Intrinsic rate of population increase of Amitus fuscipennis MacGown and Nebeker (Hym., Platygasteridae) according to climatic conditions and bean cultivar

Data on adult longevity, reproduction and intrinsic rate of population increase of insect parasitoid Amitus fuscipennis MacGown and Nebeker (Hym., Platygasteridae) were obtained under different climatic conditions on two bean cultivars. The insect host was the greenhouse whitefly Trialeurodes vaporariorum (Westwood) (Hom., Aleyrodidae). On cv. Chocho, at 19°C, 75 ± 5% RH and at 22°C, 70 ± 5% RH, mean longevity of adult Amitus females on the host insect was 9.3 and 5.7 days; mean fertility was 64.1 eggs and 52.7 eggs; and r_m values were 0.102 day^–1 and 0.144 day^–1 for the respective conditions. On cv. ICA-Pijao, at 19°C, 75 ± 5% RH, mean longevity was 15.2 days; mean fertility was highest (162.8 eggs); and r_m value was 0.117 day^–1. The r_m values of Amitus were higher than those of its host under the same test conditions. This parasitoid may therefore be a suitable candidate for use in inoculative or seasonal inoculative control programs against T. vaporariorum .     

Efficacy of Beauveria bassiana (Bals.) Vuill. against the spruce bark beetle, Ips typographus L., in the laboratory under various conditions

Abstract:  In laboratory bioassays, the efficacy of the entomopathogenic fungus Beauveria bassiana against the spruce bark beetle, Ips typographus , was tested under various conditions. Four of the tested isolates and the commercial product Boverol^® caused 99–100% mortality when tested at a concentration of 1.0 × 10⁷ conidia/ml at 25°C. Using B. bassiana isolate 138 at a concentration of 1.0 × 10⁶, the median survival time (MST) was 6.1 d and significantly longer compared with the MST of 4.2 and 4.0 d at 1.0 × 10⁷ and 1.0 × 10⁸ conidia/ml, respectively. In the next experiment, the beetles were maintained on spruce bark, filter paper or artificial diet during the bioassay with Boverol^®, and significant differences in the MST of 3.6, 2.5 and 5.3 d, respectively, were noticed. The experiment with Boverol^® at different temperatures showed that the beetles lived significantly longer at 15°C (MST 8.7 d) than at 20, 25, 30 and 35°C. At 25°C, the beetles died most rapidly (MST 3.5 d). At different relative humidities (RH) of 40, 70 and 100%, nearly all beetles were dead after treatment with a suspension of Boverol^® at 1.0 × 10⁷ conidia/ml. At 40% RH, 49% of the untreated beetles died after 7 d. The best effects were achieved with the following bioassay: beetles were fed for three days on artificial diet, then dipped into a solution of 1.0 × 10⁷ conidia/ml and transferred on a piece of spruce bark in Petri dishes at 25°C and 70% RH.     

INFLUENCE OF RELATIVE HUMIDITY ON SURVIVAL OF THE CITRUS LEAF-MINER, PHYLLOCNZSTZS CITRELLA STAINTON (LEPIDOPTERA: PHYLLOCNISTIDAE)

Abstract The relationshLps between relative humidity (RH) and survival rates of eggs, all larval stages and pupae of the citrus leaf-miner, Phyllooiistis citrella Stainton, were determined by laboratory experiments. The survival of the citrus leaf-miner was observed at seven levels of relative humidity from 35% RH to 95% RH at intervals of 10% RH, with 12 L: 12 D photoperiod and temperatiure (29±0.5) C. The relative humidity was controlled by saturated solutions of MgCl₂ 6H₂O, K₂CO₃ 2H₂O, C₆H₁₂O₆, NaNO₂, NaCl, KCl, and Pb(NO₃)₂. The results showed that lower relative humidity is unfavorable for incubation of the eggs, survival of the larvae and eclosion of the pupae. The survival rates increased generally with rising of relative humidity within the range of 35% - 85% RH, and the maximum survival rates occurred at 85% RH for different life stages. The variations in hatching rates of the eggs, survival rates of the larvae and emergence rates of the pupae were great, but unimodal at different relative humidity. The effect of relative humidity on survival rates of the citrus leaf-miner could be simulated by regression analysis, using a polynomial function of three orders, and the results of fitting the model to the observed data are presented and discussed.     

