Effect of larval selection with two bioinsecticides on susceptibility levels and reproductive capacity ofAedes aegypti (L.)

Two bacterial insecticides,Bacillus thuringiensis H-14 andB. sphaericus 1593 were evaluated for larvicidal potency against mosquito larvae ofAedes aegypti. LC₅₀ values showed thatB.thuringiensis H-14 (4×10⁵ spores/ml) had a higher pathogenicity against fourth larval instars ofA. aegypti thanB. sphaericus (3.1×10⁶ spores/ml) by about 7.75 times. Larval selection with LC₉₀ of both pathogens for 8 successive generations caused a decrease in the susceptibility levels of selected strains ofA. aegypti as compared with the original strain. Moreover, the results indicated that the effect of larval selection with the above bioinsecticides led to an obvious reduction in the egg production and hatchability of eggs produced by mosquito adults that developed from surviving larvae.     

Activity ofBacillus thuringiensis Berl. on the lesser cotton leafwormSpodoptera exigua Hbn. (Lep., Noctuidae) in corn and sunflower cultivations in Egypt

Field applications usingBacillus thuringiensis (Dipel 2 X) againstSpodoptera exigua infesting corn and sunflower cultivations were carried out in two different localities in Egypt. The percentage of infested corn plants decreased to 2.5%, seven days after treatment with Dipel 2x, (250 g/fed) and the yield was significantly increased compared with untreated plots. The carbamate insecticide (Lannate) at 300 g/fed caused complete kill to the larvae and the highest yield was obtained. Application of Lannate, Dipel (250 g) or a combination of both (150 g/each/fed) caused a high reduction of the larvae existing in sunflower after seven days from application, while Dipel at 200 g/fed gave a lower effect. Ten days after application, the number of larvae and infested plants increased significantly in plots treated with Lannate alone, while plots treated with either Dipel (250 g) or Dipel combined with Lannate (150 g/each) still maintained a lower infestation. The estimated yield showed the highest increase in plots treated with Lannate followed by Dipel (250 g) and then a combination of both.     

Control ofAgrotis ypsilon (Hufn.) (Lep., Noctuidae) on some vegetable crops in Egypt using the microbial agentBacillus thuringiensis

The effective threshold rate of application of Dipel 2X was 250g/f. Incorporation of some chemical additives such as calcium sulphate (CaSO₄) or calcium oxide (CaO) significantly potentiated the effectiveness of Dipel 2X on larval population. The addition of calcium carbonate (CaCO₃) and zinc sulphate (ZnSO₄) to Dipel 2X greatly reduced the larval population and led to a significant increase in the yield of some vegetable crops. Dipel 2X baits at 250g/f were almost as effective as the chemical insecticide Hostathion when used at 1.5l/f in controllingA. ypsilon larvae attacking vegetable crops. Control of the greasy cutwormAgrotis ypsilon population was better achieved when the biological control agent Dipel 2X was used as baits.     

Evaluation of microbial and chemical insecticides for the control ofSpodoptera exigua (Lep., Noctuidae) on soybean plants

Field experiments have been carried out to evaluate the potency of the biological control agentBacillus thuringiensis (Dipel), the pyrethroid Fenvalerate and their combinations for the control of the lesser cotton leafwormSpodoptera exigua on soybeans in Qualubia governorate. Molasses was combined with all treatments to enhance their effectiveness. One spray application with either Dipel or Fenvalerate showed an obvious reduction in larval counts ofS. exigua, associated with a significant increase in the crop yield but in varying degrees, in correlation with the tested dose. Treatments with combinations of both biological and chemical insecticides at the lowest tested doses (62 g ofB. t. +50 ml of Fenvalerate/feddan) showed to be highly potential, and caused 2.8 fold increase in the crop yield. It may be recommended that a combination of both preparations may be used for the control ofS. exigua.     

