Effect of five diatomaceous earth formulations against Tribofium castaneum （Coleoptera： Tenebrionidae）, Oryzaephflus surinamensis （Coleoptera： Silvanidae） and Rhyzopertha dominica （Coleoptera： Bostrychidae）

Laboratory bioassays were conducted to determine the effect of food source on the survival of Tribolium castaneum Herbst, Oryzaephilus surinamensis L. and Rhyzopertha dominica F., after exposure to five diatomaceous earth （DE） formulations： Protect-It, Insecto, Perma-GuardTM, Dryacide and SilicoSec. Adults of these species were exposed to DEs at the rate of 0.5 mg/cm^2 for 1 day on filter paper inside plastic Petri dishes. After exposure, the initial mortality was counted and live individuals of the three species were held for a week in glass vials containing 50 mg wheat flour, rice and whole wheat, respectively. In the second experiment, after 1 day exposure to DEs, beetles were transferred to Petri dishes without food and held for a week to determine if the presence of food source would decrease the mortality of beetles. Experiments were carried out at 27℃ and 55% RH in the dark. The initial mortality in both of the experiments reached 100% for the three species exposed to Protect-It and in the case ofR. dominica and O. surinamensis exposed to Dryacide. In contrast, low level of mortality （〈 10%） was observed for T. castaneum exposed to Perma-GuardTM and Insecto. The mortality after the post-treatment period on food was decreased for the three species exposed to Perma-GuardTM and in the case of T. castaneum and R. dominica exposed to Insecto and SilicoSec. Adults of O. surinamensis were the most susceptible followed by R. dominica and 100% adult mortality was obtained, whereas T. castaneum were the least susceptible beetles to DEs. Protect-It and Dryacide were the most efficient DE formulations and can be used effectively in a stored grain integrated pest management program.     

Laboratory and field evaluation of entomopathogenic nematodes for control of Agriotes obscurus (L.) (Coleoptera: Elateridae)

The susceptibility of the dusky wireworm, Agriotes obscurus (L.) (Coleoptera: Elateridae), to different species and strains of entomopathogenic nematodes was tested in a virulence assay in the laboratory. Larvae were exposed to different nematode doses of 50 and 100 IJs/cm². At a dose of 50 IJs/cm², only a commercial strain Heterorhabditis bacteriophora Poinar and the native strain Steinernema carpocapsae (Weiser) B14 caused increased mortality compared with the control (11.1% and 13.3% mortality, respectively). At the higher dose tested, all strains (except Steinernema sp. D122) were virulent to A. obscurus larvae. Steinernema carpocapsae B14 caused higher mortality of wireworm (75.6%) and was used for the assay conducted in cages, with a dose of 100 IJs/cm², in field conditions. The results showed that S. carpocapsae B14 controlled 48.3% of A. obscurus larvae, demonstrating that some entomopathogenic nematodes have the potential to control larvae of A. obscurus. However, further work is needed to improve their efficacy.     

The genus Sterechinm (Echinodermata: Echinoidea) on the Weddell Sea shelf and slope (Antarctica): distribution,abundance and biomass

Summary Two species of the echinoid genus Sterechinus were documented from 92 trawl stations and 55 photographic stations in the eastern and southern Weddell Sea between 100 and 1200 m water depth. We found two species occuring along the whole shelf and slope, S. neumayeri being more abundant above 450 m water depth and S. antarcticus dominating the deeper regions. The size-frequency distributions of both species indicate differences in growth, mortality and longevity. First estimates of abundance and biomass of S. neumayeri and S. antarcticus are 0.085 ind/m² & 0.005 gAFDW/m² and 0.022 ind/m² & 0.005 gAFDW/m², respectively.AWI Publication No. 392     

Isolation and pathogenicity of some South African entomopathogenic fungi (Ascomycota) against eggs and larvae of Cydia pomonella (Lepidoptera: Tortricidae)

