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PubMed1997

The effect of various host species in the feeding performance of immature stages of the tick Hyalomma truncatum (Acari: Ixodidae).

In order to determine the effect of various hosts on the feeding performance of the tick Hyalomma truncatum, were used three mammalian species as hosts. Larvae and nymphs of H. truncatum were fed, under controlled laboratory conditions, on gerbils, guinea-pigs and rabbits. The larvae fed for 4.3 +/- 1.4 days on gerbils, 5.6 +/- 1.3 days on guinea-pigs and 4.7 +/- 1.2 days on rabbits. The mean weights of the larvae which fed in the rabbits, guinea-pigs and gerbils were 0.58 +/- 0.09, 0.46 +/- 0.04 and 0.45 +/- 0.04 mg, respectively. The feeding periods of the nymphs on gerbils, guinea-pigs and rabbits were 7.9 +/- 1.3 and 9.6 +/- 2.2 days respectively. The mean weights of the nymphs which fed on the gerbils, guinea-pigs and rabbits were 22.5 +/- 2.8, 19.7 +/- 1.3 and 15.8 +/- 1.4, respectively. Hyalomma truncatum demonstrated a life cycle of a three-host tick on gerbils and guinea-pigs and of a two-host tick on rabbits. The evolutionary advantage of a two-host cycle over a three-host cycle in metastriate ticks is discussed.

Animals↗
PubMed2000

Immunization of cross-bred cattle against Hyalomma anatolicum anatolicum by purified antigens.

Extracts prepared from unfed larvae of Hyalomma anatolicum anatolicum were purified by immunoaffinity chromatography using anti-gut IgG as ligand. Affinity purified antigen (Aff-GHLAg) was used to immunize cross-bred (Bos taurus x B. indicus) calves of 6-7 months of age. Immunized calves rejected 70.6% larvae, 54.5% nymphs and 61.9% adults. No significant changes in the engorged weight of females was observed; however, significant decrease in the engorgement weight of larvae and nymphs was recorded. There was a significant decrease in the emerging nymphs (p < 0.05) and adults (p < 0.01) of the tick stages fed on immunized animals. SDS-PAGE analysis revealed three antigenic proteins of 100, 59.4 and 37 kDa responsible for induction of resistance in the host.

Animals↗
PubMed2004

Chemical and physical signals mediating conspecific and heterospecific aggregation behavior of first instar stink bugs.

We investigated cues that mediate the aggregation behavior of immature pentatomid bugs by using nymphs of six different pentatomid bug species (Nezara viridula, Acrosternum hilare, Chlorochroa ligata, Chlorochroa sayi, Thyanta pallidovirens, and Euschistus conspersus). When first instars of any two species were put together in a Petri dish, they readily formed heterospecific aggregations similar to their natural conspecific aggregations. The chemical profiles of first and second instar nymphs of each species were determined by solvent extraction with pentane, followed by GC-MS analysis. Immature bugs of the different species had some compounds in common, and some that were more species specific. Within a species, there were distinct differences in the profiles of compounds extracted from first and second instars. Bugs did not aggregate around untreated polysulfone beads (1 mm diam) that were glued together in groups approximating bug egg masses, suggesting that tactile cues alone were insufficient to induce aggregation. Furthermore, when tested over a range of doses, groups of polysulfone beads treated with crude whole-body extracts of bugs did not induce or maintain aggregations. However, first instar N. viridula nymphs did respond to beads treated with two of the three major components of bug extracts. 4-Oxo-(E)-2-decenal induced significant aggregations at two doses, whereas tridecane, the major component in extracts from all six species, did not, and (E)-2-decenal was repellent. The repellence of (E)-2-decenal may explain why we and previous researchers were unable to induce aggregations of first instar N. viridula using whole-body extracts.

Animals↗
PubMed1990

Sites of attachment in Amblyomma triguttatum triguttatum Koch (Acari: Ixodidae) on natural hosts.

The sites of attachment of Amblyomma triguttatum truguttatum were studied from June to September 1981 on 146 feral pigs (Sus scrofa) and from March to August 1982 and January 1983 on 68 grey kangaroos (Macropus giganteus), naturally infested. Two hundred fifty hour (81%) of 314 nymphs were detected on the ears of the pigs; neither adults nor larvae of A. t. triguttatum were found on S. scrofa. Six hundred ninety four (97%) of 715 larvae; 283 (96%) of 295 nymphs and 11 (79%) of 14 adults of A. t. triguttatum were found on the ears of the kangaroos. The proportion of the larvae and nymphs on the ears of kangaroos and pigs respectively, decreased with the increase of tick load.

