Showing papers on "Infestation published in 2002"

Control of witchweed Striga hermonthica by intercropping with Desmodium spp., and the mechanism defined as allelopathic.

Abstract: During investigations into the control of insect damage to maize crops in subsistence farming in Kenya, which involved intercropping with repellent plants, the fodder legumes silverleaf (Desmodium uncinatum) and greenleaf (D. intortum) were also found to reduce dramatically the infestation of maize by parasitic witchweeds such as Striga hermonthica. This effect was confirmed by further field testing and shown to be significantly greater than that observed with other legumes, e.g., cowpea, as were the concomitant yield increases. The mechanism was investigated, and although soil shading and addition of nitrogen fertilizer showed some benefits against S. hermonthica infestation, a putative allelopathic mechanism for D. uncinatum was observed. In screenhouse studies, a highly significant reduction in S. hermonthica infestation was obtained when an aqueous solution, eluting from pots in which D. uncinatum plants were growing, was used to irrigate pots of maize planted in soil seeded with high levels of S. hermonthica. Growth of the parasitic weed was almost completely suppressed, whereas extensive infestation occurred with the control eluate. Laboratory investigations into the allelopathic effect of D. uncinatum, using samples of water-soluble chemical components exuded from cleaned roots, demonstrated that this involved a germination stimulant for S. hermonthica and also an inhibitor for haustorial development.

A review of the population biology and host-parasite interactions of the sea louse Lepeophtheirus salmonis (Copepoda: Caligidae).

Abstract: Lepeophtheirus salmonis is a specific parasite of salmonids that occurs in the Atlantic and Pacific Oceans. When infestations are heavy fish mortality can occur although the factors that are responsible for causing epizootics, especially in wild salmonid populations are still largely unknown. Over the past 20 years this parasite has caused significant economic losses in farmed salmon production and possibly in wild salmonid populations locally. Understanding the connectivity between populations is crucial to an understanding of the epidemiology of infections and for management of infections in aquaculture. Data from genetics, pesticide resistance, larval dispersal models and spatial and temporal patterns of infestation in wild and farmed hosts suggests a spatially highly structured metapopulation the components of which have different levels of connectivity, probabilities of extinction and influence on the development of local infestations. The population structure is defined mainly by the dispersal dynamics of the planktonic stages and the behaviour of the host. Until recently virtually nothing was known about the relationship between the parasite and the host, or how the host may influence lice at local or population level. Typically, impacts on the host have usually been reported in terms of pathological lesions caused by attachment and feeding of the adult stages, as well as localised mild epithelial responses to juvenile attachment. However many studies report pathology associated with severe infestation. Recent new studies on the host-parasite interactions of L. salmonis have shown that this parasite induces stress-related responses systemically in the host skin and gills and that the stress response and immune systems are modulated. In the second part of this review, these new studies are presented, together with results from other host-parasite model systems where data for caligid sea lice are missing. One of the most revealing methods reported recently is the application of a net confinement stressor to examine modulation of the stress response and immune system of the host fish. This approach has shown that although until now, infective stages of L. salmonis were not thought to affect the host, they do induce systematic effects in the host that result in a stress response and modulated immune system. Host-parasite interactions affecting these stress responses and the immune system may be key factors in facilitating epizootics by reducing the host's ability to reject the parasites, as well as reducing disease resistance under some environmental conditions. The host-parasite interaction therefore needs to be incorporated into any model of population structure and dynamics.

