Biological Control of Insects Research Laboratory

Prostaglandins and other eicosanoids are oxygenated metabolites of certain polyunsaturated fatty acids. These compounds are well known for their important actions in mammalian physiology and disease. Recent work has revealed the presence and biological actions of eicosanoids in insects and many other invertebrate animals. In insects, eicosanoids mediate cellular immunity to microbial and metazoan challenge. Notably, some infectious organisms secrete factors responsible for impairing host insect immune reactions by inhibiting biosynthesis of eicosanoids. Eicosanoids also act in insect reproductive biology, in ion transport physiology, and in fever response to infection as well as in protein exocytosis in tick salivary glands. Aside from ongoing actions in homeostasis, certain eicosanoid actions occur at crucial points in insect life histories, such as during infectious challenge and important events in reproduction.

Traditional methods for mounting insects in Canada balsam have often proven unsatisfactory because of shrinkage of delicate structures such as the antennae and palpi in the highly viscous mounting medium. Clearing in potassium hydroxide and subsequent gradual dehydration in a series of alcohols are very time consuming and often require isolation of individual specimens, and separate treatment of the wings when adults are being mounted. While satisfactory mounts may easily be made of relatively large and heavily sclerotized insects, mounts of fragile insects are often inadequate for detailed taxonomic study. This problem has led many workers to try other mounting media, but none has proven entirely satisfactory.

Eight strains of red flour beetle, Tribolium castaneum (Herbst), and 21 of the lesser grain borer, Rhyzopertha dominica (F.), collected from wheat stored on farms in Oklahoma were tested for resistance to malathion, chlorpyrifos-methyI, and phosphine. Results of discriminating dose tests of the red flour beetle indicated that all strains were resistant to malathion, one strain was resistant to phosphine, and none was resistant to chlorpyrifos-methyl. Similar discriminating dose tests for the lesser grain borer indicated that all strains were resistant to malathion, dichlorovs, and to chlorpyrifos-methyl, and 8 of 21 strains were resistant to phosphine.

We present a method to analyze serial time–mortality data from bioassay experiments where successive observations are made on the same group of organisms exposed to 1 concentration of a stimulus (for example, a pesticide). Standard probit techniques are not applicable because such data are correlated. Methods are presented for calculating statistics for the time–mortality line by regressing complementary log-log, logit, or probit transformations of proportion of responders on untransformed time or logarithmic transformations of time; and for calculating confidence limits on lethal time values corresponding to given mortality levels. As a result we have developed a computer program to facilitate use of the method.

Various combinations of six candidate attractants--butanone, carbon dioxide (CO2), honey, octenol, lactic acid and mixed phenols--were tested against natural populations of mosquitoes in Everglades National Park, Florida, U.S.A., using unlighted CDC-baited traps. With few exceptions, the attractancy of these candidate compounds to mosquitoes, when used alone, was less than that of CO2 alone. The exceptions were that octenol and honey extract alone attracted larger numbers of Coquillettidia perturbans (Walker). Addition of lactic acid and/or octenol to CO2 increased trap collections of Aedes taeniorhynchus (Wiedemann), Anopheles atropos D. & K., and An. crucians Wiedemann by 1.4-13.8 times. Culex nigripalpus Theobald collections were increased 2.7 times by the addition of lactic acid, while the addition of octenol produced mixed results. Whereas the addition of lactic acid reduced collections of Cx (Melanoconion) spp., the addition of octenol generally increased collections. The opposite happened for Wyeomyia mitchellii (Theobald). For the biting midge, Culicoides furens (poey), octenol (1.6-23.4 x ) and phenol (2.7 x ) alone attracted larger numbers, and lactic acid alone attracted approximately the same numbers as CO2 alone. The combinations octenol + phenol and octenol + 200 ml/min CO2 increased C. furens collections c. 100 times over CO2 alone. The combination of octenol + CO2 increased (1.6 x ) collections of the tabanid Diachlorus ferrugatus (Fabricius). Butanone appeared to decrease the trap collections of all species when combined with CO2 or octenol + CO2.

