Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) is one of the most destructive pests of several vegetables and fruits worldwide. In spite of various control methods, this pest has still continued to cause significant damage. In this study, the culturable bacterial flora of S. littoralis was determined. New isolates from S. littoralis, as well as 12 different Bacillus isolates belong to 5 species that were previously isolated from different pests, were tested on S. littoralis larvae. In total, 9 bacteria were characterized based on their morphological, biochemical, physiological, and molecular characteristics. The bacterial flora of S. littoralis was determined as Flavobacterium sp. (SL1), Klebsiella pneumonia (SL2), Enterobacter sp. (SL3), Enterobacter sp. (SL4), Klebsiella sp. (SL5), Serratia marcescens (SL6), Pseudomonas aeruginosa (SL7), Acinetobacter baumannii (SL8), and Staphylococcus sp. (SL9). The insecticidal activity tests were performed on the third-instar larvae of S. littoralis. SL1 and SL5 from S. littoralis caused the highest mortalities with 67% and 77%, respectively. Among previously isolated Bacillus isolates, Bacillus thuringiensis subsp. kurstaki (MnD) and B. thuringiensis subsp. kurstaki (BnBt) were found to be the most effective, causing 100% mortality within 10 days after treatment. A concentration-response test was conducted with these isolates and it was found that the isolate MnD was more effective than BnBt. Therefore, further bioassay experiments were conducted with the isolate MnD and results were discussed with respect to the biocontrol potential of the bacterial isolates.
IntroductionCorn is the largest grown cereal crop in the world with doubled grain yield per unit area compared to wheat and barley. Although corn production holds second place in Mediterranean agricultural production, there has been a sharp decline in this value due to infestation by the Mediterranean corn borer (Özcan, 2009). The Mediterranean corn borer, Sesamia nonagrioides (Lefebvre) (Lepidoptera: Noctuidae), is a major multivoltine pest of maize in Mediterranean countries (Tsitsipis, 1988;Alexandri and Tsitsipis, 1990). S. nonagrioides is a polyphagous species with a fairly wide range of host plants, including corn, sorghum, millet, rice, sugar cane, grasses, melon, asparagus, palms, and banana (Uygun and Kayapınar, 1993;Sannino et al., 2004). The population levels of this species, which has considerable potential to establish itself in an area and become abundant, may therefore depend on the abundance of these hosts (Eizaguirre and Fantinou, 2012). If insecticides are not applied, losses could rise to 100% in late and second crop production (Alexandri and Tsitsipis, 1990).Application of chemical insecticides against this harmful insect is recommended 2-3 times per growing season. However, yield losses could rise to 30% during seasons with severe insect outbreaks, even after 4-5 insecticide applications (Özcan, 2009). As well as causing significant maize crop losses, the insects reduce the nitrogen/protein content of grain by tunneling into the stem and cobs, where they are likely to interfere with the uptake of plant nutrients (Bayram, 2003). Furthermore, mycotoxigenic fungi associated with the pest often invade wound sites and can greatly depreciate the crop value (Avantaggiato et al., 2003). Although several control methods have been previously applied to this pest, damage is still pervasive. Chemical insecticides have been frequently used against it. While chemicals decrease pest population, they cause major threats to the environment and human health. Mechanical, cultural, and biological Abstract: Sesamia nonagrioides (Lep.: Noctuidae) is one of the most serious pests of corn in Turkey and other Mediterranean countries. Although various cultural, chemical, and biological methods are used to control this pest, its damage still continues in all Mediterranean countries. In this study, to find an effective bacterium that can be used as a biocontrol agent against S. nonagrioides, we isolated 15 bacteria from S. nonagrioides larvae and evaluated the larvicidal potency of all isolates on the pest. According to their morphological, physiological, biochemical, and molecular properties, the isolates were identified as Achromobacter insolitus (Sn1), Morganella morganii (Sn2), Klebsiella pneumoniae (Sn3), Citrobacter freundii (Sn4), Arthrobacter protophormiae (Sn5), Chryseobacterium indologenes (Sn6), Bacillus thuringiensis (Sn7), Bacillus safensis (Sn8), Bacillus thuringiensis (Sn9), Bacillus thuringiensis (Sn10), Klebsiella pneumoniae (Sn11), Staphylococcus sciuri (Sn12), Enterobacter kobei (Sn13), Serratia marce...
Cimbex quadrimaculatus (Hymenoptera: Cimbicidae) is one of the serious pests of almonds in Turkey and worldwide. Since there is no effective control application against this pest, it has been a serious problem up to now. Therefore, we aimed to find an effective bacterium that can be utilized as a biocontrol agent against C. quadrimaculatus in pest management. We isolated seven bacteria from dead and live C. quadrimaculatus larvae, and evaluated the larvicidal potency of all isolates on the respective pest. Based on the morphological, physiological, biochemical and molecular properties (partial sequence of 16S rRNA gene), the isolates were identified to be Bacillus safensis (CQ1), Bacillus subtilis (CQ2), Bacillus tequilensis (CQ3), Enterobacter sp. (CQ4), Kurthia gibsonii (CQ5), Staphylococcus sp. (CQ6) and Staphylococcus sciuri (CQ7). The results of the larvicidal activities of these isolates indicated that the mortality value obtained from all treatments changed from 58 to 100 %, and reached 100 % with B. safensis (CQ1) and B. subtilis (CQ2) on the 3rd instar larvae within 10 days of application of 1.89 × 10(9) cfu/mL bacterial concentration at 25 °C under laboratory conditions. Findings from this study indicate that these isolates appear to be a promising biocontrol agent for C. quadrimaculatus.
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