The effect of host density on ectoparasite distribution: an example of a rodent parasitized by fleas

Abstract: The pattern of parasitism of the flea species Xenopsylla dipodilli and Nosopsyllus iranus theodori on the desert rodent species Gerbillus dasyurus was studied to test the hypothesis that the relationships between flea abundance and host density conform to pre-existing models of R. M. Anderson and R. M. May, with the correction that the density of those host individuals that possess permanent burrows (residents) is substituted for the overall host density. It was predicted that: (1) the intensity of flea infestation would increase in curvilinear fashion with increase of host density to a plateau that would be attained at a lower level of host density than would be expected from the basic model, and (2) the prevalence of flea infestation plotted against host density would be hump-shaped. The results indicated that intensity of flea infestation increased in either curvilinear fashion to an asymptote (for X. dipodilli) or linearly (for N. i. theodori) with increase of host density. As host density increased, the prevalence of infestation changed either unimodally (X. dipodilli) or logarithmically (N. i. theodori). In addition, there was a positive relationship between the mean number of fleas per host and the percentage of hosts infested. Both basic and corrected models describing the relationships between flea burden and host density fit the observational data well. However, simulations of the fraction of resident hosts demonstrated that this parameter influences the relationship between host density and flea burden only when residents comprise ≤50% of all host individuals.

Salmon lice, Lepeophtheirus salmonis (Krøyer), infestation in sympatric populations of Arctic char, Salvelinus alpinus (L.), and sea trout, Salmo trutta (L.), in areas near and distant from salmon farms

Abstract: Bjorn, P. A., and Finstad, B. 2002. Salmon lice, Lepeophtheirus salmonis (Kroyer), infestation in sympatric populations of Arctic char, Salvelinus alpinus (L.), and sea trout, Salmo trutta (L.), in areas near and distant from salmon farms. – ICES Journal of Marine Science, 59: 131–139. The abundance of salmon lice was examined in two stocks of sympatric anadromous Arctic char and sea trout in sub-Arctic regions in northern Norway in June, July, and August 1992 and 1993. One stock feeds in a coastal area exposed to moderate salmon farming activity (exposed area), while the other feed in a region without salmon farms (unexposed area). The salmon lice infestation on both species differed significantly between the exposed and unexposed area as well as between years and also between weeks within the same year. We did not detect, however, any clear significant differences in salmon lice abundance between sympatric populations of Arctic char and sea trout, or between different size groups of the species. The 1992 and 1993 infestation pattern in the exposed area showed an epidemic tendency in both Arctic char and sea trout, characterised by a sudden increase in both prevalence and abundance of lice larvae in July 1992 (23.625.7 lice/fish) and August 1993 (19.920.8 lice/fish). We therefore suggest that salmon lice epidemics, previously only observed on sea trout, may also occur in populations of Arctic char, and that fish farming contributes to the elevated lice level in wild fish. The fish in the unexposed area were also infested, although at significantly lower levels than fish from the exposed area. The infestation peaked in August 1992 at 13.018.1 lice/fish and August 1993 at 3.94.5 lice/fish, suggested that lice originating on ascending wild Atlantic salmon, or lice larvae drifting from farming areas, may infest Arctic char and sea trout also in unexposed localities in Subarctic areas. 2002 International Council for the Exploration of the Sea

Yield losses in maize due to Striga hermonthica in West and Central Africa

Abstract: Striga hermonthica (Del.) Benth. is the most important species of parasitic weed affecting cereal crop production in Africa. Yield losses due to the parasite and yield advantages offered by tolerant maize varieties were estimated from experiments conducted in West and Central Africa between 1983 and 1989. The experiments were carried out under natural infestation in experiment stations and farmers' fields, and under uniform artificial infestation in the screenhouse. TZB and PR7843, the two most widely grown open-pollinated (OP) varieties in West and Central Africa, were susceptible to Striga with yield losses of 68 and 79%, respectively. Yield losses of 100 randomly drawn (hybrid and OP) varieties averaged 68%. Yield loss was determined by the level of tolerance of the host variety and by the severity of infestation. Tolerant varieties suffered lower yield reductions and, often, produced 2.0 - 2.5 times the yield of susceptible varieties, especially under high infestation. Grain yield was significantly co...