Feeding adaptations in five species of predaceous heteropterans (Geocoris punctipes (Say), Nabis alternatus Parshley, Podisus maculiventris (Say), Zelus renardii Kolenati and Sinea confusa Caudell) representing four families (Lygaeidae, Nabidae, Pentatomidae, and Reduviidae) were studied. Mouthparts were examined with scanning electron and light microscopy. Radio-labeled (14C) inulin was used to determine that preoral digestive enzymes originate in the salivary glands rather than the gut. All species tested positive for proteinase and phospholipase, but only N. alternatus and P. maculiventris tested positive for salivary amylase. Evidences of salivary stylet collars were observed in all five species, and flanges were studied in detail in G. punctipes and appear to be related to leverage for stylets. Direct observations and video replays showed that the toothed mandibular stylets penetrate, rasp, and cut prey tissues; maxillary stylets form salivary and food canals that deliver saliva and remove liquified prey contents from within. Movements of invading stylets within prey as they probe narrow recesses, such as legs and antennae, are amazingly quick and agile, sometimes bending back upon themselves. These morphological, physiological, and behavioral adaptations permit a concerted pre-digestion of prey from within and allow these predators to feed efficiently upon prey that equal or exceed them in size.

Planthoppers are serious rice pests in Asia. Their population resurgence was first reported in the early 1960s, caused mainly by insecticides that indiscriminately killed beneficial arthropods and target pests. The subsequent resurgence involved two mechanisms, the loss of beneficial insects and insecticide-enhanced planthopper reproduction. In this review, we identify two forms of resurgence, acute and chronic. Acute resurgence is caused by traditional insecticides with rapid resurgence in the F 1 generation. Chronic resurgence follows application of modern pesticides, including fungicides and herbicides, with low natural enemy toxicity, coupled with stimulated planthopper reproduction. The chemical-driven syndrome of changes leads to later resurgence in the F 2 or later generations. Chronic resurgence poses new threats to global rice production. We review findings on the physiological and molecular mechanisms of chronic planthopper resurgence and suggest research directions that may help manage these new threats.

Prostaglandins (PGs) and related eicosanoids are signal moieties derived from arachidonic acid and two other C20 polyunsaturated fatty acids. They were discovered in the 1930s in the context of mammalian reproductive physiology; PGs were associated with the prostate gland, hence their name, and they stimulate uterine smooth muscle contraction. Determining PG chemical structures in the early 1960s and demonstrating that they mediate many human pathophysiological events in the 1970s stimulated intensive research over the following decades in universities, governments and the private sector. Interest in the biological significance of PGs in insects arose in the 1970s and 1980s, which opened a new research frontier. PGs act in reproduction, releasing egg-laying behaviors in some species and signaling egg-maturation events in the Drosophila and silk moth models. They act in insect immunity, mediating and coordinating cellular and humoral responses to wounds, infection and invasion. PGs act in ion transport physiology in insect Malpighian tubules and recta. These compounds also mediate physiological trade-offs between insect immunity and reproduction. Finally, they are central players in the molecular ecology of interactions between blood-feeding insects and their vertebrate hosts. Some PG functions are critical at specific, crucial moments in insect lives, moments we consider ‘emergencies,’ such as the immediate reactions to infection. Certain microbial species have keyed into insect PG signaling and they evolved mechanisms to disable insect immune reactions to infection by inhibiting key enzymes in PG biosynthesis. We provide proof-of-principle that RNA interference treatments designed to silence genes in PG signaling disrupts insect immunity. In this review we describe the history, chemistry and biology of PGs. We use this background to argue that because PGs and other eicosanoids act in emergency situations, they are visible targets for development and deployment of novel insect pest management technologies.

Journal Article Life History of Immature Maize Weevils (Coleoptera: Curculionidae) on Corn Stored at Constant Temperatures and Relative Humidities in the Laboratory Get access James E. Throne James E. Throne Stored-Product Insects Research and Development Laboratory, USDA-ARS, 3401 Edwin Street, Savannah, GA 31405 Search for other works by this author on: Oxford Academic PubMed Google Scholar Environmental Entomology, Volume 23, Issue 6, 1 December 1994, Pages 1459–1471, https://doi.org/10.1093/ee/23.6.1459 Published: 01 December 1994 Article history Received: 18 February 1994 Accepted: 13 June 1994 Published: 01 December 1994