Sensitivity of wild and genetic sexing strain Ceratitis capitata to high-temperature disinfestation of Valencia oranges

Abstract:  The purpose of this research was to investigate post-harvest heat treatment of Valencia oranges as an effective disinfestation protocol (fast, no fruit damage) for the Mediterranean fruit fly Ceratitis capitata (Wiedemann). Forced high-temperature air was applied under the following conditions: (a) exposure to air temperature of 56°C, for fast increase of temperature in the interior of the fruit, (b) reduction in air temperature to 47°C when the fruit centre reached 47°C and (c) maintenance of fruits in the chamber for another 30 min. Relative humidity in the treatment chamber was kept between 50% and 65% during treatment. Forced air at 47°C applied for 30 min on eggs before hatch or late third instar larvae (the most heat-tolerant stages) resulted in complete kill. Egg and larval sensitivity to high temperature differed between a wild strain and a laboratory genetic-sexing strain based on white pupa mutation. In this strain males emerge from brown pupae and females from white pupae. In particular, mature eggs from the wild strain were significantly more temperature resistant than eggs from the laboratory strain. Exposure of Valencia oranges of a diameter of 7–7.5 cm to 56°C forced air for about 86 and 99 min was required to increase temperature to 47°C at 1.5 cm depth and the fruit centre respectively. Treated oranges showed no substantial peel or interior deterioration, or change in colour and taste when kept at 25°C and 50–60% RH for a period of up to 1 month following treatment. Treatment in 1% O₂ atmosphere, produced by flushing of CO₂ into the treatment chamber, resulted in about 1°C reduction in killing temperature and faster increase in temperature inside the fruit to a lethal level.     

Synchronization of larval emergence in winter moth (Operophtera brumata L.) and budburst in pedunculate oak (Quercus robur L.) under simulated climate change

1. The hypothesis that a 3 °C elevation in temperature and doubled CO₂ concentration would have no effect on the synchronization of winter moth egg hatch with budburst in oak was tested by comparing the separate and interactive effects of ambient and elevated (+ 3 °C) temperature and ambient and elevated (doubled to 340 p.p.m.) CO₂ in eight experimental Solardomes. In addition, an outdoor control was compared with the ambient temperature/CO₂ treatment combination.
2. Elevated temperature accelerated darkening (preceding egg hatch by about 5–10 days) and hatching of eggs developing off the trees; elevated CO₂ had no effect. The same effects were observed in eggs developing on the trees.
3. Within treatments, date of egg hatch was the same on trees with early or late budburst.
4. Egg darkening and budburst were closely synchronized at both ambient and elevated temperatures.
5. Both eggs and trees required fewer cumulative heat units (day degrees > 4 °C), for hatching and budburst, respectively, at ambient than elevated temperatures. The requirements in the outdoor control treatment were similar to those in the ambient Solardome treatment.
6. Egg hatch between 10 and 25 °C, on a temperature gradient in the laboratory, required a constant number of heat units; fewer were required below 10 °C.
7. Elevated temperatures, in the Solardomes and the field, delayed adult emergence from the pupae.
8. The results suggest that a general increase in temperature with climatic change would not affect the closeness of the synchronization between egg hatch of winter moth and budburst of oak.     