Acari↗
PubMed2004

Phase-related morphological changes induced by [His7]-corazonin in two species of locusts, Schistocerca gregaria and Locusta migratoria (Orthoptera: Acrididae).

The effects of a neurohormone, [His(7)]-corazonin, on phase-related morphological traits (F/C and E/F ratios; F = length of the hind femur, C = maximum width of the head; E = length of fore wing) were re-examined in the desert locust, Schistocerca gregaria Forskål. The F/C ratio was significantly different between adults with five and six nymphal instars, respectively, indicating that they need to be analysed separately. Injections of the synthesized peptide (1 nmol) into individually-reared (solitary) nymphs at the second and third instars caused a shift in classical morphometric ratio towards the value typical for crowded (gregarious) individuals in both sexes. The E/F ratio, which is smaller in solitary locusts than in gregarious ones, was also influenced significantly by injections of [His(7)]-corazonin into individually-reared locusts. The effect of [His(7)]-corazonin on E/F ratios was shown more clearly when the nymphs were injected at a higher dose (2 nmol) at the beginning of the third instar. Single injections of the peptide into individually-reared nymphs at different instars revealed that the earlier the injection the larger the 'gregarizing' effects of the peptide on F/C and E/F ratios. The same tendency was also detected in Locusta migratoria Linnaeus. These results supported the hypothesis that [His(7)]-corazonin plays an important role in the control of phase polymorphism in locusts.

Animals↗
PubMed2006

Ovipositional preferences, damage thresholds, and detection of the tomato-potato psyllid Bactericera cockerelli (Homoptera: Psyllidae) on selected tomato accessions.

The tomato-potato psyllid Bactericera [Paratrioza] cockerelli (Sulc) has recently caused losses exceeding 50% on fresh market tomatoes in California and Baja, Mexico by injecting a toxin that results in a condition known as 'psyllid yellows'. The objectives of this study were to: (i) document oviposition preferences on a range of tomato cultivars; (ii) determine threshold levels for psyllid densities that would cause psyllid yellows on tomatoes within the first three weeks following transplanting; and (iii) identify the most important 'psyllid yellows' symptoms that might be used in surveying and monitoring for this pest. Plant lines tested included the commonly-planted commercial cultivars 'Shady Lady' and 'QualiT 21', an older, previously commercial cultivar '7718 VFN', a common cultivar planted by consumers 'Yellow Pear', and a wild type plant accession, PI 134417. When given a choice, psyllids significantly preferred 'Yellow Pear' and avoided PI 134417 for oviposition. Under no-choice conditions psyllids laid significantly fewer eggs on PI 134417, but all the other plant lines were equally good substrates for laying eggs. Thus, oviposition preference is not likely to provide a functional management strategy in large plantings. On 'Shady Lady', psyllids preferred to oviposit on plants already infested with adults. On both 'Shady Lady' and '7718 VFN' oviposition was significantly greater on plants previously infested by nymphs as compared to uninfested control plants. This suggests that, at least for some cultivars, there is a physiological change in plant attractiveness following psyllid feeding. 'Yellow Pear' and 'QualiT 21' were relatively tolerant of psyllids, requiring 18 nymphs per plant to produce the disease symptoms. Only eight nymphs per plant were needed on 'Shady Lady' and '7718 VFN'. For all cultivars, the pest density showed strong correlations with measurements such as the number of yellowing leaves and leaflets and distorted leaves, which were as good as or better than the first factor extracted from principal component analysis. Therefore, such measurements have the potential to simplify field surveys.

Analysis of Variance↗
PubMed1992

Dietary effects of allopurinol and sulfinpyrazone on development, survival, and reproduction of German cockroaches (Dictyoptera: Blattellidae).

Diets containing two gout medications, allopurinol and sulfinpyrazone, were fed ad libitum to first- or second-instar German cockroaches for 15 wk or until 100% mortality was reached. Cockroaches fed greater than or equal to 0.10% allopurinol diets weighed significantly less than those fed the control diet. Mortality of cockroaches fed diets containing greater than or equal to 0.05% allopurinol was significantly greater than those fed the control diet. The LT50 (6.1 wk) of cockroaches fed diets containing 0.10% allopurinol was significantly less than those fed any other diet containing allopurinol. LT50s and slopes were proportional and inversely related, respectively, to percentage of allopurinol in the diet. The addition of sulfinpyrazone to allopurinol diets minimally enhanced the blatticidal nature of the diets. Nymphs fed diets containing greater than or equal to 0.05% allopurinol experienced significant delays in adult emergence. Cockroaches fed greater than or equal to 0.01% allopurinol diets aborted a significantly greater percentage of their oothecae than those fed the 0.001% allopurinol or control diets. Hatched oothecae from cockroaches fed the 0.01% allopurinol diet had significantly fewer nymphs than those fed the 0.001% allopurinol or control diets. Percentage of oothecae aborted and number of nymphs per hatched ootheca from cockroaches fed a 2% sulfinpyrazone diet did not differ significantly from the control.