Abstract Determining relative strengths of trophic links is critical for ranking predators for conservation biological control. Molecular gut‐content analysis enables ranking by incidence of prey remains in the gut, but differential digestive rates bias such rankings toward predators with slower rates. This bias can be reduced by indexing each predator’s half‐life to that of the middle‐most half‐life in a predator complex. We demonstrate this with data from key species in the predator complex of Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), comprising adults and immatures of four taxonomically diverse species. These animals display order‐of‐magnitude variation in detectability half‐life for the cytochrome oxidase I DNA sequence of a single CPB egg: from 7.0 h in larval Coleomegilla maculata (DeGeer) (Coleoptera: Coccinellidae) to 84.4 h in nymphal Perillus bioculatus (Fabricius) (Hemiptera: Pentatomidae). The raw species‐specific incidence of L. decemlineata DNA in the guts of 351 field‐collected predators ranged from 11 to 95%, ranking them as follows: C. maculata adults < Lebia grandis Hentz (Coleoptera: Carabidae) adults < Podisus maculiventris (Say) (Hemiptera: Pentatomidae) adults < P . maculiventris nymphs < P. bioculatus adults < P. bioculatus nymphs. Half‐life adjustment reorders the rankings: C. maculata adults < P. bioculatus adults < P. bioculatus nymphs < P. maculiventris nymphs < L. grandis adults < P. maculiventris adults. These changes in status demonstrate the value of half‐life‐adjusted molecular gut‐content data for ranking predators. This is the first study to measure prey detectability half‐lives for the key arthropod predators of a major insect pest, and to use them to evaluate the relative impact of all adults and immatures in this predator complex.

Insects express 3 lines of protection from infections and invasions. Their cuticles and peritrophic membranes are physical barriers. Infections and invasions are quickly recognized within insect bodies, and recognition launches 2 lines of innate immune reactions. Humoral reactions involve induced synthesis of antimicrobial peptides, the bacteriolytic enzyme lysozyme and activation of the prophenoloxidase system. Cellular immune reactions include phagocytosis, nodulation and encapsulation. These reactions entail direct interactions between circulating hemocytes and the invaders. Cellular immune reactions begin immediately after an invasion is detected while antimicrobial peptides typically appear in the hemolymph some hours after infection. Microaggregation is a step in the nodulation process, which is responsible for clearing the bulk of bacterial infections from circulation. Coordinated cellular actions lead to encapsulation of invaders, such as parasitoid eggs, that are very much larger than individual hemocytes. In this paper, we review the roles of eicosanoids as central mediators of insect immune reactions, particularly cellular reactions. We briefly describe insect immune functions, outline eicosanoid biosynthesis and treat eicosanoid actions in cellular immunity of insects. Eicosanoids act in several cellular defense functions, including phagocytosis, microaggregation, nodulation, encapsulation, cell spreading and hemocyte migration toward a source of a bacterial peptide. We also describe our most recent work on the influence of one group of eicosanoids, prostaglandins, on gene expression in an established insect cell line.

Journal Article Pesticide Resistance in Tribolium castaneum and T. confusum (Coleoptera: Tenebrionidae) from Flour Mills in the United States Get access Larry J. Zettler Larry J. Zettler Stored-Product Insects Research and Development Laboratory, USDA-ARS, Savannah, Georgia 31403 Search for other works by this author on: Oxford Academic PubMed Google Scholar Journal of Economic Entomology, Volume 84, Issue 3, 1 June 1991, Pages 763–767, https://doi.org/10.1093/jee/84.3.763 Published: 01 June 1991 Article history Accepted: 16 January 1990 Received: 17 August 1990 Published: 01 June 1991

Journal Article Meridic Diet for Rearing Successive Generations of Lygus hesperus Get access Jack W. Debolt Jack W. Debolt Biological Control of Insects Laboratory, Agricultural Research, Science and Education Administration, U.S. Department of Agriculture, Tucson, Arizona 85719 Search for other works by this author on: Oxford Academic Google Scholar Annals of the Entomological Society of America, Volume 75, Issue 2, 15 March 1982, Pages 119–122, https://doi.org/10.1093/aesa/75.2.119 Published: 15 March 1982 Article history Received: 17 February 1981 Published: 15 March 1982