Desiccation tolerance in fully developed embryos of two cicadas, Cryptotympana facialis and Graptopsaltria nigrofuscata

In two Japanese cicadas, Cryptotympana facialis and Graptopsaltria nigrofuscata , with different habitat distributions, fully developed embryos hatch in response to high humidity due to rainfall. Despite the advantage of hatching on rainy days, this trait burdens embryos with an extra period of desiccation until the unpredictable advent of rain. We compared the ability of the fully developed embryos of these cicadas to endure periods of low humidity. Eggs were exposed to a combination of different humidities (43% and 75% relative humidity, RH) and durations (0–15 days), and then transferred to an environment with 100% RH to stimulate hatching. In both species, total hatching rates decreased as duration increased, although there was no significant effect of humidity. In C. facialis , a considerable proportion of the eggs hatched during the desiccation period, and the hatching rate was higher at 75% RH than at 43% RH. After transfer to 100% RH, most hatching occurred within a day regardless of the desiccation level. In G. nigrofuscata , no nymphs hatched during the desiccation periods. However, more eggs required more than a day after transfer to 100% RH to hatch after desiccation at 43% RH than at 75% RH. Consequently, the overall proportion of timely hatching of eggs (eggs hatching within a day of moisture supply) was higher after desiccation at 43% RH in C. facialis , but it was higher after desiccation at 75% RH in G. nigrofuscata . These different physiological responses of the two species may reflect adaptation to habitat dryness.     

Effects of copper, lead and zinc in soil on egg development and hatching of Folsomia candida

Effects of CaCl₂, CuCl₂, ZnCl₂ and PbCl₂ on development and hatching success of eggs of Folsomia candida (Collembola) were studied under laboratory conditions. Thousands of healthy eggs from synchronized cultures were incubated in soils treated with different concentrations of the metals. Compared with the water control, egg hatch significantly decreased when concentrations of Cu, Pb and Zn reached 400, 1600 and 800 mg/kg dry soil, respectively. Values of EC_{50 (hatching)}, calculated according to the exponential model (with 95% confidence limits in brackets), were 625 (407–875), 2361 (2064–2687) and 1763 (1548–2000) mg/kg dry soils for Cu, Pb and Zn, respectively. When Cu concentration reached 1600 mg/kg dry soil, eggs became green and the percentage of green eggs changed from 5%–20% after incubation for 2 days to 15%–30% after incubation for 4 days. At 3200 mg Cu/kg dry soil, tissues inside eggs were black and shrunken.     

Geographic variation in diapause induction and mode of diapause inheritance in Tetranychus pueraricola

Abstract:  Diapause induction and photoperiodic response curves were determined for 33 strains of Tetranychus pueraricola derived from kudzu vine at three constant temperatures (15, 18 and 20°C) under a short-day condition (10 : 14 h; light : dark). Females of all but one of the strains entered diapause at all three temperatures with little variation in diapause percentages among the strains. The exception was the southernmost strain, which was found to be a non-diapause (ND) strain. The critical photoperiod gradually decreased towards the south at a rate of about 1 h for each 5 degrees of latitude. The diapause strains (D1 and D2) exhibited 100% diapause, whereas the ND strain exhibited 0% diapause. By crossing these strains, we determined that 'non-diapause' was a dominant character over 'diapause' and the character was controlled by simple Mendelian inheritance. To clarify why the female progeny from the crosses between the D1 and ND strains did not segregate into the diapause and non-diapause phenotypes in a 1:1 ratio in the B₁ generation, round-robin crosses were carried out among the three strains. The results showed that the F₁ generation was reproductively compatible and showed high egg hatchability with a female-biased sex ratio. In the B₁ generation, the crosses between the D1 and ND strains and between the D1 and D2 strains exhibited extremely low egg hatchability and produced mostly female progeny, whereas offspring from the crosses between the D2 and ND strains showed more than 50% hatchability for B₁ eggs and a female-biased sex ratio. Thus, the absence of segregation observed in the crosses between the D1 and ND strains appears to be due to the severe hybrid breakdown that occurred in the B₁ generation.     

The compatibility of the fungicide azoxystrobin with Pochonia chlamydosporia, a biological control agent for potato cyst nematodes (Globodera spp.)

