Location: Southern Insect Management Research2013 Annual Report
1a. Objectives (from AD-416):
The long-term objective of this project is to develop an improved understanding of how the changing cropping landscape impacts insecticide resistance development and management of various insect pest species in order to increase profitability and sustainability of mid-South row crops. Objective 1: Improve tarnished plant bug control and insecticide resistance management by gaining new information on the pest’s ecology and biology using multi-disciplinary approaches, e.g. molecular genetic tools, stable carbon isotope analysis, gene expression and proteomics, and insecticide resistance assays coupled with field sampling. Objective 2: Determine the effect of bollworm ecology (corn earworm) on resistance to pyrethroid insecticides by developing and utilizing genetic markers linked to resistance traits, stable carbon isotope analysis, gossypol detection in adult insects, and insecticide resistance monitoring. Objective 3: Develop pest control strategies for the U.S. Mid-South’s Early Soybean Production System by determining accurate treatment thresholds, understanding the impact of changing cropping systems on farm-scale pest ecology, and developing effective insecticide resistance management practices for the stink bug complex, three-cornered alfalfa hopper, bean leaf beetle and soybean looper. Objective 4: Improve low input systems of pest control for sweet potato by evaluating the efficacy and proper use of newly registered insecticides to enhance their integration with crop rotation and other low cost control strategies.
1b. Approach (from AD-416):
We plan to improve tarnished plant bug control and insecticide resistance management by gaining new information on the pest’s ecology and biology using multi-disciplinary approaches. Analytical techniques, such as stable carbon isotope analysis, will be used to determine the influence of C4 host plants, such as field corn or pigweed, on populations of tarnished plant bug adults infesting cotton fields. This information will identify sources of tarnished plant bugs that may lead to alternative control measures prior to infestations into cotton fields. Tarnished plant bug populations will be monitored for resistance to various classes of insecticides commonly used by mid-South producers. This will provide real-time information to decision makers that will allow them to adjust their control recommendations based on the type of resistance that is found in their area of the mid-South. Detoxification enzyme activity surveys will be conducted in an effort to correlate and quantify insecticide resistance levels in field populations of the tarnished plant bug. Molecular genetics techniques will be conducted on tarnished plant bug populations that could lead to assays to evaluate the extent of field resistance in tarnished plant bug populations and provide input for insect management decisions. We also plan to determine the effect of bollworm ecology (corn earworm) on resistance to pyrethroid insecticides. Analytical techniques, such as stable carbon isotope analysis and a gossypol detection technique, will be used to determine the impact of bollworm larval plant host on pyrethroid resistance levels measured in adults collected from pheromone traps. Molecular genetics tools will be used to identify candidate genes and biological pathways associated with insecticide resistance in bollworm populations. Successful identification of loci associated with insecticide resistance and the development of genetic markers for those will provide a method to obtain quantitative estimates of field evolved resistance by estimating the allele frequencies via population studies. We will also develop pest control strategies for the U.S. Mid-South’s Early Soybean Production System by determining accurate treatment thresholds and developing effective insecticide resistance management practices for the stink bug complex and bollworm. Field studies will be conducted to evaluate treatment thresholds for stink bugs and bollworms in early season soybeans. Stink bug populations will be monitored for potential resistance to various classes of insecticides, and this effort will provide real-time information to decision makers regarding the proper use of insecticides for control of these pests. We also plan to improve low input systems of pest control for sweet potato by evaluating the efficacy and proper use of newly registered insecticides to enhance their integration with crop rotation and other low cost control strategies. Field and laboratory studies will be conducted to determine the impact of crop rotation on populations of insect pests of sweet potatoes, as well as information of insecticide efficacy and proper application techniques.
3. Progress Report:
Insecticide resistance monitoring in tarnished plant bug (TPB) populations indicated that control issues with acephate and pyrethroid insecticides continued. Populations continued to be susceptible to thiamethoxam and novaluron. Mississippi producers utilize the information when selecting insecticides for TPB control. A reference transcriptome of tarnished plant bug containing 47,637 expressed Ribonucleic Acid (RNA) sequences that included 20,576 transcripts with database matches to expressed genes from other organisms was obtained at various time intervals after exposure to acephate. Putative odorant binding proteins were identified from the reference transcriptome using bioinformatic analyses and used in expression analysis by microarray and real-time quantitative polymerase chain reaction. In studies with bollworm, a series of back-cross families were developed by mating a laboratory colony established from a field collected female with a highly inbred laboratory strain. Second filial generation progeny of two backcross families were screened for single nucleotide polymorphisms (SNPs) using genotype by sequencing (GBS) technology. Novel microarray analysis of 6,688 genes in imidacloprid-selected tarnished plant bug revealed 955 up- and 1,277 down-regulated (=2-fold) genes with 369 and 485 of them annotated. Detection of metabolic genes in both up- and down-regulated genes indicated a significant alternation of metabolic pathways. Five P450 and nine esterase genes were significantly up-regulated, and only one esterase gene and no P450 genes were down-regulated. Pathway analyses identified 65 up-regulated cDNAs, that encode 51 different enzymes involved in 62 different pathways, including P450 and esterase genes for drug and xenobiotic metabolisms. Sixty-four down-regulated cDNAs code only 17 enzymes that are associated with only 23 pathways mostly related to food digestions. Partial cDNA sequences were obtained from cDNA library sequencing. There sequences were assembled into at least eleven different P450s. To examine and compare any structural difference of the P450s between insecticide-selected and not selected strains, reverse transcription and 5'/3'-RACE (rapid amplification of cDNA end) were applied to clone full P450 cDNA sequences. At least seven of the P450s have full coding region, and the other four may be a little shorter. Field plots have been established across the Mississippi Delta to examine potential damage of stink bugs and lepidoteran pests on soybean. Yield differences between insecticide treated and untreated plots at varying densities of insect occurrence will be used to examine appropriate action thresholds. Species composition of stink bugs and loopers in various locations across the Mississippi Delta is continually being examined. Limited numbers of stink bugs have been encountered the past two seasons. Stable carbon isotope studies continue on bollworm moths captured in southern states from 2007 through 2012. Associations of crop origin with insecticide resistance levels will be determined once the isotopes analyses are complete.
1. Gene transcripts modulated by acephate intoxication during the time course were identified by Ribonucleic Acid (RNA)-Seq and microarray technologies. A total of 165 transcripts with known functions and 706 transcripts without assigned function were found to be enriched in tarnished plant bug (TPB) within 180 min of exposure to acephate, indicating that the physiological response to acephate intoxication is rapid and involves many genes that are not normally characterized as detoxification genes.
2. A total of 32 novel putative odorant binding proteins (OBP) were identified and characterized in tarnished plant bug (TPB). This number of OBPs is significantly higher than the 15 and OBPs identified in the pea aphid and Lucerne plant bug, respectively. Examination of the expression patterns in antennae, proboscis, and legs of male and female TPB indicated that several OBPs were highly expressed in antennae and some OBPs were expressed at a higher level in male antennae than in female antennae.
3. A total of 2,664 single nucleotide polymorphisms suitable for developing a genetic linkage map were identified from the high-throughput nucleotide analysis of the two bollworm backcross families.
Snodgrass, G.L., Jackson, R.E., Perera, O.P., Allen, K.C., Luttrell, R.G. 2012. Effect of food and temperature on emergence from diapause in the tarnished plant bug (Hemiptera: Miridae). Environmental Entomology. 41:1302-1310.