Potential of two entomopathogenic fungi,Beauveria bassiana and Metarhizium anisopliae (Coleoptera: Scarabaeidae), as biological control agents against the June beetle

The aim of this study was to evaluate the effectiveness of the entomopathogenic fungi (EPF), Beauveria bassiana (Bals.) Vuill. (Deuteromycotina: Hyphomycetes) strain PPRI 5339 [BroadBand, an emulsifiable spore concentrate (EC) formulation] and Metarhizium anisopliae (Metsch.) Sorokin (Hypocreales: Clavicipitaceae) strain F52 [Met52, both EC and granular (GR) formulations] against the larvae of Polyphylla fullo (L.) (Coleoptera: Scarabaeidae). Larvicidal bioassays were performed in foam boxes (100 by 75 by 50 cm; length by width by height), containing moist soil medium with some humus and potato tubers as food. Although the B. bassiana product (min. 4 × 10⁹ conidia/ml) was applied at 100, 150, and 200 ml/100 l water; M. anisopliae strain F52 was applied at 500, 1,000, and 1,500 g/m³ of moist soil medium for GR (9 × 10⁸ cfu/g) and 75, 100, and 125 ml/100 l water for EC (5.5 × 10⁹ conidia/ml) formulation. Both fungi were pathogenic to larvae of the pest; however, young larvae (1st and 2nd instars) were more susceptible to infection than older ones (3rd instar). Mortality rates of young and older larvae varied with conidial concentration of both fungi and elapsed time after application. The B. bassiana product was more effective than both of the formulations of the M. anisopliae product, causing mortalities up to 79.8 and 71.6% in young and older larvae, respectively. The highest mortality rates of young and older larvae caused by the M. anisopliae product were 74.1 and 67.6% for the GR formulation, 70.2 and 61.8% for the EC formulation, respectively. These results may suggest that both fungi have potential to be used for management of P. fullo.     

Biological Activity of trans-2-Hexenal Against Bradysia odoriphaga (Diptera: Sciaridae) at Different Developmental Stages

trans-2-Hexenal, one of the C6 green leaf volatiles, is potentially useful for the control of Bradysia odoriphaga Yang et Zhang. In this study, the biological activity of trans-2-hexenal on B. odoriphaga was assessed in the laboratory. trans-2-Hexenal was observed to kill B. odoriphaga in different developmental stages at a relatively low concentration under fumigation. The respiration rate in the male treatment group decreased from 131.44 to 4.07 nmol/g·min with a prolonged fumigation time, while the respiration rate in females decreased from 128.82 to 24.20 nmol/g·min. Male adults exhibited a more sensitive electroantennogram response at 0.05–500 μl/ml at the dose of 10.0 μl than female adults. Moreover, trans-2-hexenal had a repellent effect on adults based on the results with a Y-tube olfactometer at 10.0 μl, as shown by the deterrent rate of male and female adults with 96.67% and 98.33%, respectively. The results showed that trans-2-hexenal had good biological activity in different developmental stages of B. odoriphaga, which could reduce the need for, and risks associated with, the use of traditional insecticides and enable nonharmful management.     

Sublethal effect of avermectin and acetamiprid on the mortality of different life stages of Brontispa longissima (Gestro) (Coleoptera: Hispidae) and its larvae parasitoid Asecodes hispinarum Bouček (Hymenoptera: Eulophidae)