The biological control potential of Pochonia chlamydosporia against root-knot ( Meloidogyne spp.) and cyst-forming ( Heterodera and Globodera spp.) nematodes is widely appreciated. In spite of this, little has been undertaken to determine the compatibility of this fungus with modern fungicides. A series of experiments were undertaken to investigate the effect of azoxystrobin on P. chlamydosporia . Initial Petri dish experiments found a significant reduction in the growth of P. chlamydosporia . EC₅₀ values were calculated at 7 and 14 mg L⁻¹, respectively, for hyphal growth and chlamydospore germination. A microcosm experiment based on counts of the colony-forming units of the re-isolated fungus showed a reduction in EC₅₀ values for azoxystrobin in soil after 12, 20 and 40 days incubation (1.25, 1.00 and 3.00 mg kg⁻¹ soil, respectively). There was evidence the fungus recovered over time in response to azoxystrobin application. This was also demonstrated in a glasshouse experiment where EC₅₀ values of 1.32 and 4.4 mg kg⁻¹ soil were obtained for 35 and 49 days after planting (DAP), respectively.     

Influence of temperature, photoperiod and humidity on oviposition and egg hatch of the root-feeding flea beetle Longitarsus bethae (Chrysomelidae: Alticinae), a natural enemy of the weed Lantana camara (Verbenaceae)

The root-feeding flea beetle Longitarsus bethae Savini & Escalona, was introduced into South Africa as a candidate biological control agent for the noxious and invasive weed, Lantana camara L. As part of the study to predict the beetles' survival in its new range, the influence of climatic conditions on its egg development and reproductive performance were investigated in the laboratory. The threshold temperature (T degrees) and degree-days (DD) required for egg hatch were determined after exposing the eggs to various constant temperatures (12, 17, 22, 27 and 32 degrees C) in separate growth chambers. The DD required for egg hatch was 178.6, and the temperature threshold required for egg hatch was 11.3 degrees C. Survival of eggs varied from 27 to 56% at 32 and 17 degrees C, respectively, and was optimum between 17 and 25 degrees C. Oviposition was examined under high and low relative humidity (RH) regimes while egg hatch was determined at six RH levels, each maintained in a separate controlled growth chamber set at a constant temperature (25 degrees C). Whilst RH had no influence on oviposition, eggs were highly susceptible to aridity, and continuous exposure to relative humidity below 63% for more than three days was wholly lethal at 25 degrees C. Optimum egg hatch occurred at RH between 85 and 95% for up to 12 days. The effect of day length on oviposition and subsequent egg hatch was investigated under two photoperiod regimes. Neither oviposition nor subsequent egg hatch was influenced by photoperiod. The knowledge obtained will be useful for mass rearing as well as field release programmes for L. bethae.     

Chemical constituents and fumigant toxicity of essential oil from Carum copticum against two stored product beetles

Plant secondary metabolites play an important role in plant-insect interactions and therefore such compounds may have insecticidal or antifeedant activity against insects. Carum copticum C. B. Clarke （Apiaceae） is one of these plants that have medicinal effects on humans. The chemical composition of the essential oil from dry seeds of C. copticum was studied by gas chromatography （GC） and gas chromatography mass spectrometry （GC-MS）. Thymol （41.34%）,α-terpinolene （17.46%） and ρ-cymene （11.76%） were found to be the major constituents of the oil. In fumigant toxicity tests with the essential oil against adults of Sitophilus oryzae （L.） and Tribolium castaneum （Herbst） at 27 ±1℃ and 60% ± 5% RH, it was observed that S. oryzae （LC50 = 0.91 μL/L） were significantly susceptible than T. castaneum （LC50 = 33.14 μL/L）. The mortalities of the insect species reached 100% at concentrations higher than 185.2 μL/L and 12-h exposure time. The findings indicate the strong insecticidal activity of C. copticum oil and its potential role as a fumigant for storedproduct insects.     