Virulent entomopathogenic fungal strains against Cydia pomonella (Lepidoptera: Tortricidae) were isolated and identified in the Western Cape Province of South Africa. Thirty-nine isolates belonging to six species were obtained using the insect bait method. Generally, Metarhizium robertsii (Ascomycota: Hypocreales) was the most frequently encountered species representing 51% of the total number of isolates collected from the soil samples. This is the first report of M. robertsii from southern Africa. Mortality data from an immersion bioassay indicated that the 39 fungal isolates were pathogenic against fifth instar larvae of C. pomonella inducing 47–85% insect mortalities. Two M. robertsii strains, MTL151 and GW461, induced 85% larval mortality and were selected for further evaluations. The exposure of freshly laid eggs to wax papers that were pre-treated with fungal spores ranging from 10³ to 10⁸ spores ml^?1 of MTL151 and GW461 resulted in a significant reduction of egg hatchabilities, from 95 to 66% and 93 to 71%, respectively as spore concentration increased. First instar larval neonates were exposed to apples that were pre-sprayed topically with varied conidia suspensions (10³?10⁸ spores ml^?1). The mean percentage of participating apples with larvae in their cores/flesh significantly reduced from 53 to 10% (MTL151) and 76 to 10% (GW461) of 10 apples, and a concurrent decrease in the incidence of apple fruit rot was observed as conidia concentration increased. Up to 90% of apples treated with 1 × 10⁸ spores ml^?1 had no larvae present in their cores and this result compared favourably with the commercial pesticide Fruitfly®, containing the active ingredient cypermethrin (20 g/l) used at a recommended dose of 0.25 ml/250 ml of water.     

Stage-specific mortality of Rhagoletis indifferens (Diptera: Tephritidae) exposed to three species of Steinernema nematodes

Mortality of larval, pupal, and adult western cherry fruit fly, Rhagoletis indifferens (Tephritidae) exposed to the steinernematid nematodes Steinernema carpocapsae, Steinernema feltiae, and Steinernema intermedium, was determined in the laboratory and field. Larvae were the most susceptible stage, with mortality in the three nematode treatments ranging from 62 to 100%. S. carpocapsae and S. feltiae were equally effective against larvae at both 50 and 100 infective juveniles (IJs)/cm². S. intermedium was slightly less effective against larvae than the other two species. Mortalities of R. indifferens larvae at 0, 2, 4, and 6 days following their introduction into soil previously treated with S. carpocapsae and S. feltiae at 50 IJs/cm² were 78.6, 92.5, 95.0, and 77.5% and 87.5, 52.5, 92.5, and 70.0%, respectively, and at 100 IJs/cm² were 90.0, 92.0, 100.0, and 84.0% and 90.0, 50.0, 42.0, and 40.0%, respectively. There was no decline in mortality caused by S. carpocapsae as time progressed, whereas there was in one test with S. feltiae. Larval mortalities caused by the two species were the same in a 1:1:1 vermiculite:peat moss:sand soil mix and a more compact silt loam soil. In the field, S. carpocapsae and S. feltiae were equally effective against larvae. Pupae were not infected, but adult flies were infected by all three nematode species in the laboratory. S. carpocapsae was the most effective species at a concentration of 100 IJs/cm² and infected 11–53% of adults that emerged. The high pathogenicity of S. carpocapsae and S. feltiae against R. indifferens larvae and their persistence in soil as well as efficacy in different soil types indicate both nematodes hold promise as effective biological control agents of flies in isolated and abandoned lots or in yards of homeowners.     

Differential susceptibility of Amblyomma maculatum and Amblyomma americanum (Acari:Ixodidea) to the entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae

Nymph and adult ticks from Ambylomma americanum and Ambylomma maculatum were treated with conidia and blastospores of the entomopathogenic fungi Beauveria bassiana (90517) and Metarhizium anisopliae (20500). Fungal suspensions of conidia harvested from potato dextrose plates containing 10⁸ conidia/ml caused greater than 90% mortality in adult A. maculatum but less than 10% mortality in adult A. americanum over a 28 day time course. Similarly, infection with M. anisopliae (10⁸ conidia/ml) resulted in 60 and 15% mortality in A. maculatum and A. americanum, respectively. Nymphs of both tick species were more susceptible to fungal infection reaching mortality rates of almost 100% for A. maculatum and over 35% for A. americanum. Scanning electron microscopy of infected ticks showed rapid attachment, germination, and proliferation of fungal spores on A. maculatum cuticles, and to a much lesser extent on A. americanum cuticles. Pentane extracts of A. americanum cuticle hydrocarbons inhibited germination and hyphal growth of B. bassiana conidia, whereas no inhibition was observed using A. maculatum extracts. Significant mortality towards A. americanum was observed (>60%, 28 days) only when the ticks were treated with B. bassiana directly from the growth medium (10⁷ blastospores/ml, grown for 3–4 days in Sabouraud dextrose + 0.5% yeast extract liquid media). These results indicate tick species display differential susceptibility to the entomopathogenic fungi B. bassiana and M. anisopliae, and that the ability to overcome fungistatic compounds present in the tick epicuticle may determine the likelihood of successful infection and virulence.     