BACKGROUND: Bursicon is a heterodimer neuropeptide composed of two cystine knot proteins, bursicon α (burs α) and bursicon β (burs β), that elicits cuticle tanning (melanization and sclerotization) through the Drosophila leucine-rich repeats-containing G protein-coupled receptor 2 (DLGR2). Recent studies show that both bursicon subunits also form homodimers. However, biological functions of the homodimers have remained unknown until now. METHODOLOGY/PRINCIPAL FINDINGS: In this report, we show in Drosophila melanogaster that both bursicon homodimers induced expression of genes encoding antimicrobial peptides (AMPs) in neck-ligated adults following recombinant homodimer injection and in larvae fat body after incubation with recombinant homodimers. These AMP genes were also up-regulated in 24 h old unligated flies (when the endogenous bursicon level is low) after injection of recombinant homodimers. Up-regulation of AMP genes by the homodimers was accompanied by reduced bacterial populations in fly assay preparations. The induction of AMP expression is via activation of the NF-κB transcription factor Relish in the immune deficiency (Imd) pathway. The influence of bursicon homodimers on immune function does not appear to act through the heterodimer receptor DLGR2, i.e. novel receptors exist for the homodimers. CONCLUSIONS/SIGNIFICANCE: Our results reveal a mechanism of CNS-regulated prophylactic innate immunity during molting via induced expression of genes encoding AMPs and genes of the Turandot family. Turandot genes are also up-regulated by a broader range of extreme insults. From these data we infer that CNS-generated bursicon homodimers mediate innate prophylactic immunity to both stress and infection during the vulnerable molting cycle.

The maximum finite rate of increase for apterous populations of the cabbage aphid, Brevicoryne brassicae (L.) was 1.14 times per day at 20°C; for the green peach aphid, Myzus persicae (Sulzer), 1.32 times at 25°C; and for the turnip aphid, Hyadaphis pseudobrassicae (Davis), 1.45 times per day at 25°C. The cabbage aphid had the smallest rate of increase at all temperatures, the green peach aphid the greatest rate between 5° and 15 °C, and the turnip aphid the greatest rate between 20° and 30°C. No aphids reproduced at 35°C, only the population of turnip aphids increased at 30°C, and only the population of the green peach aphids increased at 5°C. Other populations decreased at 5° and 30°C. The components of the rate of increase (nymphal development, age-specific survival and fecundity, length of generation, and net reproductive rate) were determined for each aphid at each temperature. Their effect on the rate of increase was examined, as was the age at which 95% of the contribution to the next generation was made. The proportion of each stage in a population with a stable age distribution was also examined. Equations for predicting the rate of increase, and models comparing the relative growth of populations of the three species with time are presented.

Abstract Insects are more or less constantly challenged with a daunting array of pathogenic organisms, including viruses, bacteria, fungi, protozoans as well as various metazoan parasites and parasitoids. At the first level of defense, the pathogens are rebuffed by physical barriers, including the cuticle and peritrophic membrane. Upon breaching these barriers, pathogens meet with an arsenal of robust and efficacious immune defense mechanisms. Two general categories of defenses are typically recognized, humoral defenses and hemocytic or cellular defenses. The former involves induced synthesis of various antibacterial proteins and peptides, such as cecropins and lysozyme. Cellular defense mechanisms are characterized by direct interactions between circulating hemocytes and the invaders. These include phagocytosis, microaggregation, nodulation, and encapsulation. Microaggregation is a step in the nodulation process, which is responsible for clearing the bulk of bacterial infections from circulation. Coordinated cellular actions lead to encapsulation of invaders, such as parasitoid eggs, that are very much larger than individual hemocytes. While the defense mechanisms are broadly appreciated, less is known about the biochemical signals responsible for mediating and coordinating the cellular actions. We now know eicosanoids mediate phagocytosis, microaggregation, and nodulation reactions to immune challenge, as well as cell spreading, a specific step in nodulation. We have several goals in this mini review. We provide a brief background on cellular immunity, outline eicosanoid biosynthesis, and review eicosanoid actions in cellular immunity in insects. Recent work indicates some pathogens have usurped eicosanoid‐mediated immunity; they disable insect immunity by inhibiting eicosanoid biosynthesis. We interpret these findings and their significance with respect to the biological control of insects. We also present preliminary work designed to test hypotheses on how eicosanoids exert their actions. We address shortcomings in our knowledge on eicosanoids in insect biology.