The beneficial parasitoid Asecodes hispinarum Bouček plays an important role in integrated pest management (IPM) of the coconut leaf beetle, Brontispa longissima (Gestro), in China. A. hispinarum females parasitize 3rd to 4th instars B. longissima larvae. Hatched parasitoid larvae develop within the host, and parasitoid adults emerge through holes that they chew through the cuticle of the host. Although chemicals serve as the main short term control agents, the compatibility of biological and chemical control has never been investigated for this system. This study examined the responses of immature and adult B. longissima and its larval parasitoid A. hispinarum to avermectin and acetamiprid. Avermectin caused complete mortality of 2nd to 4th instar larvae, and of adults of B. longissima at 10, 15 and 2 d after treatment, respectively. However, 26.7% of the 2nd instar larvae, 55.3% of the 4th instar larvae, and 74%, of adult B. longissima were still alive 40 d after acetamiprid application. Following avermectin exposure, 17.5%, 9.2% and 23% of mummified B. longissima larvae contained viable adult parasitoids for the parasitoid egg, larva and pupa treatments, respectively, and the numbers of dead parasitoids per mummy were 3.3, 7.2 and 13.3 for the egg, larva and adult treatments, respectively. However, for acetamiprid treatment, 70–75.9% of mummified B. longissima larvae contained viable adult parasitoids in all three stage treatments, and the number of dead parasitoids per mummy was 2.8, 2 and 3.4 in egg, larva and adult treatments, respectively. This study showed that a sublethal dose of avermectin is more toxic than acetamiprid to B. longissima and A. hispinarum. Therefore, direct contact of the parasitoid with avermectin should be avoided when this insecticide is used to control B. longissima.     

Efficacy of entomopathogenic nematodes (Nemata: Rhabditida) to control Brazilian apple leafroller Bonagota salubricola (Meyrick, 1937) (Lepidoptera: Tortricidae)

The Brazilian apple leafroller, Bonagota salubricola (Meyrick, 1937) (Bonagota cranaodes) (Lepidoptera: Tortricidae), is one of the main pest problems in apple orchards is Brazil. The purpose of this work was to evaluate B. salubricola larval and pupal susceptibility to different species of entomopathogenic nematodes, isolated in Rio Grande do Sul state in Brazil, under laboratory and field (apple orchard) conditions. Bioassays for isolates selection and determination of lethal concentration were performed in tubes of 1.5 ml (eppendorf), each containing one B. salubricola third instar larvae and filter paper. Field experiments were performed in commercial orchard, with application of 100 infecting juveniles (IJs)/cm² for each apple plant previously infected with five B. salubricola larvae covered with plastic trays containing thin cloth. Nematodes H. bacteriophora RS107 and H. bacteriophora RS57 had LC₅₀ of 13 and 4.5 IJs/larvae (4.3 and 1.5 IJs/cm²), respectively. In the field, H. bacteriophora RS107 and H. bacteriophora RS57, applied with sorbitol as an adjuvant, reached 70.2 and 61.1% larval mortality, respectively. The results showed that both isolates had biological activity against B. salubricola under laboratory and field conditions.     

Histopathological Changes in Third-Instar and Adult Anastrepha ludens (Diptera: Tephritidae) After in vitro Heat Treatment

The Mexican fruit fly, Anastrepha ludens Loew (Diptera: Tephritidae), is one of the most harmful pests of mango causing direct damage by oviposition on the fruit pulp. Mango for export is subjected to hydrothermal treatment as a quarantine method for the control of this pest, but exposure to heat for long periods of time reduces considerably the quality and shelf-life of treated fruit. The aim of this work was to study morphological changes of third-instar larvae and adults of A. ludens after in vitro exposure to high temperature at sublethal times. A heating block system was used to expose larvae at 46.1°C for 19.6 and 12.9 min, producing 94.6 and 70% mortality, respectively. Treated larvae were processed for optical microscopy. A fraction of surviving treated larvae was separated into containers with artificial diet to allow development into adults. Adult sexual organs were dissected and processed for transmission electron microscopy analysis. Results showed that 94.6% of the treated larvae died at 46.1°C for 19.6 min and none of the surviving larvae eclosed to adulthood, as they developed as malformed puparia. For the in vitro treatment at 46.1°C during 12.9 min, 70% of the treated larvae died and only 3.75% reached the adult stage, but ultrastructural damage in the male testes and in the female ovaries was observed. Additionally, 11.1% of the adult flies from the in vitro treatment also showed wing malformation and were incapable of flying. The analysis showed that surviving flies were unable to reproduce.     

