sensitivity of caterpillars of Adoxophyes orana and Laspeyresia pomonella to diflubenzuron

The sensitivity to diflubenzuron varies considerably among species of caterpillars that cause damage to fruit. The cause of this difference in sensitivity was studied in larvae of Adoxophyes orana F. R., a not so sensitive species and Laspeyresia pomonella L., a species that is highly sensitive. Results indicate that the ingestion pattern of diflubenzuron and significance of chitin synthesis to these species are of importance for explaining the difference. It is uncertain whether there is a difference in the affinity of the sites of action of A. orana and L. pomonella for diflubenzuron.

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Résumé La sensibilité au diflubenzuron varie considérablement suivant les espèces de lépidoptères qui provoquent des dégâts aux fruits. La cause de ces différences de sensibilité a été étudiée chez les larves d'Adoxophyes orana, une espèce peu sensible, et de Laspeyresia pomonella qui est très sensible. Les résultats soulignent l'importance du processus d'ingestion du diflubenzuron et de la synthèse de la chitine pour expliquer cette différence. Il n'est pas sûr qu'il y ait une différence d'affinité au diflubenzuron des cibles de A. orana et L. pomonella.

     

Antifungals: Mold control and safe levels in artificial media forTrichogramma [Hymenoptera: Trichogrammatidae]

Ten chemicals known to be fungicides are tested in artificial media forTrichogramma dendrolimi Matsu. [Hymenoptera: Trichogrammatidae]. Tests are performed in France by using artificial host egg capsules. Most of the fungicides cannot control fungus or are toxic forTrichogramma at effective levels. Geneticin, Amphotericin B and Nystatin, used at proper levels are able to control molds efficiently without modifyingTrichogramma development. These antifungals are also tested in actual conditions of mass production, in Guangzhou (China).      

Spatial discrimination of pheromones and behavioural antagonists by the tortricid moths Cydia pomonella and Adoxophyes orana

Male moths responding to their species-specific sex pheromone, may cease their upwind flight when pheromone components of sympatric species are added to the mixture. The interspecific interaction between the pheromone response of the tortricid moths Cydia pomonella and Adoxophyes orana was investigated in field-trapping and wind-tunnel studies. Addition of the A. orana pheromone [(Z9)-tetradecenylacetate and (Z11)-tetradecenylacetate] to a source containing the C. pomonella pheromone [(E8, E10)-dodecadienol] resulted in a significant inhibition of attraction by male C. pomonella. It is demonstrated that this behavioural antagonist for C. pomonella must be emitted from the same point source to induce this inhibitory effect. A spatial separation of the two interspecific pheromones (at 14 cm, 5 cm and 0.5 cm crosswind) restored the attraction of the conspecific pheromone for male C. pomonella. In contrast to C. pomonella, male A. orana were not inhibited by point sources releasing both the C. pomonella and A. orana pheromone. We suggest that the discrepancy in the interspecific pheromone interaction between these two tortricids can be explained if we consider the evolutionary ecology of interspecific pheromone communication in C. pomonella and A. orana. Accepted: 18 July 1999     

Differential response of fourTrichogramma species to low temperatures for short term storage

Differential response was noticed when 4 species ofTrichogramma egg parasitoids were stored at 2°, 5° and 10°C for 7 to 49 days. Pupal stage was found to be most appropriate for storage. Emergence ofTrichogramma achaeae Nagaraja and Nagarkatti andTrichogrammatoidea eldanae Viggiani was greater in comparison toTrichogramma chilonis Ishii andTrichogramma japonicum Ashmead at all 3 temperature regimes. Fecundity and longevity declined drastically after storage of 14 days at 2° and 5°C and 21 days at 10°C, when removed to room temperature. 10°C was found to be the best temperature for storage up to 49 days. Contribution No. 51004 of Biological Control Centre (NCIPM), Bangalore.     

IndigenousTrichogramma (Hym.: Trichogrammatidae) parasitizing eggs ofRhopobota naevana (Lep.: Tortricidae) on cranberries in British Columbia

Two indigenous species ofTrichogramma were reared from natural populations of the blackheaded fireworm,Rhopobota naevana (Hübner) infesting cranberries in British Columbia, Canada. One was identified asTrichogramma sp. nr.sibericum Sorokina and the other wasTrichogramma minutum Riley. Percentage of parasitized hosts increased during the season in an abandoned field, but decreased in a commercial field where pesticides were used. The potential ofTrichogramma as a biological control agent against the fireworm is discussed.     

