Effect of60Co gamma radiation on the rice weevil,Sitophilus oryzae (L.)

The effect of gramma radiation on the rice weevil,Sitophilus oryzae (L.) was studied. Adults were subjected to 12 doses ranging from 0 to 180 Gy of gamma radiation from a⁶⁰Co source. The time to onset of death and the duration of the period of mortality were investigated. Survival of the adults was decreased with increase of the doses. LD₅₀ and LD_99,9 values were calculated.With one figure and one table     

Gamma radiation sensitivity of larvae and adults of the red flour beetle, <Emphasis Type="Italic">Tribolium castaneum</Emphasis> Herbst

In this study, the susceptibility of larvae and adults of Tribolium castaneum (Herbst) to gamma radiation was investigated in the laboratory in Turkey. Gamma radiation was applied at 6 dose levels between 20 and 200Gy to 13–15day-old adults and at 5 dose levels between 20 and 180Gy to 18–20day-old larvae of T. castaneum. All experiments were performed in growth chambers maintained at 27±1°C and 70±5% r.h. The larvae proved to be the more susceptible stage, survival to the adult stage being prevented by exposure of the eggs to 100Gy; the adult stage was less susceptible. LD₅₀ and LD₉₉ values were determined as 19,75 and 42,97Gy for larvae and 33,21 and 64,50Gy for adult stage, respectively. It was concluded that 100Gy is the effective dose for both larval and adult stages.     

Effects of gamma radiation on life stages of the Mediterranean flour moth, Ephestia kuehniella Zeller (Lepidoptera: Pyralidae)

We report the results of experiments conducted with Ephestia kuehniella Zeller to determine the effects of gamma radiation on life stages. Eggs, larvae, pupae and adults were irradiated with increasing doses of gamma radiation (seven dose levels between 50 and 400 Gy for eggs and larvae, six dose levels between 50 and 350 Gy for pupae and four dose levels between 250 and 550 Gy for adults). All the experiments were conducted in a growth chamber maintained at 27 ± 1°C, 65 ± 5% r.h., and alternating 14 h light:10 h dark cycles. The number of adults that developed from irradiated eggs and larvae was lower than the untreated control. Doses of 200 Gy and above prevented adult emergence from irradiated eggs. Although a dose of 200 Gy was enough to prevent adult emergence from young larvae, 250 Gy should be used to prevent adult emergence completely from last instar larvae. Delayed developmental periods were observed for the treated eggs and larvae. Fecundity and egg hatchability were decreased depending on the doses applied. Decreased fecundity and egg hatchability were more prevalent when both the male and female pupae were treated compared to the treatment of female pupae only. There was no significant decrease in the fecundity of irradiated adults except 550 Gy, and no eggs hatched at doses of 300 Gy and above.     

Potential of zimtaldehyde, 4-allyl-anisol, linalool, terpineol and other phytochemicals for the control of the confused flour beetle (Tribolium confusum J. d. V.) (Col., Tenebrionidae)

Toxicity and repellency effects of several pure compounds (of plant origin) against the confused flour beetle (Tribolium confusum) were investigated in a filter paper test. The compounds were α-pinen, β-pinen, 4-allyl-anisol, camphor, 1,8-cineol, eugenol, linalool, menthol, piperin, terpineol, thymol and zimtaldehyde. Five compounds (4-allyl-anisol, linalood, terpineol, thymol and zimtaldehyde) caused enough mortality of this insect to allow the determination of LD₅₀ and LD₉₅ values. Zimtaldehyde and 4-allyl-anisol showed the strongest toxicity effects with LD₅₀ values of 0.04–0.05 μl/cm² within an exposure period of 24 h. When the isolated fumigant effects were tested by separating the insects from the filter paper, the toxicity of zimtaldehyde (LD₅₀=0.29 μl/cm²) was much lower than that of 4-allyl-anisol (LD₅₀=0.10μl/cm²).     

