Environmental and behavioral constraints on the infection of wireworms by Metarhizium anisopliae

Environmental and behavioral factors that affect the infection of wireworms [Agriotes obscurus L. (Coleoptera: Elateridae)] by a unique isolate of Metarhizium anisopliae Sorokin (Hypocreales: Clavicipitaceae) were studied. After wireworms were placed in soil containing 10(6) M. anisopliae conidia/g and incubated at 6, 12, or 18 degrees C, significant disease development and wireworm mortality occurred only in those wireworms incubated at 18 degrees C. At this temperature, mortality was found to be dependant on the time exposed to the contaminated soil, and a minimum exposure time of 48 h was required to cause significant levels of mortality. Despite the restrictive effect of cooler temperatures on disease development and mortality, infected wireworms did not choose temperatures that inhibited disease development when given the opportunity to do so in a separate experiment. Finally, wireworms were repelled by M. anisopliae-contaminated soil at a rate that increased with the soil conidia concentration, but the rate of emigration was reduced when a food source was present. The results of this study indicate that factors including temperature, time exposed to M. anisopliae, conidia soil concentration, and food availability will affect mortality rates of wireworms and are likely to affect field performance of M. anisopliae as a biological control.     

Note on the effect of wireworms of the genera Agriotes and Corymbites on crop yields

Experiments were made to illustrate the regular falling off of yield of crops due to increasing wireworm populations under controlled conditions. The genus Corymbites was shown to cause as much damage as Agriotes; Athous was less harmful. The damage caused to various cereals by Agriotes is contrasted.     

Aggregation and mortality of Agriotes obscurus (Coleoptera: Elateridae) at insecticide-treated trap crops of wheat

Agriotes obscurus (L.) wireworms assembled in increasing numbers at rows of treated (Agrox DL Plus seed treatment) and untreated wheat, Triticum aestivum L., planted at increasing densities (0, 0.15, 0.30, and 0.60 seeds/cm). In treated wheat plots at all planting densities, no wireworm damage to seedlings was apparent, and total wireworms taken in core samples in wheat rows increased according to the asymptotic equation y = B0(1 -e(-Blx)), where B0 is the asymptote, B1 is the slope of the initial rise, and x is the seeding density. The number of dead wireworms in treated plots increased linearly and intercepted the asymptotic models (theoretical point at which 100% mortality of assembled population occurs) at 0.95 seeds/cm on 11 June and 1.14 seeds/cm on 18 June 1996. Untreated wheat at all densities planted had severe wireworm damage and significantly reduced stand. Populations that had assembled at the surviving untreated wheat were fewer than in the treated wheat plots, and although increasing with seeding density, did not follow the asymptotic model. The data suggest that A. obscurus populations can be assembled and killed in fallowed fields in large numbers at treated trap crops of wheat over a 19-d period when planted in rows spaced 1 m apart at a linear seeding density of 1.5 seeds/cm.     

Predation of Thereva nobilitata (Fabricius) (Diptera: Therevidae) on Agriotes obscurus L. (Coleoptera: Elateridae)

Little is known about the natural enemies of wireworms (Coleoptera: Elateridae), but there are frequent anecdotal reports of (usually unnamed) stiletto fly larvae (Diptera: Therevidae) preying on various species. We observed larvae of Thereva nobilitata (Fabricius) feeding on larvae of the dusky wireworm, Agriotes obscurus L., during the summer of 2011, in Agassiz, British Columbia. This finding is of interest as: both the predator and the wireworm are introduced species to this area from Europe; T. nobilitata is uncommon in North America; and this predator has not been associated with any wireworm species previously. We observed that larvae of male and female T. nobilitata will feed on various sizes of A. obscurus larvae, most feeding being carried out by the smallest T. nobilitata larvae. These findings suggest future work should assess the potential for therevid larvae as top‐down regulators of Agriotes larvae under field conditions.     

