PubMed Health⌕ Search

Biomedical subjects

J P Michaud

Publications and source records attributed to J P Michaud.

16 recordsLinked to original sources
PubMed2006

Resistance to biotype 2 Russian wheat aphid (Homoptera: Aphididae) in two wheat lines.

Biotype 2 of the Russian wheat aphid, Diuraphis noxia (Mordvilko), was identified in the United States in 2003 and is virulent to all commercially available cultivars of winter wheat, Triticum aestivum L., that are resistant to biotype 1. We compared the development and reproduction of biotype 2 D. noxia at 21.7 +/- 0.12 degrees C on 'Trego' (PI 612576), a susceptible commercial cultivar, and on lines CI 2401 and 03GD1378027 that represent putative resistance sources. CI 2401 is a pure wheat line originating in the former USSR (Tajikistan), whereas 03GD1378027 is a USDA-ARS breeding line originally developed from crosses with a South African line that carried a large rye translocation conferring D. noxia resistance. Both lines previously showed resistance to biotype 1 and are currently being used in the development of D. noxia-resistant wheat cultivars. Both solitary apterous virginoparae of biotype 2 and their progeny experienced a reduction in survival and prolonged developmental times on CI 2401 and 03GD1378027 compared with Trego, but the former lines did not differ significantly from each other with respect to either measure of aphid performance. Progeny developed faster than did their foundress mothers on CI 2401 and Trego, but not on 03GD1378027. Mean foundress fecundity did not differ between CI 2401 and 03GD1378027 but was reduced on these lines relative to Trego. Foundresses also were more often found off plants of CI 2401 and 03GD1378027 than Trego. Estimates of intrinsic rate of increase were higher on Trego than on either CI 2401 or 03GD1378027, the latter two lines yielding similar values. The negative impacts of CI 2401 and 03GD1378027 on development and reproduction of biotype 2 indicate that these lines represent sources of resistance effective against this biotype.

Animals↗
PubMed2006

Positive correlation of fitness with group size in two biotypes of Russian wheat aphid (Homoptera: Aphididae).

Changes in fitness parameters as a function of colony size (one versus 10 aphids) were measured in two biotypes (RWA1 and RWA2) of the Russian wheat aphid, Diuraphis noxia (Mordvilko) (Homoptera: Aphididae), feeding on three cultivars of wheat, Triticum aestivum L., at two temperatures. 'Trego' is a cultivar with no specific resistance to D. noxia, whereas, 'Stanton' and 'Halt' express Dny and Dn4 resistance sources, respectively. Feeding in a group accelerated the development of RWA1 on Trego and Stanton at 20 degrees C, but not at 24 degrees C, whereas grouped RWA2 developed faster than solitary RWA2 on all three cultivars at 24 degrees C, but not at 20 degrees C. Survival (first instar-adult) of RWA2 also was improved by grouping on Stanton and Halt at 24 degrees C, but solitary RWA2 survived better at 20 degrees C on all three cultivars. The reproductive rate of RWA1 was improved by grouping on Trego and Stanton at both temperatures, but only on Halt at 24 degrees C. Lifetime fecundity of RWA1 also was increased by grouping in all cases except for Trego at 20 degrees C. Grouped development increased the reproductive rate of RWA2 on all three cultivars at 24 degrees C, but had no effect at 20 degrees C. Grouped RWA2 developed and reproduced faster than grouped RWA1 on all three cultivars at 24 degrees C. Thus, the fitness of D. noxia was positively correlated with group size during colony establishment, but the effects were sensitive to temperature, being more pronounced at 20 degrees C for RWA1 and at 24 degrees C for RWA2.

Animals↗
PubMed2005

The biology and behavior of the longhorned beetle, Dectes texanus on sunflower and soybean.

