Showing papers on "Infestation published in 1977"

Parasites of domestic and wild animals in South Africa. I. Oestrus ovis in sheep.

Abstract: Separate groups of 3 oestrid-free lambs were exposed to infestation on irrigated pasture for periods of approximalely 33 days each over30 months, and on dry-land pasture for approxomately 42 days over a period of 18 months. With some exceptions, the lambs slaughtered from October-June were found to be infested with Oestrus ovis while, with one exception, those slaughtered from July-September were free. A minimum of 4 sheeps' heads, obtained weekly over 24 months from the Pretoria Municipal Abattoir, was examined for infestation. Of a total of 542 heads examined, 73,4% were infested, having a mean burden of 15,2 larvae. Mean larval burdens were slightly greater in hornless than in horned sheep in Dorper-type than in Merino-type sheep, and in lambs than in sheep with 2 or more permanent incisors. The largest larval burdens were recovered from sheep slaughtered during May and June and the smallest during September and October. The greatest number of 1st instar larvae were recovered during May and June and the smallest during September, but those recovered during the latter month were the largest. With one exception, mature larvae which pupated after 21 March or before 16 August failed to hatch as viable flies. Those which pupated after 16 August hatched as flies after a pupal stage of approximately 50 days and the first flies to hatch were invariably recovered during the first 2 weeks of October. The pupal stage decreased to approximately 25 days during December and January and increased again to approximately 50 days for flies hatching during May. No flies hatched between 18 May and 1 Cctober. The following life cycle ofr Oestrus ovis is suggested: sheep are repeatedly infested from October-June; thereafter infestation survives in the sheeps' heads until August, mainly as 1st instar larvae, then as pupae and larvae until fresh infestation takes place during October.

Classification of canopy, stem, crown status and climber infestation in natural tropical forest in nigeria

Abstract: SUMMARY Several investigations have shown that the growth increment of tropical tree species is strongly correlated with initial basal area. This investigation examined whether prediction of basal area increment could be improved by initially classifying trees according to canopy status, stem or'crown form, or degree of climber infestation. Classification according to stem form improved the prediction of tree basal area increment of Khaya ivorensis; canopy status also had a large effect but it was not significant. Classification according to climber infestation improved the prediction for Sterculia rhinopetala; greater infestation was associated with a reduction of the regression constant. The gain in accuracy was small in all cases. The ecological and silvicultural implications of these results are discussed. The correlations between successive increments did not substantially diminish over the 14 year period of observations.

‘Banker’ Plant Production of Encarsia formosa Gahan and its Use in the Control of Glasshouse Whitefly on Tomatoes

Abstract: SUMMARY ‘Banker’ plants on which a whitefly/parasite interaction had been well established successfully controlled glasshouse whitefly (Trialeurodes vaporariorum (Westw.)) when introduced on to a commercial tomato crop at rates of 89 or 50 plants per hectare. Each plant produced about 8000 parasites over a minimum period of eight weeks and the presence of whiteflies and honeydew on these plants provided the adult parasites with a source of food during the early stages of the infestation. The principal advantages of the ‘banker’ system over existing methods in which parasites are introduced on detached leaf material are the ease of rearing the parasites and the need for only a single introduction to the glasshouse.

Effects of Tarnished Plant Bug, (Lygus lineolaris), Infestation on Presquaring Cotton (Gossypium hirsutum)

Abstract: Tarnished plant bug ( Lygus lineolaris Palisot de Beauvois) infestation of presquaring cotton ( Gossypium hirsutum L.) resulted in plants with aborted terminals (98%), swollen nodes, shortened internodes, deformed leaves, and excessive branching of the main stem. Fruiting and boll maturity were delayed. Dry weight and overall plant height were reduced. There was no interaction between cultivars or presquare stages in response to plant bug infestation.

Parasites of domestic and wild animals in South Africa. IV. Helminths in sheep on irrigated pasture on the Transvall Highveld.

Abstract: The seasonal incidence of helminth infestation in sheep on newly established irrigated pastures was determined by the slaughter of pairs of tracer lambs exposed for periods of approximately 33 days from October 1968--July 1970 and of sets of 3 lambs from March 1971--May 1973. It took several months for the infestation to become established on the pasture, but thereafter, of the various species present; Haemonchus contortus was most prevalent. In general, peak burdens of this species were recovered from January--May or June, while marked inhibition of larval development was evident from April--August. Ostertagia circumcinta usually occurred in increased numbers from April--October, and larval development was inhibited during July and August. Although the sizes of the burdens varied considerably from year to year, Trichostrongylus spp. were present mainly from April--August. Oesophagostomum columbianum, although present in the lambs slaughtered during the first 5 months of the survey, virtually disappeared until May 1971. After this it reappeared in small numbers in nearly all the sheep, reaching peak burdens during April and May 1972, and May 1973. Moniezia expansa were generally recovered from the lambs slaughtered from November--May.