Mortality of a wireworm, Agriotes obscurus (Coleoptera: Elateridae), after topical application of various insecticides

Ten insecticides representing seven chemical groups were applied at various concentrations topically by using a Potter Spray Tower to evaluate their relative toxicities on the European wireworm Agriotes obscurus L. (Coleoptera: Elateridae). Wireworms were stored at 15 degrees C after exposure to organophosphate (OP) (chlorpyrifos, diazinon), pyrethroid (tefluthrin), thianicotinoid (thiamethoxam, clothianidin), chloronicotinoid (imidacloprid, acetamiprid), phenyl pyrazole (fipronil), organochlorine (lindane), and spinosyn (spinosad) insecticides, and their postapplication health was evaluated weekly for up to 301 d. LC50, LC90, LT50, and LT90 values were calculated for each chemical except acetamiprid, and compared with those of lindane, clothianidin, and chlorpyrifos. Wireworms exposed to OPs died or recovered more quickly (LT50 < 20 d, LT90 < 50 d), than those exposed to all other insecticides tested except tefluthrin (LT50 = 25.5 d, LT90 = 66.5 d). Wireworms exposed to sublethal concentrations of all neonicotinoids quickly became moribund after application but made a full recovery. Wireworms exposed to fipronil at concentrations near the LC90 value showed no intoxication symptoms for up to 35 d, and they did not recover after symptoms developed. For each chemical, increasing the concentration increased the time required for wireworms to recover but decreased the time required to kill wireworms. Fipronil was highly toxic to wireworms (LC50 = 0.0001%), but acetamiprid (LC50 = 1.82%), imidacloprid (LC50 = 0.83%), tefluthrin (LC50 = 0.23%), diazinon (LC50 = 0.54%), and spinosad (LC50 = 0.51%) were not. The toxicity of both clothianidin (LC50 = 0.07%) and thiamethoxam (LC50 = 0.17%) were similar to those oflindane (LC50 = 0.06%) and chlorpyrifos (LC50 = 0.10%).     

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.     

Susceptibility of spinosad in Musca domestica (Diptera: Muscidae) field populations

The toxicity of spinosad was determined in one susceptible and five insecticide-resistant laboratory strains of house fly, Musca domestica L. Spinosad was relatively slow-acting, but highly toxic to house flies. In a feeding bioassay, spinosad LC50 at 72 h was 0.51 microg of spinosad per gram of sugar, making it 6.3- and 3.5-fold more toxic to house flies compared with azamethiphos and methomyl, respectively. In topical application bioassay, the LD50 at 48 h of spinosad in susceptible house flies was 40 ng per 20 mg of house fly, making spinosad less toxic than the pyrethroid bioresmethrin synergized by piperonyl butoxide and the organophosphate dimethoate. The insecticide-resistant laboratory strains had resistance factors to spinosad at LC50 in feeding bioassay from 1.5 to 5.5 and at LD50 in topical application bioassay from 2.5 to 4.7, indicating that in house fly cross-resistance to the major insecticide classes will not initially be of major concern for the use of spinosad for house fly control. The toxicity of spinosad was also evaluated against 31 field populations of house flies collected from livestock farms across Denmark. The field populations were 2.2- to 7.5-fold resistant to spinosad at 72 h in feeding bioassay, but based on steep slopes in the bioassay and the limited variation of spinosad toxicity against the various field populations, we consider the field populations to be spinosad-susceptible. We propose a diagnostic dose of 12 microg of spinosad per gram of sugar in feeding bioassay with impregnated sugar for determination of resistant house flies, which is 10x the LC95 of the susceptible strain WHO and approximately = 2x the LD95 of the field populations. Spinosad showed no substantial cross-resistance to the pyrethroid bioresmethrin synergized by piperonyl butoxide, the anticholinesterases dimethoate, azamethiphos, methomyl, and spinosad in house fly field populations.     