A biochemical approach to potentiate the activity ofBacillus thuringiensis against corn borers

Due to the fact that the persistence ofBacillus thuringiensis (B.t.) is very short in the field as affected by exposure to ultraviolet radiation, some biochemical approaches have been adopted in an attempt to increase potentiation of the pathogen against the two lepidopterous corn borers,Chilo agamemnon andOstrinia nubilalis. These approaches were based on the incorporation of some selected non-toxic chemical compounds with different modes of action with the endotoxin ofB.t. fed to the larvae and thus resulting in its potentiation. Among the compounds tested, some representatives of inorganic salts, organic acids, protein and lipid solubilizing agents, amino acids and amides showed an obvious potentiation to the endotoxin activity against the target insects. Inorganic salts, such as, calcium oxide, calcium carbonate, zinc sulphate and potassium carbonate at 0.1% potentiated the activity of the product Dipel 2X (B.t. var.kurstaki) against the two tested species in varying degrees. With regard to protein solubilzing agents, urea, sodium thioglycollate and EDTA enhanced the potency ofB.t. againstO. nubilalis with a fold increase of 1.4–2.3. The lipid emulsifying agent Tween 80 (0.5%), caused 1.3 fold increase in the potency ofB.t. With respect toC. agamemnon, sodium thioglycollate and EDTA (0.1%) were effective in potentiating the activity ofB.t. with fold increase of 3.1 and 1.2, respectively, while urea caused a decrease in the potency ofB.t as compared with the control. The lipid emulsifying agent Tween 80 (0.5%) caused 1.3 fold increase in the potency ofB.t. The potentiating effect of aromatic compounds is not obvious with respect to the tested insect species. With amino acids and amides, it appears that some of the tested compounds enhanced the potency ofB.t. against the tested insect species but in varying degrees. The mode of action of the tested compounds has been discussed in the light of the results obtained.     

Über kombinierte Wirkungen eines Juvenoids (Altosid) und eines Bacillus-thuringiensis-Präparats (Bactimos) auf Larven der Stechmücken Culex pipiens molestus Forsk. und Theobaldia longiareolata Macq. (Dipt., Culicidae)

Exposing second and fourth instar larvae ofCulex pipiens molestus for 24 h to Altosid increased their tolerance to Bactimos. The interaction was apparent in fourth instar larvae treatment especially at the higher concentrations. Exposure bactimos to Altosid for 72 hours decreased its efficacy against the fourth instar larvae ofCulex pipiens molestus. The LT₅₀ values were significantly lower in larvae treated with Bactimos only than that treated with Altosid and Bactimos. Altosid briquets increased significantly the tolerance ofTheobaldia longiareolata larvae toBacillus thuringiensis var.israelensis at all concentrations tested. Generally, pretreatment mosquito larvae with Altosid followed by Bactimos, increased the tolerance of larvae to the bacterium, this may be due to the toxic effect of Altosid on the bacterium or to the changes in the physiological status of the treated larvae to tolerate the effect of bacterium. On the light of these studies, Altosid exhibited detrimental effect on the efficacy ofB. thuringiensis var.israelensis againstC. pipiens molestus andT. longiareolata larvae. Therefore, interactions between Altosid and Bactimos could not fit the integrated control of mosquitoes.     

Empfindlichkeit der Raupen vonLymantria dispar L. (Lep., Lymantriidae) gegenüberBacillus thuringiensis und 2 Häutungshemmstoffen,allein und in Mischung

Field trials were made on the efficacy of the new inhibitor of chitin synthesis in insects, Nomolt 15 SC with teflubenzuron as an effective substance, to larvae ofLymantria dispar, using Nomolt pure or in combination withBacillus thuringiensis. In further experiments another moulting inhibitor, Dimilin, was tested pure or in combination with the Bacillus. The mixture of Bathurin 82 S (Bac. thuring. var.kurstaki), 16 BIU/ha and Nomolt, 10 or 50 ml/ha proved to be very efficacious even during cold and rainy weather, when it showed 20% higher efficacy than the pure biopreparation. The combination with Nomolt as stressor proved to have higher selectivity and efficacy against the pest larvae than those with Dimilin.     

Field evaluation of the potency ofBacillus thuringiensis on lepidopterous insects infesting some field crops in Egypt

Agrotis ypsilon andSpodoptera littoralis can be successfully controlled on various field crops usingBacillus thuringiensis (Dipel 2X) baits and sprays. Baits based on the pathogen at 200–250 g/Feddan, scored the best efficacy againstA. ypsilon in clover fields followed by potato, tomato, and cotton cultivations. Addition of some chemical additives (inorganic salts) toB. thuringiensis bait formulations greatly enhanced its potency. This was associated with an obvious increase in the yield of clover, potato and tomato crops; calcium oxide showed to be highly afficient in this respect. Sprays of Dipel 2X were also found as affective as lannate in controllingS. littoralis on clover cultivations.

