Peak Infestation Research Articles

Influence of Plant Direction, Layer, and Spacing on the Infestation Levels of Anthonomus eugenii (Coleoptera: Curculionidae) in Open Jalapeño Pepper Fields in North Florida

Pepper weevil, Anthonomus eugenii Cano (Coleoptera: Curculionidae), is a most serious pest of peppers in North Florida. To analyze A. eugenii infestation levels on jalapeno peppers as a reference for effectively controlling pepper weevil, we investigated infestation and population dynamics of A. eugenii, and influence of plant direction, layer, and spacing in open fields in North Florida. The results showed that adult pepper weevil infestation started in late Apr when plants started to produce buds and flowers. Three infestation peaks were recorded on 9 Jun, 24 Jul, and 11 Sep. The second peak showed the highest infestation level (14.6 ± 2.7 infested fruits per plant). The density curve of A. eugenii larvae within fruits lagged about 2 to 4 wk behind the curve of infestation level in the field. Three peaks occurred on 10 Jul, 21 Aug, and 25 Sep. Fruits on the eastern part and top third of pepper plants had the lowest infestation levels, as did plants spaced 40 cm apart. This study, focusing on the preferred locations of A. eugenii, will help improve sampling technique and pest management applications, and thus enhance the effectiveness of pesticide application, and ultimately reduce ecological damage. Resumen El picudo de chile, Anthonomus eugenii Cano (Coleoptera: Curculionidae), es la plaga mas grave de chile en el norte de la Florida. Para analizar el nivel de infestacion de A. eugenii en chiles jalapenos como referencia para controlar eficazmente el picudo del chile, investigamos la infestacion y la dinamica de la poblacion de A. eugenii, y la influencia de la direccion, la capa y el espaciamiento de las plantas en campos abiertos en el norte de la Florida. Los resultados mostraron que la infestacion de los adultos del picudo del chile comenzo a fines de abril, cuando las plantas comenzaron a producir brotes y flores. Se registraron tres picos de infestacion, el 9 de junio, el 24 de julio y el 11 de septiembre. El segundo pico mostro el nivel mas alto de infestacion (14.6 ± 2.7 frutas infestadas por planta). La curva de densidad de las larvas de A. eugenii dentro de las frutas se retraso aproximadamente 2 a 4 semanas por detras de la curva del nivel de infestacion en el campo. Tres picos ocurrieron en el 10 de julio, el 21 de agosto y el 25 de septiembre. Las frutas en la parte hacia el oriente y en el tercio parte superior de las plantas de chile tuvieron los niveles mas bajos de infestacion, al igual que las plantas separadas por 40 cm. Este estudio, que se enfoca en las ubicaciones preferidas de A. eugenii, ayudara a mejorar la tecnica de muestreo y las aplicaciones de manejo de plagas y, por lo tanto, aumentara la efectividad de la aplicacion de pesticidas y, en ultima instancia, reducira el dano ecologico. Key Words: pepper weevil; preference; pest management; population dynamics View this article in BioOne

Population, Fluctuation of Aphid on the different Wheat Varieties from Larkana District

The present investigation has been carried on the population fluctuation of aphids on the different wheat varieties i-e TD-1, Benazir, Tj-83, QS-4, NIAamber from larkana district. Triticium astivum (wheat) is considered very important food crop in Pakistan including Sindh. This crop is attacked by numbers of insect including aphids, which is responsible for reduction of its yield. The occurrence of aphid has been started in the month of January and its peak infestation was observed during mid March when wheat crop was fully grown. During the present study significant large numbers of specimens were collected from the different varieties of wheat. The collected material was sorted out in to two species viz: Rhopalosiphum padi (L.), Schizaphis graminum (Rondani). During this study it was noted that TD-1 was significantly affected by R.padi and S.gramium as compare to other tested varieties. It was observed that aphid reached peak point in mid February on leaves then in the end of February aphids started shifting from leaves to ears and their population start to decline in month of April.