Induced resistance by Myzus persicae in the peach cultivar ‘Rubira’

Abstract: The effect of a previous infestation by the green peach aphid Myzus persicae (Sulzer) on the settling behaviour and reproduction of the same aphid species was investigated in the resistant peach cultivar Rubira, and compared with that observed in the susceptible control cultivar GF305. A previous infestation of 48 h triggered induced resistance in Rubira. There were significantly fewer aphids settling on preinfested than on uninfested plants, indicating an increased rejection of Rubira as a host plant. The level of induced resistance in preinfested plants was positively related to the duration of the first infestation. In GF305, previous infestation had no detrimental effect on aphid settlement and even slightly enhanced larviposition by adult females. The aphid probing behaviour after a 48-h preinfestation was also monitored for 8 h with the electrical peneration graph (EPG) technique. On preinfested GF305, most EPG parameters indicated an enhanced host plant acceptance. On preinfested GF305, aphids produced less sieve element salivation and more continuous sap ingestion than on uninfested GF305, indicating that the previous aphids provoked changes in plant properties beneficial to the test aphids. In Rubira, a major induced factor of resistance was thought to be expressed in the sieve element as phloem sap ingestion was 4-fold shorter on preinfested than on uninfested plants. The time taken by the aphid stylets to reach a sieve element was also significantly increased on preinfested Rubira, suggesting the induction of resistance factors outside the phloem. The originality of the Rubira/M. persicae interaction is discussed in the perspective of a better understanding of plant induced responses to aphids.

Development and distribution of predators and parasitoids during two consecutive years of an Ips typographus (Col., Scolytidae) infestation

Abstract: The development of the natural enemy complex, its within-tree distribution and the resulting mortalities imposed on bark beetles were investigated during two consecutive years (1994, 1995) at the peak of an Ips typographus infestation. For this reason bolts from infested spruce trees were incubated until the inhabiting insects had emerged. Some 17 000 antagonists were identified and found to belong to 16 predatory and 14 parasitic insect species. Among the predators the Dolichopodidae (Dip.) were most abundant, while among the parasitoids the Pteromalidae (Hym.) ranked first. Parasitoids preferred the upper tree parts, while predators were more abundant in the lower parts. Total bark beetle mortality was assessed based on the literature data on the per capita consumption of the antagonistic larvae. In the first year, the most destructive group were the dolichopodid flies, killing three to seven times more bark beetle larvae than the second ranking Lonchaeidae (Dip.) and the Pteromalidae. In the second year, the pteromalid parasitoids killed 2.5 times more larvae than the dolichopodids. Total bark beetle survival was assessed to decrease from 46 to 18% in the course of the 2 years.

The Effect of Endophytic Fusarium verticillioides on Infestation of Two Maize Varieties by Lepidopterous Stemborers and Coleopteran Grain Feeders.

Abstract: A series of experiments were conducted to test the effect of the presence of Fusarium verticillioides in the maize plant on subsequent infestation by coleopteran and lepidopteran pests. The effect of percent internodes 1 to 5 infected with F. verticillioides, time after planting, and maize variety on attacks of stem and ears by lepidopterous and coleopteran pests was assessed in field experiments in early and late season 1998 and early season 1999 in Benin Republic. Artificial inoculation of the first internode with fungal-treated toothpicks was compared with a hot-water-fungicide seed treatment and a control. In 1998, two varieties that differed in husk tightness, the improved DMRLSR-W and the local Gbogbe, were used. Percentage of node 1 to 5 and plants infected was highest with the inoculation treatment but tended to be similar in the seed treatment and the control. The infection rate tended to increase with time and, within sampling date, decreased with node level. Ear infection was strongly correlated with percent infected nodes, indicating that F. verticillioides in the stem predisposed kernel infection. F. verticillioides incidence was higher in Gbogbe than in DMRLSR-W. Stem and ear infestations by the pyralid Eldana saccharina, the major pest in the area, tended to be highest in inoculation and lowest in the protection treatment. The same trends were found for the pyralid Chilo spp., the tortricid Cryptophlebia leucotreta, and beetles pooled across species. Significant positive correlations were found between ear/stem F. verticillioides infection and E. saccharina, Cryptophlebia leucotreta, Mussidia nigrivenella, and the noctuid Sesamia calamistis, but the latter three pest species were only significantly correlated with fungal infection of the upper nodes of the plant. Similar to disease incidence, E. saccharina numbers in stem and ear were higher in Gbogbe than DMRLSR-W in late 1998, whereas for the pyralid ear feeder M. nigrivenella, it was reversed. It was suggested that some lepidopterous and coleopteran pests are attracted by and survive longer (or have lower mortality) on plants infected with F. verticillioides.