Virulence, horizontal transmission, and sublethal reproductive effects of Metarhizium anisopliae (Anamorphic fungi) on the German cockroach (Blattodea: Blattellidae)

Virulence of Metarhizium anisopliae (Metschnikoff) Sorokin strain EAMa 01/121-Su against the German Cockroach, Blatella germanica (L.), was determined using four concentrations ranging from 4.2 x 10(6) to 4.2 x 10(9) spores per milliliter. The LD50 value was 1.4 x 10(7) spores per milliliter (56,000 spores per cockroach) and LT50 values were 14.8 days and 5.3 days for 4.2 x 10(8) and 4.2 x 10(9) spores per milliliter, respectively. An experiment was conducted to evaluate whether a fungal transmission could exist among infected and healthy cockroaches. Percentage mortality at a ratio of 1:10 of infected to unexposed cockroaches was 87.5% and LT50 was 12.2 days, which indicated the potential of this strain to be horizontally transmitted and to rapidly spread the infection in the insect population. The effect of a sublethal dose (ca. LD60) of M. anisopliae EAMa 01/121-Su strain, applied topically on German cockroaches, was studied by reciprocal crossing. Othecal production, oothecal hatchability, and nymphal production declined upon exposure to M. anisopliae EAMa 01/121-Su strain. The mean number of oothecae laid by female was progressively and significantly reduced by fungal treatment from second oviposition period onwards. Oothecal hatch of fungally challenged females was reduced by 46-49%, oothecal viability by 48-85%, and nymphal production by 22-35%. Only treated females showed an effect on oothecal production, oothecal hatch, and nymphal production, although oothecal hatch was also governed by treated males at a higher significance level. Our results on virulence and horizontal transmission of fungal conidia of M. anisopliae EAMa 01/121-Su strain and its sublethal reproductive effects on German cockroach females are discussed in terms of its potential to decrease the pest status of B. germanica in the short and long terms.     

Sex pheromone of Nearctic Agriotes mancus and its similarity to that of three Palearctic Agriotes invasive in North America

1. The wheat wireworm, Agriotes mancus (Coleoptera: Elateridae), is a predominant elaterid pest species in the Nearctic region, with a life history and morphology similar to those of Agriotes obscurus, Agriotes lineatus and Agriotes sputator, three Palearctic pest elaterids invasive in North America. Here, we report the identification and field testing of the sex pheromone of A. mancus.
2. We collected headspace volatiles from female beetles on Porapak Q, and analysed aliquots of Porapak extract by gas chromatography with electroantennographic detection (GC-EAD) and by GC-mass spectrometry. In GC-EAD recordings, two esters—geranyl butanoate and geranyl hexanoate—elicited antennal responses from A. mancus males. In field experiments, trap lures containing both geranyl butanoate and geranyl hexanoate afforded large captures of A. mancus males, which were—on average—approximately 30-fold higher than captures in traps baited with a single ester.
3. Traps baited with geranyl butanoate as a single-component lure captured a significant number of Palearctic A. sputator, indicating the establishment of A. sputator in its invaded Nearctic range.
4. With the A. mancus sex pheromone now known, it can be included in the development of pheromone-based programmes to monitor and manage native and invasive Agriotes pests in North America.

     