The Ability of Barley Powdery Mildew to Grow in vitro

A technique was developed for the in vitro culture of Blumeria graminis f. sp. hordei , an obligate biotrophic pathogen of barley. Optimal growth occurred at pH 5.6 on a medium containing 39 gl^–1 potato dextrose agar, 40 gl^–1 shredded fresh barley leaves, 20 gl^–1 sucrose, 13 mgl^–1 kanamycin and 80 mgl^–1 benzimidazole. At 20°C (90% relative humidity), conidia germinated 48 h after inoculation, producing an average colony diameter of 1 cm after 10 days. However, numerous colonies were present on the medium after 15 days. Light microscopy showed that there was a positive relationship between the amount of leaf in the medium and fungus growth. The fungus retained its virulence during 60 days of storage in vitro , and was able to infect barley. This is a useful and novel technique that could be beneficial in barley pathology breeding programs.     

Ovicidal and larvicidal effectiveness of several insect growth inhibitors and regulators on the codling moth Cydia pomonella L. (Lep., Tortricidae)

Several insect growth inhibitors (IGIs) and regulators (IGRs) were tested in the laboratory for their ovicidal and larvicidal properties on the codling moth C. pomonella , by dipping apples in solutions of them. The IGIs which block chitin synthesis – diflubenzuron, hexaflumuron and teflubenzuron – were noticeably more effective against eggs than on newborn larvae with preventive ovicidal 50% lethality concentrations (LC₅₀) values of approximately 0.6, 1.3 and 15 p.p.m., respectively, and larvicidal LC₅₀ values of 104, 1208 and 204 p.p.m. Flufenoxuron, on the other hand, is almost as effective on larvae (LC₅₀ : 9.9 p.p.m.) as on eggs (LC₅₀ : 5.4 p.p.m.). Fenoxycarb, an IGR juvenile hormone analogue, acts as an excellent ovicidal product with an LC₅₀ value of 0.05 p.p.m. Tebufenozide, an IGR ecdyson (moulting hormone) agonist, is exclusively larvicidal with an LC₅₀ at 0.4 p.p.m. Methoxyfenozide, an IGR of the same family and currently being developed, acts as effectively on eggs as on larvae with ovicidal and larvicidal LC₅₀ values of about 0.6 and 0.8 p.p.m., respectively. When ovicidal products are applied as a curative treatment on eggs less than 24 h old, their effectiveness is much lower than that obtained from preventive application.     

Effects of Beauveria bassiana and Metarhizium anisopliae on mortality, fecundity and egg fertility of Tetranychus evansi

Abstract:  The susceptibility of various developmental stages of Tetranychus evansi Baker & Pritchard (eggs, larvae, protonymphs, deutonymphs and adults) to the entomopathogenic fungi Metarhizium anisopliae (Metschnikoff) Sorokin and Beauveria bassiana (Balsamo) Vuillemin was evaluated under laboratory conditions. Three concentrations (3.0 × 10⁶, 1.0 × 10⁷ and 1.0 × 10⁸ conidia/ml) of both fungi were used for each stage. The effect of fungal infection on fecundity and egg fertility was also investigated using both fungal species. Deutonymphs that survived the infection and developed into adult females were allowed to oviposit. Adults and deutonymphs were more susceptible to fungal infection than larval and protonymphal stages at all the concentrations. Nevertheless, the concentration level influenced the mortality of the different mite stages. Eggs were also susceptible to fungal infection and mortality was dose-dependent. Fungus-treated female mites laid fewer eggs than the controls but there was no significant difference in egg hatchability between the treatments.     

Relations between carbohydrate, water status and adventitious root formation in leafy pea cuttings rooted under various levels of atmospheric CO2 and relative humidity

Three levels of atmospheric CO₂ and 2 levels of relative humidity (RH) during the rooting period were tested for their effect on several factors presumed to influence adventitious root formation in leafy pea ( Pisum sativum L. cv. Alaska) cuttings. Compared to normal CO₂ levels (350 μl l⁻¹), neither 1800 nor 675 μl l⁻¹ CO₂ affected the rooting percentage or the number of roots per cutting. However, 1800 μl l⁻¹ CO₂ increased root and shoot dry weight, root length, carbohydrate levels in the base of the cuttings and water potential (Ψ_w) of cuttings compared to normal levels of CO₂. Compared to 87% RH. 55% RH decreased all of the above parameters, including the number of roots per cutting. A polyvinyl chloride antitranspirant (which partially blocks stomata and slows photosynthesis) applied simultaneously with 87% RH increased Ψ_w and root length but lowered all of the other above parameters, compared to 87% RH without antitranspirant. Increasing current photosynthate (products of photosynthetic activity after excision), carbohydrate, or Ψ_w either alone or together was associated with increased root system size but not necessarily with increased rooting percentage or root number. The data are consistent with a hypothesis that the number of roots per cutting increased with increasing current photosynthate and carbohydrate until some other factor became limiting. Also, the effect of Ψ_w on rooting percentage and root number was mediated through its effect on current photosynthate and carbohydrate.     