Incidence and Population Density of Plant-Parasitic Nematodes Associated with Olive Planting Stocks at Nurseries in Southern Spain

Abstract: Nematode population densities were determined in 259 soil and root samples collected from 18 olive nurseries in Cordoba, Jaen, and Sevilla provinces (southern Spain), between October 1997 and May 1998. The most important plant-parasitic nematodes detected, in order of decreasing frequency of infestation (percentage of samples), were Mesocriconema xenoplax (39.0%), Pratylenchus penetrans (32.1%), P. vulnus (25.9%), Meloidogyne incognita (14.7%), M. javanica (11.2%), and M. arenaria (2.7%). No disease symptoms were noted on aboveground organs of infected plants. However, population densities of Pratylenchus and Meloidogyne spp. were at potentially damaging levels in most of the olive nurseries surveyed. Histopathological studies of galled roots from the naturally infected olive planting stocks showed a susceptible response to root-knot nematode infection. Large numbers of egg masses were present within the galled root tissues that might contribute to secondary infections. Feeding by root-knot nemat...

A comparison of infestation patterns by Ixodes ticks in urban and rural populations of the Common Blackbird Turdus merula

Abstract: Although spatial variation in the patterns of parasite infestations among host populations may have important ecological and epidemiological consequences, the causes underlying such variation are poorly known. In the context of a long-term study on the population biology of Common Blackbirds Turdus merula , we examined the prevalence and intensity of infestation by Ixodes ticks between birds living in rural vs. urban habitats. The overall prevalence of tick infestations was significantly higher in the rural habitat where 74% of individuals ( n = 130) were infested. This result contrasted markedly with the situation in the urban habitat where less than 2% of individuals ( n = 360) carried ticks. There was no significant effect of the sex of the host on the intensity or prevalence of tick infestations. There was a significant effect of the age of the host on tick infestations essentially due to the absence of ticks on nestlings. Possible mechanisms responsible for the differences between habitats could include differences in tick survival and/or host resistance towards ticks. Previous studies have shown higher population densities and suggested longer survival for Blackbirds in urban than in rural habitats. Given that ixodid ticks are known to transmit pathogens like Borrelia spp. to wild birds, and that Blackbirds can act as reservoirs for these pathogens, the infection patterns observed in our study area provide a suitable situation to study the interrelations between ticks, Blackbirds and pathogens.

Field infestation of Phaseolus vulgaris by Acanthoscelides obtectus (Coleoptera: Bruchidae), parasitoid abundance, and consequences for storage pest control