Paralysis of calves by the tick, Ixodes Holocyclus.

Abstract: Adult female Ixodes holocyclus were collected from the field at Fig Tree Pocket, a Brisbane suburb, at Tamborine Mountain, Queensland and at Lismore, New South Wales, in November 1974. Females were also reared from engorged nymphs collected off bandicoots from Tamborine Mountain July 1974 and 1975. In November 1974 unexposed 2-3 week old British breed calves, weighing between 26 and 46 kg were infested with 2,4,8 or 10 ticks. Neither 2 nor 4 females per calf caused paralysis. A challenge of 8 to 10 females induced paralysis 6 to 9 days after infestation by which time most ticks had engorged. There was little difference between ticks from different geographic localities. The site of attachment had no influence on tick toxicity. In September 1975, 2-3 week old British breed and Sahiwal x Jersey calves were infested with female ticks which had moulted 2-4 weeks prior to infestation. All but one calf with 10 ticks and all calves with 4 ticks became paralysed 8 to 13 days after infestation. At the time of paralysis only 1 of the 86 ticks had engorged and the remainder were small (30 to 50 mg). The greater toxicity of the latter ticks may have been due to the different treatment of ticks prior to infestation or to variations in the production of toxin associated with slow feeding. Four of 7 paralysed calves were saved using canine antitick serum.

Effectiveness of controlled-release formulations of mch for preventing douglas-fir beetle (coleoptera: scolytidae) infestation in felled trees

Abstract: Five controlled-release granular formulations were developed that eluted 3-methyl-2-cyclohexen-1-one (MCH) in the laboratory at a rate ≥ 0.5µg/h for 60 days. Elution rate was determined by trapping gaseous radioactive MCH followed by scintillation counting. The inert components of these formulations consisted either of a wax-coated molecular sieve, polyethylene emulsion-coated ground corncob, or dimer acid polyamide beads. These formulations and a liquid standard were applied 9 May just prior to Douglas-fir beetle ( Dendroctonus pseudotsugae Hopk.) flight to plots containing single, freshly felled Douglas-fir ( Pseudotsuga menziesii var. glauca ) trees. Three months later, infestation by Douglas-fir beetle and other insects was evaluated. All treatments except coated corncobs and certain applications of the molecular sieve significantly reduced Douglas-fir beetle attacks. Douglas-fir beetle brood in three treatments was significantly less than in controls. Abundance of entomophagous insects was proportional to density of host beetle attacks. Douglas-fir beetle attack density was negatively correlated with degree of infestation by the scolytid Pseudohylesinus nebulosus (Lee).

Artificial Infestation of Corn with Western Corn Rootworm Eggs in Agar-Water

Abstract: The following 4 aspects of the efficacy of the wet method (suspension of eggs in agar-water) and the earlier dry method (mixture of eggs in dry fine soil) for infesting corn with eggs of Diabrotica vergifera LeConte were compared: homogeneity of mixtures; viability of eggs after extended periods in the mixtures; results of artificial field infestation of corn; and time requirement for preparing the mixtures. Results indicated that the agar-water method gave a much more homogeneous mixture, methods had no adverse effect on egg hatch when stored at 10°C for up to 30 days, there was no significant difference in mean numbers of corn rootworms per plant and mean root damage ratings between the wet and dry methods of field infestation of corn, and the wet method can be prepared in half of the time and would save much time.

The relationship between infestation by Mytilicola intestinalis, Steuer (Copepoda, Cyclopoidea) and the condition index of Mytilus edulis in southwest England

Abstract: Seasonal cycles in the condition index of Mytilus edulis from three sites in southwest England are described. These are analysed in relation to host length, stage of gonad development and parasite burden by linear regression analysis. An effect on the condition index due to the presence of Mytilicola intestinalis can be detected only in the sublittoral mussels in those few winter months when the mean intensity of infestation is over about 25 parasites per host. In all cases studied, the magnitude of the effect due to variation in host length, stage of gonad development, seasonal cycles and environmental factors is greater than that due to parasitism.

