Good Biocontrol Agent Research Articles

BEHAVIORAL REACTION OF THE ORIENTAL WASP, Vespa orientalis L ADULTS IN RESPONSE TO SOME OLFACTORY STIMULANT MATERIALS

The relative attractiveness of some olfactory stimulant materials to the oriental hornet wasp, Vespa orientalis L. was evaluated under laboratory and field conditions. Olfactory stimulant materials included some volatile oils ( cinnamon, bananas, camphor and mint) and other natural materials (yeast, chicken litter, asber fermented grapes and sugar syrup as control). The obtained results revealed that the oriental wasp exhibited different degrees of selectivity in response to the tested olfactory stimulant materials. V.orientalis adults exposed to different volatile oils showed the highest attractiveness to cinnamon followed by camphor and mint oils with significant differences. The waspsexhibited the lowest preferability to bananas. The present study indicated that the oriental hornet wasp exhibited significantly positive response to asber fermented grape and chicken litter in comparison with yeast and sugar syrup. So, asber fermented grape and chicken litter successfully attracted the wasp; these materials can be used in monitoring populations of Vespa orientalis. Traps baited with cinnamon oil proved to be good bio control agent against the oriental wasps as they strongly attractive to them. The oriental wasps, V. orientalis population was considerably decreased in treated apiary in comparison with untreated one. Therefore, cinnamon oil could be used against the oriental wasps in IPM programs.

Rhamnolipid biosurfactant against Fusarium sacchari—the causal organism of pokkah boeng disease of sugarcane

Pokkah boeng disease on sugarcane caused by the fungus Fusarium sacchari results considerable damage to the crop leading to top rot, the most serious and advanced stage of pokkah boeng, where the growing point is killed and the entire top of the plant dies. In the present study, the effect of rhamnolipid biosurfactant as an antifungal agent against F. sacchari to control pokkah boeng disease was investigated. On the basis of surface tension reduction, 12 bacterial isolates were selected as potent biosurfactant producers and eight of them showed antagonistic effect against F. sacchari. Among the eight, the isolate DS9 was found as the effective inhibitor of the fungus in vitro which was further evaluated using its biosurfactant present in whole culture, cell-free culture supernatant and crude biosurfactant at various concentrations. Reductions of fungal growths were found more with crude biosurfactant. By sequencing 16S rRNA, DS9 was identified as P. aeruginosa and the produced biosurfactant was characterized as rhamnolipid by Liquid Chromatography-Mass Spectrometry (LC-MS) analysis. The rhamnolipid biosurfactant inhibits phytopathogenic fungi F. sacchari and therefore seems to be a good biocontrol agent to control pokkah boeng disease of sugarcane.

Evaluation of yeasts obtained from Antarctic soil samples as biocontrol agents for the management of postharvest diseases of apple (Malus × domestica)

Psychrotrophic yeasts were isolated from Antarctic soils, selected based on their ability to grow in apple juice at low temperatures, and were evaluated as potential biocontrol agents for the management of postharvest diseases of apple during cold storage. Among the species recovered, an isolate of Leucosporidium scottii, designated At17, was identified as a good biocontrol agent for blue and gray mold of two apple cultivars. The selected isolate produced soluble and volatile antifungal substances that were inhibitory to apple pathogens. Siderophore production was also demonstrated, but it did not appear to play a role in pathogen inhibition. The selected yeast had the capacity to form a biofilm when grown in apple juice, which is considered an important attribute of postharvest antagonists to successfully colonize wounds and intact fruit surfaces. At17 was resistant to commonly used postharvest fungicides, so application of a combination of low-dose fungicide along with the biocontrol agent could be used as an integrated management practice.