Abstract: Over a period of 3 yr we collected 19 samples (1 kg each) of recently harvested beans (Phaseolus vulgaris L.) from eight small-scale farms in Restrepo, Valle de Cauca, Colombia. Initial infestation by Acanthoscelides obtectus (Say) was low, but frequent. At harvest, 90% of the bean samples were infested by the weevil. The average level of infestation was 16 weevils per 1,000 beans, with a maximum of 55 weevils. Infested beans usually carried multiple larvae with a maximum of 13 larvae per bean. Emergence data indicate that oviposition by A. obtectus in the field is confined to a very short period before harvest. This relatively narrow time window can be exploited for proper timing of control measures. Only one species of parasitoid, Horismenus ashmeadii (Dalla Torre) (Hymenoptera: Eulophidae), was recorded, emerging from 21% of the samples. Samples with parasitoids had an average of five parasitoids per 1,000 beans, with a maximum of 12 parasitoids. This represented a parasitization level of 18%. During the 16 wk of storage, two weevil generations emerged, which caused visible damage in 0.5 and 34% of the beans (average of 14%). Although H. ashmeadii was successful in attacking the first generation of A. obtectus in the field, it failed to attack or develop under storage conditions. This indivates H. ashmeadii cannot serve as a postharvest control agent.

Relationship between nutritional composition of plant species and infestation levels of thrips.

Abstract: Levels of soluble protein and carbohydrate (raffinose, sucrose, glucose, and fructose) in leaves from a selection of plant species were measured to determine if a relationship existed between these nutrients and infestation by Frankliniella occidentalis and Heliothrips haemorrhoidalis. Most species of host plant examined contained a higher proportion of protein than carbohydrates, and overall, leaves from species of plants that supported populations of thrips had greater levels of protein than leaves from nonhost species. New leaves and flowers that supported F. occidentalis contained high levels of carbohydrate and protein. The quantity of protein in leaves at the top of the tree, Peumus boldus, was greater than in leaves from lower levels, and the amount of feeding damage accrued by H. haemorrhoidalis was greater on the upper foliage than lower foliage. Oviposition by H. haenmorrhoidalis was positively correlated to levels of protein in host plants but not to levels of carbohydrates. Overall, levels of soluble protein in plants influenced their susceptibility to thrips more than levels of carbohydrates.

Divergent responses of two cereal aphids to previous infestation of their host plant

Abstract: We examined the effects of prior infestation by the Russian wheat aphid [Diuraphis noxia (Mordvilko)] and the bird cherry-oat aphid [Rhopalosiphum padi (L)] on the subsequent feeding preferences and performance of each species Aphid colonies fed and reproduced on wheat seedlings for five days and were then removed After a period of plant recovery, we estimated aphid population growth and feeding preferences on control and previously infested plants Previous infestation by D noxia had no effect on the subsequent population growth of either aphid species Previous infestation by R padi reduced its own subsequent growth by 50%, but had little effect on the population growth of D noxia When presented leaves from control plants and D noxia-infested plants, D noxia adults preferred to feed on leaves from control plants; R padi adults showed no preference Both aphids preferred leaves from control plants to those from R padi-infested plants In free-flight cages, alates of R padi settled more often and produced more progeny on control plants than on plants previously infested by R padi, but their rates of settling and reproduction were unaffected by prior D noxia infestation Together, our results suggest specificity in both the plant response to the two aphid species (plant quality for R padi was lowered by prior R padi infestation but not by D noxia infestation) and in each aphid's response to the same modification of the host plant (infestation by R padi reduced plant quality for itself but not for D noxia) Effects of prior infestation on the feeding preferences of R padi were correlated with effects on performance

Studies on Seasonal Dynamics of Ticks of Ogaden Cattle and Individual Variation in Resistance to Ticks in Eastern Ethiopia

Abstract: In this study the dominant tick species identified were Amblyomma cohaerens 52.2%, Rhipicephaluspravus 19.3% and A. variegatum 14.6%. A. cohaerens occurred throughout the sampling period and showed a peak during March. Their number declined significantly (P < 0.01) from August to December. R. pravus occurred from July to December only and peaking in September (P < 0.01). A. variegatum occurred in low numbers throughout the study period with a marked seasonal variation (P < 0.01) and abundant numbers of ticks were observed from May to July. The other tick species identified were Boophilus decoloratus, R. bergeoni and R. evertsi evertsi. Individual variation in tick infestation level was observed among the animals (P < 0.05). Since all the animals were of the same breed, age group and were managed similarly the selection of animals with low infestation level can be a component of tick control strategy.

