Showing papers on "Infestation published in 1985"
TL;DR: Losses in yield of spring wheat due to infestations of Sitodiplosis mosellana (Gehin) were determined for 700 000 ha of arable land in northeast Saskatchewan, Canada in 1983 and losses in total gross revenue of about $30 million were estimated.
Abstract: Losses in yield of spring wheat due to infestations of Sitodiplosis mosellana (Gehin) were determined for 700 000 ha of arable land in northeast Saskatchewan, Canada in 1983. The proportion of kernels infested (y) was a power function of the number of wheat-midge larvae (x) (y = 35.3x0.725). One, 2, 3, and 4 larvae per kernel resulted in a level of infestation of 38, 58, 78, and 96%, respectively. There was no significant difference between infestation levels from fields sampled at the heading stage of crop growth and the estimates of infestation levels for these fields at harvest time. Yield of grain (y) was negatively exponential to an increase in level of infestation (x) (ln y = 5.7−0.017x). Infestations of 30, 60, and 90% reduced yields of spring wheat by 40, 65, and 79%, respectively. The average decrease in crop yield in the study area was about 30%, which resulted in estimated losses in total gross revenue of about $30 million.
85 citations
TL;DR: Strain-2 guinea-pigs given SRBC at the end of an initial infestation, or during a second tick exposure, produced significantly fewer direct haemolytic plaque-forming cells than did uninfested controls given a similar SRBC immunization regimen.
Abstract: Strain-2 guinea-pigs were given two five-day infestations with Dermacentor andersoni larvae. Each exposure consisted of 100 larvae, and the first and second infestations were separated by a seven-day tick-free period. Tick-exposed animals were given an intravenous injection with sheep red blood cells (SRBC) at selected times during and after infestation: (a) the last, fifth day, of a first exposure, (b) the second day of a second infestation, (c) the fifth day of a second infestation and (d) four days after termination of the second infestation. Ability of these animals to respond immunologically to the SRBC injection was assessed by the direct haemolytic plaque-forming cell assay, a very sensitive test used to determine the number of spleen cells producing IgM to SRBC target cells. Strain-2 animals given SRBC at the end of an initial infestation, or during a second tick exposure, produced significantly fewer direct haemolytic plaque-forming cells than did uninfested controls given a similar SRBC immunization regimen. Spleen cells of animals administered SRBC on the fourth day after termination of a second infestation displayed a haemolytic plaque-forming cell response which did not differ significantly from that of uninfested controls.
52 citations
Journal Article•
TL;DR: It was found that infestation could be explained partly by the dispersive flight of the bugs according to the distances between houses, and part by the predisposition of houses to infestation by virtue of their construction, since houses with cracked mud walls were particularly susceptible to infested houses.
Abstract: Dispersive flight by Triatoma infestans was modelled by assuming either unidirectional flight in a straight line, or that flight followed a pattern of 'random walk' analogous to two-dimensional Brownian motion. Parameter estimates for the models were derived from previous fieldwork in Argentina and Brazil. Calculated probabilities of houses becoming infested over a 1 year period were compared with actual changes of house infestation in a small farming community in central Brazil. It was found that infestation could be explained partly by the dispersive flight of the bugs according to the distances between houses, and partly by the predisposition of houses to infestation by virtue of their construction, since houses with cracked mud walls were particularly susceptible to infestation. Infested houses lying more than 200 m from uninfested houses appeared to make an almost negligible contribution to infestation of the uninfested houses. This suggests that buffer zones of this size around treated areas could help to minimize the risk of reinfestation after treatment.
51 citations
TL;DR: Results indicate that high densities of immatures have a deleterious effect on number, size, longevity, and fecundity of adult western corn rootworms.
Abstract: Field tests with controlled infestations of eggs of Diabrotica virgifera virgifera LeConte showed that larvae at higher infestation rates were stressed for food. The percentage of insects reaching the adult stage was significantly reduced at infestation rates above 600 eggs per 30.5 cm of row. Adults were significantly smaller at infestation rates above 300 eggs, they were shorter-lived at rates above 600 eggs, and they were less fecund at infestation rates above 1,200 eggs per 30.5 cm of row. These results indicate that high densities of immatures have a deleterious effect on number, size, longevity, and fecundity of adult western corn rootworms.