Chemical and growth traits of the peach tree may induce higher infestation rates of the green peach aphid, Myzus persicae (Sulzer).

The green peach aphids, Myzus persicae, are a predominant pest in peach orchards as they can alter fruiting and shoot development for several years. This aphid developed resistance against pesticides. Among the alternative control strategies is the reduction of the trees' attractiveness to aphids. In order to identify the plant variables related to plant susceptibility, young peach trees were submitted to various supplies of water and nitrogen, and then artificially infested with aphids. Shoot development, plant water potential and aphid abundance were then monitored on a weekly basis. The apex concentrations in total N, amino acids, soluble sugars and polyphenols were determined at infestation start and infestation peak. Until infestation peak, the thermal time requests for aphid development were independent of infestation severity. The aphid populations then collapsed more rapidly on the low infested shoots than on the high infested ones. Aphid abundances appeared to be positively related to shoot development (leaf expansion and secondary ramification), to shoot growth (stem length and diameter) and to apex concentrations in amino acids and non-structural carbohydrates (NSC). Polyphenols had the opposite effect. Peach susceptibility to aphids depends on shoot development and apex composition, and could be lowered by decreasing the water and nitrogen inputs. © 2019 Society of Chemical Industry.

Population dynamics of major arthropod pests and their natural enemies on okra

An investigation was carried out on the population dynamics of major pests and their natural enemies on okra during kharif, 2016 and 2017. Results revealed that during both seasons, whitefly (Bemisia tabaci) and leafhopper-Amrasaca (Sundapteryx) biguttula occurred from the last week of July (30th Standard Meteorological Week) whereas, fruit borer (Earias vitella) and red spider mite (Tetranychus cinnabarinus) appeared in 34th and 37th SMW during 2016 and 2017, respectively. Peak population of B. tabaci (29.00/15 leaves) and A.biguttula (179.25/15 leaves) was observed in 32nd and 37th SMW, respectively. The peak infestation of E. vitella (52.43%) and T. cinnabarinus (247.25/sq.cm/15 leaves) was observed in 34th SMW and 40th SMW, respectively. Incidence of B. tabaci showed significant negative (r=-0.786) correlation with maximum temperature and with minimum temperature (r= 0.904) and evening humidity (r= 0.766) showed significant positive correlation; T. cinnabarinus showed significant negative correlation (r=-0.964) with minimum temperature; and E. vitella having significant positive (r= 0.867) correlation with maximum temperature, while minimum temperature(r=-0.800) and evening relative humidity (r=-0.960) had significantly negative correlation. Among the natural enemies viz., coccinellids (r = 0.911), spiders (r = 0.918), rove beetles (r= 0.895), Geocoris bug (r= 0.672) and carabid beetles (r= 0.701) had significant positive correlation with A. biguttula, whereas, coccinellids (r =-0.991) and Geocoris bug (r =-0.984) had significantly negative correlation with T. cinnabarinus.

Consequences of ecological factors and crop phonological stages on seasonal incidence of bud borer, Anarsia achrasella Bradley on sapota

The damage due to bud borer (A. achrasella) was found round the year on the new buds/flowers with the peak activity during April (10.85–12.53%), May (13.42–14.10%) and June (11.35–12.97%) at peak flowering flush in sapota cv. Kalipatti. Regarding linear correlation of ecological factors and infestation during all three years of survey, bud borer damage had positive influenced due to preceding and current minimum temperature and evaporation during summer coincide with peak flowering phase of sapota. The regression equation was found significant with few ecological factors only like maximum temperature and their correlative factor of bright sunshine hrs and evaporation. Sapota bud borer peak infestation was associated with crop phenology which coincides with encouraging incident of summer season and peak flush of flowering phase under round the year incidence pattern.