A study of pediculosis capitis among primary school children in Delhi.

Abstract: A cross-sectional study was conducted among primary school children of four of the government run schools of Delhi during July-October 2001. Out of a total of 940 study subjects studied 156 (16.59%) were found to be infested with head louse. Significantly higher proportions of girls (20.42%) were found to be infested as compared to boys (13.86%). 65.38% of those infested were aware of the infestation. Those who shared both bedding and comb showed a statistically higher significance as compare to others. Manual removal of head louse and nits was practiced by 69.60% of those aware of the infestation. Majority had knowledge of transmission of head louse by comb/brush, 66.08% had knowledge about control of head louse infestation spread by manual removal 7.34% mentioned other means like kerosene oil and lime powder. Since head louse infestation is a common problem of school going children both parents and teachers along with the students should be taught how to recognize the infestation. Also school health teams should be responsible for treatment and prevention of louse infestation besides carrying our other school health service functions.

Sea lice infestations on farmed Atlantic salmon in Scotland and the use of ectoparasitic treatments

Abstract: A recently compiled national database on sea lice infestations on farmed Atlantic salmon, contains detailed records for the period 1996 to 2000 from over 30 commercial sites on the west coast of Scotland. The data indicate that the two prevalent species of lice, Lepeophtheirus salmonis and Caligus elongatus, have different trends in abundance and distinctive seasonal patterns of infestation on farmed salmon. For the economically important species L salmonis, its abundance on fish varies with the time of the production cycle, the time of year and the particular year. Weekly fluctuations in sea lice counts indicate that treatment can be very effective in controlling infestations but that the counts recover rapidly and regular treatments are necessary to ensure control. A comparison of sites using medium or large numbers of treatments suggests that they do not reduce sea lice infestations to the same levels. There is also evidence that sites using treatments based on different chemical constituents had significantly different levels of infestation.

Varroa destructor infestation impact on Apis mellifera carnica capped worker brood production, bee population and honey storage in a Mediterranean climate

Abstract: This study investigated the impact of Varroa destructor infestation on the amount of capped worker brood, the adult bee population and honey production of authenticated Apis mellifera carnica colonies kept in a Mediterranean climate. For this purpose, colonies were set-up and either maintained mite-free or artificially mite-infested and allowed to develop an infestation. Periodical evaluations of those colonies unravelled the pattern of the previously mentioned variables across the season, and allowed for comparative numerical analyses. Progressive reductions on the amount of capped worker brood, bee population and honey storage in mite-infested colonies only became in- creasingly evident during spring and summer, apparently associated with impressive mite population increases. By the end of the experiment, mite-infested colonies showed a unitary average reduction of 45% in the amount of capped honey they stored, meaning an average annual loss of < 24 kg of honey per colony. However, the amount of capped honey stored per bee and day was found to be independent from colony V. destructorstatus, indicating a lack of direct effect of mite infestation on honey hoard- ing behaviour. Varroa destructor / Apis mellifera /population dynamics / honey production

DNA technology, interstate commerce, and the likely origin of formosan subterranean termite (Isoptera: Rhinotermitidae) infestation in Atlanta, Georgia.

Abstract: This study was the first to use DNA sequencing data to infer the origin of a Formosan subterranean termite, Coptotermes formosanus Shiraki, infestation. Cytochrome oxidase II gene sequence was used to define eight specific maternal lineages from 14 geographic locations across the southeastern United States, Hawaii, and China. One maternal lineage, A, was unique to all the Atlanta collections and one New Orleans collection, which indicated that termites at these sites shared a common maternal ancestor. The impact of interstate commerce in terms of Formosan subterranean termite introductions is addressed as is the industry response needed to arrest the spread of these termites via commercial traffic in used railroad cross ties.