51 citations
TL;DR: Heifers with a heavy infestation of cattle lice gained significantly less weight than heifers treated with stirofos or trichlorfon and feed efficiency was not significantly affected by the three lice infestation levels evaluated.
Abstract: Heifers with a heavy infestation of cattle lice (10 or more per 6.452 cm2 [1 in2] of Bovicola bovis (L.), Linognathus vituli (L.), and Solenopotes capillatus Enderlein) gained significantly less weight (0.09 kg [0.21 lb]/day) than heifers treated with stirofos or trichlorfon. No significant weight gain differences were found between heifers with a light to moderate or moderate to heavy infestation and treated heifers. Feed efficiency was not significantly affected by the three lice infestation levels evaluated in these trials.
45 citations
TL;DR: In the field in Iraq Ectomyelois ceratoniae had four generations on an artificial diet and four to five generations on pomegranate fruits and Insect population increased progressively during the fruiting season.
Abstract: In the field in Iraq Ectomyelois ceratoniae had four generations on an artificial diet and four to five generations on pomegranate fruits. On an artificial diet the mean time for development from egg to adult ranged from 41 to 59 days for the first three generations. Fourth-generation larvae entered diapause in the fall and averaged 241 days. Insect population increased progressively during the fruiting season. Mean percentage of infestation increased from 20% by early generations to more than 80%. High infestation was observed in southcentral areas of Iraq. Orchards in which sanitation was poor were highly infested.
43 citations
TL;DR: This study has shown that, at the expense of some loss in productivity, zebu cattle, immunised against ticks and theileriosis, can be kept despite tick infestation.
41 citations
TL;DR: The distribution, population density and regeneration of some prominent spp.
Abstract: The distribution, population density and regeneration of some prominent spp. of understorey and overstorey (dominant Eucalyptus spp.) were monitored over a period of 20 yr in seasonally well drained dry sclerophyll forest. Changes varied with susceptibility to the pathogen and to fire. Changes in spp. composition and crown density of the overstorey were attributed to fire. Population density, basal area and crown cover of the Eucalyptus spp. which were associated with the pathogen, also declined in 1962-82. Both distribution and population density of Xanthorrhoea australis and Isopogon ceratophyllus declined markedly following the spread of infestation, whereas those of Hakea sericea and Lepidosperma semiteres increased. Regeneration of X. australis but not of I. Ceratophyllus was observed in certain areas of the infested plots 12-20 years after infection. This is the first record of such regeneration. It is postulated that a bush fire in 1967 both stimulated X. australis seed production and reduced further an already declining pathogen inoculum density.
30 citations
Journal Article•
TL;DR: The present study establishes the need for anti-louse campaign in the study area to reduce human sufferings caused by head louse particularly among children of primary and post-primary school age.
Abstract: The prevalence of head louse Pediculus capitis Deg. among inhabitants of the Niger Delta was investigated. 5.7% of 7,360 subjects harboured head lice. The infestation was highest among the 6-13 year age group (13.5%) and decreased progressively with increase in age of the subjects. Overall, more female subjects than male subjects harboured lice. The present study establishes the need for anti-louse campaign in the study area to reduce human sufferings caused by head louse particularly among children of primary and post-primary school age.
27 citations
TL;DR: An examination of 62 one-bushel bags of cowpeas revealed an extremely low preharvest infestation level, which indicates populations either slowly dwindled away or after an 18-week delay increased exponentially.
Abstract: An examination of 62 one-bushel bags of cowpeas, representing 49 different fields, revealed an extremely low preharvest infestation level (mean 2.33 Callosobruchus maculatus [F.] adults) emerging per bushel per 2 weeks of storage. From similar initial infestation levels, populations either slowly dwindled away or after an 18-week delay increased exponentially.
26 citations
TL;DR: It was found that growing soft plants and keeping de-leafing to the minimum would maximise yields, and it appeared that the direct effect of these cultural practices on yield was more important than their indirect effects on leaf miner damage.
TL;DR: Using the Sterile Insect Technique, Mediterranean fruit fly Ceratitis capitata (Wiedemann), was eradicated in December 1984 from Carnarvon in Western Australia.