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Zusammenfassung Die Untersuchungen ergaben, daßAgrotis ypsilon undSpodoptera littoralis an verschiedenen Feldfrüchten erfolgreich mitBacillus thuringiensis (Dipel 2X) als Köder oder Sprühmittel bekämpft werden können. Die Köder auf der Grundlage von 200–250 gBacillus/Feddan erzielten die besten Ergebnisse gegenA. ypsilon auf Kleefeldern, gefolgt von Kartoffel, Tomate und Baumwolle. Die Beimengung von chemischen Zusatzmitteln (anorganische Salze) zu denBacillus-Ködern erhöhte die Wirksamkeit beträchtlich. Daraus resultierte eine auffallende Steigerung der Klee-, Kartoffel- und Tomatenernte. Dabei war Kaliumoxid das wirksamste Zusatzmittel. Das Sprühen mit Dipel 2X erwies sich in Kleefeldern als ebenso wirksam wie die Anwendung des chemischen Pestizids Lannate.

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With 4 tables     

Evaluation of nine strains ofBacillus thuringiensis Berliner against the giant looper,Boarmia (Ascotis) selenaria Schiffermüller (Lepidoptera,Geometridae)

Nine isolates ofBacillus thuringiensis Berliner belonging to var.kenyae, var.aizawai and var.entomocidus, were bioassayed against 1st instar larvae ofBoarmia (Ascotis) selenaria Schiffermüller and compared withB. thuringiensis var.kurstaki, HD-1-S-1980. None were found to have a higher potency than HD-1-S-1980, which is used for commercial control of young larvae of this pest in avocado plantations in Israel.     

Efficacy of aerial application ofBacillus thuringiensis to controlSpodoptera littoralis (Lepidoptera, Noctuidae) infesting soybean cultivations in Egypt

The calculated percentage of droplets deposition ofBacillus thuringiensis var.kurstaki HD-1 Dipel 2X on the foliage of soybean plants in relation to the sensitive “Ciba Geigy” papers showed to be the highest (92.4%) after ground spray application, compared to an average of 67.4, 85.8 and 89.3% following aerial application of the same preparation in spray volumes of 10, 20 and 30 l/F, respectively. Aerial application ofB. t. showed to be more effective during the first 3 days after spraying soybean cultivations and the mortality ofSpodoptera littoralis larvae varied between 36.9–67.2% in correlation to the spray volume. The volume achieving the highest and significant suppression of infestation was 20 l/F. On the other hand, the yield of soybeans obtained from plots receiving a spray volume of 30 l/F was higher compared to plots sprayed with a volume of 20 or 10 l/F, but with no significant difference when compared to those plots receiving ground spray application.     

Effect of parathion on honey bee larvae rearedin vitro

First instar honey bee larvae (0.2–0.4 mg) from outdoor (summer season) and flight-room colonies (winter season) were reared in an incubator on a semisynthetic diet. Parathion was either dissolved in the diet (0.01–10.0 μg/ml) or topically applied (0–0.5 μg) to the 3rd instar larvae. Increasing doses of parathion caused a delay in larval development and prepupal mortality. The half lethal concentration (LC₅₀) of the insecticide, if applied in the diet, was 0.02 and 0.14 μg/larva, respectively, for summer and for winter larvae. The half lethal dose (LD₅₀) after topical application was 0.18 μg parathion/larva. The utility of rearing honey bee larvaein vitro for evaluation of pesticide toxicity is also discussed.     

Bio-efficacy of bacterial insecticide,Bacillus thuringiensis Berl. as biological control agent against snails vectors of Schistosomiasis in Egypt

The molluscicidal activity of Thuricide used as bacterial insecticide,Bacillus thuringiensis, againstBiomphalaria alexandrina andBulunus truncatus was tested.The obtained results indicate that Thuricide possess a mollus-cicidal activity against both snails species.B. truncatus was more sensitive to the action of Thuricide. However the slope function of the LC₅₀ forB. alexandrina was significantly higher than that forB. truncatus. The mortality rate of exposedB. alexandrina increased by increasing the exposure time.Exposure ofB. alexandrina to low concentration of Thuricide caused a significant decrease in both ovipository activity and size of egg masses and reduced the percentage of egg hatchability.

