Importance of timing,spore concentrations,and levels of spore carrier in applications of Nosema locustae (Microsporida: Nosematidae) for control of grasshoppers

In a study of microbial control of grasshoppers, Nosema locustae was applied to 10-acre plots in 2 replications of 24 treatment combinations in which the factors were (1) times of applications: 4 applications spaced over 22 days; (2) concentrations of spores: 1, 30, and 900 spores/in²; and (3) levels of the spore carrier: 1 and 4 lb wheat bran/acre. The concentrations of spores had the most effect in reducing the densities of grasshoppers and the incidence of infection among the survivors at the last sampling (coincided with the initiation of oviposition), the average reduction in density attributed to application of 1 spore/in² was 21%, that attributed to 30 spores/in² was 46%, and that attributed to 900 spores/in² was 73%. The first and second applications caused the greatest reductions in density; the second, third, and fourth applications produced the highest incidence of infections. Also, a higher incidence of infection was observed among grasshoppers from plots treated with 30 spores/in² on 1 lb bran/acre than from plots treated with 30 spores/in² on 4 lb of bran/acre. Therefore, a ratio of about 0.63–0.94 billion spores/lb bran applied at a rate of 1–1.5 lb/acre (= 100–150 spores/in²) at the time when the principal early summer species are third-instar nymphs would have resulted in overall reductions in density of 50–60%, with 35–50% of the survivors sufficiently infected so that fecundity would probably be affected. The reductions and incidence of infections would be higher in species that readily accept and use wheat bran, among which are some of the more economically important species of grasshoppers.     

Effect of prolonged storage of spores on field applications of Nosema locustae (Microsporida: Nosematidae) against grasshoppers

Spores of Nosema locustae that were freshly prepared, stored in water at ?10°C for 8 months to 3 years, or stored in cadavers for 1 year at ?10°C were applied on bran at the rate of 10⁹ spores/1.5 lb bran per acre. Applications of fresh spores resulted in higher density reductions and higher incidence of infection among survivors than applications of spores stored in water or cadavers in both a complex of grasshoppers predominated by a single species and in a mixed species complex. Density reductions due to treatment with fresh spores were similar in the two populations, but the mixed species complex had a lower incidence of infection than the complex in which one species predominated. Applications of fresh spores reduced grasshopper densities in both complexes to levels below the economic thresholds.     

Operational-scale application of entomopathogenic fungi for control of Sahelian grasshoppers

Locusts and grasshoppers regularly threaten agricultural production across large parts of the developed and developing worlds. Recent concerns over the health and environmental impacts of standard chemical control measures have led to a demand for alternative, more environmentally benign control technologies. Here we present the results of a field study to investigate the potential of inundative biological control for control of grasshoppers in the Sahelian region of Africa. The biocontrol agent was an oil-based biopesticide formulation of a naturally occurring entomopathogenic fungus, Metarhizium flavoviride. This was applied at a rate of 2l ha^-1 to a total area of 150 ha using standard equipment normally used for the application of chemical pesticides. Twenty-one days after application, an 80 per cent reduction in grasshopper populations was recorded in treated plots, relative to control populations in equivalent unsprayed areas. We think that this is the first operational-scale application of a biopesticide to demonstrate significant population reductions of key Sahelian grasshopper pests. This represents a substantial development in locust and grasshopper control, and should open the way for a new era of integrated control strategies where reliance on conventional chemicals is reduced.     

Effects of manipulating spray-application parameters on efficacy of the entomopathogenic fungus Beauveria bassiana against western flower thrips,Frankliniella occidentalis,infesting greenhouse impatiens crops