Effects of gamma radiation on the Mediterranean flour moth, <Emphasis Type="Italic">Ephestia kuehniella</Emphasis>, eggs and acceptability of irradiated eggs by <Emphasis Type="Italic">Trichogramma cacoeciae</Emphasis> females

The sensitivity of the Mediterranean flour moth, Ephestia kuehniella, eggs in different stages of development to gamma irradiation was studied and the acceptability of irradiated eggs by Trichogramma cacoeciae females was examined. Eggs ranging in age from 1–24 to 49–72 h were exposed, at 24 h intervals, to gamma radiation dosages ranging from 25 to 400 Gy and effects of gamma radiation on egg hatch and adult emergence was investigated. In addition, the developmental rate of immature stages (larvae and pupae), resulting from irradiated eggs, to the adult stage was examined and the acceptance of irradiated eggs to T. cacoeciae females was evaluated. Results showed that the radio-sensitivity of E. kuehniella eggs decreased with increasing age. Egg hatch in 1–24-h-old eggs was significantly affected at 25 Gy dose and at 75 Gy dose, no egg hatch was observed. When irradiating 25–48-h-old eggs, however, egg hatch was less than 5% at 100 Gy dose, and eggs 49–72-h-old were more resistant; 50 Gy had no significant effect on egg hatch and 300 Gy did not completely prevent it. Irradiation also negatively affected survival to the adult stage. When 25–48-h-old eggs were irradiated, survival to the adult stage was completely prevented at 75 Gy dose and no survival was observed beyond 100 Gy dose in 49–72-h-old eggs. In addition, the rate of development of immature stages resulting from irradiated eggs was negatively affected. While more than 97% of control moths emerged within 30 days, this ratio decreased to 53 and 69% in 1–24 and 25–48-h-old eggs exposed to 25 Gy dose. Furthermore, irradiation positively affected the degree of acceptance of eggs to parasitization; irradiated eggs (≤49-h-old) were more acceptable to T. cacoeciae than cold-treated ones.     

Zur Wirkung einiger organischer Phosphor-Präparate in subletaler Dosis aufSpodoptera littoralis (Boisd.) (Lep. Noctuidae)

Zusammenfassung Das 4. Stadium der Larven von.S. littoralis wurde mit der maximalen nichtletalen Dosis (LD₀) sowie den subletalen Dosen (LD₁₀ und LD₅₀) der 3 Insektizide Cyolane, Monocrotophos und Phosvel im Laboratorium behandelt. Die überlebenden Individuen wurden bis zum Ausschlüpfen der Falter gezogen und anschließend auf ihre Biproduktion untersucht. Die max. LD₀ wirkte stimulierend auf die Eiproduktion, So betrug der prozentuale Anstieg der täglich abgelegten Eizahl je Weibchen in 5 Tagen 70,6% nach Cyolane-, 60,4% nach Monocrotophos- und 34,5% nach Phosvelbehandlung.Die subletalen Dosen wirkten unterschiedlich auf die Eiproduktion. Die LD₁₀ verursachte eine Vermindung, dagegen eine Erhöhung der Eizahl um 12,2% derung der Eizahl um 12,4% nach Cyolane-Anwenper female during 5 days was the following: 70,6%, nach Monocrotophos- und um 7,3% nach Phosvelanwendung. Die LD₅₀ verminderte die Eizahl um 34,6% bei Monocrotophos, führte dagegen bei Phosvel zu einem geringen Anstieg von 3,3%.Die LD₅₀ der 3 Insektizide hatte, verglichen mit der Kontrolle, eine Abnahme des Verpuppungsprozentes, eine Erhöhung der Sterberate bei den Larven und Puppen und eine Störung der Sexualrate zugunsten der mä nnlichen Falter zur Folge, während sich die max. LD₀ und LD₁₀ der o. g. Insektizide auf die Sexualrate, verglichen mit der Kontrolle, zugunsten der weiblichen Falter auswirkten. Im allgemeinen verhielt sich das Verpuppungsprozent umgekehrt proportional zur Insektiziddosis, während die Sterberate für Larven und Puppen proportional der Insektiziddosis war. Alle max. LD₀ hatten nur einen geringen Einfluß auf das Verpuppungsprozent.