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Zusammenfassung Es wurde die molluscizide Wirkung von Thuricide (Bac. thuringiensis) gegen die SchneckenBiomphalaris alexandrina undBulunus truncatus getestet. Die Ergebnisse zeigen, daß Thuricide für beide Schnecken molluscizid war.B. truncatus erwies sich als empfindlicher, doch war die Neigungs-Funktion des LC₅₀-Wertes fürB. alexandrina signifikant höher als fürB. truncatus. Die Mortalitätsrate vonB. alexandrina erhöhte sich mit zunehmender Expositionszeit. Die Exposition vonB. alexandrina gegenüber geringen Konzentrationen von Thuricide verursachte eine signifikante Verringerung sowohl der Eiablage-Aktivität als auch der Größe der Eigelege sowie des Schlüpfprozents der Eier.

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With 3 tables     

Laboratory evaluation of shellac as ultraviolet screen for theBacillus thuringiensis var.entomocidus againstSpodoptera littoralis larvae

Shellac was evaluated as radiation protection for the bacteriumBacillus thuringiensis var.entomocidus againstSpodoptera littoralis larvae. Shellac provided excellent protection toB. thuringiensis. The efficacy of shellac in the protection of entomocidal activity ofB. thuringiensis var.entomocidus against UV irradiation has been studied. Results obtained by the absorbtion and the bioassay of residual entomocidal activity ofB. thuringiensis var.entomocidus after exposure to UV irradiation showed that shellac is an excellent photoprotective agent.     

Bio-efficacy of two bacterial insecticide strains ofBacillus thuringiensis as a biological control agent in comparison with a nematicide,nemacur, on certain parasitic nematoda

A greenhouse experiment was conducted to determine the possibility use of commercial bacterial pathogen insecticide,Bacillus thuringiensis, as biocontrol agent againstMeloidogyne javanica andTylenchulus semipenetrans nematodes.The obtained results indicate that the two strains ofB. thuringiensis suppressed the total nematode populations and eggmasses of the two nematode genera. Also, the two strains ofBacillus remarkably reduced the percentages of hatchability of eggs of the two nematode genera. SAN 415Bacillus strain was highly effective than Dipel strain and surpassed it in this respect, but it was approximately similar to the standard nematicide Nemacur.

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Zusammenfassung Es wurde ein Gewächshaus-Versuch durchgeführt zur Untersuchung der Möglichkeit,Meloidogyne javanica undTylenchus semipenetrans (Nematoda) mittelsBac. thuringiensis biologisch zu bekämpfen. Die Ergebnisse zeigen, daßB. thuringiensis die Eigelege und die Populationsdichte beider Nematoden stark reduzierte. Auch wurde die Schlüpflähigkeit der Eier beider Nematodenarten durch Anwendung der zweiBacillus-Präparate deutlich verringert. Der SANBacillus-Stamm zeigte höhere, Wirkung als Dipel und entsprach etwa dem Standard-Nematizid Nemacur.

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With 2 tables     

Übertragung zweler bakterieller Pathogene in den Körper von Sesamia cretica Led. (Lep., Tortricidae) mittels des Legebohrers von Bracon brevicornis Wesm. (Hym., Braconidae)

Laboratory trials were undertaken to investigate the transmission of 2 bacterial pathogens (Serratia marcescens Bizio andBacillus thuringiensis Berliner) by the ovipositor of a braconid parasitoid,Bracon brevicornis Wesmael into the body cavity ofSesamia cretica Lederer. The braconid's ovipositor was able to transmit the 2 bacterial pathogens and plays as inoculating needle. The host larvaeS. cretica were significantly immobilized faster by the contaminated ovipositor of a parasitoid (in case of the 2 pathogens). After successful transmission of the bacterial pathogen into the body cavity of host larvae, different deleterious effects were significantly found for the parasitoid and its progeny specially in case ofS. marcescens. Through contamination of the ovipositor, the non-sporeforming bacterium,S. marcescens has more pathogenic effects on the parasitoid and its progeny than the sporeforming bacterium,B. thuringiensis.     

Persistenz und Wirksamkeit von Bacillus thuringiensis — Präparaten in Freilandversuchen

The field persistence and efficacy of Bacillus thuringiensis formulations The persistence of spores ofBacillus thuringiensis (commercial formulation Dipel and Bathurin) on oak leaves under different climatic condition in field trials was determined. The killing activity of these preparations against wintermothOperophthera brumata and green oak tortrix Tortrix viridana was parallely tested. Within the first week after the application of bacterial preparations the viable spore count on leaves was reduced of two up to three orders. The efficacy of bacterial preparations depends, however, on the environmental temperature occurring within the first week after the application. The adequate temperature is the primary deciding for the feeding activity of caterpillars and for the virulence of the preparations. For aerial application doses of 0.5 to 1.0 kg of the preparation in 50 100 l of water per one ha were sufficient. In the contrary, Dipel WP in oil suspension was unsufficient for aerial application because of mechanical blocking of the nozzles. The optimal time for the procedure was the first week of May in our climatic conditions.      