Are egg parasitoids of the genus Trichogramma (Hymenoptera: Trichogrammatidae) promising biological control agents for regulating the invasive Box tree pyralid,Cydalima perspectalis (Lepidoptera: Crambidae)?

The Box tree pyralid, Cydalima perspectalis Walker (Lepidoptera: Crambidae), is an invasive species in Europe, not yet regulated by natural enemies. It is highly destructive to ornamental and native Buxus due to defoliation by larval feeding. The ability of eight Trichogramma species (T. brassicae Bezdenko, T. bourarachae Pintureau & Babault, T. cacoeciae Marchal, T. cordubensis Vargas & Cabello, T. dendrolimi Matsumura, T. evanescens Westwood, T. nerudai Pintureau & Gerding and T. pintoi Voegele) to parasitise and locate eggs of C. perspectalis was assessed in the laboratory. In direct observation tests, all species started to examine and oviposit into exposed eggs. Resulting egg parasitism was low and ranged between 4% and 20% for most of the parasitoid species after three days of exposure. Only T. dendrolimi parasitised significantly more host eggs with parasitism rates above 40%. On average, two to three progeny emerged from one host egg and the resulting sex ratio was female-biased, indicating suitability of the target host for progeny production. In subsequent cage tests on potted Buxus plants, again T. dendrolimi was the most efficient species in locating host eggs on foliage. We conclude that C. perspectalis eggs are attractive to various Trichogramma species. T. pintoi had the highest number of egg encounters and active females. T. dendrolimi females were most able to locate host eggs and to oviposit and produce successfully on them. Nonetheless, further study is needed to clarify the suspected role of potentially egg defensive mechanisms that may impede higher parasitisation in C. perspectalis.     

Natural occurrence of Wolbachia-infected and uninfected Trichogramma species in tomato fields in Portugal

Minute egg parasitoids of the genus Trichogramma (Hymenoptera; Trichogrammatidae) are promising candidates for biological control of lepidopteran pests in tomato in Portugal. This certainly applies to native Trichogramma strains that have thelytokous reproduction, i.e., produce only daughters. In Trichogramma wasps, thelytoky is mostly induced by the intracellular bacterium Wolbachia. In this study, we carried out a field survey of native Trichogramma species in four locations in Ribatejo, the main processing tomato region of Portugal, and determined the prevalence of Wolbachia in those species. Five Trichogramma species were found to emerge from lepidopteran eggs collected in the field, namely Trichogramma bourarache, Trichogramma cordubensis, Trichogramma evanescens, Trichogramma pintoi, and Trichogramma turkestanica. T. evanescens and T. pintoi were by far the dominating species representing, respectively, 64.9 and 26.4% of the trichogrammatids collected. Total natural parasitism rates of the collected lepidopteran eggs by Trichogramma wasps ranged from 28.2 to 64.6%. Three Trichogramma species were found to be infected with Wolbachia, namely T. cordubensis, T. evanescens, and T. turkestanica. All the wasp broods belonging to T. cordubensis were infected, whereas low infection rates were found in T. evanescens (0.9% of the broods) and T. turkestanica (4.5% of the broods). The latter represents the first record of a Wolbachia infection in T. turkestanica. Sequencing of the Wolbachia surface protein, wsp, revealed this Wolbachia infection to be related to other Wolbachia infections in Trichogramma wasps. As Wolbachia-infected thelytokous strains exist for T. evanescens, the most abundant Trichogramma species naturally occurring in the tomato fields of the Ribatejo region, this species offers interesting and powerful options for biological control of lepidopteran pests in processing tomato in this region.     