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Summary The 4th instar larvae ofS. littoralis (Boisd.) was treated in the laboratory with the maximal non lethal dose (max. LD₀) and the sublethal doses (LD₁₀ and LD₅₀) of 3 insecticides (Cyolane, Monocrotophos and Phosvel). Surviving larvae reared to imagines, and then tested on the egg production. The max. LD₀ of the aforementioned insecticides showed a stimulation effect on the egg production of the females. The percentage of increase in the number of eggs produced 60,4%, 34,5% after Cyolane, Monocrotophos, and Phosvel treatment respect.The sublethal doses showed different effects on the egg production: LD₁₀ decreased the percentage of eggs of 12,4% after Cyolane treatment, while Monocrotophos and Phosvel increased the same (12,2% and 7,3% respect.). LD₅₀ decreased the percentage number of eggs (34,6% after Monocrotophos treatment) and there was a slight increase after Phosvel treatment (3,3%). LD₅₀ furthermore decreased the percent pupation, increased the mortality of the larvae and pupae and disturbed the sex ratio for the benefit of the males, compared with the control, while the max. LD₀ and LD₁₀ of the 3 insecticides affected the sex ratio for the benefit of the females. The percent pupation in general was in inverse relation to the insecticide dose, while the mortality of the larvae and pupae was in proportional relation to the insecticide dose. All max. LD₀ have shown a slight influence on the percent pupation compared with the Control.

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Faris El- Lakwah, Dozent, Polytechn. Institut Cairo, Dep. Agriculture, Moshtohor, A. R. E. — Farid A. Abdel-Salam, Ass.-Prof., Central Laboratory for Pesticides (CAPL), Ministry of Agriculture, Cairo-Dokki, A. R. E.     

Insecticidal efficacy of <Emphasis Type="Italic">Isaria farinosa</Emphasis> in different life stages of <Emphasis Type="Italic">Pissodes punctatus</Emphasis> (Coleoptera: Curculionidae)

The insecticidal activity of an entomopathogenic fungus, Isaria farinosa on pine bark-weevil (Pissodes punctatus) at different life stages underwent laboratory testing. Larvae, pupae and adults of Pissodes punctatus were exposed to a range of concentrations of fungal conidia in suspension for 5 s; mean mortality and LC₅₀ values were calculated. The results showed I. farinosa can effectively infect larvae, pupae and adult pine bark-weevils, and the highest mean mortalities at each life stage can exceed 88%. The mean mortalities increased with higher concentrations of I. farinosa. Larvae were most susceptible with LC₅₀ 1.2 × 10⁶ conidia ml⁻¹ (15 days), pupae (30 days) exhibited the second largest effects, and adults (15 days) with LC₅₀ 1.72 × 10⁶ and 1.99 × 10⁶ conidia ml⁻¹, respectively, at end of the experiments. This suggests that I. farinosa could be a potential bio-control agent against the pine bark-weevil.     

Effect of cold storage and different diets on <Emphasis Type="Italic">Ephestia kuehniella</Emphasis> Zeller (Lep:Pyralidae)

Ephestia kuehniella adults were stored at 10°C for 1–10 weeks. Reproductive ability and number of living adults decreased depending on the length of the storage period. Long-term exposure to cold lengthened the life of the adults and 50% mortality was reached after 6 weeks. To obtain complete mortality and sterility 10 weeks of storage was needed. The larvae reared on corn flour diet developed to the adult stage more rapidly than that of the other treatments. The adults reared on oat flour produced significantly more eggs than the other diets. There was no difference among diets with regard to emergence rate, longevity or sex ration of E. kuehniella adults. Trichogramma evanescens did not differentiate among hosts from different food sources with respect to parasitization, adult emergence and sex ratio. The suitability of the eggs from cold-exposed adults with respect to parasitization was found to be the same as the control during the first 3 weeks.     

Zur Bekämpfung des Reiszünslers,Corcyra cephalonica (Stainton) (Lep., Pyralidae) unter Ausnutzung der Kälteempfindlichkeit der Eier und Larven

Zusammenfassung Experimente mit Eiern und Larven verschiedenen Alters des MehlzünslersCorcyra cephalonica (Staint.), welche unterschiedlich langen Temperaturen von 5, 0 und –10°C ausgesetzt wurden, ergaben, daß Eier bei Kurzzeitbehandlung (10h) mit –10°C oder bei Langzeitbehandlung (10 Tage mit 0°C, 15 Tage mit 5°C) zu 100% abstarben. Die Kältebehandlung von Erstlarven führte bei 2 h mit –10°C oder 5 Tagen mit 5°C zum völligen Absterben. Wurde mit verschiedenen Entwicklungsstadien (außer Puppen) vonC. cephalonica befallenes Weizenmehl 5 Tage lang 0°C oder 15 Tage lang 5°C ausgesetzt, starben alle Stadien ab, so daß keine Falter schlüpften. Somit ist unter diesen Bedingungen eine wirksame Bekämpfung des Schädlings in befallenem Mehl möglich, solange noch keine Puppen ausgebildet sind.