The distribution and abundance of adult grasshoppers (acrididae) in crops in alberta, 1918–1975

Abstract: Annual surveys of the adults show that outbreaks of grasshoppers in cultivated crops in Alberta have occurred in 32 of 58 years. Five outbreaks have occurred, lasting from 3 to 14 years, interspersed by periods of low infestation lasting from 3 to 9 years. Some control measures, however, were required every year even during periods of low infestation. The highest recorded adult populations occurred in 1933, 1936, and 1962, and the lowest in 1952 and 1969.During most periods with low populations, infestation were confined mainly to the area south of the Bow and South Saskatchewan rivers. When high populations occurred, the infested areas increased in size and extended north to the Battle River. The largest infested area covered 48,600 sq. miles and the smallest was 300 sq. miles.Two species of grasshoppers, Camnula pellucida (Scudder) and Melanoplus sanguinipes (Fabr.), generally predominated in separate regions. Melanoplus bivittatus (Say) predominated only during periods of low grasshopper infestation. Melanoplus packardii Scudder was restricted in its range and became noticeable when the grasshopper outbreaks were declining.

Variation in intestinal helminth infestation of the helmeted guineafowl

Abstract: Intestinal tracts from 206 helmeted guineafowl (Numida meleagris) shot during June and July of 1974 and 1975 from two discrete habitat types were examined for helminths. Six species (three cestodes, two nematodes and one acanthocephalan) were identified. Helminths were found in all but one of the tracts. Nematodes were found only in the caeci, cestodes and acanthocephalans in the intestinal lumen. Using a volumetric index of level of infestation, juvenile guineafowl had higher levels of infestation by cestodes and acanthocephalans than did adults. The highest levels of helminth infestation of adult guineafowl were found in specimens collected in July 1975. In savanna habitat, adults had higher levels of nematode infestation in June 1974 than in June 1975. In July 1975, adult guineafowl in riverine habitat had higher levels of helminth infestation than those in savanna habitat. In June 1975, in riverine habitat, adult males had higher levels of nematode infestation than females. High levels of infestation in juvenile guineafowl are presumed to be the result of a greater intake of intermediate hosts and a lower resistance to infection. High levels of infestation in adult guineafowl are attributed to an interaction between high population density and soil moisture content at the time of infection. None of the guineafowl showed any signs of gross pathological condition. Therefore observed infestation is presumed to be at a tolerable level

Effect of insect infestation on the chemical composition and protein efficiency ratio of the proteins of kaffir corn and green gram

Abstract: Sorghum (Sorghum vulgare) was infested with Sitophilus oryzae and green gram (Phaseolus radiatus) with Callosobruchus chinensis for 3 and 4.5 months, respectively. Final total uric acid contents were for Sorghum 90.6 and for green gram 213 mg/100 g. Lysine and threonine contents fell significantly with infestation. The protein efficiency ratio (PER) values of 3:1 and 1:1 blends of uninfested sorghum and green gram were 2.27 and 2.53 while that of sorghum alone was 1.30. The PER values of the blends after infestation were 1.70 and 1.89, respectively

Multiple Aphid Resistance in CUF-101 Alfalfa

Abstract: A new experimental alfalfa, CUF-101, has been successfully developed that is resistant to 3 species of aphids, Acyrthosiphon kondoi Shinji, the pea aphid, A. pisum (Harris), and the spotted alfalfa aphid. Therioaphis maculate (Buckton). In greenhouse tests, 70.3, 71.0, and 87.3% of CUF-101 seedlings survived infestation to 3 aphid species, respectively, compared with 70.3, 85.6, and 93.3% of the resistant checks.

Loss of yield in potato selections infested with potato leafhoppers

Abstract: The loss of yield resulting from infestation with potato leafhoppers,Empoasca fabae (Harris), was measured in a group of potato selections (Solatium tuberosum subsp.tuberosum). For 6 years in which 300 different clones were tested, the average loss of yield was 39%. The correlation over clones between level of infestation and percent hopperburn equaled 0.56; between level of infestation and loss of yield 0.36; and between percent hopperburn and loss of yield 0.41. Each coefficient is significant at P=0.01. Significant differences were found in levels of infestation and in percent hopperburn among the selections, but even those selections with the most resistant foliage had greatly reduced yields when infested. No selections were found that consistently produced a normal yield when infested with leafhoppers. The low level of infestation on the more resistant clones, however, may make chemical control at lower rates more effective.

Parasites of comestic and wild animals in South Africa. II. Oestrus ovis in goats.

Abstract: During a period of 13 months, 130 goats' heads, obtained form the Johannesburg Municipal Abattoir, were examined for infestation with Oestrus ovis. Investation was present in 73,8% of the heads and the mean burden comprised 4,4 larvae. Such a small nuber of larvae were present that no clear seasonal incidence pattern could be determined. Pupal periods could be as long as approximately 60 days for flies hatching during October and May and as short as approximately 24 days for those hatching from December-February. The findings are compared with those obtained from surveys in sheep in south africa.