Allopurinol↗
PubMed1992

Differential development and reproduction of the German cockroach (Dictyoptera: Blattellidae) on three laboratory diets.

Development of nymphs and oocyte maturation in adults were examined in Blattella germanica (L.) reared on three commercial diets. Nymphs fed rat food developed significantly faster than nymphs fed two commercial dog foods. Similarly, oocytes matured more quickly in adult females that were raised on rat food than in females raised on dog food. Nymphal development and oocyte maturation were slower in insects that were fed whole dog food pellets than in insects fed ground dog food, suggesting that grinding the diet diminishes a mechanical barrier in whole dog food pellets. Comparisons of processed canine food and unprocessed canine food indicated that diets were significantly inferior after the steam extrusion process. Rat food is normally not subjected to such conditions and both processed and unprocessed rat food are equally suitable for B. germanica. The significance and implications for comparative studies with cockroaches are discussed.

Animal Feed↗
PubMed2003

Categories of resistance at different growth stages in halt, a winter wheat resistant to the Russian wheat aphid (Homoptera: Aphididae).

This study was designed to categorize the resistance to the Russian wheat aphid, Diuraphis noxia (Mordvilko), resistant hard red winter wheat, Halt, as compared with susceptible wheat, TAM 107, at four different growth stages. Antixenosis was expressed in Halt at growth stage Zadoks 30. Antibiosis in Halt affected fecundity, number of aphids produced per reproductive day, maximum number of nymphs produced in one day, and intrinsic rate of increase. Fecundity was lower on Halt than TAM 107, and more nymphs were produced on both varieties at growth stage 20 than 10 and 40. Fewer nymphs were produced per reproductive day and on maximum production days by aphids reared on Halt than by those reared on TAM 107. The intrinsic rate of increase of Russian wheat aphids reared on Halt was lower than aphids reared on TAM 107. Differences in plant height and plant dry weight did not occur. Chlorosis ratings showed greater damage at the earlier stages in Halt and TAM 107 and significantly more damage in TAM 107 than Halt at growth stages 10, 20, and 30. Leaf rolling occurred on infested plants of TAM 107 at growth stages 10, 20, and 30, but not growth stage 40. Halt plants did not exhibit leaf rolling. The presence of a significant level of tolerance could make Halt compatible with other integrated pest management programs. However, care should be taken with cultivars containing evidence of antixenosis or antibiosis that could cause selective pressure on the Russian wheat aphid, potentially causing biotypes to be produced.

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

Host-parasitoid interactions relating to penetration of the whitefly, Bemisia tabaci, by the parasitoid wasp, Eretmocerus mundus.

It has been reported that the aphelinid wasp Eertmocerus mundus parasitizes all four nymphal instars of the sweet potato whitefly, Bemisia tabaci (Biotype B), with 3rd instars being the preferred hosts. The parasitoid lays its egg on the leaf underneath the host nymph. First instars hatch and later penetrate the whitefly. Previous studies have shown that the initiation of parasitoid penetration induces the host to form a cellular capsule around the parasitoid. As described here, females never oviposited once the 4th instar whitefly nymph had initiated adult development. First instar E. mundus larvae were observed under 2nd, 3rd and 4th instar whitefly nymphs, however, penetration did not occur until the whitefly had reached the 4th instar. The non-penetrating E. mundus larva almost always induced permanent developmental arrest in its 4th instar whitefly host and also caused a reduction in whole body host ecdysteroid titers. Therefore, unless there is a peak in molting hormone titer in the area local to penetration, it appears that the induction of capsule formation is not due to an increase in ecdysteroid titer. As the capsule formed around the penetrating parasitoid, host epidermal cells multiplied and became cuboidal and columnar, and relatively thick layers of new cuticle were deposited within the developing capsule, particularly near its ventral opening. The newly formed host cuticle was thinner in the dorsal part of the capsule and appeared to be absent at its apex. These results provide new information regarding the timing and dynamics of parasitoid oviposition and egg hatch as related to larval penetration, parasitoid-induced changes in whitefly development, molting hormone titers and the process of capsule formation.