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Use of cold susceptibility of eggs and larvae of the rice mothCorcyra cephalonica (Stainton) (Lep., Pyralidae) for their control

Experiments were conducted to evaluate the effect of storing wheat flour for various length of time at –10°, 0°, and 5°C, on the mortality of the egg and larval stages ofCorcyra cephalonica (Stainton). Treating eggs with –10°C for 10 h, 0°C for 10 and more days, or 5°C for 15 days, stopped all embryonic development, and hence 100% mortality of eggs was obtained. Also, 100% mortality was observed when first-instar larvae were treated with –10°C for 2 h and more; or 0°C or 5°C for 5, 10, or 15 days.Storing wheat flour infested with different stages at 0°C for 5 days and more, or at 5°C for 15 days prevented the development of immature stages and thus no adults emerged. It can be concluded that storing small quantities of flour at 5°C for 15 days, or at 0°C for 10 or 15 days would be effective in controllingC. cephalonica, if no pupae are present at the time of treatment.

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Mit 2 Tabellen     

Influence of mixed biocide GCSC-BtA on the pupae and adult stages of Apanteles plutellae Kurd. (Hym., Braconidae) and its host. Plutella xylostella (L.) (Lep., Plutellidae)

This paper deals with the influence of the mixed biocide GCSC-BtA on the pupal and adult stages of Apanteles plutellae Kurd. (Hym., Braconidae) and its host, Plutella xylostella (L.) (Lep., Plutellidae). The results show that mortalities of the pupae of P. xylostella in the direct-dip bioassay were 84.67?%, that of the adults in the residue bioassay at 1.2500?mg/ml concentration of GCSC-BtA were 78.00?% which were significantly higher than the mortality values for the pupae with 54.62?% and adults with 48.13?% of A. plutellae. In contrast, cypermethrin showed extremely high toxicity to the pupae with 94.58?% and adults with 86.00?% mortality values of A. plutellae as compared to the low mortality values of 42.14?% for the pupae and 32.11?% for the adults of P. xylostella, with the same concentrations and bioassay methods. The LC₅₀ values of GCSC-BtA were 0.3402, 0.5516 and 1.2405, 1.9480?mg/ml for the pupae and adults of P. xylostella and A. plutellae, respectively, while the LC₅₀ values for cypermethrin were 1.5652, 2.3471 and 0.1096, 0.1152?mg/ml, respectively. GCSC-BtA was found more toxic to the pupae and adults of P. xylostella and safer to the pupae and adults of A. plutellae than cypermethrin. The possibilty of using GCSC-BtA against P. xylostella under partial control by A. plutellae in vegetable fields is discussed.     

Interception of photosynthetic photon flux density in a mangrove stand of <Emphasis Type="Italic">Kandelia candel</Emphasis> (L.) Druce

The canopy structure and interception of photosynthetic photon flux density (PPFD) in a 10-year-old Kandelia candel (L.) Druce stand were investigated before and after artificial defoliation. Leaf and wood areas for different layers were measured through area–weight relationships of subsamples. PPFD was measured at specified heights before and after leaf clipping. The leaf area index (LAI) and wood area index (WAI) were 4.501m²m^–2 and 1.412m²m^–2, respectively. There was a strong linear relationship between the cumulative wood area © and leaf area (F) densities from the top down to a given depth of the canopy, C = aF (r ² = 0.950), with a proportional constant a of 0.096 ± 0.008 (mean ± SE). The PPFD relative to that above the canopy (relative PPFD; I _R) at a given depth of the canopy was assumed to be given by the equation I _R = e^–(KCC+KFF ) = e^–KF , where the apparent light extinction coefficient K (= K _F + aK _C , where K _F and K _C are respectively the light extinction coefficient of leaves and woody organs) was calculated to be 0.502 ± 0.041 (mean ± SE) m^–2m² before leaf clipping. After leaf clipping, I _RC = e^–KCC is satisfied. As a result, the value of K _C was estimated to be 0.785 ± 0.046 (mean ± SE) m^–2m². The light extinction coefficient of leaves K _F was calculated to be 0.427m^–2m² using the indirect method, K _F = K – aK _C, and 0.432 ± 0.026 (mean ± SE) m^–2m² using the direct method, I _R/I _RC = e^–KFF . Of the total PPFD intercepted by the canopy, the fraction K _F/K due to leaves alone was estimated to be 85.0%–86.1% and the rest was contributed by woody organs.     