Differential responses of three Agriotes click beetle species to pheromone traps

1 Previous work had suggested that adult male click beetles (Agriotes spp.) show differential responses to species specific pheromone traps. This hypothesis was tested using mark–release–recapture methods to estimate the maximum sampling range and the effective sampling area of traps for three species. 2 Captured beetles of the species Agriotes lineatus, Agriotes obscurus and Agriotes sputator were marked to show the direction of release, the distance of the release point from the trap and the replicate. Analysis of variance showed that there were significant differences in recapture rates between species and release distances. There were no significant differences between release direction and replicates. 3 Calculated linear speeds suggested differences in movement rates in the order: A. lineatus > A. obscurus > A. sputator. There were also substantial differences between the species in the maximum sampling ranges and effective sampling areas of the traps. These placed the species in the same order. 4 The results are used to estimate the minimum cost of mass trapping programmes to prevent males from mating, giving values of €165/ha/year (A. lineatus), €247.5/ha/year (A. obscurus) and €2343/ha/year (A. sputator). 5 Implications for the use of pheromone traps in wireworm pest management are discussed. It is concluded that current U.K. recommendations based on the cumulative total catch of the three species over a sampling season can be improved by considering the spatial relationships between the adult trapping system and larval distribution. The current constraint to this is the general inability to separate wireworms into species.     

Infection of the malaria mosquito Anopheles gambiae with the entomopathogenic fungus Metarhizium anisopliae reduces blood feeding and fecundity

The entomopathogenic fungus Metarhizium anisopliae is being considered as a biocontrol agent against adult African malaria vectors. In addition to causing significant mortality, this pathogen is known to cause reductions in feeding and fecundity in a range of insects. In the present study we investigated whether infection with M. anisopliae affected blood feeding and fecundity of adult female malaria vectors Anopheles gambiae Giles sensu stricto. Mosquitoes were contaminated with either a low or a moderately high dose of oil-formulated conidia of M. anisopliae, and offered a single human blood meal 48, 72, or 96 h later to assess feeding propensity and individual blood meal size. In a second experiment, individual fungus-infected females were offered a blood meal every third day (to a total of 8 gonotrophic cycles), and allowed to oviposit after each cycle in order to quantify feeding propensity and fecundity. Infected females took smaller blood meals and displayed reduced feeding propensity. It was found that mosquitoes, inoculated with a moderately high dose of fungal conidia, exhibited reduced appetite related to increasing fungal growth. Of the fungus-infected females, the proportion of mosquitoes taking the second blood meal was reduced with 51%. This was further reduced to 35.3% by the 4th blood meal. During 8 feeding opportunities, the average number of blood meals taken by uninfected females was 4.39, against 3.40 (low dose), and 2.07 (high dose) blood meals for the fungus-infected females. Moreover, infected females produced fewer eggs per gonotrophic cycle and had a lower life-time fecundity. Epidemiological models show that both blood feeding and fecundity are among the most important factors affecting the likelihood of a mosquito transmitting malaria, which suggests that this fungus may have potential as biocontrol agent for vector-borne disease control.     

Assessment of the range of attraction of pheromone traps to Agriotes lineatus and Agriotes obscurus

• 1 The range of attraction of YATLOR pheromone traps was studied to gain information on the number of traps needed for mass trapping of males of two Agriotes species.
• 2 Male click beetles of the species Agriotes lineatus (L.) and Agriotes obscurus (L.) (25–30 individuals per release point) were marked and released at a distance of 2, 5, 10, 15, 20 and 60 m from a pheromone trap both along and opposite to the known prevailing wind direction. Traps were regularly inspected over approximately 1 month. The percentage of recaptured beetles was calculated and analyzed using analysis of variance. Maximum sampling ranges and effective sampling areas were calculated.
• 3 Averaged over all five trials and distances, approximately 40% of the released beetles (A. lineatus and A. obscurus) were recaptured. The percentage recapture of male adults was significantly affected by release distance, whereas no differences were found for species and release direction.
• 4 Males were recaptured from all release points and the percentage recapture decreased (in part significantly) with increasing distance from 76% (2 m) to 35% (15 m) and 9% (60 m), respectively. Most of the beetles were recaptured within the first 3 days after release, independent of the distance, except 60 m. The effective sampling area for A. lineatus was 1089 m² after 12 days and increased to 1735 m² after 30 days. Corresponding values for A. obscurus were considerably higher: 1518 m² for 12 days and 2633 m² for 30 days.
• 5 We conclude that the range of attraction of the pheromone traps for A. lineatus and A. obscurus is comparatively low, providing high percentage recapture only for release distances up to 10 m. Accordingly, any approach targeted on preventing mating by male mass trapping would require a dense network of pheromone traps.