Microbiological indexes of mutton at monieziosis

Today, one of the most objective indicators of safety and quality are microbiological. Although it is practically impossible to completely avoid meat contamination and a wide range of factors may affect the microbial contamination of meat, despite this, microbiological risk analysis is the most effective system for assessing and controlling the safety of meat and meat products, in particular lamb. Therefore, the purpose of our study was to determine the microbiological parameters of lamb obtained from animals affected by monitors, in particular during peak infestations in the southern region. We investigated 125 lamb’s carcasses killed in Berezovsky and Saratsky districts of the Odessa region within 3 months. 35 carcasses from that quantity were infected by monieziosis. This amounts 28%. Percentage of moniezia disease was 20% in May, in June and July respectively 39.1% and 22.7%. The results of study showed that the defeat of lambs at the age of 4−6 month by moniezia leads to decrease of quality of mutton. The microbiological indexes indicate it. Study of common bacterial contamination established that the QMAFAnM in samples of experimental group didn’t exceed the allowable level in May and June. So, in May allocated 3.01 ± 0.28×103* CFU per 1 g (Р ≤ 0.05). This is true toward control. The quantity of Colonies Forming Units per 1 g increased in June and was 3.13 ± 0.23×105 (Р ≤ 0.05). The increase is related to gradual height of the inflammatory process, intoxication, allergization of lamb’s organism that caused by moniezia. The QMAFAnM exceed the allowable level in July and was 5.22 ± 0.11×106 CFU per 1 g (Р ≤ 0.05). This indicates a questionable quality of meat. That raw materials can’t be used by consumers on general grounds. It can cause outbreaks of food poisoning. The QMAFAnM during experimental period didn’t exceed the allowable level and was within the 1.81 ± 0.34−4.31 ± 0.12×102 CFU per 1 g in carcasses from non-invasive by moniezia (control group) animals. Collibacillus bacterias have indentified during all experimental period in samples from invasion by moniezia animals. At the same time collibacillus bacterias in samples from non-invasion animals were found only in June and July. Average content of colibacillus baсterias was within the 1.68 ± 0.12−4.65 ± 0.26×102 (Р ≤ 0.05) CFU per 1 g for experimental group. The index didn’t exceed the allowable level but it was higher than indexes in control group. Salmonella contamination was not detected in any groups of samples.

Ecological and Biological Studies on the Citrus Flower Moth Prays citri (Millière) (Lepidoptera: Hyponomeutidae) in Qalyubia Governorate, Egypt

The investigation was carried out during two years in citrus orchards in Qalyubia Governorate 2015 – 2016, to study ecological and biological aspects of the Citrus Flower Moth Prays citri (Milliere) (Lepidoptera: Hyponomeutidae). Data illustrated from ecological and biological points of view. Ranjpure lime (Citrus auranifolia) was the most preferred variety (highly susceptible) of infested by P. citri. While lemon (Citrus limon) which is considered as “moderately susceptible” exhibit less preferable to P. citri, but not seen any infested flowers in navel orange (Citrus sinensis) was the lowest preferred variety, throughout the investigation 2015 – 2016. One peak of infestation of P. citri in spring under weather conditions of Qalyubia Governorate. Predatory potential of Chrysoperla carnea (Steph) larvae on citrus flower moth P. citri larvae, under laboratory conditions was highly significant in mean consumption rate of 2nd and 3rd instars The total consumption by the third instar of C. carnea was significantly than the second instar . Biological results indicated that Female laid eggs both individually 54.6 eggs in average per female, Incubation period lasted 1.07 days, hatchability was 67.7 % in average, Larval and pupal stage period was 6.37 and 5.33 days respectively, female and male longevity lasted 4.3 and 3.6 days respectively. Life cycle 12.77 days while Generation lasted 13.79 days under 29.4°C and 62.7 % RH.