Susceptibility of different life stages of Tribolium confusum to pyrethrin aerosol: effects of a flour food source on insecticidal efficacy

Accumulated grain dust and flour residues in flour mills can potentially decrease the efficacy of contact surface treatments and aerosol insecticides used for control of adult and immature stages of stored product insects. A study was conducted to evaluate the effects of flour residues on the efficacy of piperonyl butoxide-synergized pyrethrin aerosol against different life stages of the confused flour beetle, Tribolium confusum Jacquelin du Val. Twenty individual adults, pupae, or larvae of T. confusum, confined in Petri dishes containing 0, 0.1, 1, 5, or 10 g of wheat flour, were exposed separately inside an empty shed to the label rate of the aerosol. The formulation contained 1 % active ingredient pyrethrin and the label application rate was 1.04 ml/m³. After 2 h of exposure, all dishes were removed from the shed and placed in an incubator set at 27 °C and 60 % RH. Mortality of T. confusum adults decreased with increasing amount of flour. Recovery of moribund adults 15 days after exposure was greater in the 5 and 10 g flour dishes (15 and 46 %) compared to the 0.1 or 1 g flour dishes (0.7 and 5 %). As the flour amounts increased, more larvae and pupae were able to emerge as adults. Results show accumulated flour residues during aerosol application can compromise aerosol efficacy, and also suggest the flour impaired penetration ability of the aerosol. These results also emphasize the importance of sanitation and cleaning to remove spillage and extraneous material prior to an aerosol application.     

Biological studies on the olive leaf moth, <Emphasis Type="Italic">Palpita unionalis</Emphasis> Hübner (Lepid., Pyralidae), and the olive moth, <Emphasis Type="Italic">Prays oleae</Emphasis> Bernard (Lepid., Yponomeutidae)

Abstract The biology of two important lepidopterous pests, Prays oleae Bernard and Palpita unionalis Hübner, was studied. The target pests were reared on olive plants, Oleae europaea L. (Oleaceae) under laboratory conditions for two successive generations, from March to June 2002. For P. oleae, the duration of larval stage development in the first generation was 21.4 ± 0.18 days at 19.3–20.9 °C, 65–68 % R.H, while in the second generation it was 14.8 ± 0.10 days at 20.8–24.2 °C, 65–69 % R.H. The number of eggs laid per female ranged from 58 to 109 eggs in the first generation, and from 47 to 113 in the second. The larval stage duration of P. unionalis was 16.3 ± 0.12 days at 16.8–22.9 °C, 65–69 % R.H. and 15.5 ± 0.12 days at 21.6–25.5 °C, 66–69 % R.H. for the first and second generations, respectively. Also, the number of eggs laid per female ranged from 630 to 653 eggs, and from 425 to 493 eggs in the second generation under the same previous laboratory conditions. P. oleae laid eggs at night mostly singly on flower-buds, more on the calyx. than on the petals. The larvae mined on leaves and damaged groups of flowers. P. unionalis adults were active at night, laid eggs singly at twilight usually on the lower surface of foliage. Larvae fed on leaves spinning several leaves together to form shelter for the pupa.     

The influence of trees on nitrogen dynamics in an agrisilvicultural system in Sweden

