In the recent years earlier appearance of late blight on potato crops and the increase of infection pressure of Phytophthora infestans has been observed due to the changes in its population. The occurrence of P. infestans on potato plants at early plant growth stages points to the possibility of existence of other infection sources such as infected seed tubers or volunteer plants and their increasing role in the disease epidemiology. These changes have led to late blight epidemics developing earlier and more severely than previously and changes in the occurrence and development of first symptoms of P. infestans infection on potato plants. In the years 1997–2006, field studies were conducted at the Plant Breeding and Acclimatization Institute of Bonin with the emphasis on comparison of time of the occurrence and incidence level of late blight of potato. The criteria for pathogen infection pressure assessment were assumed to be the percentage of haulm destruction at the end of growing season and area under the disease progress curve (AUDPC), the late blight development rate defining the increase of destruction of above ground plant parts in unit time and also tuber yield and its healthiness. The observations carried out at Bonin revealed that both time of occurrence and severity of late blight differed and were dependent upon meteorological conditions and upon the year. Late blight occurred the earliest at Bonin in 2001 (42 days after planting). The time of occurrence of late blight depends upon rainfall in May and June. A very high infection rate of the pathogen was observed, particularly in 2006 (0.517) and in 2004 (0.400) despite late time of late blight appearance in the season. In these years AUDPC on the unprotected cultivar was 0.071 and 0.508, respectively. The 10 years of observations conducted at Bonin revealed that the yield and occurrence of tuber late blight depended mostly upon meteorological conditions in particular years.
Tomato farms in Arusha, Morogoro, Dodoma, Iringa, Kilimanjaro and Coast regions of Tanzania were surveyed to assess the incidence of the yellow leaf curl disease, and to collect infected tomato leaf samples for sero-diagnosis. The triple antibody sandwich enzyme linked immunosorbent assay (TAS-ELISA) format was adopted for the detection of disease using commercial polyclonal antiserum and monoclonal antibodies SCRI 17, SCRI 20, SCRI 23 and SCRI 33. ELISA readings were rated on a scale of 0–4. The results of the tests indicated that all the Tomato yellow leaf curl virus (TY-LCV) isolates recorded high reaction values (4) with the polyclonal antibody. However, the Dodoma and Arusha isolates were rated highest in optical density (OD) reading with MAb SCRI 20 and 23. The remaining isolates produced lower OD values. All the isolates rated low (2) when tested with SCRI 33. The differences in reaction to the monoclonal antibodies of TYLCV indicated that variability exists between the coat protein epitopes of TYLCV and Tomato yellow leaf curl Tanzania virus (TYL-CTZV) on one hand, and among the TYLCTZV isolates on the other. Only the isolates from Arusha and Dodoma share a high sequence homology in coat protein with the European and related TYLCV isolates. Furthermore, the reaction with either SCRI 20 or SCRI 23 show that the isolates from Arusha and Dodoma share a high degree of homology, and could belong to one serotype. The other isolates from Morogoro, Coast and Kilimanjaro could form another serotype, while the isolate from Iringa is a different serotype. On the other hand, reaction with SCRI 17 groups the isolates in two serotypes, the Dodoma isolate alone, and another that groups the other five isolates together. It is recommended that other procedures such as DNA-DNA hybridization assays, polymerase chain reaction, restriction fragment length polymorphisms and sequencing can be combined with the use of monoclonal antisera for the detection and prediction or inference of Tomato yellow leaf curl disease (TYLCD) virus relationships at the quasi-species or strain levels in Tanzania.
The evaluation of effect of the grass and broadleaf weed control of different mixture rates of mesotrione plus pethoxamid and terbuthylazine applied postemergence in maize was conducted in the field experiments during the 2005 and 2006 growing seasons. There was no phytotoxicity observed on maize after herbicide treatments. Herbicide mixture provided higher levels of Echinochloa crus-galii (L.) Beauv. control than mesotrione used alone. In the postemergence trials, the broadleaf weeds, except Chenopodium album L., were not well controlled by the mesotrione-alone treatment. The addition of pethoxamid plus terbuthylazine to mesotrione significantly improved the control of broadleaf weeds. Mesotrione and mesotrione plus pethoxamid and terbuthylazine treated plots were always among the highest yielding as compared to untreated plots. Any reductions in cob and grain yield were always associated with high weed fresh matter yields indicating that it was the weed competition that led to reduced yield and not herbicide phytotoxicity.