Abundance of Three Sap Sucking Pests on Three Eggplant Cultivars With Utilization of Phytoseiulus persimilis Athias-Henriot against Tetnlnychus urticae Koch

Abundance and fluctuation of Tetranychus urticae Koch, Aphis gossypii Glover and Bemisia tabaci (Gann.) were studied on three eggplant cultivars (i.e. Baladi-White, Florida Market and Baladi-Black) during 2009 and 2010 successive seasons. T. urticae occurrence continued almost all the season and reached its maximum at the end of June or the beginning of July. A gossypii reaching the highest abundance in the middle of September while B. tabaci reached its maximum abundance at the end of July and first half of August. Variance in susceptibility among tested cultivars was recorded based on the abundance averages overall the two seasons. Florida Market, Baladi-White and Baladi-Black recorded the lowest abundance of T. urticae, A gossypii and B. tabaci, respectively. Phytoseiulus persimilis proved to be a good biocontrol agent against T. urticae at release ratios of 1 :5 and 1:10 predator : prey. A reduction appeared one week after release, generally it revealed 68.60 and 88.20 % mean reduction for both release ratios, respectively.

Physiological variability and in vitro antifungal activity against Botrytis cinerea causing botrytis gray mold of chickpea (Cicer arietinum L.)

Physiological variability was studied in 10 isolates of Botrytis cinerea causing botrytis gray mold of chickpea, collected from diverse agro climatic areas in Bangladesh. The optimum temperature and pH for the best mycelial radial growth of B. cinerea were 20°C and 4.5, respectively. The mycelial radial growth increased with the temperature up to 20°C thereafter it decreased gradually up to 30°C and no growth was observed at 35°C. Chickpea dextrose agar (CDA) medium supported the highest mycelial radial growth (79.17 mm). The quickest (in 5 days) sclerotia initiation was recorded on chickpea destrose agar and lentil dextrose agar (LDA) culture media while the highest number of spores (2.5104 mL–1) were recorded on LDA medium. The antagonist Trichoderma harzianum was found to be a good bio-control agent against B. cinerea. Among the seven fungicides Bavistin® 50 WP (Carbendazim), CP-Zim 50 WP (Carbendazim), Sunphanate 70 WP (Thiophanate methyl) and Rovral 50 WP (Iprodione) were the most effective to inhibit the mycelial radial growth of B. cinerea at 500 mg L–1 concentration.

Isolation and characterization of entomopathogenic fungi from hazelnut-growing region of Turkey

Although Turkey is the first among all hazelnut-producing countries, yield per unit area of this crop is low in comparison to other countries, mainly because many insect species seriously damage hazelnut trees and their fruit. To find effective and safe biocontrol agents, we conducted a survey study to isolate entomopathogenic fungi from the hazelnut-growing region of Turkey and characterized the isolated strains in detail. In addition, we determined the effectiveness of seven selected strains from this region against Melolontha melolontha (Coleoptera: Scarabaeidae) which is one of the most serious pests of hazelnut. In 2006 and 2007, 301 soil samples were collected randomly and analyzed for presence of entomopathogenic fungi using the Galleria bait method. Entomopathogenic fungi were found to occur in 20.59% of the soil samples studied. Based on morphology, ITS sequence and partial sequencing of the 18S (SSU rDNA) and EF1-α genes, the isolates were identified as Metarhizium anisopliae var. anisopliae, Metarhizium sp., Beauveria bassiana, Beauveria cf. bassiana, Isaria fumosorosea and Evlachovaea sp. Metarhizium anisopliae var. anisopliae was isolated from 34 sites and was the most frequent and abundant entomopathogenic species recovered. All the isolates tested were pathogenic to M. melolontha. M. anisopliae var. anisopliae KTU-27 and Evlachovaea sp. KTU-36 produced the highest insecticidal activity (86.6%) within 15 days after inoculation. Our results suggest that entomopathogenic fungi could be good biocontrol agents against M. melolontha, and are discussed with respect to ecology of fungi in relation to habitat in order to evaluate biocontrol potential of these isolates. This is the first study of the distribution of entomopathogenic fungi in the hazelnut-growing region of Turkey and of their pathogenicities against M. melolontha.

