Recipient Organization
NORTH DAKOTA STATE UNIV
1310 BOLLEY DR
FARGO,ND 58105-5750
Performing Department
School of Natural Resource Sciences
Non Technical Summary
Agriculture has to innovate to stay ahead of a changing world.Markets and regulatory agencies are demanding toxic chemical use be reduced or eliminated, both on produce and in the environment, so as to mitigate adverse human health issues or deleterious effects on natural biota.Onetoolused to control insect pests are semiochemicals, chemicals that influence the behavior of target organisms. These chemicals can be used to attract, repel or manipulate the behavior of insects to protect or enhance a crop. While these semiochemicals are potent and environmentally benign, they can be expensive toproduce and use, a problem exacerbated by the inefficiency of many synthetic controlled release systems currently employed. In this project we will study the storage and release properties of insect exocrineglands that produce and release specific semiochemicals. Then, we will mimic these properties to develop an artificial system for potentialuse in agricultural systems. Our long-term aim is to develop an inexpensive artificial system that mimics the favorable properties of an insect exocrine gland; i.e., it is ableto store and release insect semiochemicals over a relatively long period with a high degree of efficiency in chemical use. This work should provide increased tools for environmentally heathy pest control in food production.
Animal Health Component
20%
Research Effort Categories
Basic
80%
Applied
20%
Developmental
(N/A)
Goals / Objectives
Agriculture has to innovate to stay ahead of a changing world . For insects of agricultural importance, both pests and beneficials, this necessitates the development of new methods for controlling or manipulating target populations so as to cope with changing pest complexes, as well as changing market needs and constraints.One of the niche tools available for environmentally benign insect pest control is the use of semiochemicals, chemicals that influence the behavior of target organisms. These chemicals can be used to attract, repel or manipulate the behavior of either pest or beneficial insects to protect a crop or enhance its production. Themajor goal of this project is to devise an approach and protocol for developing semiochemcial controlled release systems based on mimicking the function of real insect semiochemcial systems (exocrine glands. Since moth sex pheromones are the most uniform (across species) and widely used semiochemical in agriculture, we will base our work on the functon of the sex pheromone gland of the tobaccobudworm, Chloridea virescens, a major pest of field crops throughout the US.Specifically, our objectives are:(1) Determine how a semiochemical gland functions in an insect.(2) Mimic semiochemical gland function/design to assist development of new controlled release technologies for use in agriculture.
Project Methods
Objective 1. Determine how a semiochemical gland functions.For the first part, we will determine the rate of pheromone translocation in femaleChlorideavirescensmoths using a stable isotope tracer (U-13C-glucose). Insects will be fed the tracer and the incorporation of label into the pheromone aldehyde and its precursor alcohol quantified throughout the gland (including release) using mass isotopomer distribution analysis(Foster and Anderson 2011). Dynamic sampling will allow us to determine the quantitative change of these compounds in and on the surface of the gland. This will allow us to calculate the rate of translocation of pheromone to the surface using best curve fitting in the program JMP (SAS Institute).This rate of translocation will be incorporated as an additional factor into our compartmental model . This will alow us tomodel for the limiting effect of translocation rate on evaporation rate.Next, we will manipulate insects by decapitation and multiple PBAN injections to increase the rate of synthesis and amounts stored to those considerably above normal levels. This approach can yield synthesis rates and storage levels 3-4X above those of normal females (Foster, unpublished). This overloading of the gland, combined with differential gland and release sampling), will allow us to model the fluxes (synthesis or translocation) and how they affect quantity of pheromone released by moths. Again, we will use curve fitting of the dynamic data to determine the respective rates at different initial loads (initial amount stored). In essence this should enable us to tell whether evaporation rate is limited by gland function (synthesis, translocation rates) or surface topography (e.g., area).In the second part of the Objective, we will characterize the physicochemical structure of the gland surface. In particular, we want to determine how physical and chemical structures on the surface of the gland influence translocation and evaporation rates. First, we will chemically analyze the cuticular surface