Evaluation of seed treatment insecticides for management of the rice water weevil,Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae), in commercial rice fields in Louisiana

The rice water weevil, Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae), is the most injurious insect pest in US rice production. Yield losses in excess of 25% can occur from severe infestations. Management demonstrations were conducted in the 2008, 2009, 2010, and 2011 growing seasons to evaluate the use of commercially available insecticides to control L. oryzophilus in commercial rice fields. The demonstration tests, conducted on farms throughout Louisiana, compared the efficacies of recently registered seed treatment insecticides to untreated controls and to foliar applications of pyrethroids. Efficacy was assessed by collecting root/soil core samples three to four weeks after application of permanent flood and counting numbers of larvae and pupae in core samples. Tests were replicated across locations in multiple rice-producing Louisiana parishes. Densities of larvae and pupae in core samples exceeded the larval threshold (three larvae or pupae per core sample) in over 80% of untreated plots/cuts, confirming the ubiquity and severity of this insect as a pest of rice. Use of chlorantraniliprole (Dermacor^® X-100, DuPont™ Crop Protection, Wilmington, DE), thiamethoxam (CruiserMaxx^® Rice, Syngenta^® Crop Protection, Greensboro, NC), and clothianidin (NipsIt Inside^®, Valent^® USA Corporation, Walnut Creek, CA) seed treatments significantly reduced L. oryzophilus infestation compared to untreated checks. Fewer larvae and pupae were observed in rice treated with chlorantraniliprole than in rice treated with other insecticides.     

Influence of Different Types of Phyllostachys pubescens (Poales: Poaceae) Leaves on Population Parameters of Pantana phyllostachysae (Lepidoptera: Lymantriidae) and Parasitic Effects of Beauveria bassiana (Moniliales: Moniliaceae)

We found that Pantana phyllostachysae, a dangerous pest of moso bamboo (Phyllostachys pubescens), showed differences in growth and development after feeding on diverse types of moso bamboo leaves. The mortality rate of Pa. phyllostachysae due to Beauveria bassiana, an entomopathogenic fungus, was also affected by the varied larval diet. Larval and pupal developmental duration of Pa. phyllostachysae was longer when feeding on “off-year” bamboo leaves. Pupal weight and adult fertility were higher when feeding on “on-year” bamboo leaves. Mortality due to B. bassiana was significantly lower in larvae fed on on-year bamboo leaves than in larvae fed on off-year bamboo leaves. Larvae fed on new bamboo leaves had a shorter development period and higher survival rate than those fed on off-year bamboo leaves. However, mixed feed (mixture of new, on-year, and off-year bamboo leaves) decreased the egg production of Pa. phyllostachysae. After infection by the second generation of B. bassiana, the survival time of Pa. phyllostachysae fed on mixed feed increased significantly compared with the first generation. We also fed Pa. phyllostachysae different proportion of new bamboo leaves in mixed feed to simulate natural conditions. We found that increasing the proportion of new bamboo leaves in the food promoted pupal development and increased egg production; it also increased the resistance of larvae to the first generation of B. bassiana. The pathogenicity of the second generation of B. bassiana declined in all mixed feed treatments.     

Efficacy of endophytic and applied Metarhizium anisopliae (Metch.) Sorokin (Ascomycota: Hypocreales) against larvae of Plutella xylostella L. (Yponomeutidae: Lepidoptera) infesting Brassica napus plants

The internal colonization of Brassica napus plants by Metarhizium anisopliae was demonstrated and the endophytic and direct effects of the fungus against Plutella xylostella larvae were assessed. Internal colonization of the plant by the fungus was shown by re-isolating the fungus from leaves, petioles and stems of the plant that were not the initial site of inoculation. Results indicated that significant differences (at P = 0.05) were obtained in mean % successful re-isolation of the fungus from leaves, petioles and stems at 2, 3 and 4 weeks after inoculation. To assess the endophytic effect of the fungus, larvae of P. xylostella were introduced onto plant leaves distant from the initial site of inoculation with the fungus (one leaf per plant). Results indicated that significant differences (at P = 0.05) were obtained in mean % mortality of larvae that were introduced at 2, 3 and 4 weeks after inoculation compared to the non-inoculated control. Similar significant results were obtained when the direct effect of the fungus against the larvae was assessed. In conclusion, this research provides evidence for the first time of the endophytic action of M. anisopliae against P. xylostella larvae and the ability of the fungus to colonize the internal tissues of B. napus plants.     

