Showing papers on "Infestation published in 1980"

Parasitism and ecological relationships among deep-sea benthic fishes

Abstract: We have studied the metazoan parasite fauna of 52 species of deep-living benthic fishes from depths of 53 to 5000m off the New York Bight (39–49°N; 70–72°W). 17144 parasites were recovered from 1712 fishes. The infestation rate was 80%, with an average of 12.5 worms per host. Percentage occurrence by group among all fishes was Monogenea 12.9%, Digenea 48%, Cestoda 22.1%, Nematoda 54.5%, Acanthocephala 3.8%, and Copepoda 4.5%. Differing composition of the parasite fauna in different fish species reflects differences in diet. Specialized feeders are rather distinct; generalized feeders, which predominate, show overlaps in parasite fauna. In individual species, changes in diet with growth are reflected in changes in the parasite fauna. Infestation rate is directly related to abundance of the free-living fauna; hence, fish from within the submarine canyon are more heavily infested than those living without. Although it contains fewer families and genera than shallow faunas, the deep-sea parasite fauna is not extremely unusual in terms of its abundance, diversity, or host specificity. At the greatest depths, parasite abundance and diversity dramatically decline.

European Corn Borer: Yield Losses in Relation to Hybrid and Stage of Corn Development

Abstract: Losses in yield due to damage by Ostrinia nubilalis (Hubner) at different stages of plant development and different levels of infestation were ascertained for 4 corn hybrids, Zea mays L., commonly grown in the Midwest. Yield losses resulted primarily from physiological damage due to the corn borer infestation rather than losses due to unharvestable ears. During the whorl stage (stage 2) of plant development, yield losses per unit of infestation were greater for the susceptible, long-season hybrid than for the mid-season hybrid with an intermediate level of resistance to corn borer leaf feeding. However, the yield potential of the long-season hybrid, especially B73 × Mo 17, was great enough to compensate for the greater loss. During the pretassel (stage 4) and pollen-shedding (stage 5) stages, losses tended to be greater for the long-season than for the mid-season hybrids. B37 × Oh 43 was more tolerant to damage than the other hybrids as expressed by yield loss during these stages. Physiological yield losses tended to be lower when an infestation was initiated in stage 6 (kernels blistered), but losses due to unharvestable ears were greater.

Relationship of Incidence of Seedborne Xanthomonas campestris to Black Rot of Crucifers

Abstract: SCHAAD, N. W., W. R. SITTERLY, and H. HUMAYDAN. 1980. Relationship of incidence of seedborne Xanthomonas campestris to black rot of crucifers. Plant Disease 64:91-92. The relation of amounts of seedborne Xanthomonas campestris, determined by laboratory assays, to the incidence of black rot in the field was determined. Seeds infested naturally with X. campestris were mixed with healthy seeds, assayed for X. campestris, and seeded in a field in South Carolina. The pathogen was detected in laboratory assays in two of four samples with 0.01% infestation, whereas black rot developed in the field in three of four such samples. In 1976, field plots that initially contained 0.03, 0.07, and 0.14% infected plants resulted in high incidences of black rot. In 1977, the incidences of black rot were high in plots that initially contained 0.05% infected plants but not in plots that initially contained 0.01% infected plants. We conclude that laboratory assays can be used to detect levels of seed infestation that may or may not result in a high incidence of black rot in the field. Xanthomonas campestris is seedborne (3,5,7), and infested seed is an important source of inoculum (2,4,8,14,15). Several methods have been described for detecting the pathogen in or on seeds (1,9,11,13), but the number of infested seeds needed to initiate black rot in the field has not been determined. This information is essential to establish a minimum allowable percentage of seed infestation. This study was designed to determine the relationship of amounts of seed infestation to disease incidence in the field.

Plant response to stress induced by artificial infestations of western corn rootworm.

Abstract: In a uniform infestation with eggs of the western corn rootworm, Diabrotica virgifera LeConte, the root damage rating was found to be a more sensitive measurement of root worm damage than vertical pulling weight, root lodging and goosenecking, plant stunting, or adult recovery. Also, root damage ratings, unlike vertical pulling weight, were independent of the size of the root system. Adult insects began to emerge from the artificial infestation at the same time as from a nearby natural infestation. The maximum damage the test corn hybrids were able to sustain was reached at ca. 1200 eggs/30.5 cm of row (row-ft); any increase beyond this level resulted in a decrease in the number of adults recovered. The relationship established between yield reduction and a known number of corn rootworms showed that even with almost ideal growing conditions, as few as 100 eggs/30.5 cm of row caused a highly significant reduction.