During 1992 and 1993, nitrogen dynamics and microbial activity were investigated in an agrisilvicultural system consisting of oats or barley cyltivated along the sides of a poplar plantation in Sweden. At each of three experimental sites (two silt loams and one silty clay loam), sampling for mineral nitrogen was carried out in three layers down to 90 cm at two distances from the trees, A (0.5–1.5 m) and B (4.0–5.0 m), two times each year (spring and autumn). Sampling of soil for organic amtter, carbon and nitrogen, potential nitrification, N ineralization, basic respiration and substrate-induced respiration was carried out in the 0–10 cm layer at three distances from the trees: A (0.5–1.5 m), B (2.5–3.5 m) and C (4.0–5.0 m).Significantly larger amounts of organic matter, total carbon and nitrogen at A than at B and C, indicated increased inputs from the trees through litter, decaying roots and root exudates. This could explain that the rates of nitrogen mineralization, potential nitrification and respiration were significantly higher at A than at B and C. The presence of trees resulted in a better utilization of nitrogen and moisture in the soil, reducing the potential for nitrate leaching and accumulating nitrogen close to the trees. The higher concentration of ammonium, lower concentration of nitrate and the consistently lower NO ₃ ^– –N/NH ₄ ⁺ –N-ratios observed at A than at C might be explained by a combined effect of increased nitrogen mineralization and efficient nitrate uptake by the trees.     

The toxicity of selected acaricides against five stored product mites under laboratory assay

In laboratory tests, the toxicity of acaricides targeted against house dust mites was tested on five species of stored product mites (Acarus siro, Aleuroglyphus ovatus, Carpoglyphus lactis, Lepidoglyphus destructor, and Tyroborus lini). The formulations of benzyl-benzoate, benzyl-benzoate/permethrin/pyriproxyfen, and neem were diluted in water and applied to filter paper in an unventilated chamber. The mortality of mites was observed after 24 h of exposure to acaricide-impregnated filter paper. All of the tested acaricides were toxic to all of the mite species. There were significant differences in mortality among the species and the acaricides. Benzyl-benzoate/permethrin/pyriproxyfen was the most effective, followed by benzyl-benzoate and neem. L. destructor (LD₅₀ 0.01–0.11 μg) was the most sensitive mite species, followed by A. siro (LD₅₀ 0.04–0.12 μg), T. lini (LD₅₀ 2–21 μg), A. ovatus (LD₅₀ 3–18 μg), and C. lactis (LD₅₀ 4–64 μg). Based on the highly toxic effects of the tested acaricides against the stored product mites, the acaricides should be considered as a potential tool in the control of stored product mites, although next screening is necessary.     

Insecticidal effects of the powdery formulation based on clay and essential oil from the leaves of <Emphasis Type="Italic">Clausena anisata</Emphasis> (Willd.) J. D. Hook ex. Benth. (Rutaceae) against <Emphasis Type="Italic">Acanthoscelides obtectus</Emphasis> (Say) (Coleoptera: Bruchidae)

The bioefficacies of essential oil and aromatized clay powder based on the mixture of clay and essential oil extracted from Clausena anisata were evaluated for their insecticidal activities and their effects on progeny production of Acanthoscelides obtectus. Contact toxicity assayed by coating on bean grains showed that these chemicals caused significant mortality of the test insect. Beetle mortality was dose dependant and after 2-day exposure the aromatized clay powder was more toxic (LD₅₀ = 0.069 μl/g grain) than the pure essential oil (LD₅₀ = 0.081 μl/g grain). There was, however, a highly significant loss of toxicity after 24 and 36 h following treatment with essential oil and aromatized powder, respectively. Both aromatized clay powder and pure essential oil considerably reduced the F₁ progeny insect production. The essential oil evoked moderated repellent action and high fumigant toxicity (LC₅₀ = 0.093 μl/cm³) against adults of A. obtectus. These results suggest that the clay powder could be used to stabilize the essential oil to increase its efficacy for use as an alternative to synthetic insecticides.     

Lethal and sublethal effects of cycloxaprid,a novel cis-nitromethylene neonicotinoid insecticide,on the mirid bug Apolygus lucorum