繁殖寄主对赤眼蜂羧酸酯酶和乙酰胆碱酯酶的影响

通过测定赤眼蜂Trichogramma羧酸酯酶和乙酰胆碱酯酶的活性、对底物的亲和力以及对抑制剂的敏感度研究了繁殖寄主对松毛虫赤眼蜂T.dendrolimi和螟黄赤眼蜂T.chilonis的影响。柞蚕卵和米蛾卵繁殖的赤眼蜂羧酸酯酶对底物的亲和力有不同程度的影响,柞蚕卵繁殖的赤眼蜂羧酸酯酶对α-乙酸萘酯或β-乙酸萘酯的亲和力最高是米蛾卵的2倍以上。繁殖寄主对乙酰胆碱酯酶对底物亲和力没有明显的影响。米蛾卵繁殖的松毛虫赤眼蜂羧酸酯酶活性明显高于柞蚕卵繁殖的种群,而米蛾卵繁殖的螟黄赤眼蜂种群羧酸酯酶的活性明显低于柞蚕卵繁殖的种群。用柞蚕卵繁殖的松毛虫赤眼蜂种群对对氧磷的敏感度明显低于米蛾卵繁殖的种群,而增效磷则正好相反。繁殖寄主对松毛虫赤眼蜂吉林种群乙酰胆碱酯酶对DDVP和毒扁豆碱的敏感度没有明显的影响,而在松毛虫赤眼蜂广东种群和螟黄赤眼蜂中,柞蚕卵繁殖的种群乙酰胆碱酯酶对DDVP和毒扁豆碱的敏感度明显低于米蛾卵繁殖的种群。     

The influence of host's age on the selectivity of parasitism and fecundity ofTrichogramma

Laboratory studies showed that ♀♀ ofTrichogramma embryophagum (Hartig) andT. semblidis (Aurivillius) when offered an alternative of young and old eggs of the grain moth,Sitotroga cerealella Oliv., prefer ovipositing into young eggs. The fecundity of ♀♀ that are simultaneously offered both young and old eggs was lower in comparison to ♀♀ offered only young eggs (inspite of the fact that in both variants young eggs were in excess). The results suggest that old eggs can inhibit the oviposition of some species ofTrichogramma.      

Biological Control of Postharvest Diseases of Apple and Pear under Semi-commercial and Commercial Conditions Using Three Saprophytic Yeasts

The yeastsCryptococcus laurentii(strain HRA5),Cryptococcus infirmominiatus(strain YY6), andRhodotorula glutinis(strain HRB6) were tested as biocontrol agents of postharvest diseases of apple and pear in semi-commercial and commercial trials. The yeasts effectively controlled decay when applied in a drench or line spray. The yeasts were not adversely affected when treated fruits were stored in a controlled atmosphere consisting of 1% oxygen and 99% nitrogen. In a commercial trial, the most effective treatments for control of blue mold of pear were a combination ofC. laurentiiandC. infirmo-miniatus(91% control) and the commercially recommended high rate (528 μg/ml) of thiabendazole (88% control). In the commercial apple trial, the most effective treatments for blue mold wereC. infirmo-miniatuscombined with 264 μg/ml thiabendazole (91% control),C. infirmo-miniatuscombined withC. laurentii(84% control), and thiabendazole alone at 528 μg/ml (79% control). The combination ofC. laurentiiwith 264 μg/ml of thiabendazole was significantly more effective for control of blue mold on pear than thiabendazole at 528 μg/ml whenever any thiabendazole-resistant spores were present in the inoculum.     

Der Einfluss des Wirtes in der Massenzucht auf die Qualität des EiparasitenTrichogramma evanescens bei der Bekämpfung des Maiszünslers,Ostrinia nubilalis

Zusammenfassung In vier Feldversuchen wurde die Wirksamkeit eines an den Maiszünsler besonders angepassten Stammes vonTrichogramma evanescens Westw. bei der Bek?mpfung des MaiszünslersOstrinia nubilalis Hübner geprüft. Die Parasiten wurden entweder auf Eiern der GetreidemotteSitotroga cerealella (Oliv.) oder auf Eiern der MehlmotteEphestia kuehniella Zell. gezüchtet. Die Freilassung erfolgte in den Versuchsparzellen durch Anbringen von Eikarten mit jeweils etwa 1000 parasitierten Wirtseiern an Bl?ttern von Maispflanzen in Abst?nden von 14 Metern. VierTrichogramma-Freilassungen in w?chentlichen Abst?nden mit jeweils 45000 Parasiten pro Hektar ergaben hohe Parasitierungsraten bei denO. nubilalis-Eiern und starke Verminderungen des Larvenbefalls. In den Parzellen, in denen aufS. cerealella-Eiern gezüchtete Parasiten freigelassen wurden, lagen die Parasitierungsraten zwischen 81,7 und 82,3% im Vergleich zu 63,0 und 84,3% bei den aufE. kuehniella gezüchteten Trichogrammen. Die Verminderung des bei der Ernte festgestelltenO. nubilalis-Larvenbefalls im Vergleich zur unbehandelten Kontrolle lag bei den aufS. cerealella gezüchteten Parasiten zwischen 75,5 und 94,8% verglichen mit 77,6 und 89,9% bei den aufE. kuehniella gezüchteten Tieren. Es gab somit keine signifikanten Unterschiede zwischen den beiden getestetenTrichogramma-St?mmen.