The effects of various spray application parameters on the efficacy of a clay-based wettable powder formulation of Beauveria bassiana strain GHA conidia against western flower thrips, Frankliniella occidentalis, were evaluated in a series of greenhouse tests. With the aim of optimizing spray application methods to maximize biopesticide efficacy, a series of independent experiments was conducted that varied four spray parameters: application interval, rate, volume, and spray-program timing. Impatiens crops infested with western flower thrips were treated with (1) multiple sprays at the rate of 5×10¹³ conidia in 935 L aqueous carrier ha^?1 applied at 3-, 5-, and 7-day intervals, (2) weekly sprays at rates of 5×10¹³, 1×10¹⁴, and 2.0×10¹⁴ conidia in 935 L carrier ha^?1, (3) weekly sprays at a rate of 2.0×10¹⁴ conidia in volumes of 935, 1870, and 3740 L water ha^?1, and (4) multiple sprays at the rate of 2.0×10¹⁴ conidia in 3740 L carrier ha^?1 applied at 5-day intervals in spray programs initiated before versus after the onset of flowering. Pollen-bearing impatiens flowers were sampled twice weekly to estimate thrips population density, and adult female and second-instar thrips were collected 24 h post application for determination of acquired dose (conidia/insect). Numbers of conidia inoculated onto thrips increased with increasing spray frequency and volume. Dose was unexpectedly not directly correlated with application rate when volume was held constant, suggesting that thrips avoided concentrated spray residues. Statistically significant thrips population reductions relative to controls were achieved only when three to four sprays were applied at the highest label rate in the highest volume at < 7-day intervals. Applications against thrips infesting young, preflowering impatiens crops were not consistently more effective than applications in older crops. The most effective treatment programs reduced pest populations by 30–40% compared to untreated controls; this slowed, but did not stop, the growth of pest populations. Results indicate that use of fungi for thrips management will require integration with other control agents.     

Comparative efficacy of Beauveria bassiana, Bacillus thuringiensis, and aldicarb for control of Colorado potato beetle in an irrigated desert agroecosystem and their effects on biodiversity

Five weekly applications of Beauveria bassiana (Balsamo) Vuillemin, a genetically engineered isolate of Bacillus thuringiensis Berliner (Raven^®), and aldicarb (Temik^®) were compared for control of Colorado potato beetle, Leptinotarsa decemlineata (Say) in an irrigated desert cropping system. B. thuringiensis was applied using low and high label rates (1.17 and 7.0 l ha^–1). B. bassiana was applied at 5×10¹³ spores ha^–1. Aldicarb (Rh^one-Poulenc), applied at 3.37 kg a.i. ha^–1 provided the greatest beetle control and potato yields (45 metric tons ha^–1), but overall lowest biodiversity in nontarget organisms, particularly predatory Heteroptera. Low and high rates of B. thuringiensis produced fair to excellent beetle control, yielded 33 and 40 metric tons ha^–1 and enabled good survival in predatory Heteroptera and other nontargets. Plots treated with B. bassiana resulted in poor control of beetles prior to row closure after which fair to good control was achieved. Yield in the Beauveria-treated plots was 33 metric tons ha^–1 and effect on biodiversity was comparable to the Bt-treated plots. The lowest number of overwintering adult L. decemlineata was found in the plots treated with bacteria and fungi (0.68–0.84 adults/0.03 m^–3 of soil) and the highest was found in control and aldicarb plots (3.44 and 1.84 adults/0.03 m³ of soil). Aphids and leafhoppers showed higher densities in plots treated with microbial control agents, but were eliminated from plots treated with aldicarb.     

Combined field efficacy of <Emphasis Type="Italic">Paranosema locustae</Emphasis> and <Emphasis Type="Italic">Metarhizium anisopliae</Emphasis> var. <Emphasis Type="Italic">acridum</Emphasis> for the control of sahelian grasshoppers