Animals↗
PubMed1990

Systemic activity of ivermectin on the human body louse (Anoplura: Pediculidae).

Eighty-one to 100% of nymphs and females of the human body louse (Pediculus humanus humanus) that fed artificially on blood containing 2.5-10 ng ivermectin/ml died. The mortality of nymphs and female lice fed on rabbits treated with 200 micrograms/kg ivermectin was very high during the first two to three days, then declined sharply, reaching the level of the controls on day six. Nymphs were more sensitive than females. The average number of eggs laid by surviving females and the percentage that hatched from those eggs were lower than in controls.

Animals↗
PubMed1991

Stimulation of vitellogenesis by pyrethroids in mated and virgin female adults, male adults, and fourth instar females of Ornithodoros moubata (Acari: Argasidae).

The effects of several pyrethroids on vitellogenesis, i.e., vitellogenin (Vg) synthesis and ovarian development in unfed mated female adults of Ornithodoros moubata were investigated. Survival of ticks treated with pyrethrin, resmethrin, and etophenprox was very low. Ticks treated with cypermethrin (CyM), fenvalerate (Fev), and flucythrinate (Flu) survived even when high concentrations were used. Vg titer in the hemolymph of unfed mated females was the same level on day 5 and about three times higher on day 10 after treatment with CyM, Fev, and Flu, as that of engorged adult females. CyM was the most effective in inducing vitellogenesis and was further evaluated in unfed virgin females, males, and fourth instars. CyM was shown to stimulate vitellogenesis in unfed virgin females adults. Oviposition did not occur but ovaries were well developed. CyM also was shown to stimulate Vg in the hemolymph of unfed and fed adult males; however, the Vg levels were very low compared to that of engorged adult females. Extremely high concentrations of Vg were observed in the hemolymph of female nymphs (fourth instar), particularly engorged nymphs, treated with CyM (10 micrograms). No ovarian development was observed in these nymphs. Vg stimulated by CyM was shown to be immunologically and electrophoretically the same as that of normal engorged females.

Animals↗
PubMed1991

Experimental transmission of African swine fever virus by the tick Ornithodoros (Alectorobius) puertoricensis (Acari: Argasidae).

The soft tick Ornithodoros puertoricensis Fox has been found on the Caribbean island of Hispaniola (Haiti and the Dominican Republic) where African swine fever (ASF) was endemic from 1978 to 1984. To evaluate the vector potential of O. puertoricensis for African swine fever virus (ASFV), second-instar nymphs were experimentally infected by feeding on a viremic pig that was infected with the Dominican Republic isolate (DR-II) of ASFV. Subsequent infection rates and mean virus titers for individually triturated ticks were: second-instar nymph (95.4%, 10(4.38 +/- 0.85)), third-instar nymph (48.9%, 10(4.59 +/- 0.61)), male (46.7%, 10(4.36 +/- 0.61)), and female (35.3%, 10(4.38 +/- 1.09)). Infected ticks transmitted ASFV to susceptible pigs by bite 23, 85, 126, 160, 182, and 239 d after the infective blood meal. These findings show that ASFV is passed transstadially among O. puertoricensis and that O. puertoricensis can be an efficient vector of African swine fever virus.

African Swine Fever↗
PubMed1992

Biology of Hyalomma schulzei (Acari: Ixodidae) on rabbits under laboratory conditions.

Hyalomma schulzei was reared on rabbits and held under laboratory conditions at 28 degrees C, 75% RH, and 12:12 (L:D) photoperiod with high productivity. The completion of the life cycle required an average of 107.4 d. The unfed females increased 2.7-fold and unfed males became one-third wider, as a result of feeding. Larvae and females exhibited host-seeking behavior less than 1 d after hatching and molt, respectively. The tick behaved as two-host tick species. The larva-nymph attachment period (mean +/- SE) was 24.7 +/- 0.15 d and female feeding period was 14.3 +/- 0.33 d. Nymphs molted 24.3 +/- 0.05 d after engorgement, and the percentage of molting was 90.3%. Females began molting from nymphs 3 d before males emerged. A sex ratio of 1.3:1 (male/female) was determined from emerged adults. Females began oviposition 10.6 +/- 0.56 d after engorgement and produced 10,259 +/- 728 eggs per female. Egg hatch was 97.4% +/- 0.75 after an incubation period of 32.3 +/- 0.24 d. Females converted 57% of engorged weight into eggs and produced 6,821 +/- 254 eggs per g of engorged body weight. A freshly laid egg on the first day of oviposition weighed 58.6 micrograms. An inverse relationship between egg weight and rate of egg production was observed.