Application of some bacterial varieties ofBacillus thuringiensis and its bioproduct Delfin onSynanthedon myopaeformis Borkh. (Lep. Aegeriidae) in apple orchards

Field experiments were conducted using the biological agentBacillus thuringiensis to control the clearwing moth,Synanthedon myopaeformis (Lep. Aegeriidae) in apple orchards at Alexandria governorate during 1995, 1996 and 1997. Three bacterial varieties ofB. thuringiensis showed significant influence on the reduction of borer infestation. Four applications with the sporic concentration 12×10⁷ spores/ml of each ofB. th. var.kurstaki, B. th. var.alesti andB. th. var.thuringiensis induced 82.5, 51.1 and 42.1% reduction of infestation, respectively. Methods of application showed highly significant effect on infestation level. Sparying after scraping was the best method (80.0%, reduction) followed by painting after scraping (71.5%, reduction) then spraying alone (59.7%, reduction) or painting alone (43.0%, reduction). A control programme was carried out using three applications of the biomaterial, Delfin at the rate of 200 g/100 I.w. during mid-March, early June and mid-August resulted in 88.5–91.4% reduction of infestation.     

Über die Wirkung vonBacillus thuringiensis var.thuringiensis-Exotoxin auf Wachsmotten-Raupen (Galleria mellonella)

Zusammenfassung Es werden die kürzlich (1966) vonVaková publizierten Befunde bestätigt und ergänzt, wonach Exotoxin vonBacillus thuringiensis var.thuringiensis aufGalleria mellonella-Raupen nach peroraler Applikation wirksam ist. Die Tatsache, daß andere Autoren bisher mit ihren Exotoxin-Präparaten keine Wirksamkeit gegenüber diesem Wirt erzielen konnten, kann verschiedene Ursachen haben. Die bisher vorliegenden Versuchsergebnisse bringen allerdings auch weiterhin noch keinen Entscheid in der Frage, obB. thuringiensis var.thuringiensis qualitativ verschiedene Exotoxine zu produzieren vermag oder nicht.

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Summary Laboratory trials withGallelia mellonella have shown that the caterpillars are susceptible to peroral application of the exotoxin ofBacillus thuringiensis var.thuringiensis. These results confirm and complete findings ofVaková (1966) which were obtained with another application technique. The fact that other authors could not find any reaction ofG. mellonella. larvae against exotoxin may be based on several reasons: The results presented here cannót decide whetherB. thuringiensis var.thuringiensis is able to produce qualitatively different exotoxines or not. Such a decision can only be made by an adequate comparison of different exotoxin-preparations on the same test-insects.

     

Unterschiedliche Wirkungen vonBacillus thuringiensis (B.) aufOrgyia antiqua (L.) in Abhängigkeit von der Frapflanze

Summary Effects of foodplants on the toxicity ofBacillus thuringiensis againstOrgyia antiqua.The effects ofB. thuringiensis onO. antiqua in dependence of various foodplants were investigated. The food showed a great effect on the virulence ofB. thuringiensis. The results are summarized in a table.

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Herrn. Prof. Dipl.-Ing. Dr. ERWIN SCHIMITSCHEK zum 75. Geburtstag.     

Utilization ofBacillus thuringiensis to controlSpodoptera littoralis in Egyptian clover fields

The efficacy of the commercial product Dipel 2X (Bacillus thuringiensis var.kurstaki), was assessed as a biological control means of the cotton leaf wormSpodoptera littoralis attacking clover cultivations (Trifolium alexandrinum) in Egypt. Field experiments using the biological agent were carried out in two localities as compared with the conventional chemical insecticide lannate. The percentage of reduction in the larval population increased at higher doses ofB. t. and the infestation levels reached very low levels, almost similar to those obtained after using lannate. The yield of the first cut of clover was estimated. The data obtained indicate that the yield significantly increased after treatment with eitherB. t. or lannate. In Menoufia, the yield was significantly higher after two successive spray applications withB. t. at 750 g/f compared to that obtained withB. t. when used at 500 g/f. In Giza Governorate, the yield was slightly higher after a single treatment withB. t. at 500 g/f as compared with lannate.