The work involved assessment of the Myzus persicae (Sulz.) capability to infect successively potato plants with PVY and PVM after a Sunspray 850 EC mineral oil application. The tests were carried out in the greenhouse, with 4-week-old, healthy potato plants possessing low ressistance to viruses, derived from in vitro (test plants). Any time, for each combination and each virus, 10 successive plants were inoculated in 6 repetitions. Virus sources were potato plants infected with PVY or PVM, kept in isolated rooms. As a result of oil application, feeding of the M. persicae specimens on plants previously treated with this oil was delayed. The highest reduction as regards PVY and PVM transmission by M. persicae was obtained in the treatment where both plants constituting virus sources and test plants were protected, because only two of ten plants were infected with PVY, and only one with PVM. Mineral oil application only on potato test plants (healthy ones) reduced to a small degree M. persicae capability to transmit PVY to six successive plants (to seven in control), whereas it was much higher for PVM – to three (to six in control). In the case when only plants constituting virus sources were oil-protected, aphid’s capability to transmit PVY was limited only to four plants, and PVM – to two. These results seem to confirm much more the hypothesis that mineral oil inactivates virus particles in the stylets of aphids while they attempt to acquire it from plants which have been previously protected with mineral oil.
Studies on the relative toxicity of different bio-rational insecticides against second instar larvae and adults of onion thrips, Thrips tabaci were carried out on Experimental Farm and in the laboratory, Faculty of Agriculture, University of Suez Canal. Eight insecticides Dipel 2x, BioFly, Agrin, BioGuard, Spinosad, Neemix, Mectin and Match were all evaluated for their relative toxicity towards T. tabaci with recommended dose, half of recommended dose and quarter of recommended dose in the laboratory and only recommended dose under field conditions. Spinosad was the most toxic among the tested insecticides followed by Mectin, Match and Agrin when used against thrips adults. The respective values of LC50 of those insecticides were 0.048 cm/l, 0.070 cm/l, 0.079 cm/l and 0.137 g/l. Also, Spinosad was the most effective insecticide against second instar larvae followed descendingly by: Agrin, Match and Dipel 2x. Toxicity index values at LC50 level show such superior efficiency of Spinosad (100%) when applied against adults and second instar larvae of onion thrips under labora tory conditions. All insecticides under field conditions caused reduction of infestations of thrips. For the residual effect post application, all insecticides gave significant reductions in thrips numbers at the 21 day post treatment except for: Agrin and Match. Spinosad, Mectin, Neemix and BioFly gave the best control and continued to suppress thrips populations till 21 days after treatment. Spinosad was non harmful and Dipel 2x, Agrin were slightly harmful, BioGuard was significantly harmful whereas BioFly, Match and Mectin were very harmful to Orius albidipennis.
Phytophthora cryptogea was isolated from diseased stem base of Aquilegia discolor and rotted leaves of Saxifraga and Sempervivum spp. Additionally, Fusarium species and Botrytis cinerea were frequently isolated from diseased parts of plants. Most of Sempervivum species and cultivars except S. soculiferum were colonized in laboratory conditions by P. cryptogea. The isolates from Alstroemeria aurantiaca, Gerbera jamesonii, Saxifraga arendsii, S. paniculata, Sempervivum arachnoideum colonised houseleek leaves with the fastest spread of necrosis on plant parts inoculated with cultures from Gerbera and S. arendsii. The isolate from S. arendsii colonized 5 species and cultivars of saxifrage as well as Iberis sempervivum, Lavendula angustifolia, Sempervivum sobuliferum and Vinca minor with the slowest development on periwinkle. In laboratory trials isolate of P. cryptogea from houseleek grew on PDA and colonized leaves of that plant at temperature ranging from about 10 to 32.5°C with optimum at 20–30°C.
New host-plants of ergot pathogen Claviceps purpura (Fr.) Tul. were identified in Poaceae (R. Brown) Barnharth family in Lithuania during the surveys arranged over the period 2001–2006. There were identified 8 new Poaceae family plant species affected by C. purpurea: Melica altissima L., Bromus secalinus L., Deshampsia flexuosa (L.) Trin., Festuca pseudalmatica K., Helictotrichon sempervirens (Vill.) Pilg., Phalaris paradoxa L., Secale montana L., Stipa turkestanica K. The results of previous research as well our findings indicate that 87 Poaceae family plant species are known to be affected by ergot in Lithuania.
The population of spider feeding on insect pests of cotton was observed throughout the growth period of the crop, being maximum in the month of July. Chrysoperla was observed from second fortnight of June to harvesting of the crop being maximum in November. The incidence of coccinellids was recorded from the middle of August to middle of September and remained till harvesting of the crop being maximum in the first fortnight of November. A positive significant effect of maximum and minimum temperature on spider and negative significant effect on population of chrysoperla and coccinellids was recorded. Evening RH exerted positive significant effect on spider and negative significant effect on coccinellids.
Basal Stem Rot (BSR) disease caused by Ganoderma lucidum (Leys) Karst. is the most destructive disease and a major constraint in coconut production. Fifty five endophytic strains of bacteria were isolated from coconut roots of different regions. Among the isolates, EPC5 (Endophytes coconut), EPC8, EPC15, EPC29, EPC52 and Pf1 (Plant growth promoting rhizobacteria) promoted the rice seed ling growth in roll towel and pot culture method. EPC5 (Plant growth promoting endophytic bacteria), Pf1 and Trichoderma viride (Plant growth promoting fungus) effectively inhibited the G. lucidum growth in vitro. When bioagents along with farm yard manure (FYM) were heaped for different days interval the population was increased in twenty days both in sterilized and unsterilized conditions.