Host plant resistance through physico-chemical characters against major insect pests of okra occurring in the Gangetic plains of eastern India

Okra production in the tropics is threatened by attack of insect-pests, fruit and shoot borer (FSB), jassid and whitefly causing severe loss in marketable yield particularly in the Gangetic plains of eastern India. No developed varieties/hybrids are free from attack of these pests. However, improved lines of okra have potential to broaden the genetic variability may improve resistance to these pests. Therefore, the population dynamics of these pests were recorded from 24 advance breeding lines/varieties of okra during peak infestation period over two consecutive years. Morphological leaf traits and biochemical parameters were assessed as potential mediators of resistance. The population of these pests reached above economic threshold levels during the month of September. Significant genotypic differences in terms of infestation of these pests were observed. Negatively correlated physico-chemical characters might be considered as important indices for selection of genotype tolerant to these pests. As indicated by the low infestations, the tolerance of BCO-1 to FSB, whitefly and that of Arka Anamika to jassid is based on both antixenotic properties of the genotypes. The donor parents BCO-1 and Arka Anamika should, therefore, be introduced into okra breeding programs to enhance tolerance against these pests.

Anatomical distribution and population dynamics of Rhipicephalus (Boophilus) microplus in cattle in the municipality of Óleo, São Paulo

Rhipicephalus (Boophilus) microplus infestation is responsible for significant economic losses in cattle industry. The use of acaricides at strategic times and selection of resistant animals can minimize economic losses. This study aimed to determine the anatomical distribution and population dynamics of R. microplus in the municipality of Óleo, state of São Paulo. This study was conducted using eight male cattle, crossbred zebu-taurine (in accordance with the regional herd). Female R. (B.) microplus, greater than 4 mm, present in the right side of the animals were counted between April 2012 and March 2013. The highest tick number per animal was noted in October (128.25), and the lowest in April (35.5), with three infestation peaks during the study, in May, October, and December, which were influenced by the minimum and maximum mean temperature and rainfall. Among the cranio-caudal regions (anterior, median, and posterior), the posterior had the highest mean tick number, and the anterior had the lowest. The minimum temperature, rainfall, and solar radiation interfered with infestation of dorsoventral regions: in cold months, the lowest infestations were found in the mixed area (ear and tail); in the warm months, in the high region (head, neck, upper ribs, flank, and rump). The lower region (dewlap, cranial limb, lower ribs, abdomen, prepuce, scrotum, and lower limb) always had the highest mean tick number. The tick numbers of the caudal limb and crotch showed strong correlation with the total tick number (+0.88 and +0.70, respectively). These data, grouped according to median, posterior, and crotch regions, showed a stronger correlation with the total tick number (+0.96, +0.90, and +0.70, respectively).

Piroplasmoses bovines dans les provinces de Skikda et d’Oum El Bouaghi (nord-est de l’Algérie) : étude épidémiologique et estimation des pertes de production laitière

Au cours d’une enquête menée dans 88 fermes de deux provinces du nord-est de l’Algérie – Oum El Bouaghi et Skikda –, 89 cas cliniques de piroplasmoses, soit un taux d’infection de 11,6 % des bovins examinés, ont été enregistrés entre mai et septembre 2011 dans 86,4 % des fermes visitées. Trois espèces de piroplasmes ont été identifiées dans les étalements sanguins colorés au Giemsa : Theileria annulata (chez 94,0 % des bovins malades), Babesia bovis (33,7 %) et Babesia bigemina (3,4 %), avec 31 % de co-infections. Il n’y avait pas de différence significative de prévalence entre les deux provinces ni entre les races bovines. La theilériose tropicale a provoqué une baisse significative de la production laitière, estimée à 319 litres par vache infectée pendant les deux mois suivant la maladie. Sept espèces de tiques ont été collectées dans les fermes pendant l’étude. Le pic d’infestation a été observé en juillet pour Hyalomma scupense (syn. H. detritum), H. lusitanicum, H. anatolicum, Rhipicephalus bursa et R. turanicus, et en août pour H. marginatum et H. excavatum. Une corrélation positive a été observée entre les cas cliniques de theilériose tropicale bovine et la charge parasitaire en H. scupense, d’une part, et entre les cas cliniques de babésioses et la charge parasitaire en R. bursa, d’autre part.