Entomopathogenic Nematodes for Control of Codling Moth,Cydia pomonella(Lepidoptera: Tortricidae): Effect of Nematode Species, Concentration, Temperature, and Humidity

The susceptibility of codling moth diapausing larvae to three entomopathogenic nematode species was assessed in the laboratory using a bioassay system that employed cocooned larvae within cardboard strips. The LC₅₀values forSteinernema carpocapsae, S. riobrave,andHeterorhabditis bacteriophorawere 4.7, 4.8, and 6.0 infective juveniles/cm², respectively. When a discriminating concentration of 10 infective juveniles/cm²of each of the three nematode species was evaluated at 15, 20, 25, and 30°C,S. carpocapsaewas the most effective nematode with mortalities ranging from 66 to 90%. Mortalities produced byS. riobraveandH. bacteriophoraat the four temperatures were 2–94 and 25–69%, respectively. Studies were also conducted to test infectivity at 10, 35, and 40°C. No mortality was produced by any of the nematode species at 10°C.S. riobravewas the most infective nematode at 35°C producing 68% mortality which was more than twice that observed forS. carpocapsaeorH. bacteriophora.Codling moth larvae treated with 10 infective juveniles/cm²ofS. carpocapsaeand kept in 95+% RH at 25°C for 0–24 h followed by incubation at 25–35% RH indicated that more than 3 h in high humidity was needed to attain 50% mortality. Trials ofS. carpocapsae, S. riobrave,andH. bacteriophoraat 50 infective juveniles/cm²against cocooned larvae on pear and apple logs resulted in reductions of codling moth adult emergence of 83, 31, and 43%, respectively, relative to control emergence. Trials of the three entomopathogenic nematodes at 50 infective juveniles/cm²against cocooned larvae in leaf litter resulted in 99 (S. carpocapsae), 80 (S. riobrave), and 83% (H. bacteriophora) mortality, respectively. Our results indicate good potential of entomopathogenic nematodes, especiallyS. carpocapsae,for codling moth control under a variety of environmental conditions.     

Interactions among vegetable-infesting aphids,the fungal pathogen Metarhizium anisopliae (Ascomycota: Hypocreales) and the predatory coccinellid Cheilomenes lunata (Coleoptera: Coccinellidae)

Entomopathogenic fungi are among biocontrol agents being considered for the control of aphids on a variety of crops. Predatory coccinellids, although generalist, are also among important natural enemies that must be conserved for aphid management. Laboratory studies were carried out to investigate the interaction between three vegetable-infesting aphids, Metarhizium anisopliae isolate ICIPE 62 and the coccinellid predator Cheilomenes lunata. At a concentration of 1?×?10⁸?conidial?ml^–1, the fungus was found to cause mortality of 7.5% to C. lunata, compared to 2.5% mortality in the control at 10?days post-treatment. Female adult C. lunata to which fungus-infected aphids were offered as prey never accepted them as food source in non-choice bioassays. However, live and dead non-infected aphids were fed upon. In choice bioassay, a total of 1–3 out of 24 infected non-sporulating aphids per species (average of 0.1–0.4 aphids per arena) were consumed by 48?h-starved C. lunata within a period of 60?min, but avoided sporulating cadavers. Foraging adult C. lunata enhanced the spread of conidia of M. anisopliae from infected cadavers to fourth instars Aphis gossypii feeding on okra (0.8–15.0% mortality), Brevicoryne brassicae (3.3–15.0% mortality) and Lipaphis pseudobrassicae (0.8–14.2% mortality) on kale plants. Results of this study demonstrate compatibility between M. anisopliae and C. lunata, and could provide a sustainable strategy for effective management of aphids on crucifers and okra cropping systems.     