The biology and behavior of the longhorned beetle Dectes texanus LeConte (Coleoptera: Cerambycidae) was studied on two host plants that suffer economic losses from this pest; sunflower, Helianthus annuus, and soybean, Glycines max. Reciprocal crosses of D. texanus collected from the two plants all produced viable progeny, indicating that conspecific insects attack both crops. Pupae from soybean stalks weighed about 40% less than those from sunflower, and adults fed on soybean lived a mean of 23 days, compared to a mean of 53 days (males) and 76 days (females) for those fed sunflower. A female's larval host plant had no effect on her tendency to ovipuncture plants of either type in a greenhouse trial. A field-tested population collected exclusively from sunflower contained three types of females in similar proportions: those that laid eggs only on sunflower, those that laid only on soybean, and those that laid equally on both host plants. Females in field trials fed more on the plant they had fed on in the laboratory, but soybean-fed females fed more on soybean than did sunflower-fed females. Females fed soybean also made more ovipunctures on soybean plants in field trials than sunflower-fed females, but their responses to sunflower plants were similar. Females displayed higher total ovipositional activity when they encountered sunflower first in the field, and lower total activity when they encountered soybean first. Feeding scores were significantly correlated with ovipunctures and eggs on both plant types. We conclude that sunflower is the preferred host plant, although females will accept soybean when it is the only available food. The results suggest that D. texanus is still in the initial stages of a host range expansion with female host selection behavior demonstrating both genetic influences and phenotypic flexibility. Sunflower represents a nutritionally superior, ancestral host plant and relatively high fitness costs are still associated with utilization of the novel host plant, soybean, costs that may be offset by benefits such as reduced intraspecific competition. These potential benefits and their consequent implications for D. texanus host range evolution are hypothesized and discussed.

Animals↗
PubMed2005

Interactions among three species of cereal aphids simultaneously infesting wheat.

Interactions among greenbug, Schizaphis graminum (Rondani), Russian wheat aphid, Diuraphis noxia (Mordvilko), and bird cherry-oat aphid Rhopalosiphum padi (L.) were examined on wheat plants (Triticum aestivum L., cultivar TAM 107). Nymphs were released on the plants as conspecific and heterospecific pairs of either first or fourth instars and evaluated for survival, developmental time, fecundity, intra-plant movement, and affinity to plant tissues. Survival from first instar to onset of reproduction averaged 90-100% across all pair combinations. Diuraphis noxia developed faster as conspecifics than in any heterospecific combination, and faster as conspecifics feeding on the same plant tissue than on different tissues. Fecundity of S. graminum was higher for conspecifics that developed on the same plant tissue than for those feeding separately. There was evidence of amensalism (one species was harmed while the other was unaffected) in that D. noxia experienced delayed development feeding in tandem with S. graminum, and reduced fecundity with both S. graminum and R. padi. Furthermore, S. graminum nymphs had reduced survival when their mothers matured on a same plant with R. padi. Both D. noxia and R. padi changed position on the plant more often when developing with S. graminum. Survival of second generation S. graminum nymphs was reduced when this species developed and reproduced in tandem with R. padi. Preferred feeding locations were S. graminum--primary leaf, D. noxia--tertiary leaf and R. padi--stem and these were not altered in any heterospecific combinations. Heterospecific aphids had no impact on fecundity or progeny survival in any species combination when fourth instars matured and reproduced on plants not previously exposed to aphid feeding, supporting the inference that systemic, aphid-induced changes in plant physiology mediated the effects observed when first instars developed and reproduced on the same plants.

Animals↗
PubMed2005

Comparative biology of a novel strain of Russian wheat aphid (Homoptera: Aphididae) on three wheat cultivars.