In 1985–2002 thirteen weeds resistant to atrazine were selected by a repeated application of triazine herbicides on arable land, in orchards, non-agricultural land and at railways in the Czech Republic. Recently Digitaria sanguinalis biotypes resistant to atrazine have been found at three railway junctions. Long-lasting application of the active ingredient imazapyr at railways caused selection of resistant Kochia scoparia biotypes. High resistance to chlorsulfuron has been discovered in five Apera spica-venti biotypes originating in winter cereals fields. The molecular basis of resistance to atrazine has been identified in the following weeds: Kochia scoparia, Solanum nigrum, Senecio vulgaris, Conyza canadensis, Digitaria sanguinalis, Amaranthus retroflexus and Chenopodium album. The resistance was conferred by a glycine for serine substitution at residue 264 of the D1 protein in all of those weeds. The resistance to imazapyr in Czech Kochia scoparia biotypes was conferred by a mutation at codon 574 of the ALS gene. Analysis of the results of DNA sequencing indicated, that the mutation induced a leucine for tryptophane substitution. There was excellent correspondence between the phenotypic resistance to herbicides of individual plants and the presence of mutations.
Research over a three year period indicated that P. ramorum occurred rarely in Poland on Rhododendron spp., in spite of established monitoring in nurseries, trade stands, forest and water from early spring to late autumn each year. The pathogen was not found in forests on Vaccinium vitisidaea, Calluna vulgaris, Fagus sylvatica and Quercus rubra, proving its limited spread. The species was detected, however, from 2 rivers. P. citricola was isolated from most of surveyed plants. Besides this P. cactorum, P. cinnamomi, P.citrophthora and P. nicotianae var. nicotianae were isolated from diseased plants. Additionally Pestalotia sydowiana, species of Fusarium, Botrytis cinerea and Trichoderma were often found in diseased plant tissues. Laboratory and glasshouse research showed slight differences in colonization of plants by P. ramorum and P. citricola. However, taking into account the range of host plants, and frequency of pathogen occurrence in infected plant material and water, it became clear that P. citricola poses a much greater danger than P. ramorum to the natural environment in Poland.
Nucleopolyhedrovirus (NPV) of the satin moth Leucoma (=Stilpnotia) salicis L. was produced by infecting the larvae with the LesaNPV strain obtained from epizootic center in Katowice. The infected larvae were reared under laboratory, greenhouse and insectarium conditions. Because L. salicis can not be reared on a semi-synthetic food, the insects were maintained on natural products. Efficiency of the mass virus production depended on an insect growth stage, virus concentration and number of infected larvae in a rearing container. The fourth-instar larvae were the best for LesaNPV replication. Inoculation of younger larval stages (third instar stadium) provided less number of inclusion bodies (insects were dying sooner and did not meet their maximum body weight). On the contrary inoculation of older stages (fifth and sixth instars) resulted in slower virus replication and low larva mortality. The virus concentration of 3 x 109 of inclusion bodies per container was the optimum inoculum for the mass virus production (double infection with the virus concentration of 1.5 x 109 inclusion bodies/1000 larvae). The larvae reared at high-density became more infected and it caused their earlier death and in consequences low virus efficiency. Rearing the insect at low density (less than 10 larvae per 1.0 L container) was conducive for both an increase of insect body mass and virus replication as well. The highest number of inclusion bodies per one larva(5.3 x 109 – 7.7 x 109) and the highest total number of inclusion bodies (152 x 1011 – 188 x 1011) were achieved under these rearing conditions in a greenhouse and insectarium.
The most important factors influencing the human development and health condition are nutrition habits. The quality of food including first of all health safety as well as usable attributes of products often decides about the consumer choice. Safe food should be characterized by both, adequate nutritive value and the tolerably low content of substances which presence could be a risk and threat for health, e.g. pesticide residues. The aim of the study was to estimate long-term and short-term intake of pesticide residues in Polish fruit and vegetables in 2006. The estimation of dietary exposure was based on pesticide residue data from official control of domestic crops carried out by Institute of Plant Protection and on British food consumption data.The estimated dietary intake has shown the chronic dietary exposure of consumers to the pesticide residues in 2006 in Polish crops was relatively low. For fourteen pesticide residues found in apples the long-term intake did not exceed for adult 1.4% and for toddlers 7.6% of the ADI calculated for each compound and respectively 5.1% and 28.3% of the ADI for all compounds total. For eleven residues found in black currants the data were respectively for adult 1.1% and for toddlers 3.3% of the ADI calculated for each compound and 3.3% and 10.3% of the ADI for all compounds total. The long-term exposure values for other 29 commodities were much lower than those for black currant. An acute dietary exposure was estimated for residues of endosulfan in black currants, fenhexamid in raspberries and captan in sour cherries. An acute dietary exposure did not exceed 18.9% for adults and for toddlers 43.2% of the ARfD. The results show that Polish fruit and vegetables are safe in long- as well as in short-term nutrition.
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