Survival and fecundity of Dichroplus maculipennis and Ronderosia bergi (Orthoptera: Acrididae: Melanoplinae) following infection by Beauveria bassiana (Ascomycota: Hypocreales) under laboratory conditions

This study examined the effects of strain Beauveria bassiana (LPSC 1067) on nymphal development time, fecundity and adult survival in Dichroplus maculipennis and Ronderosia bergi under laboratory conditions. It was observed that infection with 1×10³ conidia/ml altered nymphal development time, fecundity and adult survival in both species. Mortality of D. maculipennis during third through the last instar (sixth) was significantly higher among treated nymphs (66±3.8%) than in controls (15±1.7%). Similarly, mortality in R. bergi during third through the last instar (fifth) was higher in treated nymphs (71±2.8%) than in controls (19±1.5%). Nymphal development times of both infected D. maculipennis and R. bergi were longer than controls. On the other hand, among survivors of both the species, control adults lived longer than infected adults. Finally, control grasshoppers of both species were much more successful reproductively than infected grasshoppers.     

Effect of entomopathogenic fungi upon adults of Stomoxys calcitrans and Musca domestica (Diptera: Muscidae)

The pathogenicity and virulence of 10 isolates of entomopathogenic fungi from the soil of lodging pens of dairy production units in Aguascalientes, Mexico, on adults of Stomoxys calcitrans and Musca domestica were determined. All isolates were pathogenic when exposed by aspersion to a concentration of 1×10⁸ conidia/ml, causing between 20.3 and 91.7% mortality in S. calcitrans and between 31 and 91.7% in M. domestica at 7 days post-exposure; in S. calcitrans isolates of Beauveria bassiana (Bb114) and Metarhizium anisopliae (Ma135), sensu lato, were the most noteworthy as mortality reached above 90% with an LC₅₀ of 3.5×10⁵ conidia/ml for Bb114, while for Ma135 reached 1.6×10⁴ conidia/ml. In M. domestica Ma134 and Ma135 showed mortality above 90% with an LC₅₀ of 4.3×10⁴ and 1.4×10⁵ conidia/ml, respectively.     

Attractiveness of bait matrices and matrix/toxicant combinations to the citrus pests Iridomyrmex purpureus (F.Smith) and Iridomyrmex rufoniger gp sp. (Hym., Formicidae)

Abstract: Six bait matrices were tested for palatability to the ants Iridomyrmex purpureus and I. rufoniger gp sp., which are important pests of citrus in south‐eastern Australia. Granulated citrus pulp and rice bran impregnated with brown sugar were not accepted by either species, but ground dry dog food and ground insects (with or without added sugar) were highly attractive to both ant species. The ground dog food was impregnated with various toxicants at concentrations of up to 1% (w/w) and tested for palatability to both ant species. Technical grade pyriproxyfen, fipronil, and fenoxycarb were incorporated using organic solvents, whereas formulated fenoxycarb (Insegar^®) was incorporated as an aqueous suspension prior to drying and granulation. Relative to the blank samples (carrier solvents only), bait acceptance by I. purpureus was not significantly reduced (P > 0.05) by any of the treatments except 1% technical fenoxycarb. Bait acceptance by I. rufoniger gp sp. was significantly suppressed by 0.2% fipronil, but not by higher concentrations. When water was used as the carrier solvent the blank sample was significantly (P < 0.05) less attractive to I. purpureus than the untreated control, suggesting that wetting of dog food‐based baits in field situations may irreversibly reduce their attractiveness. Laboratory colonies were used in choice and no‐choice tests to assess the efficacy of dog food baits containing fipronil (0.05–0.2% w/w). The corrected mortality for I. purpureus ranged from 88 to 100% and from 90 to 97% in the no‐choice and choice tests, respectively. In no‐choice tests I. rufoniger gp sp. corrected mortality varied from 52 to 60%, but in choice tests the corrected mortality did not exceed 26%. Ground dog food containing fipronil (0.05–0.2% w/w) has the potential to provide effective control of I. purpureus in citrus orchards, but alternative toxicants or lower fipronil concentrations may be required for control of I. rufoniger gp sp.     