In spring 2003, several outbreaks of the Russian wheat aphid, Diuraphis noxia (Mordvilko), were reported in fields of supposedly resistant wheat cultivars ('Stanton', 'Halt', and 'Prairie Red') in eastern Colorado. We conducted two laboratory experiments to compare the biological performance of this new biotype 2 (B2) to that of two D. noxia collections of biotype 1 (B1) from western Kansas by using three wheat cultivars as host plants: 'Trego', a susceptible cultivar, and Stanton and Halt, two cultivars with different genetic sources of resistance. Survival of solitary nymphs from first instar to adult for the two clones of B1 on Trego was 96 and 90%, respectively, compared with 67 and 43% on Stanton, and 65 and 57% on Halt. In contrast, B2 had 60% survival on Trego, 43% survival on Halt, and 85% survival on Stanton. One clone of B1 required longer to mature on Halt compared with Trego or Stanton, but no other differences in developmental time among cultivars were significant. The standardized fecundity of solitary foundresses of the B1 clones was 19.6 and 20.1 nymphs on Trego, compared with 4.6 and 0.9 on Stanton, and 2.8 and 1.1 on Halt, respectively, over the same period. In contrast, fecundity of B2 was 21.1, 20.8, and 19.7 on Trego, Stanton, and Halt, respectively. When larger colonies developed on individual plants over longer periods, Trego supported the largest number of B1 aphids by experiment's end, whereas Stanton and Halt yielded the largest numbers of B2. The order of overall plant damage was Trego > Stanton > Halt when infested with B1, with no significant differences for B2. Trego had more pronounced leaf rolling than other cultivars, independent of biotype. Collectively, the results suggest that D. noxia B2 from Colorado has evolved cross-virulence to both Dn4- and Dny-based resistance sources.

Animals↗
PubMed2003

IPM-compatibility of foliar insecticides for citrus: indices derived from toxicity to beneficial insects from four orders.

A series of compounds representing four major pesticide groups were tested for toxicity to beneficial insects representing four different insect orders: Coleoptera (Coccinellidae), Hemiptera (Anthocoridae), Hymenoptera (Aphelinidae), and Neuroptera (Chrysopidae). These materials included organophosphates (methidathion, esfenvalerate and phosmet), carbamates (carbofuran, methomyl and carbaryl), pyrethroids (bifenthrin, fenpropathrin, zeta-cypermethrin, cyfluthrin and permethrin) and the oxadiazine indoxacarb. Toxicity to coccinellid and lacewing species was assessed by treating 1st instar larvae with the recommended field rate of commercial products, and two 10 fold dilutions of these materials, in topical spray applications. Adult Aphytis melinus Debach and 2nd instar Orius insidiosus (Say) were exposed to leaf residues of the same concentrations for 24 h. ANOVA performed on composite survival indices derived from these data resolved significant differences among materials with respect to their overall toxicity to beneficial insects. Cyfluthrin, fenpropathrin and zeta-cypermethrin all increased the developmental time of the lacewing and one or more coccinellid species for larvae that survived topical applications. Bifenthrin increased developmental time for two coccinellid species and decreased it in a third. Indoxacarb (Avaunt WG, DuPont Corp.) ranked highest overall for safety to beneficial insects, largely because of its low dermal toxicity to all species tested. Zeta-cypermethrin (Super Fury), FMC Corporation) received the second best safety rating, largely because of its low toxicity as a leaf residue to A. melinus and O. insidiosus. Phosmet (Imidan 70W, Gowan Co.) and methidathion (Supracide 25W, Gowan Co.) ranked high for safety to coccinellid species, but compounds currently recommended for use in citrus such as fenpropathrin (Danitol 2.4EC, Sumimoto Chem. Co.) and carbaryl (Sevin XLR EC, Rhone Poulenc Ag. Co.) ranked very low for IPM-compatibility based on their relatively high toxicity to all species tested.

Animals↗
PubMed2003

Sub-lethal effects of a copper sulfate fungicide on development and reproduction in three coccinellid species.