Occurrence of different Lantana camara varieties across four South African provinces and their susceptibility to a biotype of the gall-forming mite Aceria lantanae

ABSTRACTA biotype of the flower-galling mite, Aceria lantanae (Cook) (Trombidiformes: Eriophyidae) collected in Florida (U.S.A.) was released in South Africa in 2007 against Lantana camara L. (Verbenaceae) but has displayed patchy establishment. The occurrence of different L. camara varieties and their susceptibility to A. lantanae were assessed across four provinces with dense infestations. Surveys were undertaken at 113 sites during the mite’s peak infestation period (April–May) in 2013–2015. The occurrence of 13 recorded L. camara varieties differed substantially across and within these provinces. Overall, five varieties accounted for 7–45% of the sampled plants at 9–51% of the surveyed sites. The remaining eight varieties accounted for <1–4% of the plants at 2–9% of the sites. The establishment and impact of A. lantanae differed significantly between L. camara varieties. The mite established best on three varieties (163 LP, 021 WP and 015 OR), with 60–90% of plants infested. Reduced establishments were observed on seven varieties, with 18–50% of plants infested, while no establishment was recorded on three varieties. Where established, A. lantanae inflicted considerable levels of damage (i.e. 51–75% of buds infested) on the most widespread and abundant L. camara variety (163 LP) and on one less common variety (021 WP). Two uncommon varieties (015 OR, 021 P) suffered moderate levels of damage with the remainder suffering only trivial levels. The mite’s impact in South Africa could be improved by complementing the established biotype with others from Central and South America that are better matched with the poorly attacked L. camara varieties.

Effects of spontaneous field margin vegetation on the regulation of herbivores in two winter crops

Non-crop vegetation of field margins provides resources for natural enemies of crop herbivores. However, it is still not well known whether this resource provisioning effect is strong enough to improve herbivore regulation within crop fields and which plant species and functional groups favour this ecosystem service. A better understanding of the interactions between field margin vegetation and herbivore regulation is crucial to evaluate management strategies and to design suppressive plant mixtures. We surveyed 64 wheat and oilseed rape fields of Western France for two years (16 fields per year and crop) in order (1) to identify plant diversity or group effects on herbivore regulation within crop fields and (2) to identify species within plant groups that improve regulation. Herbivores, herbivore damage and natural enemies were monitored on crop plants at a distance of 5 and 50m from the field margin. At the same time, the cover and phenological stage of all vascular plants were estimated in the adjacent field margin. The study demonstrated a positive relationship between the cover of entomophilous plant species that were flowering at the survey date and response variables related to herbivore regulation. Plant species richness and the cover of plant species taxonomically close to crop plants had a small influence on herbivores and natural enemies in wheat whereas related wild Brassicaceae increased herbivory and decreased herbivore regulation in oilseed rape. Within the entomophilous flowering plants, several species were significantly related to a better herbivore regulation in univariate analyses. Multivariate ordination techniques allowed the identification of plant species influencing several response variables of herbivore regulation at the same time. Our study demonstrated the importance of entomophilous species that flowered at peak infestation of crop herbivores. Spontaneous field margins rich in flowering entomophilous species provide an important ecosystem service without expensive sowing of seed mixtures.

Influence of intercropping in soybean on the girdle beetle Obereopsis Brevis (Gahan)

Field experiments were conducted during kharif 2013 and 2014 at MARS, UAS Dharwad, on soybean (JS-335) intercropped with cotton (2: 1), foxtail millet (2: 1), chilli (2: 1), onion (2: 1), castor (2: 1), pigeonpea (4: 2), groundnut (2: 1), maize (2: 1) and green gram (2: 1). It was observed that the girdle beetle infestation started from 30 DAS and persisted up to 50 DAS, with peak infestation being between 37 and 44 DAS, irrespective of intercrops; it was low in soybean+ cotton (2: 1) intercropping system, with 70% reduction in infestation compared to sole soybean. Thus wherever girdle beetle infestation was endemic, intercropping soybean with cotton in 2: 1 ratio will fit in as one of the management practices.