Synergism between Metarhizium anisopliae (Deuteromycota: Hyphomycetes) and Boric Acid against the German Cockroach (Dictyoptera: Blattellidae)

Mortality of German cockroaches, Blattella germanica (L.), caused by Metarhizium anisopliae (Metschnikoff) Sorokin strain AC-1 alone and in combination with different formulations of boric acid, was evaluated in laboratory bioassays. Topical application of M. anisopliae alone (8.96 × 10⁹ conidia/m²) required 28 days to cause >92% cockroach mortality (LT₅₀ = 10 days). In contrast, in combination with boric acid (topically applied as a dust or in drinking water), M. anisopliae killed cockroaches significantly faster than without boric acid. M. anisopliae conidial dust (8.96 × 10⁸ conidia/m²) with either 12.5% (w/w) boric acid dust or 0.1% (w/v) boric acid in drinking water killed 100% of the cockroaches in only 8 days (LT₅₀ = 5 days) and 10 days (LT₅₀ = 6 days), respectively, without compromising the fungus emergence from cadavers. Replacement of M. anisopliae with flour dust or heat-killed M. anisopliae conidia eliminated this effect, demonstrating that it was not the consequence of greater boric acid ingestion due to more extensive cockroach grooming upon exposure to M. anisopliae conidia. Moreover, injections of a low dose of M. anisopliae, which caused only 30% mortality, together with sublethal concentrations of boric acid into the cockroach hemocoel resulted in a doubling of mortality. Statistical analysis demonstrated a synergistic interaction between these two insecticides.     

Distribution of native legumes (Leguminoseae) in frequently burned longleaf pine (Pinaceae)-wiregrass (Poaceae) ecosystems

Legume species distribution and abundance and selected environmental variables were quantified across a complex gradient (varying in both water-holding capacity and fertility) for frequently burned longleaf pine (Pinus palustris)–wiregrass (Aristida stricta) ecosystems. Legumes were present in all months; however, abundance peaked in June and was minimal after killing frosts in October. Legume species were prominent in the flora (43 species encountered) ubiquitous (94% of 2-m² subplots had at least one legume species), and abundant (nearly 120 000 stems/ha). Although most species were widely distributed throughout the gradient, Lespedeza angustifolia was distinctly associated with the more hydric end of the gradient, while both Petalostemon pinnatum and Galactia microphylla were located in the more xeric extreme. The percentage variation in species that could be accounted for by environmental variation was low (27%). Of the variation that could be accounted for, a number of environmental variables were important, including soil moisture, pine basal area (i.e., light), and bivalent base cations (e.g., Ca²⁺). Although gradients in resource availability among sites did not affect the distribution of species or abundance of legumes strongly, variation in resources are likely to regulate N₂-fixation rates of the various native legume species, and thereby affect ecological functions such as maintenance of N capital and productivity.     

Pathogenicity of Beauveria bassiana (Deuteromycotina: Hypomycetes) to Larvae of the Small Poplar Longhorn Beetle, Saperda populnea (Coleoptera: Cerambycidae)

The small poplar longhorn beetle, Saperda populnea is an important pest of Lombardy poplars (Populus nigra L.) in Turkey. A survey for natural entomopathogenic fungi of S. populnea larvae was made in Erzurum, Turkey, during the period 2004–2005. Larvae (13.5%) infected with a strain of the fungus Beauveria bassiana were found. The pathogenicity of B. bassiana strain 46 was conducted with different concentrations of conidia (10⁶, 10⁷ and 10⁸ conidia/ml) of this isolate on S. populnea larvae. The lowest concentration (10⁶ conidia/ml) caused about 56% mortality within 6 days. One hundred percent mortality was achieved after median lethal time (LT₅₀) of 4.6 and 4.4 days for 10⁷ and 10⁸ conidia/ml, respectively. There were no significant differences between median lethal times. This is the first record of natural infection of S. populnea larvae by B. bassiana.     