Copper-based fungicides reliably control various foliar diseases in citrus production, although they are suspected to exacerbate mite problems through various mechanisms. Studies have shown negative effects of various copper formulations on entomopathogenic fungi, nematodes, and parasitoids, but few have sought to measure its impact on the biology of predatory insects. We exposed the larvae of three species of ladybeetle (Coleoptera: Coccinellidae) to field rates of copper sulfate in combination with petroleum oil, a formulation commonly applied in Florida citrus. First instar larvae of Curinus coeruleus Mulsant, Harmonia axyridis Pallas, and Olla v-nigrum Mulsant received a 24 h exposure to residues on Petri dishes, and another 24 h exposure in the third instar. Treated larvae of all three species survived to adulthood at the same rate as control larvae, but larvae of O. v-nigrum experienced a significant increase in developmental time. Female adults of C. coeruleus and H. axyridis receiving copper sulfate exposures as larvae did not differ from control adults in pre-reproductive period, fecundity or fertility over ten days of reproduction. Treated O. v-nigrum females had significantly longer pre-reproductive periods than control females and laid significantly fewer eggs, although egg fertility was equivalent. We conclude that copper-sulfate fungicides are unlikely to disrupt biological control processes in citrus groves that are mediated by these coccinellid beetles.

Animals↗
PubMed2003

Toxicity of fruit fly baits to beneficial insects in citrus.

Two fruit fly baits, Nu-Lure/malathion and GF-120 (Spinosad) were evaluated in the laboratory for non-target impacts on beneficial insects. Nu-Lure/malathion proved attractive and toxic to adults and larvae of the coccinellid species, Curinus coeruleus Mulsant, Cycloneda sanguinea L. and Harmonia axyridis Pallas, a lacewing species, Chrysoperla rufilabris Burmeister. The coccinellids Olla v-nigrum Mulsant, Scymnus sp. and nymphs of the insidious flower bug, Orius insidiosus (Say) did not succumb to Nu-Lure baits, even in no-choice situations. Nu-Lure was also attractive and lethal to adults of two aphidophagous flies; Leucopis sp. and the syrphid fly Pseudodorus clavatus (F.). Both Nu-Lure and GF-120 caused significant mortality to the parasitoid wasps, Aphytis melinus De Bach and Lysiphlebus testaceipes Cresson, within 24 h of exposure. However, GF-120 caused no significant mortality to any coccinellid in either choice or no-choice situations, despite considerable consumption of baits. Adults of P. clavatus tended to avoid GF-120, although mortality was significant in no-choice tests. Although larvae and adults of the lacewing C. rufilabris consumed GF-120, mortality was delayed; adults died 48 -96 h post-exposure and those exposed as larvae died two weeks later in the pupal stage. The Nu-Lure bait did not appear palatable to any of the insects, but the high concentration of malathion (195,000 ppm) caused rapid mortality to susceptible insects. Nu-Lure bait without malathion also caused significant mortality to flies and lacewings in cage trials. Although GF-120 bait appeared more benign overall, further research efforts are warranted to increase its selectivity for target fly species and reduce its attractiveness to parasitoids and lacewings. I conclude that the Florida "fly free zone" protocol in its current form is not compatible with an IPM approach to commercial citrus production.

Animals↗
PubMed2003

Intraguild predation among ladybeetles and a green lacewing: do the larval spines of Curinus coeruleus(Coleoptera: Coccinellidae) serve a defensive function?

