Studies were carried out on the bioefficacy and residual activity of Bacillus thuringiensis israelensis H-14 (Bti) (water-dispersible granules of VectoBac ABG 6511 and liquid formulations of VectoBac 12AS) and pyriproxyfen (insect growth regulator, Sumilarv 0.5%) as direct applications for control of larvae of Aedes aegypti and Aedes albopictus. Two dosages of each Bti formulation (285 and 570 international toxic units [ITU]/liter) and the integration of both Bti formulations and pyriproxyfen were used for residual tests with 45-liter earthen jars for a period of 4 wk. In 1 test series, the treated water was replenished daily with 6 liters of seasoned untreated water. In the 2nd test series, the water in the jars was topped up to the 40-liter level during evaluation. Neither Bti formulation remained effective for a full week. Water-dispersible Bti granules provided effective initial control activity against Ae. aegypti and Ae. albopictus for both test designs (with replenishment and without replenishment of water). The higher dosage (570 ITU/liter) for both Bti formulations was only partially effective at the end of 1 wk after being diluted. After 1 wk, water-dispersible Bti granules provided greater larval mortality than did liquid Bti formulation against both mosquito species when integrated with pyriproxyfen. Pyriproxyfen (79.5 and 159 mg/liter) on its own showed low larvicidal activity but provided very effective control of adult emergence. In this study, integration of Bti (285 and 570 ITU/liter) with pyriproxyfen (79.5 mg/liter) extended the duration of partial larval control somewhat, but live larvae persisted throughout the 4-wk test. The integration effect was more obvious when water-dispersible Bti granules were integrated with pyriproxyfen than when liquid Bti was used. Integration of Bti with pyriproxyfen had a negative effect on adult emergence, which was completely inhibited by pyriproxyfen after day 1. Daily replenishment of water increased Bti activity and provided slightly better larval control. Aedes albopictus and Ae. aegypti were both completely susceptible to the higher concentration of Bti and pyriproxyfen in both test designs (with replenishment and without replenishment of water).
Eggs of temperate Aedes albopictus populations are cold hardy and can diapause, but tropical populations are not cold hardy and cannot diapause. Heterozygotes possess intermediate diapause and cold hardiness. Males of a tropical strain from Malaysia with a distinctive genetic marker were released into an existing temperate population in East St. Louis, Illinois. Subsequent egg samples from the release site had genetic marker frequency of up to 24%. Reduced cold hardiness and decreased diapause incidence were also observed in the release site population. No such changes occurred at a nearby control site. The rank order of overwintering survival of eggs at the release site was: Aedes triseriatus > temperate Ae. albopictus > hybrid temperate/tropical Ae. albopictus > tropical Ae. albopictus. Eggs collected from the release population the next summer showed total absence of the genetic marker; presumably carriers were removed by the winter.
Matched MeSH terms: Pest Control, Biological/methods*
Clostridium bifermentans serovar. malaysia (C.b.m.) is toxic to mosquito larvae. In this study, we quantified its toxicity to the mosquitoes, Aedes aegypti, Ae. albopictus, Ae. caspius, Ae. detritus, Anopheles stephensi, An. gambiae, Culex pipiens and Cx. quinquefasciatus. Anopheles larvae are the most susceptible, followed by Ae. detritus and Ae. caspius, then Culex and other Aedes larvae. According to mosquito species, the LC50 varies from 7 x 10(3) to 1.3 x 10(6) cells/ml. Three concentrations (10(7), 10(6) and 10(5) cells/ml) of C.b.m., Bacillus thuringiensis var. israelensis (B.t.i.) and Bacillus sphaericus were tested on Ae. aegypti, An. stephensi and Cx. pipiens larvae in order to determine the time necessary for each concentration to kill 50 and 90% of the population. Ninety percent of the 3 mosquito populations are killed within 4-15 h by the C.b.m. concentrations. Whatever the concentrations, C.b.m. kills at least 10 times less rapidly than B.t.i. but always quicker than B. sphaericus. Bioassays of C.b.m. bacterial cells or final whole culture were not toxic to Musca domestica and Drosophila melanogaster (Diptera) as well as to Phaedon cochleariae (Coleoptera) and Spodoptera littoralis (Lepidoptera).