European Corn Borer: Yield Losses and Damage Resulting from a Simulated Natural Infestation

Abstract: A method of producing a Poisson distribution of egg masses over plants and time was developed for artificial infestation of field corn that simulates natural oviposition by Ostrinia nubilalis (Hubner). Data were collected for 2 yr on the length of cavities (cm) and subsequent yield losses by using different levels of infestation in a Poisson distribution. Yield losses and damage were greater during stage 5 (pollen-shedding) than during stage 2 (early whorl) of plant development. Statistically, significant correlations were obtained between shelled weight and ear weight (0.986), shelled weight and total cavities (-0.323 and -0.112), ear weight and total cavities (-0.321), shelled weight and entrance holes (-0.075), and entrance holes and total cavities (0.906).

Infestation by Tunga penetrans

Abstract: • Infestation by the flea Tunga penetrans , although quite prevalent in Central America, South America, and Africa, is rarely recognized or reported in North America. This report describes a case of tungiasis occurring in a New York resident who acquired the disease in Africa. The patient manifested characteristic lesions of white papules with central black pits on the dorsa of her toes. Treatment consisted of removal of the offending parasites. ( Arch Dermatol 116:80-81, 1980)

A Procedure for Artificially Infesting Field Plots with Corn Rootworm Eggs

Abstract: A procedure was developed to quantitatively and uniformily distribute eggs of corn rootworm, Diabrotica spp., in large-scale field plots. Eggs were obtained from field-collected beetles, quantitatively suspended in an agar solution, and dispensed at known rates using a mechanical-pressurized system. The artificial infestations produced are very uniform;; root damage ratings were highly correlated with rate of infestation. The technique is applicable to other soil insects where uniformity of natural infestations is a problem.

Nectria infection of beech bark in relation to infestation by Cryptococcus fagisuga Lindiger

Abstract: Wound inoculation with an isolate of Nectria coccinea produced cankers in beech bark, the size of which was related to the severity of C. fagisuga infestation. Lesions were absent in most cases following surface inoculation of bark (non wounding) with very localised but heavy infestation. Inhibition of the host's response to fungal invasion is considered to be an important part of the insect's role in producing beech bark disease.

Ctenocephalides canis infestation of sheep and goats.

Abstract: An investigation into infestation of sheep and goats with Ctenocephalides canis showed that while only a light degree of infestation was observed in the affected goats, light to heavy degrees of infestation occurred in sheep. In both species a light degree of infestation had no marked effect on the packed cell volume (PCV). Both medium and heavy degrees of infestation resulted in a significant lowering of the PCV of the affected sheep.

Populations, microhabitat preference and effects of infestation of two species of Orthohalarachne (Halarachnidae: Acarina) in the northern fur seal.

Abstract: All of 116 northern fur seals examined, except black pups (up to 3 months old), had nasal mites, Orthohalarachne attenuata and O. diminuata, with the mean density of 1,808 mites per subadult male, 435 per adult female, 251 per silver pup, and 21.5 per black pup. Only 63% of black pups examined were infested with both mites. Larvae represented as much as 99% of the total mite population (total samples), and the females of both species of Orthohalarachne accounted for more than 90% of the total population of adult mites. The O. attenuata adults inhabited the nasopharynx and O. diminuata adults were found primarily in the lungs. Larvae of both species occupied the mucus-filled turbinates. The heavy infestation with these mites appeared to result in impairment of respiration in fur seals, and could also cause lesions in the lungs and secondary alveolar emphysems, predispose to more serious diseases, or even kill the host animal.

Interactions between the coccid, Icerya seychellarum (Westw.), and its host tree species on Aldabra Atoll : I. Euphorbia pyrifolia Lam.