Laboratory experiments examined interspecific interactions between larvae of three coccinellid species, Curinus coeruleus Mulsant (Chilocorinae), Harmonia axyridis Pallas and Olla v-nigrum (Mulsant) (Coccinellinae), and between these and larvae of the green lacewing, Chrysoperla rufilabris (Burmeister). Larvae of C. coeruleus, although defended on their dorsal surface with long spines, had the smallest mandibles, were the slowest-moving, and the least successful in interspecific larval combat. The long spines of third instar C. coeruleusappeared to reduce their palatability as food to H. axyridis and O. v-nigrum larvae in choice tests with dead larvae, but were not an effective defence against these species in Petri dish arenas. Larvae of O. v-nigrum had a smooth dorsal surface, were intermediate in terms of mandible size, but were the fastest moving, a trait that benefited their survival in intraguild combat. Larvae of H. axyridis were intermediate with respect to dorsal spines and speed of movement, but had the largest mandibles. This species was the most effective intraguild combatant among the coccinellids and the only one to successfully compete against C. rufilabris larvae of similar age. The speed, manoeuverability and long mandibles of C. rufilabris enabled them to impale coccinellid larvae at a relatively safe distance. The spines of C. coeruleus larvae impeded laterally oriented attacks by C. rufilabris, but did not provide sustained protection from repeated attacks. Success in these interactions appeared largely a function of offensive weaponry (mandible size and morphology) and speed of movement, although the role of dorsal spines as defensive structures was not ruled out. Rates of larval cannibalism were highest for C. rufilabris and largely mirrored the level of aggression observed in interspecific combat for each species.

Animals↗
PubMed2001

Responses of two ladybeetles to eight fungicides used in Florida citrus: implications for biological control.

Two ladybeetles, Cycloneda sanguinea and Harmonia axyridis, were exposed in the laboratory to eight fungicide formulations commonly used in citrus production in Florida. Both benomyl and the combination of copper and petroleum oil proved toxic to larvae of C. sanguinea that were exposed to concentrations corresponding to recommended field rates, either as leaf residues or in topical spray applications. Larvae of C. sanguinea also suffered significant mortality when exposed to neem oil as a leaf residue, but not after topical application. Larvae of H. axyridis exposed to these compounds completed development with the same success as control larvae in all trials. However, H. axyridis larvae exhibited slower development following exposure to leaf residues of ferbam applied at twice the recommended rate. Exposure to azoxystrobin as a leaf residue at twice the recommended concentration resulted in accelerated larval development in both species. No compounds appeared repellent to adult beetles of either species. Adult beetles of both species were observed resting on portions of filter paper treated with fosetyl-Al more often than on untreated, control portions. Azoxystrobin, ferbam and mefenoxam similarly arrested the movement of adult C. sanguinea, whereas benomyl and the copper and petroleum oil combination arrested the movement of adult H. axyridis. The differential sensitivity of the two coccinellid species is discussed in the context of the potential displacement of the indigenous C. sanguinea by the invasive H. axyridis.

Aerosols↗
PubMed2001

Comparative residual toxicities of pesticides to the predator Agistemus industani (Acari: Stigmaeidae) on citrus in Florida.

Residual toxicities of registered and selected experimental pesticides used on citrus against Agistemus industani Gonzalez (Acari: Stigmaeidae) were compared. Pesticides considered highly toxic to A. industani were: abamectin 0.15 EC at 731 ml/ha + FC 435-66 petroleum oil at 46.8 l/ha, pyridaben 75 WP at 469 g/ha, ethion 4 EC at 7.01 l/ha + FC 435-66 petroleum oil at 46.8 l/ha, propargite 6.55 EC at 3.51 l/ha, chlorfenapyr 2 SC at 1.46 l/ha applied alone or in combination with FC 435-66 petroleum oil at 46.8 l/ha, sulphur 80 DF at 16.81 kg/ha. dicofol 4EC at 7.01 l/ha, fenbutatin oxide 50 WP at 2.24 kg/ha, benomyl 50 WP at 2.24 kg/ha, benomyl 50 WP at 1.68 kg/ha + ferbam 76 GF at 5.60 kg/ha, ferbam 76 GF at 11.21 kg/ha, neem oil 90 EC at 46.8 l/ha, and copper hydroxide DF (40% metallic copper) at 4.48 kg metallic copper/ha + FC 435-66 petroleum oil at 46.8 l/ha. Pesticides that were moderately to slightly toxic included: copper sulphate 98% at 4.48 kg metallic copper/ha + FC 435-66 petroleum oil at 46.8 l/ha, fenbuconazole 2 F at 280 ml/ha + FC 435-66 petroleum oil at 46.8 l/ha, FC 435-66 petroleum oil applied alone at 46.8 l/ha or 23.41/ha, and diflubenzuron 25 WP at 1.40 kg/ha. Pesticides that were non-toxic included: fenbuconazole 2 F at 585 ml/ha, malathion 57 EC at 5.85 l/ha, FC 435-66 petroleum oil at 46.8 l/ha, carbaryl 80 S at 3.36 kg/ha. chlorpyrifos 4 EC at 4.68 l/ha, and formetanate 92 SP at 1.12 kg/ha. Understanding the toxic effects of field weathered pesticides against key predacious mite species is important for effective IPM. The results of this study provide a comparison of direct and indirect toxic effects of various pesticides to A. industani under field conditions.