Seasonal incidence of major insect pests of brinjal, Solanum melongena L. under agro climatic conditions of Varanasi region

Seasonal incidence of shoot and fruit borer, Leucinodes orbonalis (on shoot), jassids, Amrasca bigutulla bigutulla, whitefly, Bemesia tabaci was more prevalent during vegetative phase of the crop. Peak shoot infestation was observed in second week of October (78%), on initiation of fruiting stage and declined, peak fruit infestation was observed in first week of November (63%). Peak infestation of whitefly and jassids was observed during third week of November (13.52 adults/3leaves) and (7.71 adults/3leaves), respectively. After that, the population was declined with advent of winter season. The role of rainfall and relative humidity was increased the infestation of whitefly and jassids. Temperature was negatively correlated with whitefly and jassids infestation and shoot and fruit infestation was positively correlated with maximum temperature and mean temperature.

The Role of Predators Insects in Regulating Population Densities of Certain Piercing Sucking Pests on Squash Plants in Egypt

Studieswere carried out at Diarb Negim, Sharkia governorate during two successiveseasons 2014-2015 and 2015-2016. Obtained results showed that in autumnplantation, there were two peaks of Aphis gossypii (Glover) on squashplants, one peak at last week ofNovember and other at third week of December in 2014 season. On the other hand,Bemisia tabci (Genn.) had three peaks, in second week of November, firstweek of December and third week of December in 2014 season and two peaks ofinfestation in fourth week of November and December in 2015 season of autumnplantation while, three peaks in summer plantation were obtained on fourth weekof (April &May) and second week of June in 2015 season respectively.Investigation revealed that, squash plants infested by few numbers of thripsduring autumn plantation throughout the two seasons. Statistical analysis ofthe obtained data cleared highly negative correlation between aphid&whitefly and temperature in autumn plantation in both seasons. Also, themean R.H showed a positive significant correlation on population density of A.gossypii in second season 2015 of autumn plantation. In summer plantation,the minimum R.H% showed a negative correlation with Orius spp.population and a positive significant correlation with C. carnea populationin the first season 2015. The predaceous insects found associated with pericingsucking pests were Orius spp., Coccinella undecimpuncta L.,Chrysoperla carnea Steph., Metasyrphus corolla F. and few number of Paederusalferii (Koch ) and true spider. Theresults revealed that Orius spp. had three peak in two season in autumnplantation, in first and third week of November, and third week of December inboth seasons respectively. Meanwhile there was two peaks in first week of Mayand third week of June in 2015 season of summer plantation. Chrysoperlacarnea had two peaks in autumn plantation during two seasons, third week ofNovember, second week in December in 2014 and fourth week of November, thirdweek of December in 2015 respectively. Also two peaks in summer plantationduring 2015 season in first week of April and second week of June.

SURVEY OF SCALE INSECTS AND MEALYBUGS ON MANGO TREES AND ECOLOGICAL STUDIES OF INSULASPIS PALLIDULA (GREEN) AT GIZA GOVERNORATE

