Infestation

About: Infestation is a research topic. Over the lifetime, 8308 publications have been published within this topic receiving 82305 citations.

Evaluation of Pochonia chlamydosporia and Purpureocillium lilacinum for Suppression of Meloidogyne enterolobii on Tomato and Banana.

Abstract: Meloidogyne enterolobii is one of the most important root-knot nematode in tropical regions, due to its ability to overcome resistance mechanisms of a number of host plants. The lack of new and safe active ingredients against this nematode has restricted control alternatives for growers. Egg-parasitic fungi have been considered as potential candidates for the development of bionematicides. In tissue culture plates, Pochonia chlamydosporia (var. catenulata and chlamydosporia) and Purpureocillium lilacinum strains were screened for their ability to infect eggs of the root-knot nematode M. enterolobii on water-agar surfaces. Reduction in the hatching of J2 varied from 13% to 84%, depending on strain. The more efficacious strains reduced hatchability of J2 by 57% to 84% when compared to untreated eggs, but average reductions were only 37% to 55% when the same strains were applied to egg masses. Combinations of fungal isolates (one of each species) did not increase the control efficacy in vitro. In experiments in which 10,000 nematode eggs were inoculated per plant, reductions in the number of eggs after 12 months were seen in three of four treatments in banana plants, reaching 34% for P. chlamydosporia var. catenulata. No significant reductions were seen in tomato plants after 3 mon. In another experiment with tomato plants using either P. chlamydosporia var. catenulata or P. lilacinum, the number of eggs was reduced by 34% and 44%, respectively, when initial infestation level was low (500 nematode eggs per plant), but tested strains were not effective under a moderate infestation level (5,000 eggs per plant). Under all infestation levels tested in this work, gall and egg mass indexes (MI) did not differ from the untreated controls, bringing concerns related to the practical adoption of this control strategy by farmers. In our opinion, if the fungi P. chlamydosporia and P. lilacinum are to be used as biocontrol tools toward M. entorolobii, they should focus on agricultural settings with low soil infestation levels and within an IPM approach.

Observations on infestations of undipped cattle of British breeds with the cattle tick, Boophilus microplus (Canestrini).

Abstract: A small herd of cattle infested with the cattle tick, Boophilus microplus (Canestrini) was kept in a previously unstocked paddock for 11 months without treatment for tick infestation. Frequent examinations showed that widely differing numbers of ticks developed on the cattle. The "tick resistance" of one animal, which showed no adult ticks during the summer months, could only be accounted for by mortality of the larvae and nymphs on the animal, since as many larvae were seen on selected small areas of this animal as on some animals carrying many adult ticks. The animals grazed together and thus would encounter similar numbers of tick larvae. The degree of susceptibility to adult tick infestation showed negligible correlation with skin thickness measurements and was not related to coat length. Larvae reappeared on the cattle 6 weeks after the first stocking of the paddock in March. The animals became almost free of ticks for 2 weeks in August. Although larvae were most numerous in November-December, they gave rise to fewer adults than the earlier wave of larvae in September- October. Some of the cattle suffered from "tick-worry'' in October, but thereafter their condition improved without treatment.

Patterns of Abies fraseri regeneration in a Great Smoky Mountains spruce-fir forest

Abstract: PAULEY, E. F. AND E. E. C. CLEBSCH (Graduate Program in Ecology, University of Tennessee, Knoxville, TN 37996-1610. Pattems of Abiesfraseri regeneration in a Great Smoky Mountains spruce-fir forest. Bull. Torrey Bot. Club 117: 375-381. 1990.-Abiesfraseri (Pursh) Poir. (Fraser fir) has incurred high mortality from infestation by Adelgespiceae Ratz. (balsam woolly adelgid). Vegetational changes in the spruce-fir forest since Adelges infestation have included a large increase in the density of Rubus canadensis L. (thomless blackberry). Size and age structures, microsite and aspect distributions, and growth of Abies seedlings (stems < 137 cm tall) were quantified on Mt. Collins, Great Smoky Mountains National Park in 1988 to determine pattems of co-occurrence between Abies seedlings and Rubus. The majority (87%) of seedlings were c25 cm tall, and most (62%) were at least five years old. No germinal (< 1 year old) Abies were found. Dead wood substrates and bryophyte-covered surfaces both supported more seedlings than expected by chance. Seedling growth trends showed a recent increase in terminal shoot length and recent decreases in lateral shoot lengths, suggesting a combination of normal growth pattems and recovery from Adelges infestation. Effects of Adelges infestation were noted for 26% of all seedlings and were more frequent among older seedlings. Density of Abies seedlings was low at high Rubus densities, but seedling shoot growth showed no clear relationship with Rubus density. Rubus appeared to interfere with establishment or survival of Abies seedlings but not with annual growth.

The Seasonal and Annual Incidence of the Sheep Tick, Ixodes ricinus , in Britain

Abstract: 1. Serial examinations of the degree of infestation of thirty-five flocks during a nine-year period in Argyllshire, Perthshire, Selkirk and Northumberland, showed that tick incidence is greatest in spring and decreases markedly in early summer. Evidence is given of a similar periodicity in North Wales.2. Evidence is given of the occurrence of a slight recrudescence of activity in autumn, and of the almost complete absence of activity in winter.3. The spring curve of activity terminated in early May in Argyllshire, in the middle of May in Perthshire, and towards the end of May in the Borders and Northumberland.4. The estimation of the relative annual infestation, e.g., in relation to the question of spread or increase of ticks, by single annual counts is shown to be quite unreliable.5. No evidence was obtained of an increase in density of ticks in any area during the period of observation.6. The seasonal periodicity in activity was found to bear no relation to the density of stocking of the ground by sheep.7. The seasonal activity of ticks in Argyllshire, Perthshire, Selkirkshire and Northumberland, was found to be related to the air temperature, expressed as the weekly average of maximum temperatures. The limits of the air-temperature range corresponding to active tick infestation are 45°F. and 60°F. (average weekly maximum).8. The curve of tick infestation during 1937 on a moor in North-east Scotland was found to differ markedly from the normal, and the possible explanations of the discrepancy are discussed.