Field trials were conducted to evaluate the efficacy of wheat bran bait formulations of Paranosema locustae and Metarhizium anisopliae for controlling grasshoppers in southeast Niger. Treatments consisted of wheat bran baits mixed with M. anisopliae, P. locustae + M. anisopliae or with P. locustae spores and P. locustae + sugar. Oedaleus senegalensis, Pyrgomorpha cognata and Acrotylus blondeli were the predominant species at the time of application representing ca. 94% of the total population. Bran application was done when O. senegalensis (ca. 75% of the population) was at its early developmental stages, with first, second and third instars accounting for 64–85%. Grasshopper population reduction, P. locustae prevalence and level of infections in the predominant species were monitored. Manual application of P. locustae and M. anisopliae formulated in wheat bran has proven to induce consistent pathogen infection in grasshopper populations. Population density over the three weeks monitoring, typically decreased by 44.7 ± 6.9%, 52.8 ± 8.4%, 73.7 ± 5.5% and 89.1 ± 1.8% in P. locustae, P. locustae + sugar, M. anisopliae and P. locustae + M. anisopliae treated plots respectively. Paranosema locustae prevalence in surviving adult grasshoppers at 28 after application was 48.1 ± 2.3%, 28.9 ± 4.8% and 27.4 ± 3.7%, with infection level of 6.2 ± 0.8 × 10⁶, 2.3 ± 0.3 × 10⁴ and 2.1 ± 0.3 × 10³ spores mg⁻¹ host weight in O. senegalensis, A blondeli and P. cognate respectively. Other species that each accounted for <2% of the community, namely Aiolopus thalassinus, A. simulatrix, Acorypha glaucopsis, Acrotylus patruelis, Anacridium melanorhodon, Diabolocatantops axillaris, Kraussaria angulifera and Schistocerca gregaria were found to show sign of infection. The results from this study suggest that wheat bran application of M. anisopliae and P. locustae alone or in combination, targeting early instars grasshopper could be a valuable option in grasshopper control programs.     

Persistence of spores of Pleistophora schubergi (Cnidospora: Microsporida) in the field,and their application in microbial control

Spores of Pleistophora schubergi, when applied to oak trees in the field at 2 × 10⁸ spores/ml with a uv protectant, “Shade,” infected 88% of Anisota senatoria larvae at 4 days after spray application. Spores without the uv protectant infected only 10% of the larvae at 4 days after application. When the spores were applied at the rate of 2 × 10⁸ and 2 × 10⁷ spores/ml in the field, 96 and 72% of the A. senatoria larvae and 100 and 100% of the Symmerista canicosta larvae were infected 14 days after spray application.     

The response ofAzolla pinnata R. Brown to the split application of phosphorus and the transfer of assimilated phosphorus to flooded rice plants

A field experiment was conducted at the Bangladesh Rice Research Institute, Joydebpur, Dhaka during the late wet season. Basal application of P at both 5 and 10 kg ha⁻¹ significantly increased total biomass production and nitrogen fixation byAzolla pinnata R. Brown (local strain). Addition of both 5 and 10 kg P ha⁻¹ in equal splits at inoculation and at six day intervals thereafter during growth periods of 12, 24 and 36 days increased biomass production and nitrogen fixation by Azolla over that attained with the basal application. Biomass and nitrogen fixation using a split application of 5 kg P ha⁻¹ exceeded that attained with basal application of 10 kg P ha⁻¹ and split application of 10 kg P ha⁻¹ resulted in 0.58, 11.2, and 18.3 t ha⁻¹ more biomass, and 0.47, 18.9, and 18.3 more kg fixed N ha⁻¹ at 12, 24 and 36 days, respectively, than the same amount applied as a basal application. Analyses indicated that the critical level of dry weight P in Azolla for sustained growth was in the range of 0.15–0.17%. Compared with the control, where no P was added, and additional 30 and 36 kg N ha⁻¹ were fixed after 24 and 36 days, respectively, when P was provided at 10 kg ha⁻¹ using a split application. A separate field study showed that flooded rice plants received P from incorporated Azolla with about 28% of the P present in the supplied Azolla being incorporated into the rice plants.     