asurvey of scale insects and mealybugs on mango trees (Mangifera indica L.) was carried out in a private mango orchard at El-Saff, Giza Governorate, during two successive years 2014 and 2015. The infestation of mango trees with scale insects and mealybugs was determined. The results indicated that, the mango trees were infested by 12 species of scale insects and mealybugs belonging to four families: Diaspididae, Coccidae, Monophlebidae and Pseudococcidae. From the twice monthly collection, the white mealybug, Icerya seychellarum (Westwod) was the most dangerous and abundant of the collected species followed by Insulaspis pallidula (Green) then Kilifia acuminata (Signoret) and Hemiberlesia lataniae (Signoret). The Maskell scale insect, I. pallidula was selected for further ecological studies on four mango cultivars. The selected four mango cultivars are not equally susceptible to I. pallidula infestation. Hendi mango trees cultivar (cv.) were heavily infested and severely damaged, while trees of Fagrikalan cv. are the lowest infestation with I. pallidula. However, the susceptibility levels of mango cultivars to I. pallidula could be arranged in descending order as follows: Hendi >Alphonso-Naser > Dabsha > Fagrikalan. Population of I. pallidula recorded three generations and three activity peaks per year. In the first year of study three peaks of infestation were recorded in 1st-April, mid-July and 1st October, while in the second year 2015, these peaks were recorded during mid-April, mid-August and 1st November. The calculated infestation rates of I. pallidula were high in spring, summer and autumn months, whereas, relatively low rate of infestation were recorded with winter months in both years.

Host-plant variety and not climate determines the establishment and performance of Aceria lantanae (Eriophyidae), a biological control agent of Lantana camara in South Africa.

The flower-galling mite Aceria lantanae (Cook) (Trombidiformes: Eriophyidae) was released for the biological control of Lantana camara L. (Verbenaceae) in South Africa in 2007, but has displayed variable and patchy establishment throughout the weed's range. Surveys were undertaken in 2013-2014, both seasonally and during the mite's peak infestation periods, to determine the influence of climatic factors on its performance. Although there were seasonal differences in the percentages of mite-infested inflorescences, these did not differ significantly between altitudinal zones. There were also no significant relationships between the percentages of mite-infested inflorescences and either of annual rainfall, temperature or relative humidity. A field inoculation trial revealed significant differences between 10 common South African L. camara varieties in their susceptibility to A. lantanae. Only three varieties displayed appreciable susceptibility (50-61% of inflorescences infested), whereas six displayed only slight to moderate susceptibility (8-21%) and one displayed a lack of susceptibility (no infestation). These data support the contention that differential varietal susceptibility and not climate is responsible for the variable performance of A. lantanae on L. camara in South Africa. Complementing the current biotype of A. lantanae, originally sourced from Florida (USA), with other biotypes from different L. camara genotypes in Central and South America could increase the mite's impact on the weed.

Analytic Approximation of Invasion Wave Amplitude Predicts Severity of Insect Outbreaks

Outbreaks of phytophagous forest insects are largely driven by host demographics and spatial effects of dispersal. We develop a structured integrodifference equation (IDE) outbreak model that tracks the demographics of sedentary hosts under insect infestation pressure. The model is appropriate for a spectrum of pests attacking the later age classes of long-lived hosts, including mountain pine beetle (MPB), spruce budworm, and spruce beetle, which, among them are responsible for more forest damage than fire. The model generates a train of periodic waves of infestation. We approximate the IDE with a partial differential equation and search for traveling wave solutions. The resulting ordinary differential equation predicts the shape of an outbreak wave profile and peak infestation as functions of wavefront speed, which can be calculated analytically. This culminates in the derivation of an explicit approximation of invasion wave amplitude based on net reproductive rate of the infesting insect and its host searching efficiency. Results are compared with observations taken during a recent MPB outbreak in the northern US Rocky Mountains.

The effect of northern fowl mite (Ornithonyssus sylviarum) infestation on hen physiology, physical condition, and egg quality

