Investigation of ecological behavior of two Coccinellidae beetle adults for biological control

The use of natural enemies is an effective strategy to control and suppress pest populations in a given agroecosystem; however farmers are not motivated to adopt this method because of the high cost and temporal unavailability of natural enemies. This thesis reports findings of a series of laboratory experiments carried out to investigate ecological behavioral of two major natural enemies; Harmonia axyridis and Cryptolaemus montrouzieri (Coleoptera: Coccinellidae) Laboratory studies was conducted to determine if H. axyridis could be attracted to companion plants with different olfactory and visual cues, to investigate the within-plant distribution of long-tailed mealybug, Pseudococcus longispinus (Hempitera: Pseudoccoccidae), to quantify the searching and handling time of C. montrouzieri on three different plants heights and to determine preference of C. montrouzieri to the size of P. longispinus. Ten potential plants that can attract and provide H. axyridis with nectar and pollen were selected for a preference test. The result of the olfactory preference test showed that there was significant difference in the plant preference by H. axyridis; sunflower was the most preferred attractant plants. In a visual preference test, H. axyridis preferred yellow to other colors. P. longispinus was found more on the upper parts of the plants regardless of the height. The time C. montrouzieri spent to find the first P. longispinus was significantly (P \u3c 0.05) different among the three different plant heights at two different releasing points. However, there were no significant differences in handling time and cleaning time. Cryptolaemus montrouzieri preferred smaller size of P. longispinus to medium and larger size. The results presented in this thesis suggested that H. axyridis and C. montrouzieri could potentially be used as economical and sustainable biological control agents

Effect of Plant Characteristics and Within-Plant Distribution of Prey on Colonization Efficiency of Cryptolaemus montrouzieri

Cryptolaemus montrouzieri (Coleoptera: Coccinellidae) has been widely used in classical and inundative biological control of mealybugs, including the long-tailed mealybug, Pseudococcus longispinus (Hemiptera: Pseudococcidae). This study was conducted to investigate colonization and establishment efficiency of C. montrouzieri to manage P. longispinus on three different ornamental plant species (Ficus elastica, Lilium longiflorum, and Dieffenbachia seguine). Within-plant distribution pattern of P. longispinus and the colonization ecology of adult C. montrouzieri were investigated. Significantly more P. longispinus were found on the upper parts of the plants regardless of plant species, and C. montrouzieri adults discovered P. longispinus significantly faster when they were released on the top of the plants than on the bottom. Choice tests revealed that C. montrouzieri adults preferred smaller P. longispinus nymphs. The implications for utilization of C. montrouzieri for biological control of mealybugs on various ornamental plants are discussed

Genes related to mitochondrial functions are differentially expressed in phosphine-resistant and -susceptible Tribolium castaneum

Background: Phosphine is a valuable fumigant to control pest populations in stored grains and grain products. However, recent studies indicate a substantial increase in phosphine resistance in stored product pests worldwide.Results: To understand the molecular bases of phosphine resistance in insects, we used RNA-Seq to compare gene expression in phosphine-resistant and susceptible laboratory populations of the red flour beetle, Tribolium castaneum. Each population was evaluated as either phosphine-exposed or no phosphine (untreated controls) in triplicate biological replicates (12 samples total). Pairwise analysis indicated there were eight genes differentially expressed between susceptible and resistant insects not exposed to phosphine (i.e., basal expression) or those exposed to phopshine (>8-fold expression and 90 % C.I.). However, 214 genes were differentially expressed among all four treatment groups at a statistically significant level (ANOVA, p < 0.05). Increased expression of 44 cytochrome P450 genes was found in resistant vs. susceptible insects, and phosphine exposure resulted in additional increases of 21 of these genes, five of which were significant among all treatment groups (p < 0.05). Expression of two genes encoding anti-diruetic peptide was 2- to 8-fold reduced in phosphine-resistant insects, and when exposed to phosphine, expression was further reduced 36- to 500-fold compared to susceptible. Phosphine-resistant insects also displayed differential expression of cuticle, carbohydrate, protease, transporter, and many mitochondrial genes, among others. Gene ontology terms associated with mitochondrial functions (oxidation biological processes, monooxygenase and catalytic molecular functions, and iron, heme, and tetrapyyrole binding) were enriched in the significantly differentially expressed dataset. Sequence polymorphism was found in transcripts encoding a known phosphine resistance gene, dihydrolipoamide dehydrogenase, in both susceptible and resistant insects. Phosphine-resistant adults also were resistant to knockdown by the pyrethroid deltamethrin, likely due to the increased cytochrome P450 expression.Conclusions: Overall, genes associated with the mitochondria were differentially expressed in resistant insects, and these differences may contribute to a reduction in overall metabolism and energy production and/or compensation in resistant insects. These data provide the first gene expression data on the response of phosphine-resistant and -susceptible insects to phosphine exposure, and demonstrate that RNA-Seq is a valuable tool to examine differences in insects that respond differentially to environmental stimuli.Peer reviewedEntomology and Plant Patholog

Effect of Plant Characteristics and Within-Plant Distribution of Prey on Colonization Efficiency of Cryptolaemus montrouzieri (Coleoptera: Coccinellidae) Adults