     

Attempts to control cabbage root flies Delia radicum L. and Delia floralis (Fall.) (Dipt., Anthomyiidae) with entomopathogenic fungi: laboratory and greenhouse tests

One laboratory and three greenhouse experiments were conducted to study the pathogenicity and efficacy of Finnish isolates of entomopathogenic hyphemycetous fungi against cabbage root flies. In Petri dishes, exposure to 1.5 × 10¹⁰ spores of Metarhizium anisopliae per dish caused 40–50% mortality of undifferentiated second- and third-stage larvae of Delia floralis , and 1 × 10⁷ spores per dish caused 40–50% mortality of Delia radicum larvae. In one greenhouse test, 1 × 10⁸ and 1 × 10⁹ spores of M. anisopliae and Paecilomyces fumosoroseus reduced the root damage of head cabbage by 20–70% compared with untreated controls, although this was not accompanied by significant reductions in the number of pupae. Only M. anisopliae consistently grew out of larvae and pupae of D. floralis during incubation that followed their recovery from the soil at the end of an experiment testing different formulations of M. anisopliae and Beauveria bassiana , but the frequency of the latent infections of the pest by M. anisopliae was not associated with reduced severity of damage to seedlings of head cabbage.     

Insecticidal activity of selected monoterpenoids and rosemary oil to Agriotes obscurus (Coleoptera: Elateridae)

Acute toxicities of three naturally occurring monoterpenoid essential oil constituents and the essential oil of rosemary were tested against late instars of Agriotes obscurus (L.) (Coleoptera: Elateridae). Both contact and volatile toxicities of thymol, citronellal, eugenol, and rosemary oil were determined. Also, phytotoxicity of these compounds was evaluated on corn germination and seedling development. Thymol had the greatest contact toxicity (LD50 = 196.0 microg/larva), whereas citronellal and eugenol were less toxic (LD50 = 404.9 and 516.5 microg/larva, respectively). Rosemary oil did not show any significant contact toxicity, even at 1,600 microg/larva. In terms of volatile toxicity, citronellal was the most toxic to wireworm larvae (LC50 = 6.3 microg/cm3) followed by rosemary oil (LC50 = 15.9 microg/cm3), thymol (LC50 = 17.1 microg/cm3), and eugenol (LC50 = 20.9 microg/cm3). Thymol, eugenol, and citronellal significantly inhibited corn seed germination and development, whereas rosemary oil had only minimal phytotoxic effects.     

Preventive application of an entomopathogenic fungus in cover crops for wireworm control

Efficacy of the Metarhizium brunneum Petch (Hypocreales: Clavicipitaceae) strain ART2825 for control of wireworms (Agriotes obscurus (L.), Coleoptera: Elateridae) was examined in a semi-field pot experiment. Pots were treated in late summer during sowing of spring oat as a cover crop. Survival of wireworms was assessed four weeks after their release in October 2013, and 30 weeks after release in April 2014. Viability and persistence of the fungus was determined by counting colony forming units from substrate samples and microsatellite analyses of recovered Metarhizium isolates. The number of colonies detected in the substrate in October 2013 increased with increasing concentrations of applied conidia, and no significant reduction was observed at the second evaluation date in April 2014. Increasing conidia application rates significantly increased mycosis and reduced wireworm survival, to a level comparable to that of treatment using insecticide-coated oat seeds. The preventive application of M. brunneum conidia to reduce wireworm populations in cover crops, preceding a damage-sensitive crop like potatoes, may be a promising biocontrol strategy.     