This essay reviews the discoveries, synthesis and biological significance of prostaglandins (PGs) and other eicosanoids in insect biology. It presents the most current – and growing – understanding of the insect mechanism of PG biosynthesis, provide an updated treatment of known insect phospholipase A2 (PLA2), and detail contemporary findings on the biological roles of PGs and other eicosanoids in insect physiology, including reproduction, fluid secretion, hormone actions in fat body, immunity and eicosanoid signaling and cross-talk in immunity. It completes the essay with a prospectus meant to illuminate research opportunities for interested readers. In more detail, cellular and secretory types of PLA2, similar to those known on the biomedical background, have been identified in insects and their roles in eicosanoid biosynthesis documented. It highlights recent findings showing that eicosanoid biosynthetic pathway in insects is not identical to the solidly established biomedical picture. The relatively low concentrations of arachidonic acid (AA) present in insect phospholipids (< 0.1% in some species) indicate that PLA2 may hydrolyze linoleic acid (LA) as a precursor of eicosanoid biosynthesis. The free LA is desaturated and elongated into AA. Unlike vertebrates, AA is not oxidized by cyclooxygenase, but by a specific peroxidase called peroxinectin to produce PGH2, which is then isomerized into cell-specific PGs. In particular, PGE2 synthase recently identified converts PGH2 into PGE2. In the cross-talks with other immune mediators, eicosanoids act as downstream signals because any inhibition of eicosanoid signaling leads to significant immunosuppression. Because host immunosuppression favors pathogens and parasitoids, some entomopathogens evolved a PLA2 inhibitory strategy activity to express their virulence.

An all-beef artificial diet was developed for rearing Geocoris punctipes (Say). Thus far, five complete continuous generations have developed on this diet at a cost of ca. $0 63 per 1000 adults. Eggs for a sixth generation have been laid. There was an increase in biomass from <1.0 mg for first instars that started the culture to nearly 1,200 mg biomass in the fifth generation. Numbers of G. punctipes have increased in each succeeding generation, an indication that the present diet and techniques may lend themselves to mass culture of this important predator.

Heliothis virescens larval plasma contains high levels of an antiviral activity against the budded form of the Helicoverpa zea single nucleopolyhedrovirus (HzSNPV) in vitro. Preliminary results indicated that phenoloxidase is primarily responsible for this virucidal effect. However it is known that other enzymes that generate antimicrobial reactive oxygen intermediates and reactive nitrogen intermediates are present in hemolymph that could contribute to the observed virucidal activity. To elucidate the contributions of phenoloxidase and other candidate activities to plasma innate immune response against baculovirus infection specific metabolic inhibitors were used. In vitro the general inhibitors of melanization (N-acetyl cysteine, ascorbate and glutathione), and specific inhibitors of phenoloxidase (phenylthiourea and Kojic acid), completely blocked virucidal activity up to the level seen in controls. Addition of the enzyme superoxide dismutase to plasma did not affect virucidal activity; however addition of catalase had an inhibitory effect. Inhibitors of nitric oxide synthase activity did not affect virucidal activity. Our results confirm that phenoloxidase is the predominate activity in larval plasma accounting for inactivation of HzSNPV in vitro, and that phenoloxidase-dependent H(2)O(2) production may contribute to this virucidal activity.

Autographa californica multiple nucleopolyhedrovirus (AcMNPV) recombinants, namely AcRFP produced by fusion of the red fluorescent protein (RFP) gene with the polyhedrin gene, and a recombinant (pAcUW21-23GFP) carrying the green fluorescent protein (GFP) in its viral envelope, were evaluated for their resistance to inactivation by ultraviolet light. AcRFP recombinants produced incomplete polyhedra with low infectivity for Trichoplusia ni larvae, whereas AcuW21-23GFP produced normal polyhedra with high infectivity. Electron microscopy of AcRFP CL14 showed the incorporation of very few viral particles into polyhedrin matrix protein material. The LC50 for AcuW21-23GFP was 0.10 occlusion bodies/mm2, whereas the LC50 values for several AcRFP recombinants ranged from 20 to 329 occlusion bodies/mm2. When both the RFP and GFP recombinants were exposed to ultraviolet light (UV-B 280–320 nm), the results support the conclusion that these fluorescent proteins afford some protection against its damaging effects.AcMNPV Autographa californica multiple nucleopolyhedrovirus BV budded virus CPE cytopathogenic effect ECV extracellular virus OB occlusion body ODV occlusion derived virus RFP red fluorescent protein GFP green fluorescent protein TCID50 tissue culture infective dose at the 50 % level UV-B ultraviolet light of 280–320 nm