Abstract: Using the Sterile Insect Technique, Mediterranean fruit fly Ceratitis capitata (Wiedemann), was eradicated in December 1984 from Carnarvon in Western Australia. Eradication is based on finding no infestation of adults or larvae for a period equivalent to 3 fly generations according to a standard set by Hendrichs et al. (1982).
TL;DR: In the Chitwan valley, Nepal, Chilo partellus preferred maize and sorghum over rice, teosinte, finger millet and sugar-cane, and infestation on young maize plants produced “dead hearts” and on older plants reduced growth and sometimes prevented cob formation.
Abstract: In the Chitwan valley, Nepal, Chilo partellus preferred maize and sorghum over rice, teosinte, finger millet and sugar-cane. Infestation on young maize plants produced “dead hearts” and on older plants reduced growth and sometimes prevented cob formation. The yield reduction in some maize cultivars reached 60% and stem infestation levels reached 98%. Borers produced “dead hearts” in young and “whiteheads” in older rice plants. The egg, larval and pupal periods from April through September lasted 4–5, 16–41 and 4–8 days, respectively. A complete generation took 28–48 days under summer field conditions and 192–233 days from October to May. Of the one egg, four larval and two pupal parasitoids, all hymenopterans, which were reared from C. partellus, the two most important were Trichogramma chilonis (70% egg parasitism) and Apanteles flavipes (30% larval parasitism).
TL;DR: Adaptations and microanatomic changes in the branchial chamber, as well as influence of parasitosis on the reproductive function of shrimp, are analyzed and conclude that sexual inversions were not observed in females of P. argentinus and male infestation with P. oviformis showed tertiary sexual rate bias.
TL;DR: It is concluded that the benefits of increased yield resulting from high nitrogen levels must be balanced against the greater potential for damage by aphids.
Abstract: SUMMARY
The effects of two levels each of nitrogen and sulphur nutrition and of infestation by Brevicoryne brassicae on the growth of Brussels sprout plants were studied in factorial experiments.
All the plants receiving high nitrogen treatments grew more rapidly than those with low, but in infested plants the improvement in growth at the higher levels of nitrogen was offset by the increased size of aphid populations. Low sulphur nutrition increased the growth of plants receiving high nitrogen and of the aphids feeding on them. Leaf diffusive resistances and chlorophyll concentrations were greater with high nitrogen, but were significantly lowered by infestation in all nutrient treatments. Infestation decreased leaf total nitrogen concentration at the sites of feeding, but effects on soluble nitrogen were not significant. Removal of aphids 72 days after initial infestation did not cause marked plant recovery during the next 22 days.
It is concluded that the benefits of increased yield resulting from high nitrogen levels must be balanced against the greater potential for damage by aphids.
28 Aug 1985
TL;DR: Susceptibility of Marsh grapefruit to laboratory infestation by Anastrepha suspensa was determined each month between October 1982 and May 1983.
Abstract: Susceptibility of Marsh grapefruit to laboratory infestation by Anastrepha suspensa was determined each month between October 1982 and May 1983. Criteria for susceptibility included comparisons of oviposition rates and fly developmental success. Five times as many flies were produced per fruit in May as in October. Fruit exposed in May received ca. 2.5X as many eggs as in October, and egg-adult success was ca. 2X greater in fruit exposed in May (8.0% vs. 3.9% in October). Selected chemical parameters (peel oil linalool concentration and peel sugar concentration) monitored throughout the season did not correlate with the observed increase in susceptibility of senescent fruit.
TL;DR: The effects of potato leafhopper infestations on the relative rate of photosynthesis and tuber yields of potatoes were studied in 1983 at the Hancock Experiment Station, Hancock, Wis.
Abstract: The effects of potato leafhopper ( Empoasca fabae [Harris]) infestations on the relative rate of photosynthesis and tuber yields of potatoes were studied in 1983 at the Hancock Experiment Station, Hancock, Wis. Cages were erected over plants to aid in creating known PLH infestation levels during specific postemergence growth stages of a short and long maturing cultivar, represented by ‘Superior’ and ‘Russet Burbank,’ respectively. Photosynthesis was reduced by infestations at all growth stages, but this effect was more pronounced in the bloom and postbloom growth stages, since rapid vine growth following prebloom infestations allowed plants to generate new foliage following infestation. The slower recovery of photosynthesis after bloom and postbloom infestations was reflected in significantly lower tuber yields of ‘Superior.’