Cryptolaemus montrouzieri (Coleoptera: Coccinellidae) has been widely used in classical and inundative biological control of mealybugs, including the long-tailed mealybug, Pseudococcus longispinus (Hemiptera: Pseudococcidae). This study was conducted to investigate colonization and establishment efficiency of C. montrouzieri to manage P. longispinus on three different ornamental plant species (Ficus elastica, Lilium longiflorum, and Dieffenbachia seguine). Within-plant distribution pattern of P. longispinus and the colonization ecology of adult C. montrouzieri were investigated. Significantly more P. longispinus were found on the upper parts of the plants regardless of plant species, and C. montrouzieri adults discovered P. longispinus significantly faster when they were released on the top of the plants than on the bottom. Choice tests revealed that C. montrouzieri adults preferred smaller P. longispinus nymphs. The implications for utilization of C. montrouzieri for biological control of mealybugs on various ornamental plants are discussed

Structural and functional insights into the Diabrotica virgifera virgifera ATP-binding cassette transporter gene family

Abstract Background The western corn rootworm, Diabrotica virgifera virgifera, is a pervasive pest of cultivated maize in North America and Europe, which has adapted to survive exposure to multiple insecticidal agents. Due to their role in insecticide transport, we sought to identify members of the ATP-binding cassette (ABC) transporter family in D. v. virgifera using a transcriptomics approach. Results In this study, 65 putative D. v. virgifera ABC (DvvABC) transporters were identified within a combined transcriptome assembly generated from embryo, larval, adult male, and adult female RNA-sequence libraries. Phylogenetic analysis placed the deduced amino-acid sequences of the DvvABC transporters into eight subfamilies (A to H). Of these, eight shared structural and functional conservation with Tribolium castaneum ABC transporter orthologs known to exhibit overt RNA interference (RNAi) knockdown phenotypes. Interestingly, depletion of DvvABCB_19147 and DvvABCG_3712 transcripts in adult females produced detrimental reproductive and developmental phenotypes (egg-laying or -hatching defects), demonstrating the potential of these genes as targets for RNAi-mediated insect control tactics. Conclusions By combining sequence data from four libraries covering three distinct life stages, we have produced a relatively comprehensive de novo transcriptome assembly for D. v. virgifera. Moreover, we have identified 65 members of the ABC transporter family, and provided the first insights into the developmental and physiological roles of ABC transporters in this pest species.</jats:p

Structural and functional insights into the Diabrotica virgifera virgifera ATP-binding cassette transporter gene family

Abstract Background The western corn rootworm, Diabrotica virgifera virgifera , is a pervasive pest of cultivated maize in North America and Europe, which has adapted to survive exposure to multiple insecticidal agents. Due to their role in insecticide transport, we sought to identify members of the ATP-binding cassette (ABC) transporter family in D. v. virgifera using a transcriptomics approach.Results In this study, 65 putative D. v. virgifera ABC ( Dvv ABC) transporters were identified within a combined transcriptome assembly generated from embryonic, larval, adult male, and adult female RNA-sequence libraries. Phylogenetic analysis placed the deduced amino-acid sequences of the Dvv ABC transporters into eight subfamilies (A to H). Of these, eight shared structural and functional conservation with Tribolium castaneum ABC transporter orthologs known to exhibit overt RNA interference (RNAi) knockdown phenotypes. Interestingly, depletion of DvvABCB_19147 and DvvABCG_3712 transcripts in adult females produced detrimental reproductive and developmental phenotypes (egg-laying or -hatching defects), demonstrating the potential of these genes as targets for RNAi-mediated insect control tactics.Conclusions By combining sequence data from four libraries covering three distinct life stages, we have produced a relatively comprehensive de novo transcriptome assembly for D. v. virgifera . Moreover, we have identified 65 members of the ABC transporter family, and provided the first insights into the developmental and physiological roles of ABC transporters in this pest species.</jats:p

Structural and functional insights into the Diabrotica virgifera virgifera ATP-binding cassette transporter gene family

Abstract Background The western corn rootworm, Diabrotica virgifera virgifera , is a pervasive pest of cultivated maize in North America and Europe, which has adapted to survive exposure to multiple insecticidal agents. Due to their role in insecticide transport, we sought to identify members of the ATP-binding cassette (ABC) transporter family in D. v. virgifera using a transcriptomics approach.Results In this study, 65 putative D. v. virgifera ABC ( Dvv ABC) transporters were identified within a combined transcriptome assembly generated from embryonic, larval, adult male, and adult female RNA-sequence libraries. Phylogenetic analysis placed the deduced amino-acid sequences of the Dvv ABC transporters into eight subfamilies (A to H). Of these, eight shared structural and functional conservation with Tribolium castaneum ABC transporter orthologs known to exhibit overt RNA interference (RNAi) knockdown phenotypes. Interestingly, depletion of DvvABCB_19147 and DvvABCG_3712 transcripts in adult females produced detrimental reproductive and developmental phenotypes (egg-laying or -hatching defects), demonstrating the potential of these genes as targets for RNAi-mediated insect control tactics.Conclusions By combining sequence data from four libraries covering three distinct life stages, we have produced a relatively comprehensive de novo transcriptome assembly for D. v. virgifera . Moreover, we have identified 65 members of the ABC transporter family, and provided the first insights into the developmental and physiological roles of ABC transporters in this pest species.</jats:p