Effect of culture medium on the production and virulence of submerged spores of Metarhizium anisopliae and Beauveria bassiana against larvae and adults of Aedes aegypti (Diptera: Culicidae)

Three Metarhizium anisopliae and three Beauveria bassiana isolates were cultivated in media containing casamino acids, soybean flour or sunflower seed flour and were shaken for three days. M. anisopliae presented similar yields of around 10⁶ submerged spores/ml without significant differences among them, whereas B. bassiana produced yields of around 10⁸ spores/ml, of which GHA strain produced more submerged spores in the casamino acids medium. The other two strains showed no significant difference in the production of submerged spores in the three media used. Differences in mortality on Aedes aegypti larvae were observed with the submerged spores of Metarhizium depending on isolate and medium used. M. anisopliae 2157 caused significantly higher mortality (40%) when cultivated in casamino acids medium. It presented an LC₅₀ of 8.93 × 10⁵ submerged spores/ml water against mosquito larvae five days after application, whereas it caused 27% mortality in Ae. aegypti adults 10 days after application. In conclusion, fungal nutrition affected virulence of some isolates of M. anisopliae against Ae. aegypti larvae while such an effect was not noted for B. bassiana isolates.     

Field efficacy of entomopathogenic nematodes against the beetle Maladera matrida (Coleoptera: Scarabaeidae)

Single, double and triple releases of the entomopathogenic nematode Heterorhabditis bacteriophora Poinar, reduced the population of the beetle Maladera matrida Argaman, infesting peanuts (’Shulamit’ cv.) by 70, 75 and 93% respectively in microplot tests. Simultaneous and late (2 weeks after infestation) applications reduced beetle numbers by 63 and 79% respectively, in the microplots, while early application (2 weeks prior to infestation) did not reduce the beetle population. In a field trial, reductions in insect population and damage to the crop were achieved by early treatment with the nematode as well as by Heptachlor, leading to reductions in the insect population of 60 and 90% respectively, when recorded 4 weeks after nematode application. However, the nematode treatment did not maintain its effectiveness for a longer period and pest damage increased to the same level as the untreated control after 7 weeks. When the nematodes were applied at different concentrations (0.25–1.0 x 10⁶ infective juveniles (IJs) m^‐2) their effectiveness was not related to the concentration level. The only significant (P < 0.05) reduction in insect levels was recorded in the treatment with 0.5 X 10⁶ IJs m^‐2. In a second field trial, both H. bacteriophora and Steinernema glaseri reduced insect populations significantly (P < 0.05) by approximately 50% in comparison to the control. In the third trial, treatment with H. bacteriophora resulted in a decrease in insect population of 90% while treatment with S. carpocapsae reduced the grub numbers by 40% in comparison to the control. A differential susceptibility of various grub developmental stages was recorded in the field. The small grubs (I‐4 mm long, lst‐2nd larval stage) were not affected by the nematode treatments while the numbers of medium and large size grubs were reduced by 2‐ and 3‐fold respectively in the various tests. Nematodes were recovered by ‘nematode traps’ containing Galleria mellonella larvae from treated field plots 78 days after application. The implications of the results from the present studies on the use of entomopathogenic nematodes are discussed in relation to the development of an integrated pest management programme.     

Field Infection of Zonocerus variegatus following application of an oil‐based formulation of Metarhizium flavoviride conidia

Conidia of Metarhizium flavoviride grown in diphasic culture with sporulation on rice, were extracted in kerosene and formulated with peanut oil. The formulation led to high mortality when applied to field populations of Zonocerus variegatus; between 70 and 95% of insects in samples collected from the field 0, 3 or 7 days after spraying died. Sporulation of M. flavoviride was observed in 70–80% of the dead‐treated insects, which compares favourably with results obtained in laboratory bioassays. Many dead Z. variegatus, some with internal sporulation, were found in shaded niches and oviposition sites in the treated plots. No sporulation was observed in samples collected prior to application, and both sporulation and mortality differed significantly between control and treated plots. Some infections were observed in insects collected 16 and 23 days after treatment; these late infections may be a consequence of contact with spores surviving in the environment.     