Opportunistic foraging by heteropteran mosquito predators

Tropical aquatic environments host a large number of predatory insects including heteropteran water bugs Anisops bouvieri Kirkaldy, 1704 (Heteroptera: Notonectidae), Diplonychus (=Sphaerodema) rusticus Fabricius, 1781 (Heteroptera: Belostomatidae), and Diplonychus (=Sphaerodema) annulatus Fabricius, 1781 (Heteroptera: Belostomatidae) feeding on a range of organisms. In tropical and subtropical wetlands, ponds, and temporary pools these predators play a role in regulation of dipteran populations, particularly mosquitoes and chironomids. Their relative abilities to control mosquitoes depend in part on predator preference for mosquitoes in relation to other natural prey, and the predators’ propensities to switch to mosquitoes as mosquito density increases. The prey electivity and switching dynamics of these predatory water bugs were evaluated in the laboratory under various prey densities, using two instars (II and IV) of chironomid and mosquito larvae as prey. Studies of electivity at relatively high densities (20 prey L−1) in small (5 L) vessels demonstrated that all predators showed opportunistic foraging as the mosquito:chironomid ratio changed, with some evidence that mosquito larvae were positively selected over chironomids. In particular, Anisops showed strong electivity for mosquitoes when presented with any ratio of large mosquito and chironomid prey in the high density experiment, although the preference was not expressed in lower density (2.5 prey L−1) treatments executed in 40 L vessels. In these lower density treatments, D. rusticus demonstrated higher electivity for mosquitoes when the mosquito:chironomid ratio was high, consistent with non-significant trends observed in the higher density experiment. The positive electivity of D. rusticus for mosquitoes was reinforced in an experiment executed over 16 days at varying prey ratios, in which D. rusticus mosquito electivity was high and consistent while D. annulatus showed slight avoidance of mosquito larvae, and Anisops remained largely opportunistic in foraging on prey in proportion with availability. Anisops and D. rusticus are potentially good biocontrol agents for mosquito larvae, in that they preferentially consume mosquitoes under many circumstances but can readily forage on other prey when mosquito density is low.

Trichopria khandalus (Hym., Diapridae): a new biocontrol agent of the uzifly Exorista bombycis (Dipt., Tachinidae)

AbstractBiological control of the silkworm pest (Exorista bombycis) was partly successful by using a new hymemopteran biocontrol agent Trichopria khandalus, recovered from the environs of a cocoon market in Hindupur district of Andhra Pradesh (India). T. khandalus is a tiny (1–1.5 mm) endoparasite, the females were found to parasitize the uzifly puparia. The progeny developed inside the uzi pupa, and the adults (140–160 individuals from a single pupa) emerged after about 18–25 days depending on the seasonal extrinsic factors. The lift cycle of T. khandalus averaged 32 days. Due to the favourable sex ratio (2:3 male/female) and high preference to parasitize uzi puparia it is qualified as a good biocontrol agent for the control of E. bombycis. Prospects for utilizing this hyperparasite to manage and eliminate the uzi populations are discussed in the light of its data on biology, and easily manageable mass multiplication in the insectary.

Oviposition specificity and behavior of the watermilfoil specialist Euhrychiopsis lecontei.

Eurasian watermilfoil (Myriophyllum spicatum L.) is a nuisance aquatic weed, exotic to North America. The freshwater weevil Euhrychiopsis lecontei (Dietz) is a potential control agent of Eurasian watermilfoil and is a fully submersed aquatic specialist herbivore. Its presumed original host is the native northern watermilfoil (Myriophyllum sibiricum Komarov). We conducted a set of oviposition experiments to reveal first and second oviposition preference of Euhrychiopsis lecontei when presented with seven macrophytes. We tested differences between source (lake) populations of weevils, differences in behavior between weevils reared on the exotic Eurasian watermilfoil and the native northern watermilfoil and between weevils in the presence and absence of their preferred hostplant. Oviposition assays confirmed that E. lecontei is a watermilfoil specialist. Out of the 207 females that laid eggs, only three oviposited on a non-watermilfoil plant, Megalodonta beckii. The weevils' degree of specificity was influenced by the watermilfoil species on which they were reared. Weevils reared on Eurasian watermilfoil tended to oviposit on Eurasian watermilfoil, spent more time on Eurasian watermilfoil than on other plants, and spent more time off plants and took longer to oviposit when Eurasian watermilfoil was removed. Weevils reared on northern watermilfoil did not exhibit a preference for either watermilfoil species in oviposition or in time allocation, although they oviposited on and spent significantly more time on watermilfoils than on other species. Rearing of the two populations on their complementary watermilfoil hostplant resulted in responses typical of the rearing plant, not the original host. These results show that although both weevil populations are watermilfoil specialists, Eurasian-reared weevils prefer Eurasian watermilfoil in general host attraction and oviposition, whereas northern-reared weevils do not. The results support the contention that E. lecontei may be a good biocontrol agent for Eurasian watermilfoil because of its high specificity. The results also suggest that the current host range expansion of the weevil to Eurasian watermilfoil has the potential to become a host shift due to the increased specificity. Herbivory in freshwater systems is not well studied, and the E. lecontei-M. spicatum relationship is a rare example of submersed freshwater specialist herbivore-host-plant interactions.