The Effect of Chemical Composition and Bioactivity of Several Essential Oils on Tenebrio molitor (Coleoptera: Tenebrionidae)

The major chemical components of four essential oils (EOs) extracted from dry leaves of Citrus limonum, Cymbopogon citratus, Litsea cubeba, and Muristica fragrans were analyzed with gas chromatograph-mass spectrometer and their fumigant, contact, and repellent activities against 10th instar and adults of Tenebrio molitor were also assayed. The results indicated that the major constituents of C. limonum and Cy. citrates were D-limonene (38.22%) and 3,7-dimethyl-6-octenal (26.21%), while which of L. cubeba and M. fragrans were (E)-3, 7-dimethyl-2, 6-octadienal (49.78%) and (E)-cinnamaldehyde (79.31%), respectively. Contact activities of L. cubeba and C. limonum with LC₅₀ values of 21.2 and 13.9 µg/cm² at 48 h and repellence activities (>89.0% repellence indexes) (P < 0.05) at 12 h on 10th instar were better than those of the other two EOs. Nevertheless, the fumigation activities of L. cubeba on 10th instar and adults (LC₅₀ = 2.7, 3.7 μl/liter) were stronger than those of C. limonum (LC₅₀ = 10.9, 12.0 μl/liter) at 96 h and significant (not overlapping confidence intervals). The EOs of L. cubeba and C. limonum have clearly elongated the growth and development of larvae, egg, and slightly shorten pupae and adults of T. molitor compared with the control. The mainly active ingredients of L. cubeba and C. limonum, including D-limonene and β-pinene, were demonstrated to coinhibit the actives of AChE and enhance the toxicities on 10th instar of T. molitor. These results indicate that the EOs of L. cubeba and C. limonum could have great potential as botanical insecticides against T. molitor.     

Biological response of chilli thrips, Scirtothrips dorsalis Hood (Thysanoptera: Thripidae), to various regimes of chemical and biorational insecticides

The chilli thrips Scirtothrips dorsalis (Hood) (Thysanoptera: Thripidae), a new invasive pest in the USA, is an economically important pest of certain vegetable, ornamental and fruit crops in southern and eastern Asia, Oceania and parts of Africa. These crops cannot be protected from the pest without resorting to the use of chemical insecticides. In order to forestall or delay the development of insecticide resistance in S. dorsalis, we continued our focus on the discovery of insecticides with different modes of action for rotational use. In this study we evaluated candidate insecticides to control S. dorsalis on ‘Jalapeno’ pepper, Capsicum annuum L.; these materials belong to different IRAC mode of action classes as follows: (i) 4A – neonicotinoids, i.e., imidacloprid, thiamethoxam and dinotefuran, (ii) 5 – spinosyns, i.e., spinosad and spinetoram, (iii) 3A – pyrethroids, i.e., β-cyfluthrin, esfenvalerate, ζ-cypermethrin and λ-cyhalothrin and (iv) 8D – borax mixed together with orange oil and detergents in the TriCon^® formulation. In addition we evaluated the entomopathogenic fungus, Beauveria bassiana (Botanigard^®) alone and in combination with the borax formulation at ½ of their usual rates of application. Each of the 3 neonicotinoid insecticides when applied either as a single foliar spray or as a soil drench significantly suppressed both adults and larvae for at least 10 days; indeed imidacloprid did so for 15 days. Dinotefuran was more effective as a foliar spray than as a soil drench. Spinosyns applied as a single foliar spray, significantly suppressed both adults and larvae through 15 days after treatment (DAT). None of the 4 pyrethroids provided significant suppression of either adults or larvae. The borax formulation suppressed adults and larvae through 10 DAT. B. bassiana significantly suppressed only the larvae at 5 DAT and not at 10 DAT. This study brings the number of insecticides known to be effective against S. dorsalis to 10 and these belong to 7 different modes of action classes. The use of such insecticides in rotation belonging to different classes will help delay the development of insecticide resistance in S. dorsalis.     