Spatial relationships between two Agriotes click-beetle species and wireworms in agricultural fields

1 The production of new insect pheromones for pest monitoring proceeds at a greater rate than their evaluation, with the consequential possibility of premature introduction. Fundamental to their successful deployment is the determination of a consistent relationship between adult male pheromone trap catches and pest damage. In the present study, adult pheromone traps and larval bait traps were used to examine spatial relationships between two species of Agriotes beetle and wireworms at the field scale. 2 The spatial distributions of adult male Agriotes lineatus and Agriotes obscurus in two fields were determined and compared with the distribution of their larvae. Data were assembled as spatially referenced trap counts, and analysed for evidence of aggregation and clustering using Spatial Analysis by Distance IndicEs (SADIE) methodology. Spatial stabilities of adult populations between sampling dates were tested using association tests. Spatial and quantitative linkages between adult and larval trap catches were also tested. Moreover, a new way of adapting SADIE methodologies is presented for situations where two datasets within an area do not share the same sampling points. 3 There was no significant difference in variance : mean relationships for the two species but there were differences in their spatial distributions, and this is a definitive example of the general argument stating that it is important to consider spatial as well as count data in ecological studies. The spatial distribution of A. lineatus varied between sampling occasions at both sites whereas A. obscurus had consistently significant SADIE indices over time at one site, and adult catches could also be linked to larval distributions and counts. It is proposed that observed differences between the two species can be explained by interference between traps and dissimilar movement rates. There was some evidence of an edge effect at the field boundaries. 4 The distance between pheromone traps is related to the time that elapses before adjacent traps interfere with trap captures and this limits the detection of statistically significant spatial patterns. It is shown that the current practice of adding trap counts for different Agriotes species and treating them as numerically equivalent is insufficiently robust to be recommended at this stage. 5 The implications for the use of sex pheromone traps in wireworm pest management are considered. It is concluded that pheromone traps, as currently used, will not reliably indicate where wireworms occur in a field, and that the complexity of interpreting adult male trap counts limits quantitative predictions of population size.     

Selection of Beauveria bassiana sensu lato and Metarhizium anisopliae sensu lato isolates as microbial control agents against the boll weevil (Anthonomus grandis) in Argentina

The boll weevil (Anthonomus grandis) is the main pest of cotton in the Americas. The aim of this work was to evaluate isolates of the entomopathogenic fungi Beauveria bassiana sensu lato and Metarhizium anisopliae sensu lato virulent against A. grandis. Screening was performed to evaluate the pathogenicity of 28 isolates of M. anisopliae s.l. and 66 isolates of B. bassiana s.l. against boll weevil adults. To select the isolates, LC(50) values of the most virulent isolates were calculated, and compatibility between the fungi and insecticides was studied. In addition, the effects of these isolates on the feeding behavior of the adults were evaluated. Isolates Ma 50 and Ma 20 were the most virulent against A. grandis and their LC(50) values were 1.13×10(7) and 1.20×10(7) conidia/ml, respectively. In addition, these isolates were compatible with pyrethroid insecticides, but none with endosulfan. On the other hand, infected females reduced the damage caused by feeding on the cotton squares and their weight gain. This shows that entomopathogenic fungi cause mortality in the insects, but also these fungi could influence the feeding behavior of the females. In summary, these results indicate the possibility of the use of M. anisopliae s.l. as a microbiological control agent against boll weevils. Also, this species could be included in an Integrated Pest Management program.     

Differential susceptibility of adults and nymphs of Blattella germanica (L.) (Blattodea: Blattellidae) to infection by Metarhizium anisopliae and assessment of delivery strategies