Effect of some characters on the population growth of mite Varroa jacobsoni in Apis mellifera L colonies and results of a bi‐directional selection

Abstract: Two lines of honey bees (Apis mellifera ligustica) were selectively propagated by instrumental insemination using the population growth of the Varroa mite as a criteria. Different infestation rates are at least partially genetic since selection produced significant bi-directional differences between lines over a period of three subsequent generations. There was no correlation between several behavioural and physiological characteristics which are potentially associated with Varroa resistance (hygienic behaviour, physical damage to mites, infertility of the intruding mites) and the development of the Varroa population after artificial infestation. There was a positive significant correlation between the total mites in the colonies and the amount of reared brood. Colony infestation was also positively correlated with the amount of honey harvested.

Effects of Carbon Dioxide Enrichment on Leaf Chemistry and Reproduction by Twospotted Spider Mites (Acari: Tetranychidae) on White Clover

Abstract: Plant growth and yield responses to carbon dioxide (CO2) enrichment are well es- tablished. Much less is known of the response of arthropod pests to CO2 enrichment. Reproductive response of twospotted spider mites (Tetranychus urticae Koch) on white clover (Trifolium repens L.) to a range of CO2 concentrations was measured. The CO2 treatments were applied for 24 h d 1 at395, 484, 570, 657, and 748 LL 1 on the 14 d before and 26 Ð27 d after infestation with mites. Eggs, larvae, nymphs, and adult mites were removed from leaves and counted 27Ð29 d after infestation. Leaf area and weight were measured, and leaves were analyzed to measure structural and nonstructural carbohydrates, N, amino acids and digestibility. Carbon dioxide enrichment caused linear increases in plant growth and foliar nonstructural carbohydrates, but caused linear decreases in foliar N. Carbon dioxide enrichment signiÞcantly increased the rate of mite reproduction on both clover clones. Correlations between mite population increase were signiÞcantly positive for foliar nonstructural carbohydrates and signiÞcantly negative for foliar N. Concentrations of ambient CO2 expected in the 21st century may increase the risk of mite population damage on some plant species.

Mosca-dos-chifres, Haematobia irritans: comportamento e danos em vacas e bezerros Nelore antes da desmama

Abstract: The hornfly and losses caused by it in Nellore cows and pre-weaning calves where studied, using two groups of 60 animals each, one group with a natural infestation and the other without hornfly, during four consecutive years. It was seen that the number of flies on the cows did not exceed an average of 80 flies/animal in all years of observation. The majority of the cows (83%) had few flies, whereas 17% had larger numbers. The calves were infested with few flies. Rainfall in excess of 100 mm during short periods diminished fly infestation. Weight gain in the cows without flies (treated with insecticides) as well as their calves was greater than in the control cows, but not statistically significant (P>0.05). Mean percentage pregnancy during the four years was 15% more in treated cows than the non-treated animals, and this difference was probably due to the infestation of the bulls.

A preliminary pilot survey on head lice, pediculosis in Sharkia Governorate and treatment of lice with natural plant extracts

Abstract: Twelve different representative areas in Sharkia Governorate were surveyed for head lice, Pediculus humanus capitis. The pre-valence was investigated among 120 houses containing 2,448 individual, with different age, sex and socioeconomic status. Examination was done by naked eye aided with hand-lens. A total of 137 individuals were infested. Infestation rates were higher in the rural areas with low socioeconomic levels, concrete houses with over-crowded family members. Children had significantly higher infestation rates than adults. Males had lower infestation rates than females. However, the hair length and permanent hair washing were the factors accounted for both age and sex difference in prevalence of pediculosis. Head lice infestations were found all over the year, but increased in summer and spring. One hundred infested patients (90 females and 10 males) with different aged and hair length were treated with tour mixed cream from plants Lawsonia alba L. (Henna). Trigonella faemum-gracanum (Fenugreek), Hibiscus cannabinus (Hibiscus) and Artemisia cina (Wormseed). The head lice completely disappeared within a week among those patients treated by henna mixed with aqueous extract of sheah (100%) or mixed with helba (75%) or with karkada (50%).