TL;DR: A significant degree of induced host tick resistance was expressed by reduced engorgement weight of females, reduced oviposition by those females which did obtain a blood meal, and by death of ticks at the attachment site.
Abstract: Primary tissue culture cells of developing larvae of Amblyomma americanum were administered to guinea-pigs never previously exposed to ixodid ticks. Guinea-pigs were given 1 X 10(6) primary culture cells on Days 0, 7 and 21 by subcutaneous injection and challenged with male and female A. americanum on Day 35. A significant degree of induced host tick resistance was expressed by reduced engorgement weight of females, reduced oviposition by those females which did obtain a blood meal, and by death of ticks at the attachment site. Resistance induced by A. americanum primary culture cells stimulated a significant degree of resistance to infestation with Dermacentor andersoni adults.
TL;DR: Within 10 days of infestation, aphid feeding significantly reduced plant dry weights and mean relative growth rates for the six plant–aphid combinations and the mean leaf area ratio was the same for infested and control plants.
Abstract: The effects of various densities of cowpea aphids (Aphis craccivora Koch) and pea aphids (Acyrthosiphon pisum Harris), both Homoptera: Aphididae, on the growth of cowpea (Vigna unguiculata (L.) Walp. cv. Caloona), broad bean (Vicia faba L. cv. Aquadulce), and garden pea (Pisum sativum L. cv. Victory Freezer) seedlings were investigated. Within 10 days of infestation, aphid feeding significantly reduced plant dry weights and mean relative growth rates for the six plant–aphid combinations. In all cases except one, the mean unit leaf or net assimilation rate was also significantly reduced within 10 days. The mean leaf area ratio was the same for infested and control plants. The aphid-induced changes in host plants appear to be due to changes in photosynthesis, respiration, and translocate removal from the phloem over the 10-day period. Changes in the growth patterns of the host plant within this period are similar, but the underlying physiological effects could vary among particular plant–aphid combinations.
TL;DR: Field survey experiments were conducted in 1981, 1982, and 1983 in eastern North Carolina to assess level of damage done by Ostrinia nubilalis (Hubner) to commercial maize to find a significant relationship between grain weight and cavities per plant.
Abstract: Field survey experiments were conducted in 1981, 1982, and 1983 in eastern North Carolina to assess level of damage done by Ostrinia nubilalis (Hubner) to commercial maize. There was a significant relationship between grain weight and cavities per plant in 10 of 12 fields surveyed. In controlled experiments in 1982 and 1983, a more significant relationship was observed between grain weight and cavities per plant. Reduction in maize yield by O. nubilalis ranged from 102.72 to 465.79 kg/ha per cavity. Yield reduction was affected by infestation date, infestation level, and year (rainfall). In these experiments, variation in maize yield accounted for by cavities ranged from 4.1 to 54.3%. Damage potential of O. nubilalis to maize was not significantly different at 49,000 and 69,000 plants per ha.
01 Jan 1985
TL;DR: In this article, the authors made observations on the behaviour of some Costa Rican species of Phyllophaga and found that the destruction of young maize plants by larvae of these two species and the consequent reduction in yield were significantly greater in land which was weedy or in close association with stands of old cassava plants, than where weeds had been effectively controlled and cassava was absent.
Abstract: Observations were made on the behaviour of some Costa Rican species of Phyllophaga. Studies of oviposition and early larval survival under controlled conditions indicated that P. menetriesii (Blanchard) laid most eggs under a ground cover containing grasses and that the presence of living roots in the soil was important to the survival of the young larvae of the two most common species, P. menetriesii and P. vicina (Moser). At Turrialba, Costa Rica, the destruction of young maize plants by larvae of these two species and the consequent reduction in yield were significantly greater in land which was weedy or in close association with stands of old cassava plants, than where weeds had been effectively controlled and cassava was absent. Both plant loss and yields of maize were significantly correlated with larval densities. The best correlations were with numbers of second- and third-instar larvae sampled in July and with the total numbers of third-instar larvae sampled. Regression analyses established that 4·45 seedlings, or approximately 170 kg dry grain/ha, were lost per larva per square metre sampled during the seedling stage in July. An expression to calculate the economic threshold was determined. Significantly more larvae of P. vicina were found in maize growing on ridged than on unridged land, and where applications of lime and phosphate fertilizer had been made to an acid soil. The significance of weed control on infestation is discussed.