Field evaluation of entomopathogenic nematodes for the biological control of the annual bluegrass weevil,Listronotus maculicollis (Coleoptera: Curculionidae), in golf course turfgrass

The ability of entomopathogenic nematodes to suppress larval populations of the annual bluegrass weevil, Listronotus maculicollis, was investigated under field conditions over a 3-year period (2006–2008). Combination of nematode species, application rate and timing produced strong numerical yet few statistically significant reductions. Steinernema carpocapsae Weiser, S. feltiae Filipjev, and Heterorhabditis bacteriophora Poinar applied at 2.5×10⁹ IJs/ha reduced first generation late instars between 69 and 94% in at least one field trial. Steinernema feltiae provided a high level of control (94%) to low densities (~20 larvae per 0.09 m²), but gave inadequate control for higher densities (24 and 50% suppression). No significant differences were found among treatment timings. However, applications timed to coincide with the peak of larvae entering the soil (fourth instars) generally performed better than applications made prior to (preemptive) or after the majority of the population advanced from the fourth instar. Nematode populations declined sharply between 0 and 14 days after treatment (DAT). Although nematode populations later increased (at 28 DAT), indicating an ability to recycle within hosts in the environment, they were nearly undetectable 56 DAT when the second generation host larvae were present in the soil. Applying commercially available nematode species at standard field rates cannot reliably reduce L. maculicollis immature densities on golf courses, nor will single applications suppress multiple generations. Future research will need to identify application strategies to improve biocontrol consistency.     

Mini-plot field experiments on slug control using biological and chemical control agents

In three field experiments, the rhabditid nematode Phasmarhabditis hermaphrodita was applied one or more times at the standard rate (3 × 10⁹ ha^?1) or half the standard rate to protect crops from slug damage under experimental conditions. Expt 1 was done in a field planted with the ornamental Polygonatum japonica. The treatments were: infective juveniles of the nematode at the standard field rate, metaldehyde pellets at the recommended field rate, and ioxynil (a herbicide with molluscicidal properties) at 90 mg m^?2. The treatments were repeated every 2 wk. Arion ater agg. caused most of the damage to P. japonica. There were no significant differences in damage between treatments during the 3 wk after first application, but plants on plots treated with metaldehyde or nematodes had significantly less damage than plants on untreated plots in the fourth and fifth weeks. Expts 2 and 3 were done on the same site, the first with leaf beet and the second with lettuce. The treatments in these experiments were: nematodes applied to the planted area at the standard field rate 3 days prior to planting, with or without previous application of cow manure; nematodes at half standard rate applied twice, 6 days apart, to the planted area or to the surrounding area; metaldehyde pellets and iron phosphate pellets, both applied at the recommended rate to the planted area immediately after planting. In both experiments, the two chemical molluscicides and nematodes applied once to the planted area at the standard field rate without previous application of cow manure, or twice at half standard rate, were able to reduce slug damage. Nematodes applied after manure did not reduce slug damage. None of the treatments reduced the numbers of slugs contaminating the harvested plants. Slug populations were assessed by means of soil sampling before and after Expts 2 and 3. Only after Expt 3 was there a significant effect of treatment on slug numbers, with significantly fewer in metaldehyde treated plots than in untreated plots.     

Preservation, mass production and storage ofStagonospora convolvuli, a bioherbicidecandidate for field bindweed (Convolvulusarvensis)

Different solid substrates were investigated as spore production methods for Stagonospora convolvulistrain LA39, a potential bioherbicide for field bindweed (Convolvulusarvensis L.). Up to 4 × 10⁸ spores/g of substratewere yielded on cous-cous (cracked hard wheat). Thespores were as pathogenic as those grown on artificial medium (V-8-juice agar). The air-drying on kaolin and storage at 3 °C kept spores viable and pathogenic for 180 days. Spore germination exceeded70% for the first 140 days and then declined to 50%after 175 days. Less than 5% of spores were still viable after 17 months. The preservation of stock cultures in 10% glycerine at −80 ° C and in liquid nitrogen did not affect viability orpathogenicity of the spores. This revised version was published online in July 2006 with corrections to the Cover Date.     