Abstract: (i) The growth of ca. 100 individuals of a small deciduous tree Euphorbia pyrifolia, of different ages and edaphic regimes, and with different levels of infestation by the coccid Icerya seychellarum, has been studied on Aldabra Atoll over two years (1976-1978). Infestation on leaves ranged between 0 and 1.3 mg dry weight of coccids cm-2 of total leaf area. (ii) Field observations and an experiment in which coccids were "seeded" on to transplanted trees showed a preference of coccids to feed on senescing leaves rather than on green leaves. Deterrence by green leaves is discussed. (iii) Highest infestations developed on trees which produced the most senescent leaf material early in the wet season. The rate of leaf production on the heaviest infested trees was 36% of that on lightly infested trees. (iv) The level of coccid infestation did not depend on the concentration of soluble nitrogen in senescing leaves but on the total amount of nitrogen exported. The level of soluble nitrogen in green leaves was reduced in heavily infested leaf clusters. (v) Experimental clearance of coccids by insecticide showed that 0.7 mg cm-2 of coccids reduced the rate of leaf growth by 52%. This corresponded closely to the effect of similar levels of coccids in the field. (vi) Leaf infestation was positively correlated with the percentage of dead apices per tree and negatively correlated with the degree of branch extension. (vii) It was concluded that leaf phenology influenced the development of coccid populations and that coccids significantly reduced plant growth.

Field Selection of Sweet Potato Lines and Cultivars for Resistance to the Sweetpotato Weevil

Abstract: Resistance of 79 sweet potato lines to Cylas formicarius elegantulus (Summers) in artificially infested fields was studied. The criteria used in evaluating resistance levels were percentage of hills with infested roots, number of adult weevils emerging from roots, percentage of crowns infested, and crown index based on the severity of the infestation. Five lines were found to be resistant for all criteria at both Savannah, GA, and Yoakum, TX. An additional 26 lines were found to be resistant at Savannah, and 17 of those same lines were resistant for one or more of the criteria at Yoakum. Infestation levels were more severe in Yoakum, which may explain the apparent increase in susceptibility.

Disruption of southern pine beetle infestations with frontalure.

Abstract: Frontalure contained emerging broods of southern pine beetle within active infestations when used as a bait on all host and non-host trees within the infestations. The attractant was successful in redistributing populations of the southern pine beetle and the predator, Thanasimus dubius (F.), within the infestations. The attractant also prevented new trees from being mass attacked and contained adult beetles within the infestation.

Observations on Hilda patruelis Stal. (Homoptera: Tettigometridae) and its infestation of the groundnut crop in Rhodesia.

Abstract: Infestation by Hilda patruelis (Stal) periodically damages groundnut crops in Zimbabwe and is usually discovered too late for the successful application of control measures. Observations on crop infestation and the appearance of damage symptoms are discussed. A relation between reported infestation and droughts is indicated. Laboratory and field observations on the biology of the tettigometrid are reported. One generation was completed in 37 days at 23 deg C; there were 5 nymphal instars, and all stages were gregarious. Breeding occurred continuously on subterranean and aerial parts of numerous species of food-plants. There were indications of a dispersal flight at the end of the dry season and when food-plants became unsuitable through senescence, disease or water stress. The encyrtid Psyllechthrus oophagus Ghesq. (the only known parasite of H. patruelis in Zimbabwe) was active throughout the year and appeared to parasitise eggs on both subterranean and aerial sites. No common or specific predators were recorded, but adults of the coccinellid Hyperaspis were observed feeding on the eggs of Hilda patruelis. Ants, including Pheidole megacephala (F.), Crematogaster castanea F. Sm. and Camponotus sp., were invariably in attendance and are probably essential for the maintenance of root-zone infestations. An annual cycle for H. patruelis is suggested

Infestation of the coccid, Icerya seychellarum (Westw.), on the mangrove Avicennia marina (forsk.) vierh. on Aldabra Atoll, with special reference to tree age.

Abstract: The level of infestation by the coccid Icerya seychellarum on the mangrove tree Avicennia marina was measured on a stand of ca. 670 trees on Aldabra Atoll in 1978. Trees varied in basal trunk diameter (btd) between 3 and 30 cm. Leaf infestation increased significantly with increasing btd-class and young trees (btd 3.0–4.5 cm) had a mean infestation of 0.3 mg coccids g-1 leaf whilst the heaviest infested trees (btd 13.0–14.5 cm) supported 7.6 mg g-1. Leaf and shoot growth were not correlated with coccid infestation but shoot vigour (leaf to green shoot ratio) declined significantly with increasing btd-class (or age). Leaves of older, heavily infested trees did not differ from those of young uninfested trees in the concentration of soluble or total nitrogen of in four other leaf elements, indicating that nutrient status was not an important factor in infestation. Field observations showed that many of the older trees were subjected to poor drainage which may have increased their susceptibility to attack and also that on the leaves of young trees salt secretion presented an effective barrier to the establishment of coccids. re19800212