Journal Article•
TL;DR: The fleas showed the highest indices of infestation in the warm-rainy season (October to March) while the infestation by the lice was more prevalent in the dry-cool season ( October to March), and the climatic factors most related with the hosts' infestation were rainfall, temperature and relative humidity.
Abstract: The indices of infestation by the mites Echinolaelaps echidninus and Laelaps nuttalli, the louse Popyplax spinulosa and the flea Xenopsylla cheopis, obtained monthly, from June 1980 to September 1982, on Rattus norvegicus norvegicus in the city of Belo Horizonte, Minas Gerais state, Brazil were related to seasonal period, sex of the host and area of capture. Mites and insects showed different behaviour in relation to these factors. Only the fleas and lice exhibit significant association between the rodents' infestation and the seasonal period, or between the infestation and the rodents' sex or else a variation of the distribution by the three main areas of capture. The fleas showed the highest indices of infestation in the warm-rainy season (October to March) while the infestation by the lice was more prevalent in the dry-cool season. The climatic factors most related with the hosts' infestation were, in decreasing order, rainfall, temperature and relative humidity. Fleas and lice preferentially infested male rodents, being infestation by X. cheopis highly significant.
TL;DR: The results showed that the mean leaf number and shoot weight bore significant linear relationships (P<0.001) to increased number of thrips, and the need to spray chemical insecticides to control thrips on the basis of pest numbers as against spraying to a schedule is discussed.
TL;DR: It is indicated that non-preference for oviposition is an important mechanism for resistance to shootfly in eight test cultivars and for a certain degree of antibiosis in IS 2291.
Abstract: Sorghum shootfly, Atherigona soccata, oviposition and infestation on eight resistant sorghum cultivars (IS nos: 2122, 2123, 2205, 2291, 4660, 5092, 5480 and 18551) and two susceptible cultivars (Serena and CSH-1), were studied under field conditions (natural infestation). The eight resistant cultivars and CSH-1 were also tested for preference for oviposition in a two-choice situation in the screenhouse. The eight resistant cultivars received considerably less shootfly eggs and showed fewer “dead hearts” than the susceptible cultivars. The results indicate that non-preference for oviposition is an important mechanism for resistance to shootfly in eight test cultivars. There was also evidence for a certain degree of antibiosis in IS 2291.
TL;DR: A preliminary survey of 253 Ovalipes stephensoni collected off the southeast coast of the United States revealed a 94.5% incidence of infestation by the parasitic ciliate Synophrya hypertrophica, with an infestation density ranging from 1 to 270 lesions per branchial chamber.
Abstract: A preliminary survey of 253 Ovalipes stephensoni collected off the southeast coast of the United States revealed a 94.5% incidence of infestation by the parasitic ciliate Synophrya hypertrophica. Analysis of 67 crabs indicated an infestation density ranging from 1 to 270 lesions per branchial chamber. An in depth study of 38 crabs (19 male, 19 female), ranging from 18 mm to 80 mm in carapace width (CW), provided details on the number of gill lamellae with and without parasitic lesions relative to size, sex, and branchial chamber of the crab. The mean lamellar counts of both chambers are not statistically different (P > 0.05), nor is there a significant difference in the mean count between males and females (P > 0.05). Significant differences in mean lamellar counts exist among the individual gills (ANOVA, P 0.05). The lesions are distributed evenly among the gills (ANOVA, P > 0.05). The extent of the loss of respiratory surface area due to the presence of parasitic lesions was quantified by measuring the area of lesion and total lamellar surface of 45 parasite-laden lamellae of a 55.3 mm CW crab. Distal lamellae are subject to a significantly greater loss of lamellar tissue due to infestation (ANOVA, P < 0.01). The loss of respiratory surface resulting from three levels of infestation (light, medium, heavy) was extrapolated. The resultant percentage losses (0.05, 0.85, 1.39) are low and of questionable importance in the overall natural mortality of the host species.