Effect of Infection by Beauveria bassiana and Metarhizium anisopliae on the Feeding of Uvarovistia zebra

To identify the susceptibility of long-horned grasshoppers to entomopathogenic fungi, the effect of infection with the fungi Beauveria bassiana (Balsamo) Vuillemin (Hypocreales: Clavicipitaceae) and Metarhizium anisopliae (Metchnikoff) Sorokin (Hypocreales: Clavicipitaceae) on food consumption by Uvarovistia zebra (Uvarov) (Orthoptera: Tettigoniidae) was investigated. Preliminary results showed that both fungi had a negative effect on food consumption of the insects. For both fungi a significant reduction of food consumption and faeces production by insects were observed between the highest spore concentration (5 × 10⁶ spores/ml) and other treatments. Compared with control insects, the insects treated with 5 × 10⁶ spores/ml of B. bassiana and M. anisopliae showed 60 and 63% reduction in mean food consumption/insect, respectively. The corrected cumulative percent mortality of the insects treated with the highest concentration of B. bassiana and M. anisopliae were 57.7 and 55.5%, respectively. This was the first account of these entomopathogenic fungi being used against a species from this family, therefore based on the results obtained from this research, it could be said that the fungi have pathogenicity effect on U. zebra as a long-horned grasshopper.     

Identification and Expression of Two Novel Cytochrome P450 Genes,CYP6CV1 and CYP9A38, in Cnaphalocrocis medinalis (Lepidoptera: Pyralidae)

Cnaphalocrocis medinalis Güenée can cause severe losses in rice. Cytochrome P450s play crucial roles in the metabolism of allelochemicals in herbivorous insects. Two novel P450 cDNAs, CYP6CV1 and CYP9A38, were cloned from the midgut of C. medinalis. CYP6CV1 encodes a protein of 500 amino acid residues, while CYP9A38-predicted protein has 531 amino acid residues. Both cDNA-predicted proteins contain the conserved functional domains for all P450s. Phylogenetic analyses showed that CYP6CV1 is grouped in the cluster containing CYP6B members, while CYP9A38 is in the cluster including CYP9 members. However, both clusters are contained in the same higher lineage. Homologous analysis revealed that CYP6CV1 is most similar to CYP6B8, CYP6B7, CYP6B6, CYP6B2, and CYP6B4 with the highest amino acid identity of 41%. CYP9A38 is closest to CYP9A17, CYP9A21, CYP9A20, and CYP9A19 with the highest amino acid identity of 66%. Studies of temporal expression profiles revealed that CYP9A38 showed a steady increase in mRNA level during the five instar stages, but a low-expression level in pupae, and then presented at a high-expression level again in adults. Similar expression patterns were obtained with CYP6CV1. In the fifth instar larvae, CYP6CV1 was mainly expressed in midgut and fat bodies, whereas CYP9A38 was mainly expressed in midgut. Expression studies also revealed a 3.20-fold over-expression of CYP6CV1 and 3.54-fold over-expression of CYP9A38 after larval exposure to host rice resistance. Our results suggest that both CYP6CV1 and CYP9A38 may be involved in detoxification of rice phytochemicals.     