Fate of biological control introductions: monitoring an Australian fungal pathogen of grasshoppers in North America.

In North America there are two generally recognized pathotypes (pathotypes 1 and 2) of the fungus Entomophaga grylli which show host-preferential infection of grasshopper subfamilies. Pathotype 3, discovered in Australia, has a broader grasshopper host range and was considered to be a good biocontrol agent. Between 1989 and 1991 pathotype 3 was introduced at two field sites in North Dakota. Since resting spores are morphologically indistinguishable among pathotypes, we used pathotype-specific DNA probes to confirm pathotype identification in E. grylli-infected grasshoppers collected at the release sites in 1992, 1993, and 1994. In 1992, up to 23% of E. grylli-infected grasshoppers of the subfamilies Melanoplinae, Oedipodinae, and Gomphocerinae were infected by pathotype 3, with no infections > 1 km from the release sites. In 1993, pathotype 3 infections declined to 1.7%. In 1994 grasshopper populations were low and no pathotype 3 infections were found. The frequency of pathotype 3 infection has declined to levels where its long-term survival in North America is questionable. Analyses of biocontrol releases are critical to evaluating the environmental risks associated with these ecological manipulations, and molecular probes are powerful tools for monitoring biocontrol releases.

Influence of plant species on disease suppression by Pseudomonas fluorescens strain CHAO with enhanced antibiotic production

Introduction of the recombinant cosmid pME3090 into Pseudomonas fluorescens strain CHAO, a good biocontrol agent of various diseases caused by soilborne pathogens, increased three‐ to five‐fold the production of the antibiotic metabolites pyoluteorin (Pit) and 2,4‐diacetylphlorogIucinol (Phi) in vitro. Strain CHAO/pME3090 also overproduced Pit and Phi in the rhizosphere of wheat infected or not infected with Pythium ultimum. The biocontrol activity of the wild‐type and recombinant Straitis was compared using various plant pathogen‐host combinations in a gnotobiotic system. Antibiotic overproduction affected neither the protection of wheat against P. ultimum and Gaeumannomyces graminis var. tritici nor the growth of wheat plants. In contrast, strain CHA0/pME3090 showed an increased capacity to protect cucumber against Fusarium oxysporum f. sp. cucumerinum and Phomopsis sclerotioides, compared with the wild‐type strain CHAO, The antibiotic overproducing strain protected tobacco roots significantly better against Thielaviopsis basicola than the wild‐type strain but drastically reduced the growth of tobacco plants and was also toxic to the growth of sweet com. On King's B agar and on malt agar, the recombinant strain CHA0/pME3090 inhibited all pathogens more than did the parental strain CHAO. Synthetic Pit and Phi were toxic to all fungi tested. Tobacco and sweet com were more sensitive to synthetic Pit and Phi than were cucumber and wheat. There was no correlation between the sensitivity of the pathogens to the synthetic antibiotics and the degree of disease suppression by strain CHAO pME3090. However, there was a correlation between the sensitivity of the plants and the toxicity of the recombinant strain. We conclude that the plant species rather than the pathogen determines whether cosmid pME3090 in P. fluorescens strain CHAO leads to improved disease suppression.