Non-target effects of three biorationale insecticides on two endolarval parasitoids of Liriomyza sativae (Dipt., Agromyzidae)

Abstract:  Side effects of two azadirachtin formulations [NeemAzal-U (17% azadirachtin) and NeemAzal^®-T/S (1% azadirachtin)] and two biorationale pesticides – Success^® (Spinosad) and Abamectin (Avermectin) – on two endoparasitoids Opius ( Opiothorax ) chromatomyiae and Neochrysocharis formosa of Liriomyza sativae were investigated under laboratory conditions. The eggs of O. chromatomyiae , and the eggs, larvae and pupae of N. formosa within the host or within the plant/host complex were exposed to NeemAzal, Success and Abamectin at different dose rates. Adult emergence of O. chromatomyiae from parasitized L. sativae in NeemAzal-U (0.75, 1.5, 2.25 and 3 g/l water) drenched soil was only slightly lower than from untreated control hosts. In contrast, adult emergence of unparasitized L. sativae was almost completely inhibited by NeemAzal-U, indicating a high, direct toxicity. Development of O. chromatomyiae within L3 of L. sativae was very much affected from topical applications of NeemAzal^®-T/S, Success^® and Abamectin at particular dose rates. Spraying of tomato leaves with NeemAzal^®-T/S revealed no detrimental effect on the adult emergence of N. formosa developing in mining L2 of L. sativae . This was in contrast to Success^® and Abamectin which strongly affected N. formosa adult emergence when applied at different immature developmental stages of N. formosa .     

Potential of some Metarhizium anisopliae isolates for control of Culex quinquefasciatus (Dipt., Culicidae)

Abstract: The potential of some isolates of Metarhizium anisopliae and Beauveria bassiana for use in the integrated management of Culex quinquefasciatus was evaluated. Metarhizium anisopliae isolate 1037 was selected in initial bioassays with a 50% lethal concentration (LC₅₀) of 1.97 × 10⁴ conidia/ml. This fungus caused higher mosquito larva mortality when applied as a conidial suspension to the surface of the water than as dry conidia, with a time to 50% lethal (LT₅₀) of 1 day compared with 3.6 days for the dry conidial application. However, results with UV- and heat-inactivated conidia did not confirm a possible role of fungal toxins in causing mortality when ingested by C. quinquefasciatus larvae. Metarhizium anisopliae did not remain active for as long as the bacterium Bacillus sphaericus isolate 2362. At 24 h after application, the fungus-induced mortality on mosquito larvae was significantly lower than the mortality caused by the bacterium. By the second day, almost no activity by the fungus was observed. Results suggest that M. anisopliae isolate 1037 has potential for use in mosquito control programmes.     

More effective induction of spawning with long-acting GnRH agonist in the shi drum, Umbrina cirrosa L. (Sciaenidae, Teleostei), a valuable candidate for Mediterranean mariculture