Rice growth improvement and grains bio-fortification through lime and zinc application in zinc deficit tropical acid sulphate soils

A two years field study was conducted to explain the effect of Zn and lime application on morphological characteristics, rice yield and yield components, and more broadly, grains bio-fortification (Zn and protein content (CP), and amino acid profiles). The lime and Zn interaction increased grains and straw yield more than two times (6.64 ton ha^?1) compared to the control (3.20 ton ha^?1). The maximum increase in the Zn content of grain, white rice and bran was obtained about 30% in whole grain, 42% in bran and 56% in white rice. Furthermore, CP increased by about 8% in bran, 12.3% in whole grain, and 27% in white rice compared to control. Also, the Zn and lime application and their interaction were significantly increased the amino acids, especially essential parts.     

ACTION MODE,PERSISTENCE AND CONTROL VALUE OF FIPRONIL FOR RICE GRASSHOPPERS OXYA (ORTHOPTERA: CANTANTOPIDAE)*

Abstract From June to Oct. 1996, cage and field experiments with Fipronil, a new insecticide from the phenyl pyrazole family, were carried out in Hanzhong basin, Shaanxi Prov. The aim was to evaluate the action mode, persistence and control value of Fipronil in rice grasshoppers management. The main results were as follows: ¹ at low doses of 4 g a. i. /ha and 8 g a. i. /ha, Fipronil was found to be an effective contact and stomach pesticide against Oxya spp. The knocking effect of contact was quicker than that of stomach; ² the residual effect of Fipronil on Oxya spp. was over 3 weeks, significantly longer than that of conventional insecticides; ³ the difference between effects of 4 g a. i. /ha and 8 g a. i. /ha was mainly shown in terms of survival time of the grasshoppers after treatment, and there was almost no difference as to control results; ⁴ one month after the treatment, the density of Oxya in quadrats treated by Fipronil was significantly lower than that in quadrats treated with Fenpropathoursin, and the application of Fipronil retrieved 12. 6% of rice production loss when compared with the output in control field.     

Effect of dew temperature,post-inoculation condition,and pathogen dose on suppression of scentless chamomile by Colletotrichum truncatum

Scentless chamomile, a noxious weed in western Canada, has a high natural tolerance to many herbicides. Colletotrichum truncatum, a host specific fungal pathogen, is suppressive to scentless chamomile when applied inundatively. A broadcast application was used at 200 L ha^?1 to evaluate biocontrol potential of this pathogen under a range of dew temperatures (DT), post-inoculation conditions (PIC), and pathogen doses (PD). A DT between 20 and 25°C was more conducive to infection, resulting in higher levels of disease and weed suppression as compared to 15 and 30°C. Under similar post-inoculation temperature regimes, disease was only slightly more severe in growth chambers than in the greenhouse. There was a positive linear relationship between the PD and weed suppression. An inoculum concentration >1×10⁸ spores mL^?1 reduced plant fresh weight by approximately 50% when compared to untreated controls. These results indicate that biocontrol of scentless chamomile using C. truncatum in the semi-arid Canadian prairies will likely encounter frequent non-favourable field conditions.     

Effect of drought stress,abscisic acid,and abscisic acid analogues on the efficacy of diclofop-methyl and tralkoxydim

The effects of drought stress, abscisic acid (ABA), and four ABA analogues on diclofop-methyl and tralkoxydim efficacy were investigated in oat (Avenu sativa). Drought stress conditions (6% soil moisture content) reduced the efficacy of diclofop-methyl at 350 g ha^–1, but not at 700 g ha^–1. Similarly, tralkoxydim efficacy was reduced by drought stress at 62.5 and 125 g ha^–1, but not at 250 g ha^–1. ABA (100 m), applied as a root drench 2 days before the herbicide, protected oat plants against all rates of diclofop-methyl and against low rates of tralkoxydim. Two ABA analogues protected oat plants from diclofop-methyl injury, whereas two others had no effect. Foliage applications of ABA were much less effective than root applications in protecting against herbicide injury. Protection by ABA and the two active analogues was dependent on the relative time of application with respect to the herbicides. Optimal protection by ABA and analogue I was obtained when they were applied between 2 days before and 1 day after diclofop-methyl application. Analogue IV protected plants when applied between 3 days before and 1 day after diclofop-methyl application. Partial protection against tralkoxydim activity by ABA was observed when it was applied between 1 day before and 1 day after herbicide application. Analogue I did not afford any protection against tralkoxydim, and analogue IV afforded partial protection when applied the same day or 1 day after tralkoxydim. The results indicate that protection against these postemergence herbicides, similar to that conferred by water stress, can be induced by ABA and structural analogues that apparently mimic the action of ABA.Abbreviations SMC soil moisture content - ABA abscisic acid     