The head louse in Italy : an epidemiological study among schoolchildren

Abstract: WIDESPREAD head louse infestation (Pediculus humanus capitis De Geer) among schoolchildren has been recorded in Italy. An investigation was carried out to evaluate the prevalence and to identify the factors which contribute to the spread of the ediculosis. In this study (March 23 to April 21,1978) 1,988 pupils grouped proportionally to the numerical division in three types of schools were examined. The prevalence of pediculosis in the school population studied was 9.6%; no significant differences were detected among the three types of schools examined. Distribution of cases by degree of infestation and hair length was also studied. Distribution of para sitosis seems not to depend on the number of pupils in a class, while it was influenced by the size of the family. In the Elementary and Primary schools prevalence among females was twice that of males, while no relationship was detected between infestation and sex in the Nursery schools.

The pattern of infestation of the beach-hopper amphipod Orchestoidea corniculata , by a parasitic mite

Abstract: The frequency distribution of an ectoparasitic mite, Gammaridacarus orchestoideae, on its amphipod host, Orchestoidea corniculata, was found to differ significantly from random for all monthly samples taken between October 1977 and October 1978. The negative binomial distribution provided a good fit to these aggregated distributions. The degree of aggregation was negatively correlated with the prevalence of infestation. Prevalence and intensity were highest in the winter, when the degree of aggregation was lowest, and vice-versa in the late summer. This seasonal pattern can be explained through changes in size and density of the host population, which are associated with changes in the size of the habitat of the hosts. Within each sample the host population was highly heterogeneous with regard to infestation by mites. Females carried heavier loads of mites than did males. Both prevalence and intensity were low in the post-moult stages of the moult cycle. Reproductive females showed lower prevalence and intensity of infestation than did either non-reproductive females or males. Analysis of the regression analysis of ‘mean crowding’ on mean density also indicated that aggregation stemmed from a non-random distribution of individual parasites, rather than from clumping of the infective stages of the parasite. Heterogeneity of the host population is suggested as an important cause of the aggregated distribution of the parasite population.

The distribution and abundance of the coccid leery a seychellarum Westw. on Aldabra atoll

Abstract: . Icerya seychellarum, a polyphagous phloem feeding coccid, was discovered on Aldabra atoll in 1968. It was not recorded by early expeditions to the atoll, and is probably a recent introduction. Its infestation rose to a peak density around 1975, and thereafter declined, as revealed by a comparison of fifty-one woody taxa common to three surveys. In 1975, twenty-one taxa were ‘heavily’ infested and twenty-one ‘lightly’/‘moderately’ infested. By the end of 1978, no taxa remained ‘heavily’ infested and thirty-seven were ‘lightly’/‘moderately’ infested. The state of vegetation showed negligible change between the 1976/77 and 1978 surveys, refuting an earlier prediction that it would be substantially modified by the Icerya infestation. The subsequent decline in infestation cannot here be attributed to the development of natural enemies. Possible reasons, which are discussed, include changes in the quality of the coccid or its host.

Comparison of Parasitism and Infestation of Nantucket Pine Tip Moth in Different Aged Stands of Loblolly Pine

Abstract: Colonizing, intermediate, and older aged parasite communities remained similar in differing aged stands. Percent parasitism roughly corresponded to population reduction in the following generation of tip moth. Lixophaga mediocris , Campoplex frustranae and Eurytoma pini were the dominant parasites. Trees ca. 2 m or with 4 distinct whorls have a lower rate of attack by tip moth. Mechanism for the lower attack rate are suggested.

Comparison of methods of infesting whorl-stage corn with fall armyworm larvae.

Abstract: In tests comparing the effectiveness of 3 methods of infesting whorl-stage corn with Spodoptera frugiperda (J. E. Smith), the modified “Bazooka” proved to be the best method based on resultant visual damage ratings. The “Bazooka” is a device made primarily of Plexiglas, and larvae of fall armyworms can be mechanically dispensed into whorls of corn plants. It was easier and more efficient than using the camel-hair brush or pinning egg masses into the whorl. Infestation of every plant per plot produced higher leaf-damage ratings than infestation of either every 2nd or every 3rd plant/plot. Differences in leafdamage ratings were detected at infestation rates of 10, 20 and 40 larvae/plant. Rates of 20 or 40 larvae/plant should be used to insure adequate infestations at the 10–12 leaf stage.