Three experiments of spawning induction in shi drum, Umbrina cirrosa L., were performed in six different commercial Italian hatcheries from May to August (water temperatures: 19–29 °C; salinity: 21–37 p.p.t.). In the first experiment, 119 females (1–4.7 kg), subdivided into 29 lots, were injected with a single dose (2, 5, 8, 10, 15 and 20  μ g kg⁻¹ body weight) of short-acting gonadotropin- releasing hormone agonist (GnRHa-S), des-Gly10,[D-Ala6]-LH-RH ethylamide. In the other two experiments, 85 females (0.7–5.8 kg), subdivided into 22 and four lots, were treated with one (40 or 80  μ g kg⁻¹) or three doses (40  μ g kg⁻¹) of long-acting GnRHa (GnRHa-L), respectively. GnRHa-S stimulated spawning in 69% of the 29 treated lots; the number of eggs laid reached a maximum of 130 000 and a weighted mean of 29 200 total eggs kg⁻¹. GnRHa-L elicited a spawning response in 95% of the 22 one-dose treated lots; the number of laid eggs was higher than with GnRHa-S, reaching a maximum of 213 100 and a weighted mean of 59 400 total eggs kg⁻¹. The yield of developing embryos in 67% of the single GnRHa-L treatments was higher (sometimes up to three times) than with GnRHa-S. Triple treatments of the four lots of females with GnRHa-L always resulted in spawning responses; the best result corresponded to a number of total laid eggs of 358 900 eggs kg⁻¹ with a yield of 177 300 developing embryos.     

The effects of environmental factors on rainbow smelt Osmerus mordax embryos and larvae

Experiments were conducted to identify environmental factors that influence the survival of rainbow smelt Osmerus mordax during their early life stages. Developing rainbow smelt embryos and yolk-sac larvae were cultured under controlled conditions with different dissolved oxygen (DO; 1·09, 2·18, 4·37 and 6·55 mg l⁻¹, pH (4·0, 4·5, 5·0, 5·5, 6·0 and 7·0), nitrate ( 0·7, 3·6, 7·3, 14·6 and 29·2 mg l⁻¹), phosphate (0·04, 0·21, 0·42, 2·08 and 4·17 mg l⁻¹) and salinity (0, 5, 10, 15, 20 and 30) levels. Rainbow smelt embryos were also incubated with simulated tidal salinity fluctuations (2–28), ultraviolet radiation (irradiances of 2·8, 6·2 and 5·1 W m⁻²) and under natural conditions in two rainbow smelt spawning rivers. In the laboratory, hatch was only impaired under the lowest DO and pH conditions (0 and 13% hatch, respectively) and at highest constant salinity levels (0% hatch). Larval survival was only affected by pH levels ≤5·0. The experiment that compared hatch under natural conditions was terminated when embryos became covered with silt and fungus. These results suggest that water acidification, sediment and fungal growth may affect rainbow smelt survival during their early life stages.     

Sprays of emulsifiable Beauveria bassiana formulation are ovicidal towards Tetranychus urticae (Acari: Tetranychidae) at various regimes of temperature and humidity

Aerial conidia of Beauveria bassiana in an emulsifiable formulation germinated by >95% after 24 h exposure to the regimes of 20, 25 and 30 degrees C with 51%, 74% and 95% RH. Ovicidal activities of the formulation towards two-spotted spider mite, Tetranychus urticae, were assayed at the concentrations of 0, 18, 160 and 693 conidia mm(-2) sprayed separately onto fava bean leaves including 39 (25-76) eggs per capita. All the sprayed eggs on the leaves were directly exposed to the different regimes for hatch after 24 h maintenance in covered Petri dishes. Generally, hatched proportions increased over post-spray days and decreased with the elevated fungal concentrations; no more eggs hatched from day 9 or 10 onwards. Based on the counts of the hatched/non-hatched eggs in the different regimes, the final egg mortalities were 15.0-40.4%, 48.9-66.6% and 62.9-87.5% at the low, medium and high concentrations, respectively, but only 5.6-11.3% in blank controls. The RH effect on the fungal action was significant at 20 and 25 degrees C but not at 30 degrees C whereas the effect of temperature was significant at 51% and 74% RH but not at 95% RH. Probit analysis of the egg mortalities versus the fungal sprays generated median lethal concentrations (LC(50)) of 65-320 conidia mm(-2) at all the regimes, and of only 65-78 conidia mm(-2) at 25-30 degrees C with 74-95% RH. The results highlight ovicidal activities of the emulsifiable formulation against the mite species at the tested regimes and its potential use in spider mite control.