This study explored the efficacy of Toxorhynchites splendens, predator of Aedes albopictus as a biocontrol agent. There was a negative correlation between Ae. albopictus larval population and Tx. splendens larval population in ovitraps (r=-0.287, R²=0.0821). The correlation is higher between the mean number of Ae. albopictus larvae per ovitrap and the number of Tx. splendens larvae in an ovitrap (r=-0.987, R²=0.9737). Larvae of Tx. splendens were observed to co-exist with larvae of Ae. albopictus and Culex fuscocephala in the ovitraps placed in the study area. The existence of Tx. splendens larvae in the study area coincides with their habit, preferring to breed in bamboo stumps. A total of 480 ovitraps were inspected for 30-week study period and 281 ovitraps were positive with Ae. albopictus larvae respectively. There was a significant difference between numbers of ovitrap positive for Ae. albopictus larvae with number of Tx. splendens larvae in the ovitraps (ANOVA, F((4,475)) 2.655, p<0.05). Of 281 ovitraps positive with Ae. albopictus larvae, 255 ovitraps contained only one Tx. splendens larva each. Only one ovitrap contained four, the most number of Tx. splendens larvae (p< 0.05). Thus, Tx. splendens could be utilised as an alternative for dengue vector control programme.
Matched MeSH terms: Pest Control, Biological/methods*
Studies were carried out on the residual efficacy of Bacillus thuringiensis H-14 (water dispersible granule, VectoBac ABG 6511) as direct application in the control of Aedes larvae in the field. Field Aedes sp populations in the earthen and glass jars were predetermined before initiation of the trial. On confirmation of the presence of Aedes species in the designated area, Sungai Nibong Kecil, Penang Island, Malaysia, Bti was introduced in the 55L earthen and 3L glass jars). Two test designs were carried out. The first design had treated water replenished daily with 6L of seasoned water and the second design is without the replenishment of water but evaporated water was replenished. Bti was effective in the field for at least 35 days with more than 80% reduction in the Aedes larvae in the treated containers. For earthen jars with daily replenishment of water, 100% reduction was recorded for the first 3 days, while more than 80% reduction was recorded up to day 40. At day 60, Bti still provided an efficacy of 54.32 +/- 4.61 (%) of reduction. Whilst for earthen jars without daily replenishment of water, 100% reduction was recorded for the first 5 days, while more than 80% of reduction was recorded up to day 40. For the glass jars studied, similar efficacy was observed. In jars with daily replenishment of water a better larval control was observed. Percentage of reduction from day 50 to 60 for replenishment of water was between 50 to 70% compared to without replenishment of water with less than 40%.
Matched MeSH terms: Pest Control, Biological/methods*
Laboratory efficacy and residual activity of a water dispersible granule formulation of Bacillus thuringiensis israelensis (Bti) at the dosages of 3000, 6000 and 15000 ITU/L were conducted in this study. The study was conducted in two different size containers, earthen jar (45 L) and glass jar (3 L) with or without daily replenishment of 6 L and 0.3 L of water in the earthen and glass jars, respectively. Results indicate that for both earthen jar and glass jar evaluations, Bti at the tested dosages, performed effectively against Aedes aegypti, giving a minimum of 42 days effective killing activity. When the dosage was increased from 3000 ITU/L to 6000 ITU/L or 15000 ITU/L, the effective periods of the Bti increased by an additional one to three weeks. The Bti water dispersible granule provided better larvicidal activity with replenishment of water compared with non-replenishment of water especially for the higher dosage (15000 ITU/L).