Effects of passages through a suitable host of the fungus, Metarhizium anisopliae,on the virulence of acaricide- susceptible and resistant strains of the tick,Rhipicephalus microplus

The aim of this work was to assess the virulence of strain M379 of the fungus, Metarhizium anisopliae (Metchnikoff) Sorokin (Hypocreales: Clavicipitaceae) after different passages through a suitable host and at different concentrations for the control of both acaricide-susceptible and resistant strains of the tick, Rhipicephalus (formerly Boophilus) microplus Canestrini (Ixodida: Ixodidae) in vitro. The highest value of LC₅₀ for the susceptible strain corresponded to zero passage with 7.68 × 10⁷ conidia/ml followed by the fourth passage with 2.68 × 10⁷, which reduced 2.87-fold the lethal concentration. When comparing LC50 values of the fourth vs. the seventh passage (2.59 × 10⁵ conidia/ml), the lethal concentration was reduced 103.47-fold by the seventh passage. In addition, in the resistant strain the LC₅₀ highest value corresponded to zero passage with 4.95 × 10⁷ conidia/ml followed by the fourth passage with 7.86 × 10⁶, which reduced 6.30-fold the lethal concentration. When comparing LC₅₀ values of the fourth vs. the seventh passage (1.04 × 10⁵ conidia/ml) in the resistant strain, the lethal concentration was reduced 75.58-fold by the seventh passage. These results suggest that the number of passages on M. anisopliae through a suitable host increased its virulence on both R microplus strains. When comparing LC₅₀ of the zero passage through a suitable host of both acaricide-susceptible and resistant strains, the highest LC₅₀ values corresponded to the susceptible strain with 7.68 × 10⁷ conidia/ml followed by the resistant one with 4.95 × 10⁷, showing that on the resistant strain the lethal concentration is reduced by 1.55-fold. When comparing the fourth passage, the highest values of LC₅₀ corresponded to the susceptible strain with 2.68 × 10⁷ conidia/ml followed by the resistant one with 7.86 × 10⁶ conidia/ml, showing for the resistant strain a 3.41-fold reduced lethal concentration. Moreover, when comparing the seventh passages, the highest values of LC₅₀ corresponded to the susceptible strain with 2.59 × 10⁵ followed by the resistant with 1.04 × 10⁵ conidia/ml, revealing for the resistant strain a 2.49-fold reduced lethal concentration. These results suggest that the resistant strain needs a lower concentration of conidia than the susceptible strain. In this case, the acaricide-resistant strain is more susceptible to M. anisopliae of zero- and seven-passage strains.     

Larvicidal Potential of the Halogenated Sesquiterpene (+)-Obtusol,Isolated from the Alga Laurencia dendroidea J. Agardh (Ceramiales: Rhodomelaceae), against the Dengue Vector Mosquito Aedes aegypti (Linnaeus) (Diptera: Culicidae)

Dengue is considered a serious public health problem in many tropical regions of the world including Brazil. At the moment, there is no viable alternative to reduce dengue infections other than controlling the insect vector, Aedes aegypti Linnaeus. In the continuing search for new sources of chemicals targeted at vector control, natural products are a promising alternative to synthetic pesticides. In our work, we investigated the toxicity of a bioactive compound extracted from the red alga Laurencia dendroidea J. Agardh. The initial results demonstrated that crude extracts, at a concentration of 5 ppm, caused pronounced mortality of second instar A. aegypti larvae. Two molecules, identified as (−)-elatol and (+)-obtusol were subsequently isolated from crude extract and further evaluated. Assays with (−)-elatol showed moderate larvicidal activity, whereas (+)-obtusol presented higher toxic activity than (−)-elatol, with a LC₅₀ value of 3.5 ppm. Histological analysis of the larvae exposed to (+)-obtusol revealed damage to the intestinal epithelium. Moreover, (+)-obtusol-treated larvae incubated with 2 µM CM-H₂DCFDA showed the presence of reactive oxygen species, leading us to suggest that epithelial damage might be related to redox imbalance. These results demonstrate the potential of (+)-obtusol as a larvicide for use against A. aegypti and the possible mode of action of this compound.     