Effects of exogenous nutrients on conidial germination and virulence against the silverleaf whitefly for two hyphomycetes

Exogenous protein and sugar sources were tested for their impact on conidial germination of two silverleaf whitefly (Bemisia argentifolii) pathogens: Beauveria bassiana and Paecilomyces fumosoroseus. In liquid culture, sugars stimulated only 5-27% germination of B. bassiana and < or =11% germination of P. fumosoroseus, whereas, yeast extract or peptone stimulated 95-100% germination. In the absence of additional nutrients, agar alone stimulated approximately 50% germination. Storing spores for different periods of time did not alter their general response to exogenous nutrients. When spores were germinated before being applied to third instar B. argentifolii, mortality was as much as 2.45 times greater and occurred more rapidly than that for fresh spores. For ungerminated conidia, the mean time to death from infection was 5.45 (SE = 0.16) and 4.74 (SE = 0.08) days for application rates of 37 and 144 conidia x mm(-2), respectively. When conidia were germinated before application, infection times dropped to 4.58 (SE = 0.16) and 4.45 (SE = 0.10) days, respectively. A likely explanation for the greater pathogenicity and virulence of germinated over ungerminated B. bassiana conidia is that only a fraction of the spores applied to whitefly nymphs actually germinate on the cuticle. For some specialized applications, such as greenhouse production systems, it may be beneficial to germinate spores immediately prior to application.     

Suppression of citrus leafminer, Phyllocnistis citrella, with an attract-and-kill formulation

The citrus leafminer, Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae), is a worldwide pest of citrus crops and is responsible for proliferation of citrus bacterial canker, Xanthomonas axonopodis (Hasse) pv. citri (Gamma Proteobacteria: Xanthomonadaceae). We developed and evaluated an attracticide formulation, termed MalEx, for control of P. citrella. MalEx is a viscous paste with UV‐protective properties that is dispensed as 50‐μl droplets using custom‐made calibrated pumps. A formulation containing 0.016%P. citrella pheromone [3:1 blend of (Z,Z,E)‐7,11,13‐hexadecatrienal and (Z,Z)‐7,11‐hexadecadienal] and 6% permethrin was found to suppress male response to pheromone in the field better than formulations containing 10× less pheromone. Although formulations without permethrin showed some suppression of male activity because of mating disruption, addition of 6% permethrin to the formulation was required for optimal efficacy. When MalEx, containing 0.016% pheromone and 6% permethrin, was applied at 3 000 point sources ha^?1, the application height did not influence efficacy of male P. citrella suppression within mature 4‐m tall citrus trees. Decreasing the rate of MalEx from 3 000 to 1 500 droplets ha^?1 reduced efficacy as measured by both male P. citrella activity and larval infestation. Although 4 500 droplets ha^?1 did not result in statistically better efficacy than 3 000 droplets ha^?1, there was a noticeable trend for higher efficacy as droplet density increased. Continuous treatment of 0.5‐ha blocks of citrus with MalEx over the course of 112 days reduced larval infestation of new flush, as compared with those in untreated control plots, by 3.6–7.2× depending on droplet application density. In laboratory behavioral bioassays, the attractiveness of MalEx droplets to male P. citrella was drastically reduced after 21 days of field aging. However, our laboratory investigation confirmed that 100% of males contacting MalEx droplets, aged up to 35 days in the field, were killed within 24 h. Direct observation of male P. citrella behavior in the field confirmed that attracted males made contact with droplets. Control of P. citrella with MalEx should reduce the number of required broad spectrum sprays for leafminer management in both field and citrus nursery settings.