Cx. quinquefasciatus is a common nuisance mosquito widely distributed in tropical and subtropical areas. This mosquito is also a vector of urban filariasis. Control with chemicals has been hampered by the development of resistance against chemical insecticides and rising problems of environmental contamination associated with them. Therefore, it is important to adopt more integrated mosquito management approaches that include sustainable, non chemical solutions. The mermithid nematode Romanomermis iyengari is one of several natural control alternatives to synthetic pesticides for mosquito suppression. This study evaluated the effectiveness of the nematode R. iyengari for control of Cx. quinquefasciatus. The nematode R. iyengari was mass-produced, and pre-parasitics (J2) were used for laboratory and field experiments. In laboratory experiments, two concentrations of pre-parasitics (5 and 10 J2 per larva) were tested against L1, L2 and L3 instars larvae of Cx. quinquefasciatus. Infected larvae were observed daily to determine their mortality rate and the number of postparasitic nematodes emerging from dead larvae. In field experiments, 1000, 2000 and 3000 J2/m2 were sprayed in separate natural Cx. quinquefasciatus breeding sites. After treatment, the larval mosquito density in the breeding sites was assessed every 5 days. Laboratory results showed that all tested Cx. quinquefasciatus instars larvae were susceptible to nematode infection. The mortality rates observed for each larval stage indicated that the concentration of 10 J2 kills larvae faster, and that the L1 larvae died earlier than older larvae. The average number of post-parasitic nematodes emerging per larva increases with increasing nematode concentration; also more post-parasitic nematodes emerged from the L2 larvae. Field data showed that, in breeding site treated with 3000 J2 per square meter, larval mosquito reduction reached 97% after nematode application. The dosage of 1000 J2 per square meter did not reduce the larval density. The insect parasitic nematode R. iyengari could be easily used as component of integrated mosquitoes control program in lymphatic filariasis endemic countries.
Matched MeSH terms: Pest Control, Biological/methods*
Conversion of tropical forests into oil palm plantations reduces the habitats of many species, including primates, and frequently leads to human-wildlife conflicts. Contrary to the widespread belief that macaques foraging in the forest-oil palm matrix are detrimental crop pests, we show that the impact of macaques on oil palm yield is minor. More importantly, our data suggest that wild macaques have the potential to act as biological pest control by feeding on plantation rats, the major pest for oil palm crops, with each macaque group estimated to reduce rat populations by about 3,000 individuals per year (mitigating annual losses of 112 USD per hectare). If used for rodent control in place of the conventional method of poison, macaques could provide an important ecosystem service and enhance palm oil sustainability.
Matched MeSH terms: Pest Control, Biological/methods*
Chagas disease is endemic to the Americas and is transmitted by blood-feeding kissing bugs. We evaluated the insecticidal potential of a fungus (Beauveria bassiana strain Pr-11) against Triatoma infestans, an important vector in South America. This fungal species was isolated from a locust (Schistocerca piceifrons) that inhabits the Central Andes region of Peru. Ten days post inoculation, this strain induced high insect mortality (97%) at low fungal concentrations (2 × 107 conidia/ml) at 70% relative humidity. The Pr-11 strain outperformed reference strain CCBLE-216 B. bassiana, provided by the Peruvian Ministry of Agriculture. Our results are consistent with previous reports on the virulence of this fungal strain against other insect pests. This is the first study to evaluate an orthopteran-isolated B. bassiana to control Chagas disease vectors. We conclude that strain Beauveria bassiana Pr-11 is effective against Triatoma infestans, resulting in a promising tool to control Chagas disease in Peru and may be used in integrated vector control programs.