Recently, Apolygus lucorum (Hemiptera: Miridae) has become an important insect pest of Bt cotton and fruit trees in China. At present, the application of chemical insecticides is the main control option for this pest. We investigated the lethal effect of seven neonicotinoid insecticides on A. lucorum adults, including six commercialized neonicotinoids and a novel one, cycloxaprid, which is developed in China. In addition, we assessed the sublethal physiological (longevity, fecundity) and behavioral (pre-oviposition and oviposition periods) effects of LD₁₀ (low lethal dose) and LD₄₀ (moderate lethal dose) of cycloxaprid on the mirid bug. Lethal effect of the insecticides was determined using a topical exposure method; contact toxicity against the adults was ranked as follows: cycloxaprid, nitenpyram > clothianidin > acetamiprid, imidacloprid > thiamethoxam > dinotefuran. Among these insecticides, the toxicity of cycloxaprid against the adults was the highest; its LD₅₀ value was 2.54 ng a.i. (active ingredient)/adult. Both LD₁₀ (0.74 ng a.i./adult) and LD₄₀ (1.98 ng a.i./adult) of cycloxaprid induced sublethal effects in the adults; we observed a reduced longevity in males and the LD₄₀ also shortened the longevity of females. In addition, the LD₄₀ prolonged the pre-oviposition period and shortened the oviposition period of females, and it decreased their fecundity. The hatching rate of eggs laid by the females exposed to LD₁₀ and LD₄₀ greatly decreased (two-fold lower when exposed to LD₄₀). Our results demonstrate that cycloxaprid is among the best candidate insecticides for controlling A. lucorum, and it showed significant lethal and sublethal effects on this mirid bug.     

Site index curves for Norway spruce (Picea abies (L.) karst.) planted on abandoned farm land

Growth data were collected from 157 Norway spruce (Picea abies (L.) Karst.) stands planted on farm land in Sweden from 55 to 66° N. The mean age of the stands was 41 years (range, 25–91), the mean stand density 1 640 stems ha^–1 (range, 400–3 722), and the mean diameter at breast height (outside bark) 25 cm (range, 12–48). The height growth was measured in 56 stands during the initial five years after plantation and followed systematically until the stands were 30 years old. Early height growth for spruces growing on clay soils was lower than for trees growing on sand, till and peat soils. The height increment for 5-year-old spruces predicted the height increment for mature spruces (30–50 years old).Site index curves were constructed for total age. Curves for H₄₀ (dominant height at 40 years total age) were made for both northern (50 stands, 61–66° N) and southern (107 stands, 55–61° N) Sweden. Site index curves for H₅₀ at total age are presented for Sweden as a whole (Lat. 55–66° N) and southern Sweden only. Curves based on breast height age were also constructed for H₄₀ and H₅₀. Curves fitted for H₄₀ at breast height were well in accordance with the curves presented in the past for spruce on forest lands by Nordic studies. The curves from the present study have slower growth for young spruces than curves for forest land. For 40–90-year-old spruce stands, curves from the present study indicate taller heights than from forest land curves.     

Über die Wirknug von Gamma-Bestrahlung aufCallosobruchus maculatus F.

Susceptibility of various stages of Calloso-bruchus maculatus F. to Gamma radiationLarvae and pupae of the southern cowpea weevilC. maculatus were exposed to gamma radiation from a c_o ⁶⁰ source.All the fully grown larvae ofC. maculatus when exposed to gamma radiation (3000 rad) died before adult emergence. Larval irradiation decreased fecundity and longevity of the resulting adults.The results indicated thatC. maculatus was more resistant to irradiation injury when irradiated in the pupal stage than when irradiated at earlier stages. Adults exposed to 3000 rad in the pupal stage were completely sterile.     

Effect of temperature on development and fecundity of Aphis gossypii Glover (Homoptera: Aphididae) on cucumber

The developmental time, survivorship and reproduction of Aphis gossypii Glover was evaluated on detached cucumber leaves at nine constant temperatures ranging from 15±1°C to 35±1°C in 2.5°C increments in the laboratory. Developmental periods of immature stages ranged from 10.8 days at 15°C to 4.1 days at 30°C and 32.5°C. Constant 35°C was lethal to immature stages of A. gossypii. The lower developmental threshold for the cotton aphid was estimated at 6.0°C and it required 92.6 degree–day development for a first instar to become adult. The average reproduction rate was 82.1 nymphs female^–1 at 25°C and 2.3 nymphs female^–1 at 32.5°C. The mean generation time of the population ranged from 6.8 days at 32.5°C to 22.8 days at 15°C. The highest per capita growth rate (r_m=0.526) occurred at 25°C and the lowest at 15°C (r_m=0.208) and 32.5°C (r_m=0.132). It was evident that temperatures over 30°C prolonged development, increased mortality of immature stages, shortened adult longevity and reduced fecundity. The optimal range of temperature for population growth of A. gossypii on cucumber was very broad and ranged between 22.5°C and 30°C.