Animals↗
PubMed1995

Use of tissue slices in chemical mixture toxicology and interspecies investigations.

Precision-cut tissue slices have proven to be a useful in vitro system for biotransformation and toxicity studies. Since tissue slices can be readily prepared from a variety of tissues and species, they can easily be used for interspecies investigations and comparisons. Furthermore, slices can be readily prepared from human tissue, thus comparisons (extrapolation) can be made between laboratory animals and humans. Slices can also be used to examine the toxic interactions of chemicals in vitro. It is important to use the correct experimental design to demonstrate toxic interactions and to assure that the tissue slices are properly exposed to the chemicals. Overall, tissue slices offer a valid in vitro system for performing species comparisons and chemical-chemical interaction studies.

Animals↗
PubMed1994

Toxic responses to defined chemical mixtures: mathematical models and experimental designs.

The problem and relevance of assessing biological responses to chemical mixtures is presented with reference to the literature on this problem and its possible solutions. This review is intended for a general audience as an introduction to, and comment on, assessing the interactions of defined mixtures of xenobiotics. The focus is on experimental toxicology, however, the methods are also applicable to pharmacology. Much of the literature on this topic is quite specialized in statistics, theory, or specific applications. This may deter a significant portion of the growing number of investigators in this field from using this literature, and may partially account for the persistent use of methods which have been shown to permit precarious conclusions. References are given for some of the most comprehensive and recent work and reviews on the subject. The reader is given some familiarity with this topic's basic problems and ideas, and the controversy on terminology. One example is presented of a popular experimental design and data analysis method which while applicable in some situations, has been shown to lead to precarious and even erroneous conclusions. Eight other methods of data analysis are briefly presented and some of their advantages, disadvantages, assumptions, and limitations are discussed. These methods were selected to illustrate similarities and differences in the various approaches taken in addressing this problem. Three basic types of experimental design appropriate to these kinds of studies are outlined. General considerations, suggested guidelines, and possible pitfalls in experimental design, and data analysis of biological responses to chemical mixtures are discussed.

Chemical Phenomena↗
PubMed1991

A short-term diffusive sampler for nitrogen dioxide monitoring in epidemiology.

An automated timed exposure diffusive sampler (TEDS) for sampling nitrogen dioxide (NO2) was developed for use in epidemiological studies. The TEDS sequentially exposes four passive sampling devices (PSD) by microprocessor controlled valves while a pump and air flow guide prevent sampler "starvation." Two TEDS units and two portable, real-time NO2 monitors were tested for accuracy, precision, sensitivity, and linearity of response. The accuracy of the TEDS was within 10 percent of the calibrated NO2 values, and precision was within 10 percent of the means of the measured values. The TEDS sensitivity was 20 to 30 ppb-hour for NO2. Co-location of the TEDS with a chemiluminescent NOx monitor (EPA reference method) showed similar responses to ambient NO2 (R2 = 0.9991). TEDS allows better time resolution than traditional diffusive samplers (i.e., Palmes tube) while sharing their ability to sample a variety of gases.

Air Pollution↗