Animals↗
PubMed1993

Reduction of nymphal Ixodes dammini (Acari: Ixodidae) in a residential suburban landscape by area application of insecticides.

Seven formulations of three commercially available insecticides were evaluated for their ability to reduce the density of nymphal deer ticks (Ixodes dammini Spielman, Clifford, Piesman & Corwin) in a suburban residential area endemic for Lyme disease. In total, 101 residential properties in Mount Kisco, Westchester County, NY, were treated with one of the following: carbaryl emulsifiable concentrate (EC) at 0.6 or 1.1 kg AI/ha, carbaryl granular (GR) at 4.5 kg AI/ha, chlorpyrifos wettable powder (WP) at 0.6 or 1.1 kg AI/ha, chlorpyrifos GR at 1.1 kg AI/ha, or cyfluthrin EC at 0.1 kg AI/ha. All three chemicals were found to reduce the density of nymphs on treated properties significantly compared with untreated controls. Percentage of reduction of nymphs ranged from 67.9% for carbaryl EC 1.1 kg AI/ha to 97.4% for chlorpyrifos WP 1.1 kg AI/ha. There was no difference in the amount of reduction provided by each formulation of the same chemical, but carbaryl formulations were significantly less effective than chlorpyrifos or cyfluthrin. Nymphal densities after treatment remained low throughout the course of the study, indicating that a single well-timed spring application is sufficient to provide significant reduction of nymphs for an entire transmission season.

Animals↗
PubMed1998

Infestation of the southern alligator lizard (Squamata: Anguidae) by Ixodes pacificus (Acari: Ixodidae) and its susceptibility to Borrelia burgdorferi.

To investigate the reservoir potential of the southern alligator lizard, Elgaria multicarinata (Blainville), for the Lyme disease spirochete, Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner, 14 lizards were collected from 1 county on each side of the northern Central Valley of California. Seven animals were collected from a Placer County site (Drivers Flat) and a Yolo County site (Cache Creek) where B. burgdorferi had been isolated previously from Ixodes pacificus Cooley & Kohls. Overall, the mean abundance of I. pacificus on all 14 lizards was 34.1 (range, 3-63) for larvae and 11.0 (range, 1-28) for nymphs. In captivity, field-attached I. pacificus larvae and nymphs required, on average, 12.6 (range, 1-37) and 14.4 (range, 5-44) d to feed to repletion, respectively. The prevalence of B. burgdorferi infection in host-seeking I. pacificus nymphs was 1.4% in Cache Creek Canyon and 9.9% in Drivers Flat. Attempts to isolate spirochetes from lizard blood or ticks that had fed on lizards and subsequently molted were unsuccessful as were efforts to cultivate spirochetes in lizard sera. These data suggest that the southern alligator lizard is not a competent reservoir for B. burgdorferi, although it is an important host for I. pacificus subadults.

Animals↗
PubMed2005

Borrelia burgdorferi sensu lato infection in larval Ixodes ricinus (Acari: Ixodidae) feeding on blackbirds in northwestern Italy.

Birds belonging to 59 species (n = 1,206) were live captured in Piemonte, northwestern Italy, in 2001. Ixodes ricinus (L.) larvae were collected from 59 birds belonging to nine species, and nymphs were recovered on 79 birds belonging to 10 species. Eurasian blackbirds, Turdus merula L., had significantly higher levels of infestation by ticks than other passerine species. Larval I. ricinus of blackbirds peaked in summer, when prevalence was 39% (95% confidence interval 24.2-55.5) and mean number of ticks per host was 3.3 (1.6-7.2), whereas nymphs peaked in spring, when prevalence was 72.2% (54.8-85.8) and mean number of ticks per host was 6.9 (4.4-10.7). Immature I. ricinus were coincidentally aggregated on blackbirds, with 15 blackbirds feeding 67.4% of nymphs and 40.3% of larvae, and coinfestation by both stages was relatively high in summer: Kappa = 0.64 (0.40-0.88). Borrelia burgdorferi sensu lato was identified by polymerase chain reaction (PCR) in 58.3% (35.9-78.5) of larvae with engorgement ratio > or = 3 that were collected from blackbirds. Larvae that were collected from other passerine species gave negative PCR results. Sixteen of 21 PCR-positive samples belonged to B. garinii (76.2%), and five (23.8%) were Borrelia valaisiana. Results of this study suggest that blackbirds play an important role as hosts for immature I. ricinus and as reservoir of Borrelia garinii in northwestern Italy.

Animals↗