Development of a Method for Rearing Nezara viridula (Heteroptera: Pentatomidae) on a Semi-solid Artificial Diet

A method for rearing the southern green stinkbug, (Nezara viridula L.) (Heteroptera: Pentatomidae), using a modified lygus semi-solid artificial diet was developed. First to second-instar nymph were reared in a density of 631.5 ± 125.05 eggs per Petri-dish (4 cm deep × 15 cm diam). Second instar to adult were reared in a density of 535.0 ± 112.46 s instar nymphs per rearing cage (43 × 28 × 9 cm). Mating and oviposition occurred in popup rearing cages (30 × 30 cm), each holding 60–90 mixed sex adults of similar age. Adults emerged 35.88 ± 2.13 d after oviposition and survived for an average of 43.09 ± 9.53 d. On average, adults laid 223.95 ± 69.88 eggs in their lifetime, for a total production of 8,099 ± 1,277 fertile eggs/oviposition cage. Egg fertility was 77.93% ± 16.28. Egg masses held in petri-dishes had a total hatchability of 79.38% ± 20.03. Mortality of early nymphs in petri-dishes was 0.64% ± 0.12 for the first instar and 1.37% ± 0.45 for second instar. Late nymphal mortality in rearing cages was 1.41% ± 0.10, 3.47% ± 1.27, and 4.72% ± 1.29 for the third, fourth, and fifth instars, respectively. Survivorship from nymphs to adults was 88.48% ± 2.76. Using artificial diet for rearing N. viridula could reduce cost by avoiding time-consuming issues with daily feeding fresh natural hosts and insect manipulation. It could increase reliability and simplicity of bug production, which should facilitate mass rearing of its biological control agents.     

Effect of Tithonia diversifolia Mulch on Atta cephalotes (Hymenoptera: Formicidae) Nests

Recent studies have shown an insecticidal effect of Tithonia diversifolia (Hemsl.) Gray (Asterales: Asteraceae) foliage on workers of Atta cephalotes L. and inhibitory effects of this plant on the growth of the symbiotic fungus Leucoagaricus gongylophorus (A. Müler) Singer. To evaluate the potential of T. diversifolia as a biological control treatment of this important pest, we assessed the effect of green manure (mulch) of this plant on natural nests of A. cephalotes, in Cali, Colombia. Three treatments were randomly assigned to 30 nests: 1) green mulch of T. diversifolia, 2) green mulch of Miconia sp., Ruiz & Pav. and 3) unmulched control. Every 2 wk for 6 mo, the surface of the nests was completely covered with leaves. Physical and chemical parameters of nest soil were assessed before the first and after the last application of the mulch. Ant foraging in T. diversifolia-treated nests decreased by 60% after the initial applications of the mulch, while nest surface area decreased by 40%. When the nests covered with T. diversifolia were opened, it was observed that the superficial fungus chambers had been relocated at a greater depth. In addition, microbial activity and soil pH increased by 84% and 12%, respectively, in nests covered with plant residues. In conclusion, the continued use of T. diversifolia mulch reduces foraging activity and negatively affects the internal conditions of the colonies, thereby inducing the ants to relocate the fungus chambers within the nests.     

Efficacy of entomopathogenic nematodes (Nematoda: Rhabditida) and insecticide mixtures to control Spodoptera frugiperda (Smith, 1797) (Lepidoptera: Noctuidae) in corn crops

The main insect pest in Brazilian corn is fall armyworm, Spodoptera frugiperda (Smith, 1797) (Lepidoptera: Noctuidae). Entomopathogenic nematodes (EPNs) can be used to control this pest, and can be applied together with various insecticides. Thus, the objective of this work was to evaluate the efficacy of mixtures of EPNs and insecticides to control S. frugiperda in corn crops. In laboratory bioassays three species of EPNs were tested (Heterorhabditis indica, Steinernema carpocapsae and Steinernema glaseri) together with 18 registered insecticides to control S. frugiperda in corn. Efficacy of association between insecticides and EPNs on S. frugiperda larvae was evaluated against the insect's third instar, 2 and 4 days after applications in laboratory. Experiments in the field were performed in two consecutive years, with located application of H. indica and S. carpocapsae (250 IJs/cm²) mixed with chlorpyrifos (0.3 L/ha) and lufenuron (0.15 L/ha) on the corn husk. In laboratory, after two days exposure the interaction between chlorpyrifos and H. indica was synergistic, while interaction with cypermethrin, spinosad, methoxyfenozide and deltamethrin + triazofos was additive, as was interaction between lufenuron, chlorpyrifos and cypermethrin with S. carpocapsae. In contrast, the interaction between chlorpyrifos (Vexter™ and Lorsban™) and lufenuron with S. glaseri was synergistic. In the field, the best treatment was the mixture of H. indica with lufenuron (0.15 L/ha), with 62.5% and 57.5% larval mortality in the two evaluation years in the field, respectively.     