of the pheromone gland of femaleC.virescens. Cuticular surface lipids of many insects have been analyzed by a variety of methods. We will use a recently developed method, direct insert-solid phase microextraction (SPME), in which different solvents are used to rinse the cuticular surface before a SPME fiber is dipped directly in the solvent to sample cuticular solutes. The SPME fiber is then inserted directly into an injector before analysis by gas chromatography/mass spectrometry (GC/MS). We will also sample other intersegmental tissue ofC.virescensfor chemical comparison, so as to determine whether the surface chemistry of the pheromone gland is unique and, thus, potentially implicated in controlling evaporation rate of the pheromone. Differences in cuticular chemistry between the gland surface and tissuewill be compared both qualitatively (chemical identity) and quantitatively; the latter through regular parametric statistical methods (ANOVA).If any interesting surface chemicals are revealed, we will attempt to image their distribution on the gland surface through use of mass spectrometric imaging (MSI). By relating chemical distribution to gland pore distribution (e.g., unique chemistry around gland pores), we may be able to determine whether the gland surface has evolved to control evaporation of pheromone from the surface.Objective 2. Mimic semiochemical gland function/design to help develop controlled release technologies for use in agriculture.This objective is concerned with using the results and methods developed in Objective 1 to understand and develop the mechanisms behind synthetic semiochemical slow release formulations. The main aim at this stage is to develop techniques to characterize and manipulate the essential mechanisms involved in controlled release formulations, rather than to develop a usable product. Note that, while the work in this objective is based on the approach of Objective 1, it is not contingent to successful outcomes in Objective 1. Regardless of the results of Objective 1, we will use the same methods and approach outlined in that Objective, to develop and characterize a controlled release system in this Objective.Using the sampling and analytical methods developed for insects in Objective 1, we will study translocation and evaporation rates of semiochemical from synthetic substrates. In the first part of the objective, we will quantify evaporation rates from various substrates including glass, polyethylene, rubber, Teflon and cotton. We will treat areas (of varying sizes) of these substances with known amounts of pheromone, using topical application and piezoelectric spraying, and measure the evaporation rate of pheromone over an extended time period. Using parametric statistics, we will compare evaporative rates (1) across the different substrates at each time point, and (2) changes in evaporation rate over time for each substrate. This will allow us to determine which of the substrates has (a) the least variable rate over time and (2) the greatest longevity for a sustained minimum evaporation rate.Next, we will determine the effects of surface area and airspeed on evaporation rate. We will choose a surface from the first part (e.g., glass), and spray different areas with different amounts of pheromone. We will then measure the evaporation rate at various collection speeds (airspeeds) over time. Using multiple regressions, we will determine the relationship among initial amount, surface area, airspeed and evaporation rate. Then, using the results of our chemical analyses in the first objective, we will coat the substrate with combinations of the most abundant chemicals of each major chemical class (likely hydrocarbon, long chain ester, ketones) identified on the gland cuticular surface. These chemicals will be purchased or, if not available, collected from fractionated extracts of insect glands. Next, we will coat this with a layer of pheromone and determine the evaporation rates of pheromone. Through linear regression this will show us whether the gland surface chemicals act as a modifier of semiochemical evaporation rate.In the final part, we will study translocation rates of pheromone through different polyethylene polymer tubes (Porex Filtration, GA) of different pore size (20-32 microns to 250 microns). For this, we will fill fixed lengths of tubing of different pore size with pheromone, before sealing the tubing with epoxy resin (impervious to pheromone) at either end.Then, we will sample pheromone at various times by wiping the surface of the tubing with a glass fiber paper (Whatman GF/A) saturated with solvent. The glass fibers will be extracted in solvent and the amounts of pheromone quantified by GC/MS to determine translocation rate through the different pores. Finally, using the sealed tubes (different pore sizes), we will measure evaporation rate of pheromone over time. Through linear regressions, we will relate evaporation rate to translocation rate for the different pore sizes.