Formulation and optimisation of various nuclear polyhedrosis virus isolates and assessment of their insecticidal activity against Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) larvae

Helicoverpa armigera (Hubner) is a pest that poses serious threat to the tomato crop in India. Larvae of this species are susceptible to the nucleopolyhedrovirus (NPV), which has attracted interest as a potential biocontrol agent. Rearing of larvae in natural diet resulted in less number of pupae, while in artificial diet more pupae and healthy adults were obtained. The NPV was tested for its insecticidal action against H. armigera in natural and artificial diets. The bioassay results of inoculated H. armigera nucleopolyhedrosis virus (HaNPV) with different concentrations indicate that the 4.0 g/l dosage caused maximum mortality (70.3% and 60.54%), and minimum mortality 46.83% and 44.08% was recorded in the 0.5 g/l dosage under laboratory and pot culture conditions, respectively. Polyhedral inclusion bodies (PIBs) were estimated using a standard haemocytometer. According to the estimate, purified PIBs were found at a concentration of 1 × 10⁹/ml. The different formulation of NPV, i.e. wettable fine powder with a hue of white, had a particle size of 100 μm with a concentration of 1 × 10⁸/ml. The encapsulated product was found to be in the form of beads and was red in colour with a concentration of 1 × 10⁸ PIBs/ml. The effectiveness of NPV against H. armigera larvae was noted at maximum LC₅₀ values at a concentration of 1 × 10⁹/ml. Qualitative analysis estimates showed that protein polyhedrin and enzyme chitinase had a molecular weight of 33 and 45 kDa, respectively. Viral DNA was isolated from NPV-infected larvae and was then separated using SDS-PAGE. The estimated polyhedrin with a molecular weight of 33 kDa, which is responsible for the increased mortality percent of larvae, was confirmed by the bioassay. Hence it was concluded that NPV is ecofriendly in the management of pests on tomato and other crops.     

Infectivity of Steinernema mushtaqi (Rhabditida: Steinernematidae) against insect pests and their mass production

The infectivity of entomopathogenic nematode (EPN), Steinernema mushtaqi was tested against legume pod borer, Maruca vitrata, tobacco caterpillar, Spodoptera litura, blue butterfly, Lampides boeticus, red hairy caterpillar, Amsacta moorei, brown bug, Clavigralla gibbosa, mealy bug, Centrococcus somatics, fruit borer, Earias vittella and green bug, Nezara viridula larvae and in vivo mass production of the above-tested species of EPN have been carried out during 2008. S. mushtaqi was found to be more pathogenic to A. moorei, as it brought about 100% mortality within 48 h, than to S. litura, L. boeticus, N. viriduala and E. vittella, as mortality occurred within 72 h; whereas this level of mortality was recorded in C. somatis, C. gibbosa and M. vitrata within 144 h. No mortality was observed in the control treatment. Multiplication of S. mushtaqi and the yield of infective juveniles (IJs) on these insects was the highest (0.94 × 10⁵ IJs/cadaver) from N. viriduala, followed by S. litura (0.76 × 10⁵ IJs/cadaver), L. boeticus as also C. gibbosa (0.31 × 10⁵ IJs/cadaver) and M. vitrata (0.20 × 10⁵ IJs/cadaver). Very poor populations of IJs were found from A. moorei (0.15 × 10⁵ IJs/cadaver) and C. somatics (0.01 × 10⁵ IJs/cadaver). No multiplication of IJs was found from the cadaver of E. vittella. This opens a new hope of utilising S. mushtaqi in the insect pests management programme.     

Isolation and virulence of entomopathogenic fungi against the great spruce bark beetle,Dendroctonus micans (Kugelann) (Coleoptera: Scolytidae)

Twelve fungal strains including Lecanicillium muscarium (Petch.) Zare and Gams, Isaria farinosa (Holmsk.) Fr., Fusarium sp., Beauveria bassiana Sensu Lato and Beauveria sp. were isolated from larvae and adults of D. micans. In addition, virulence of these isolates against this pest was determined. Conidia suspensions of 1×10⁶ conidia mL^–1 were applied to larvae and adults. The highest mortality and mycosis for larvae were obtained from isolate ARSEF 9271 (Beauveria bassiana) with 90% mortality and mycosis within 10 days. ARSEF 9271 also produced 93% mortality and mycosis in adults. On the other hand, the highest mortality and mycosis for adults were obtained with isolate ARSEF 9272 (Beauveria sp.), with 100% mortality and 80% mycosis within 10 days. These results indicate that isolates ARSEF 9271 and ARSEF 9272 seem to be the most promising potential fungal biocontrol agents against D. micans.     