Matched MeSH terms: Pest Control, Biological/methods*
Wheat (Triticum aestivum L.) production is significantly altered by the infestation of sucking insects, particularly aphids. Chemical sprays are not recommended for the management of aphids as wheat grains are consumed soon after crop harvests. Therefore, determining the susceptibility of different wheat genotypes and selecting the most tolerant genotype could significantly lower aphid infestation. This study evaluated the susceptibility of six different wheat genotypes ('Sehar-2006', 'Shafaq-2006', 'Faisalabad-2008', 'Lasani-2008', 'Millat-2011' and 'Punjab-2011') to three aphid species (Rhopalosiphum padi Linnaeus, Schizaphis graminum Rondani, Sitobion avenae Fabricius) at various growth stages. Seed dressing with insecticides and plant extracts were also evaluated for their efficacy to reduce the incidence of these aphid species. Afterwards, an economic analysis was performed to compute cost-benefit ratio and assess the economic feasibility for the use of insecticides and plant extracts. Aphids' infestation was recorded from the seedling stage and their population gradually increased as growth progressed towards tillering, stem elongation, heading, dough and ripening stages. The most susceptible growth stage was heading with 21.89 aphids/tiller followed by stem elongation (14.89 aphids/tiller) and dough stage (13.56 aphids/tiller). The genotype 'Punjab-2011' recorded the lower aphid infestation than 'Faisalabad-2008', 'Sehar-2006', 'Lasani-2008' and 'Shafaq-2006'. Rhopalosiphum padi appeared during mid-February, whereas S. graminum and S. avenae appeared during first week of March. Significant differences were recorded for losses in number of grains/spike and 1000-grain weight among tested wheat genotypes. The aphid population had non-significant correlation with yield-related traits. Hicap proved the most effective for the management of aphid species followed by Hombre and Husk among tested seed dressers, while Citrullus colocynthis L. and Moringa oleifera Lam. plant extracts exhibited the highest efficacy among different plant extracts used in the study. Economic analysis depicted that use of Hombre and Hicap resulted in the highest income and benefit cost ratio. Therefore, use of genotype Punjab-2011' and seed dressing with Hombre and Hicap can be successfully used to lower aphid infestation and get higher economic returns for wheat crop.
Matched MeSH terms: Pest Control, Biological/methods*
The efficacy of three formulations of Bacillus thuringiensis var. israelensis was studied against Aedes albopictus in discarded tires. The formulations were: Vectobac G (corn cob formulation), Vectobac 12AS (aqueous suspension), and Bactimos WP (wettable powder formulation). Both Vectobac G and Vectobac 12AS were effective for 24 hr with more than 80% mortality. Both Vectobac formulations were significantly more effective than Bactimos WP for 24 hr after treatment (P < 0.0005). A week after treatment, Vectobac 12AS was significantly different than Bactimos WP (P < 0.05). However, Vectobac G did not differ significantly from Bactimos WP (P > 0.05); two weeks after spraying there was no significant difference among the various formulations (P > 0.05).
Matched MeSH terms: Pest Control, Biological/methods*
Five strains of Ma. uniformis from Malaysia were tested for their susceptibility to infection with subperiodic B. malayi. All were found to be susceptible with infection rates ranging from 62% to 100%. The susceptibility rates were directly related to the microfilarial densities of the cat at the time of feeding. Statistical analysis showed no significant difference (p greater than 0.05) among the means of the indices of experimental infection as well as the percentage of infective mosquitoes of the five strains and an old laboratory colony. They were all equally susceptible to subperiodic B. malayi.
Metarhizium anisopliae Metchnikoff (Hypocreales: Clavicipitaceae) is a fungal pathogen that causes disease in various insect pests, and it can be exploited and developed as a biological control agent to combat the red palm weevil, Rhynchophorus ferrugineus Olivier (Coleoptera: Dryophthoridae). The study on indigenous isolates is crucial especially for development of bioinsecticides in the future. The M. anisopliae strain called MET-GRA4 was tested for pathogenicity against adult red palm weevil and treated in vitro with different spore viabilities. The isolates exhibited pathogenicity with 100% mortality 21 d postinfection. The median lethal time (LT50) for 85% viable spores was 8.6 d, while 39% viable spores had an LT50 value of 21.37 d, with 92 and 16.6% mycosis, respectively. The species MET-GRA4 strain was molecularly characterized using ITS1 and ITS4 from pure culture (Isolate A), mass-produced spores (Isolate B), and infected red palm weevil cadavers (Isolate C). The DNA sequences obtained matched M. anisopliae sequences, with 99% similarity. This new isolate of M. anisopliae has potential as a targeted bioinsecticide for management of red palm weevil.