Microbial insecticides for cockroach control, such as those containing entomopathogenic fungi, may be an alternative to reduce contamination by chemicals in housing and food storage environments. Virulence of isolate ESALQ1037 belonging to the Metarhizium anisopliae complex against nymphs and adults of Blattella germanica (L.), and its infectivity following exposure of insects to a contaminated surface or to M. anisopliae-bait were determined under laboratory conditions. Estimated LD50 15 d following topical inoculation was 2.69 x 10(5) conidia per adult, whereas for nymphs the maximum mortality was lower than 50%. Baits amended with M. anisopliae conidia had no repellent effect on targets; adult mortality was inferior to 25%, and nymphs were not susceptible. All conidia found in the digestive tract of M. anisopliae-bait fed cockroaches were unviable, and bait-treated insects that succumbed to fungal infection showed a typical mycelial growth on mouthparts and front legs, but not on the hind body parts. As opposed to baits, the use of a M. anisopliae powdery formulation for surface treatment was effective in attaining high mortality rates of B. germanica. Both nymphs and adults were infected when this delivery strategy was used, and mycelia growth occurred all over the body surface. Our results suggest that the development of powders or similar formulations of M. anisopliae to control B. germanica may provide faster and better results than some of the strategies based on baits currently available.     

Evaluation of entomopathogenic fungus Metarhizium anisopliae against soil-dwelling stages of cabbage maggot (Diptera: Anthomyiidae) in glasshouse and field experiments and effect of fungicides on fungal activity

The effect of two isolates of the entomopathogenic fungus Metarhizium anisopliae (Metchnikoff) Sorokin (389.93 and 392.93) on root-feeding stages of cabbage root fly, Delia radicum (L.), was studied under glasshouse and field conditions. In glasshouse studies, the effect of drenching a suspension of conidia (concentration 1 x 10(8) m(-1), 40 ml per plant, applied on four occasions) onto the base of cabbage plants infested with D. radicum eggs was compared with mixing conidial suspension into compost modules (concentration 1 x 10(8) ml(-1), 25 ml per plant) used to raise seedlings. Drench application reduced the mean number of larvae and pupae recovered per plant by up to 90%, but the compost module treatment had no statistically significant effect. Both application methods reduced the emergence of adult flies from pupae by up to 92%. Most conidia applied as a drench application remained in the top 10-cm layer of compost. Applications of the fungicides iprodione and tebuconazole, which are used routinely on brassica crops, were compatible with using M. anisopliae 389.93 against D. radicum under glasshouse conditions, even though these fungicides were inhibitory to fungal growth on SDA medium. In a field experiment, drench applications of M. anisopliae 389.93 to the base of cauliflower plants at concentrations of 1 x 10(6) to 1 x 10(8) conidia ml(-1) did not control D. radicum populations, although up to 30% of larval cadavers recovered supported sporulating mycelium. Drench applications often exhibited considerable lateral movement on the soil surface before penetrating the ground, which may have reduced the amount of inoculum in contact with D. radicum larvae.     

Laboratory and field evaluation of Metarhizium anisopliae var. anisopliae for controlling subterranean termites

The efficacy of the Metarhizium anisopliae strain ARSEF 6911 was determined in the laboratory and field against two sugarcane pests, Microtermes obesi Holmgren and Odontotermes obesus Rambur (Termitidae: Isoptera). The susceptibility of both termite species to different conidial suspensions (1 × 10(10), 1 × 10(8), 1 × 10(6) and 1 × 10(4) conidia/ml) was determined in laboratory. All conidial suspensions were able to induce mortality. Termite mortality caused by the fungal suspensions was dose dependent. There were no significant differences in the LT50 values between species. Field evaluation of M. anisopliae alone or in combination with diesel oil and thiamethoxam was carried out in two growing seasons (autumn 2005 and spring 2006) at two sites located in Punjab, Pakistan. Dipping the sugarcane setts in these suspensions was tried to determine their effects on germination and percentage of bud damage to sugarcane setts. All treatments significantly reduced termite infestation compared to the untreated control. The combined treatment of M. anisopliae and diesel oil significantly reduced insect damage by attaining higher germination > 55% and lower bud damage < 5.50% at both sites in both seasons. The results suggest that the application of M. anisopliae and diesel oil in combination might be a useful treatment option for the management of termites in sugarcane.