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Summary The effectiveness of a strain ofTrichogramma evanescens Westw. especially adapted to the European corn borerOstrinia nubilalis Hübner was examined in 4 field experiments. The parasites were reared on either the Angoumois grain mothSitotroga cerealella (Oliv.) or the Mediterranean flour mothEphestia kuehniella Zell. and were released in separate experimental plots by attaching egg cards, each containing about 1000 parasitized host eggs, to corn leaves at distances of 14 meters in the field. FourTrichogramma treatments at 1 week intervals using 45000 parasites per hectar per treatment resulted in high parasitization rates ofO. nubilalis-eggs and large reductions in larval damage. In experimental plots whereT. evanescens, reared onS. cerealella-eggs, were released, the parasitization rates ofO. nubilalis-eggs varied between 81,7 and 82,3%, compared with 63,0 and 84,3% forT. evanescens reared onE. kuehniella. The reduction inO. nubilalis larval infestation at the harvest in the treated plots, compared to untreated controls varied between 75,5 and 94,8% forT. evanescens that was reared onS. cerealella, compared with 77,6 and 89,8% forT. evanescens that was reared onE. kuehniella. There were no significant differences in efficiency between the two tested methods of rearingTrichogramma.

     

Efficacy Assessment Of Trichogramma Evanescens And T. Embryophagum ( Bdhym.: Trichogrammatidae), For Control Of Stored Products Moth Pests In Bulk Wheat

The potential ofTrichogramma evanescens Westwood andT. embryophagum Quednau to controlEphestia kuehniella andE. elutella was evaluated under laboratory conditions. BothTrichogramma species parasitised eggs of the twoEphestia spp. in bulk wheat at 1, 2 and 5 cm depth. The release ofT. evanescens was more effective than that ofT. embryophagum resulting in higher rates of parasitism, predation and parasitoid induced mortality. At 17?C and 26?C, the mortality ofEphestia due to the release ofT. evanescens was 67, 78% and ofT. embryophagum 27 and 38%, respectively. The difference in host finding efficiency between the two species was large, at 5 cm depth and 26?C,T. evanescens parasitised about four times more host eggs compared to T.embryophagum.     

Clavispora opuntiae and other yeasts associated with the mothSigelgaita sp. in the cactusPilosocereus arrabidae of Rio de Janeiro,Brazil

Summary Clavispora opuntiae was the prevalent yeast associated with the feeding sites ofSigelgaita sp. larvae in the cactusPilosocereus arrabidae. Also associated with this habitat wereCandida sonorensis, Pichia cactophila, Pichia barkeri, Candida sp. A,Geotrichum sp.,Geotrichum sericeum and the yeast like organismsPrototheca zopfii andAcremonium sp. Atypical yeast biotypes that may represent new species ofPichia, Sporopachydermia andCandida were isolated. Mating types ofClavispora opuntiae were at a ratio 70 h⁺ to 3 h^- and reduced levels of sporulation suggested low pressure for sexual reproduction in this habitat.Sigelgaita sp. probably was not an important vector forClavispora opuntiae because it was not isolated from an adult or eggs of this moth.     

Control efficacy of Bacillus thuringiensis and a new granulovirus isolate against Cydia pomonella in orchards

Abstract

Codling moth, Cydia pomonella, is one of the most serious pests of apple and pear worldwide. This study evaluates the efficacies of a granulovirus, a Bacillus thuringiensis (Bt) strain and their combination in the control of C. pomonella in China. A Cydia pomonella granulovirus (CpGV) was isolated from C. pomonella cadavers in an orchard in Gansu, China. Droplet-feeding bioassays showed the median lethal concentration (LC₅₀) of this CpGV isolate (CpGV-C1) against the third instar C. pomonella larvae was 770 OBs µl^?1. The LC₅₀ values of Bt C-33 and kurstaki HD-1 against the third instar larvae were 26.3 µg ml^?1 and 15.7 µg ml^?1, respectively. Field tests indicated the control efficacies of CpGV-C1 and the combination of CpGV-C1 and Bt against C. pomonella larvae in apple orchards were similar to that of beta-cypermethrin. Our data demonstrated that the combination of CpGV and Bt might effectively protect apple fruits from the damage of C. pomonella larvae and had the potential to be developed as a low-cost, highly effective insecticide.