Toxic and repellent properties of Xylopia aethiopica (Dunal) A. Richard on Tribolium castaneum Herbst infesting stored millets,Pennisetum glaucum (L.) R. Br.

The toxicity and repellency of Xylopia aethiopica seed extract was investigated in the laboratory against Tribolium castaneum Herbst. Concentration and days after treatment (DAT) caused a significant increase in T. castaneum adult mortality with an interaction effect of both on mortality when filter paper was impregnated with X. aethiopica extract. At 0.2 ml/60 cm² extract, significant mortality was observed at three–seven DAT when compared with one DAT. At 0.4 ml/60cm², 100% mortality was recorded at the lowest exposure period of one DAT. When 0.2 ml extract was applied to 5 g millet seeds, mortality at five–seven DAT was significantly higher than mortality observed in the control. Although repellency was dose-dependent, the percentage of T. castaneum that were repelled from treated filter paper was not significant. At 0.4 ml/60 cm², Class II repellency (26.7%) was observed. The results suggest that X. aethiopica can only effectively control T. castaneum populations that have infested millet but do not prevent cross-infestation via repellency.     

Bipolaris eleusines,a potential mycoherbicide candidate for control of barnyardgrass (Echinochloa crus-galli)

An isolate of Bipolaris eleusines was investigated as a potential candidate for biocontrol of barnyardgrass and additional weeds in paddy rice fields and for safety to selected crop species under greenhouse conditions. Barnyardgrass appeared more susceptible at the three-leaf stage than older plants, and disease severity increased as the fungal inoculum increased from 1 × 10⁵ to 1 × 10⁷ conidia/ml when sprayed till run-off. The high application rate caused 73% mortality of barnyardgrass, relative to the non-treated control, but increasing application rate to >1 × 10⁷ conidia/ml did not enhance efficacy (P >.05). This B. eleusines isolate showed no pathogenicity to rice (Oryza sativa spp. indica, O. sativa spp. japonica and an O. sativa hybrid), corn, wheat or any dicot crop species tested while causing slight infection on sorghum and barley. We conclude that B. eleusines, with high efficacy against barnyardgrass and demonstrated safety to rice, is a promising mycoherbicide candidate worthy of further evaluation and development for control of barnyardgrass in paddy rice fields.     

ROLE OF RECRUITMENT IN STRUCTURING BEDS OF SARGASSUM SPP. (PHAEOPHYTA) AT ROTTNEST ISLAND,WESTERN AUSTRALIA1

The importance of annual recruitment to the structure of adult stands of Sargassum was determined for a mixed species Sargassum bed at Rottnest Island, Western Australia. The morphologically similar species Sargassum spinuligerum Sonder, S. distichum Sonder, and S. podacanthum Sonder grew together in the shallow subtidal (6 m). Positive species determinations were only possible when thalli were reproductive, so recruits, bases, and vegetative annuals for all species were grouped together. Densities of recruits, perennial bases, vegetative annuals, and reproductive annuals were determined at monthly intervals from 20 randomly placed 0.25-m^?2 quadrats. Recruitment and mortality for recruits and adults were further determined at three monthly intervals from 6-×-1-m^?2 permanent quadrats. The density of adults varied little with season (between 32 and 58 m^?2). Growth of annuals was initiated in April, thalli became reproductive by late August–early September, and senescence occurred in December–January. Density of recruits was highly variable (1.6–210 individuals-m^?2) and peaked seasonally during late summer (January–February) and then declined rapidly. Adults showed a complete turnover of thalli in the bed over 25–27 months. Adult mortality was compensated by annual recruitment from propagules (43%) and vegetative regeneration from fragments of holdfasts left on the reef (57%). A seasonal pattern in survivorship was observed for adults that grew from recruits with higher initial numbers and lower mortalities for August and November cohorts. Little seasonally was observed in survivorship of adults that grew vegetatively from remnant crusts. Although initial cohort sizes were smaller for adults grown from recruits than from remnant crusts, mortality was lower, resulting in similar contributions to adult density from both recruits and remnant crusts. Recruitment from propagules and vegetative regeneration played an important role in buffering the adult stand from high rates of mortality and reducing seasonal variation in adult density and contributed to the persistence and seasonal structure of Sargassum beds at Rottnest Island.