Studies on the fungal infestation of five traditionally smoke-dried freshwater fish in Ago-Iwoye, Nigeria.

Abstract: Samples of traditionally smoke-dried Clarias gariepinus (Burchell), Chrysichthys nigrodigitatus (Lacepede), Sarotherodon galilaeus (Trewavas), Heterotis niloticus (Cuvier) and Heterobranchus bidorsalis (Geoffroy) were obtained from Oja Oba Market, Ago-Iwoye, Nigeria and examined for fungal infestation. The fish samples incubated on potato dextrose agar (PDA) for 7 days showed fungal infestation. Fungi isolated and identified included Mucor sp., Aspergillus sp., Rhizopus sp. and Fusarium sp. Six fungal species were isolated from C. nigrodigitatus, five each on C. gariepinus and H. niloticus.

Effect of greenbugs (Homoptera: Aphididae) on yield loss of winter wheat.

Abstract: The effect of greenbug, Schizaphis graminum (Rondani), feeding on the yield of four winter wheat cultivars commonly grown in Oklahoma was studied. Cultivars tested were ‘Karl’, a recent derivative ‘Karl-92’, and ‘2163’, all greenbug-susceptible cultivars; and ‘TAM-110’, a cultivar with resistance to biotype E greenbugs. The objectives were to determine the effect of different greenbug densities during fall and spring on yield of winter wheat, and to develop mathematical models to quantify the effect of greenbugs on yield loss. The intensity of greenbug infestations achieved in plots by artificial infestation varied among years and growing seasons within a year, but was generally sufficient to cause a reduction in yield. Among yield components, the number of heads per square meter and the number of seeds per head were frequently negatively correlated with the accumulated number of greenbug-days per tiller. Seed weight was rarely affected by greenbug infestation. A regression model estimated yield loss for greenbug-susceptible cultivars at 0.51 kg/ha loss of yield per greenbug-day in years with near normal precipitation, and a loss of 1.17 kg/ha under severe drought conditions. The susceptible winter wheat cultivars exhibited similar yield loss in relation to the intensity of greenbug infestation, as indicated by a common slope parameter in the regression model. Results suggest that the model is robust for predicting yield loss for susceptible cultivars.

Increase in cereal stem borer populations through partial elimination of natural enemies

Abstract: An insecticide exclusion method was used to evaluate the effect of parasitoids on level of infestation by the stem borers, Busseola fusca (Fuller) and Chilo partellus (Swinhoe), in grain sorghum. In field trials conducted at Brits and at Delmas, South Africa, a selective organophosphate insecticide, dimethoate, was applied twice weekly at each site to three subplots whereas three other identical subplots served as controls. Twelve plants were randomly selected from each subplot at weekly intervals and removed from the field. In the laboratory all plants were dissected to record borer infestation. In order to determine parasitism levels egg batches were kept in Petri dishes and all borer larvae and pupae were kept individually in vials until either parasitoids or moths emerged. At Brits ca. 97% of borers were C. partellus and 3% B. fusca, whereas at Delmas 37.5% were C. partellus and 62.5% B. fusca. The most abundant parasitoids of B. fusca were Cotesia sesamiae (Cameron) and Bracon sesamiae Cameron. The dominant parasitoids of C. partellus at both sites were C. sesamiae, Stenobracon spec., Dentichasmias busseolae Henrich and Pediobius furvus (Gahan). No egg parasitoids were found. At both sites, infestation levels in the sprayed plots were significantly higher than in the untreated plots. On the other hand, parasitism levels of borers in the unsprayed plots were significantly higher than in the treated plots. It was concluded that the higher infestation level of sorghum by stem borers in the sprayed plots was because of partial elimination of parasitoids and possibly other natural enemies by the pesticide.