The northern fowl mite (NFM), Ornithonyssus sylviarum, is the most common ectoparasite of laying hens in North America. Infestation can cause a reduction in egg production, egg weights, and feed conversion efficiency. However, there is a lack of information on the effects of NFM on hen physiology, physical condition, and egg quality. Singly caged beak-trimmed White Leghorn hens (N = 32) were infested with mites at 25 wk of age. The condition of each hen was assessed at wk 0 (infestation) and wk 5 and 7 post-infestation to determine comb temperatures and feather, skin, and comb condition. Heterophil-lymphocyte (H/L) ratios and body weight (BW) were evaluated at wk 0 and wk 1, 3, 5, and 7 post-infestation. Egg weight, egg specific gravity, yolk color, Haugh unit (HU), and eggshell thickness were determined prior to infestation (wk −1) and at 1, 3, 5, and 7 wk post-infestation. The H/L ratio (P < 0.0001), HU (P < 0.0001), and egg specific gravity (P = 0.001) were lowest, and the egg yolk color was lightest (P = 0.087) at wk 5, the peak of infestation. At wk 5 and 7, more than 65% of the hens had red skin and more than 75% had scabs on the vent; in addition more than 84% had grey-black vent feathers. There were no effects of infestation on comb color, comb temperature, feather cover, BW, or eggshell thickness. It was concluded that infestation with NFM has negative effects on interior egg quality and hen integument. A decrease in H/L ratio was also observed at the peak of infestation. However, the effects of NFM on the immune system are unclear, and H/L ratio might not be a good stress measure in hens highly infested with NFM.

Control of Haematobia irritans in the Minas Gerais Semiarid

Background: Beef cattle is considered to be one of the most important economic activities, however, it presents problems in the production chain such as the occurrence of parasites that reduce the growth, performance, productivity and may cause mortalities occasionally. The chemical control is the most used alternative to reduce ectoparasites. Nevertheless, inappropriate management of insecticides has contributed to the selection of population resistant to the products available on the market. This paper aimed to evaluate the practices of management and the application of insecticides used to control horn flies in farms of dairy cattle in the North of the state of Minas Gerais.Materials, Methods &amp; Results: It was visited 62 rural properties, which produce milk. Semi-structured questionnaires were applied in order to obtain information on the characteristics of the properties (location, size and type of the cattle), on the knowledge about the epidemiology of the horn flies, and on the practices adopted to the control of those parasites. The practices adopted include the moment of application of the insecticides, frequency of the cattle treatment, used products, method of application, number of animals treated, and choice and substitution criteria of insecticides. The data collected were tabulated in contingency tables, and they were analyzed using the chi-square test, considering a significance of 5%. The racial composition of the cattle in the farms was mainly mixed-race of unknown origin, representing 77% of the animals evaluated. In this research, it was reported a greater incidence of horn flies infestation on adult beef herd, and 23.6% of the producers reported occurrences of infestation in the whole herd, not differing by categories. The infestation peaks of the fly occurred from November to March. It was also found a greater frequency of pyrethroid use in the region (P &lt; 0.001), where 43.1% of the producers used associations of pyrethroid or organophosphate to control the flies, high efficiency being reported. From the properties assessed, 92% presented inadequacy in the practices of control of horn flies, for instance, the lack of using cattle manure tank, the accumulation of open waste, the lack of rotation of insecticides, which can favor the selection of resistant flies.Discussion: In this paper, it was reported 77.19% of predominance of Haematobia irritans infestation from November to March mainly in animals with a higher percentage of European or mixed-race genetics. Such results corroborate with the literature, because it was verified the influence of race and hair color in the level of infestation in the animals, although, in the same race, each individual presents different susceptibilities. Taurine beef cattle are more susceptible to infestation by horn flies than zebu cattle. Thus, the lower the proportion of zebu cattle genetics in the herd, the greater the infestation. Taurine beef cattle are more infested because shows a greater number of sebaceous glands and greater concentration of testosterone being attractive before the calves castrated, cows, and after, young animals. Cypermethrin was predominant in most part of the commercial insecticides used in the properties to control this ectoparasite, which could be justified by the large number of products available on the market with such compound in the formulations. The high efficiency of the associations of the insecticides reported by the producers could justify itself by the presence of active ingredients with different mechanisms of action. However, the limitation on the use of these associations is that not always the chemical compounds contained in the drug act simultaneously, being able to favor the selection of parasites resistant to different insecticides present in these formulations.