The use of pheromone traps can minimize the excess application of synthetic insecticides, while can also benefit the environment. The use of pheromone traps has been promoted and suggested to vegetable farmers of Bangladesh for widespread adoption. However, the majority of farmers have continued to spray insecticides instead of using pheromone traps. The present study investigated the factors influencing farmers' adoption, dis-adoption, and non-adoption behavior of pheromone traps for managing insect pests. Primary data were collected from 438 vegetable growers. Data were analyzed using descriptive statistics and multinomial logistic regression. About 27% of the farmers abandoned the technique shortly after it was adopted as it was time-consuming to manage insect pests. Marginal effect analysis revealed that the likelihood of continued adoption was 34.6% higher for farmers who perceived that pheromone traps were useful in controlling insect pests. In contrast, the likelihood of dis-adoption was 16.5% and 10.4% higher for farmers who maintained communication with private pesticide company agents and neighbor farmers, respectively. Extension services by government extension personnel might be encouraged and maintained as a key component in increasing farmer awareness regarding the use of pheromone trap. Strategies to promote pheromone traps in vegetable production should highlight the positive impacts to farmers and the environment, as this would most likely lead to their continued and widespread use after initial adoption.
The diamondback moth (DBM) Plutella xylostella (L.) has traditionally been managed using synthetic insecticides. However, the increasing resistance of DBM to insecticides offers an impetus to practice integrated pest management (IPM) strategies by exploiting its natural enemies such as pathogens, parasitoids, and predators. Nevertheless, the interactions between pathogens and parasitoids and/or predators might affect the effectiveness of the parasitoids in regulating the host population. Thus, the parasitism rate of Nosema-infected DBM by Cotesia vestalis (Haliday) (Hym., Braconidae) can be negatively influenced by such interactions. In this study, we investigated the effects of Nosema infection in DBM on the parasitism performance of C. vestalis. The results of no-choice test showed that C. vestalis had a higher parasitism rate on non-infected host larvae than on Nosema-treated host larvae. The C. vestalis individuals that emerged from Nosema-infected DBM (F1) and their progeny (F2) had smaller pupae, a decreased rate of emergence, lowered fecundity, and a prolonged development period compared to those of the control group. DBM infection by Nosema sp. also negatively affected the morphometrics of C. vestalis. The eggs of female C. vestalis that developed in Nosema-infected DBM were larger than those of females that developed in non-infected DBM. These detrimental effects on the F1 and F2 generations of C. vestalis might severely impact the effectiveness of combining pathogens and parasitoids as parts of an IPM strategy for DBM control.
Matched MeSH terms: Pest Control, Biological/methods*
On December 21, 2010, 6000 genetically modified (GM) mosquitoes were released in an uninhabited forest in Malaysia. The purpose of the deliberate release was a limited “marked release and recapture” (MRR) experiment, a standard ecological method in entomology, to evaluate under field conditions, the flight distance and longevity of the sterile male Aedes aegypti strain OX513A(My1), a GM strain. As with any other GM technologies, the release was received with mixed responses. As the scientific community debate over the public engagement strategies for similar GM releases, dengue incidence continues to rise with a heavy toll on morbidity, mortality and healthcare budgets. Meanwhile the wild female Aedes aegypti continues to breed offspring, surviving and evading conventional interventions for vector control.
Matched MeSH terms: Pest Control, Biological/methods*
To evaluate the mosquito larvicidal potential of the native Bacillus thuringiensis isolate BtReXO2, which was isolated from a tropical rain forest ecosystem in Malaysia. This study also aimed at determining the phenotypic and biochemical characteristics of the isolate.