Influence of Constant Temperature on Reproductive Parameters of Holotrichia oblita (Coleoptera: Scarabaeidae)

Holotrichia oblita Faldermann (Coleoptera: Scarabaeidae) is a major pest both in field crops and forests because the larvae could eat the roots of most crops in the field, and the adults damage the leaves of trees and field crops. In this study, we focused on the effects of temperature on H. oblita reproductive parameters. The results indicated H. oblita female adults at 25°C could lay more eggs (84.0 eggs per female) and have the shortest preoviposition period (19.1 d), the greatest oviposition rate (2.8 eggs per female per 3 d), and largest percentage of life span spent in oviposition (59.5%). The longevity and the time to 50% egg laying decreased with increasing temperature, and female longevity was always longer than male longevity. The preoviposition and postoviposition period decreased with increasing temperature from 15 to 25°C and then increased when the temperature increased from 25 to 30°C. These results show that 25°C is the optimal temperature for reproduction of H. oblita.     

球孢白僵菌对亚洲玉米螟毒力生测方法比较研究

在球孢白僵菌不同浓度下,利用饲喂法和浸渍法测试球孢白僵菌对亚洲玉米螟3龄幼虫的致病力,建立球孢白僵菌对亚洲玉米螟毒力生测标准。结果表明,处理组中白僵菌浓度为10⁵、10⁶、10⁷、10⁸ CFU/mL时,采用饲喂法和浸渍法对3龄幼虫的校正死亡率、致死中时间（LT₅₀）、致死中浓度（LC₅₀）均没有显著性差异;饲喂法3龄幼虫的死亡率显著低于浸渍法。因此,球孢白僵菌对亚洲玉米螟毒力生测的常用方法可用饲喂法替代浸渍法,饲喂法试验过程简单,避免反复移动试虫引起的误差,毒力测试结果更可靠。     

Comparative soil distribution and dissipation of phoxim and thiamethoxam and their efficacy in controlling Bradysia odoriphaga Yang and Zhang in Chinese chive ecosystems

Bradysia odoriphaga Yang and Zhang (the chive gnat) is the major insect pest affecting Chinese chives (Allium tuberosum Rottl. ex Spreng.) in Northern China. Only three insecticide products are registered for its control. In the present study, we compared the persistence and distribution of thiamethoxam and phoxim in soil and determined their long-acting control effects against B. odoriphaga and two other secondary pests, Thrips alliorum Priesner and the Asiatic onion leaf miner Acrolepia alliella Semenov and Kuznetsov (Lepidoptera: Acrolepiidae), after a single soil application using the directional spray-washing method during the early Chinese chive root-rearing period. Under the same applied dosage, the rhizosphere soil at a depth of 4.0–10.0 cm had concentrations of thiamethoxam and phoxim ranging from 2.21 to 7.44 mg/kg and 0.09–0.44 mg/kg, respectively, at the 7th day after application. The half-lives of thiamethoxam and phoxim in the soil were 27.5 and 6.7 days, respectively. Thiamethoxam persisted for 210 days, whereas phoxim only persisted for 45 days in the soil and plants. In addition, thiamethoxam applied at 6.0 kg a.i./ha maintained a low population density of B. odoriphaga, T. alliorum and A. alliella for nine months longer than phoxim. In conclusion, thiamethoxam may help farmers more effectively manage B. odoriphaga and other secondary pests on Chinese chive and reduce the costs of insecticide use while sustaining protection.