Ectoparasites of the wild rabbit oryctolagus cuniculus (l.) in victoria: the occurrence of the mites leporacarus gibbus (pagenstecher) and cheyletiella parasitivorax (megnin) and the louse haemodipsus ventricosus (denny)

Abstract: Information on the infestation of wild rabbits by Leporacarus gibbus (Pagenstecher), Cheyletiella parasitivorax (Megnin) and Haemodipsus ventricosus (Denny) for Victoria is presented and discussed. Infestation rates were lowest in the dry north-west region of the state. In other regions most rabbits were infested but there was a wide range in infestation numbers in all regions.

Changes in O 2 , Co 2 and Microflora of Stored Wheat Induced by Weevils

Abstract: Changes in oxygen and carbon dioxide concentration and fungal infection were recorded in small wheat bulks initially infested with eggs of the rice weevil, Sitophilus oryzae (L.), and the granary weevil, S. granarius (L.). Gas chromatographic monitoring showed similar trends of O2 depletion and CO2 buildup for both species. The lowest O2 concentration (35.2 mg/liter, 2.8% by vol) and highest CO2 concentration (379 mg/liter, 21.7% by vol) were recorded at the bottom of the bins having 10% infestation of grain with S. oryzae . For both species relatively more adults, in relation to the total number of infested kernels present, emerged from a 5% infestation than from a 10% one. Emergence of S. oryzae , both at 5% and 10% infestation levels, was higher than that of S. granarius . The bottom layers of the grain were less viable and more infected with the storage fungi Aspergillus and Penicillium , than the top layers. Infection by field fungi was smaller at all levels.

The Incidence of Aphis fabae Scop. on Spring-sown Field Beans in South-east England and the Efficiency of Control Measures

Abstract: SUMMARY Surveys of crops of spring-sown field beans from 1966 to 1974 in the counties of Hampshire, Berkshire, Buckinghamshire and Oxfordshire showed that the incidence of Aphis fabae Scop, infestation varied from season to season and often between counties in the same year. The heaviest infestations occurred in 1967, 1972 and 1973 and the lightest infestation was in 1968 vvhen few winged aphids colonized headland plants. Estimates for 1972 and 1973 showed that treatment was economically worth while on most fields in these years. Phorate was the most frequently used insecticide and gave good control, although it was less effective in years in which there was a dry spring. Disulfoton and sprays of demeton-S-methyl and menazon also gave good control, although menazon was less effective as an eradicant spray after colonies of aphids had become established.

Field Cage Studies to Detennine Effects of Mexican Bean Beetle Resistance in Soybeans

Abstract: The effectiveness of resistance in the soybean cultivar ‘Shore’ in reducing feeding damage and yield looses caused by Epilachna varivestis Mulsant was demonstrated in field cage studies conducted in 1973 and 1974. Caged soybeans were infested artificially at the rates of 1, 2, and 3 adults/row ft. Significant increases in foliar damage and reductions in seed yield were recorded for all 3 infestation rates in the susceptible cultivar ‘York’, as compared to the check plots. Shore suffered little defoliation and no loss in yield except at an infestation rate of 3 adults/row ft, which caused a 17% reduction in yield. Resistance in Shore at the lower infestation rates appeared to come from its ability to prevent or retard larval development which prevented the buildup of high adult numbers.

Flue-cured tobacco losses caused by the tomato hornworm, Manduca quinquemaculata (Lepidoptera: Sphingidae), at various infestation levels in Ontario.

Abstract: Studies on the flue-cured tobacco losses caused by the natural tomato hornworm, Manduca quinquemaculata (Haworth), were conducted in the field at Delhi, Ont., during 1973, 1974, and 1975. The feeding habits of the larval stage were observed and data on the subsequent damage to tobacco were recorded Two to six leaves per plant, depending on leaf size, were unmarketable due to damage caused by one hornworm larva. The most severe damage by the larva was due to destruction of terminal buds.The tobacco yield was significantly related, negatively, to the tomato hornworm infestation levels. All infestation levels influenced quantitative tobacco losses, but no qualitative differences were apparent when compared with the yield in the insect-free plots. Maximum yield losses occurred at the highest level of infestation. There were no significant differences in yield losses per larva among the infestation levels or among the years. The average yield reduction per larva for all of the population densities and years was 0.70 oz of cured leaves. A prediction equation to establish the relationship between hornworm infestation levels and tobacco yield losses was calculated. A theoretical economic-injury level for the tomato hornworm on tobacco in Ontario was established.