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Fusarium head blight (FHB) is a disease of small-grain cereals that has a proven negative impact on crop yield, quality and food safety. In this regard, it is one of the most studied diseases of small-grain cereals worldwide. This paper reports the commonly used artificial sources of inoculum and inoculation techniques employed in the study of FHB epidemiology. Spore suspensions and grain spawn are the most popular forms of artificial inoculums. Spray inoculation technique is more commonly used than the point inoculation technique for delivering the inocula to the target sites. Spray inoculation has an advantage over point inoculation in that it can be used to detect both Type I and II resistances to FHB, point inoculation can only detect Type II resistance to FHB. Grain spawn is the commonest soil-surface inoculum used in the study of FHB. Its advantage lies in the fact that it is capable of propagating inoculum over a long period of time compared to other methods. It can also detect the five types of resistances reported (Types I, II, III, IV and V). In order to gain further information regarding the epidemiology of FHB, researchers need to explore other potential sources of artificial inoculum.

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Saprophytic microflora and non-toxin producing Microdochium spp. capable of causing Fusarium head blight (FHB) have been suggested to affect the development of FHB caused by Fusarium spp., the occurrence of mycotoxins and the efficacy of fungicides for the control of the disease. The effects of metconazole and azoxystrobin on the interactions between Fusarium culmorum and Microdochium spp., Alternaria tenuissima or Cladosporium herbarum on FHB symptom development, Tri5 DNA concentration and deoxynivalenol (DON) production were studied under glasshouse conditions. Results indicated that the sequence of infection of wheat heads and the relative timing of fungicide application can significantly affect FHB severity and the resulting mycotoxin contamination of harvested grain. Introduction of A. tenuissima, C. herbarum or Microdochium spp. to wheat heads at GS 57 before inoculation with F. culmorum at GS 65 generally resulted in increased FHB severity, Tri5 DNA and DON concentration in harvested grain. The greatest increases of FHB severity (266%), Tri5 DNA (79%) and DON (152%) were observed when Microdochium spp. were introduced first at GS 57 and F. culmorum inoculation followed at GS 65. Metconazole generally reduced FHB severity, Tri5 DNA and DON concentration in grain but azoxystrobin was most efficient at reducing DNA of Microdochium spp. in grain.

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The effect of different timings of fungicide applications on Fusarium head blight severity and mycotoxin accumulation in wheat grain was investigated in two field experiments. The fungicides metconazole, tebuconazole, azoxystrobin and mixtures of metconazole + azoxystrobin and tebuconazole + azoxystrobin were applied either, 5 days pre-, 2 days pre-, 2 days post-or 5 days post-inoculation of wheat ears with Fusarium spp. and Microdochium spp. at GS 65. Fungicides applied 2 days pre-or 2 days post-inoculation were most effective at reducing Fusarium head blight severity and DON concentration in grain. Metconazole and tebuconazole applied alone within two days of inoculation were most consistent in their effects on Tri5 DNA and DON in harvested grain.

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Fusarium langsethiae is a fungus that has recently been implicated in the contamination of small-grain cereal crops such as oats, wheat and barley with high levels of HT-2 and T-2 toxins in many European countries. The epidemiology of this fungus is not well known and may therefore be a bigger problem than currently thought to be. A study was carried out investigating the in vitro growth characteristics of F. langsethiae isolates from contaminated oats and wheat at various temperatures; 15, 20, 25 and 30 °C. Results indicated similar growth trends of oats and wheat isolates of F. langsethiae. Wheat isolates grew significantly (p<0.001) faster than oat isolates although this difference may have been confounded by the age of cultures, with oat isolates collected one year earlier. The estimated optimum growth temperature for all isolates was 24 °C. Isolates were macro-morphologically categorized as having lobed or entire colony margins, and either possessing one of the following colony colours: white, orange or purple. Since the estimated optimum growth temperature of F. langsethiae is typical in temperate summers when small-grain cereals are flowering, it is possible that this species can infect, colonise and possibly contaminate the developing grains with HT-2 and T-2 toxins which are of food safety concern.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
S. Goheen
,
B. McVeety
,
T. Clauss
,
R. Lucke
,
M. Ligotke
,
J. Edwards
, and
J. Fruchter

Abstract  

Organic species from the headspace of one Hanford radioactive waste tank are described. Samples were collected either using a sorbent trap or a SUMMATM canister and were analyzed by gas chromatograph and mass spectrometry. The headspace contained several organic components, including alkanes, alkenes, ketones, aldehydes, organic nitriles, and chlorinated hydrocarbons. Sorbent trap samples were designed to collect only normal paraffin hydrocarbons (NPHs). A comparison of NPH data from sorbent traps and SUMMATM cans revealed results of 693 and 1320 mg/m3, NPH respectively. Significant differences were observed in NPH values when samples were collected at different times, or at different locations in the tank. These data suggest either the time of collection, or the position of the sampling device are important variables in the analysis of organic species from Hanford tanks.

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The Hungarian plant protection organization has been performing western corn rootworm moni- toring over the past four years.In 1998 three different trapping activities were carried out at 150 monitoring sites.Hungarian pheromone traps and Multigard ®(yellow sticky)traps were used from July 1 to September 30.The number of catches and the average catches/trap in 1998 were lower than the catch numbers in 1997. In 1998,the pest spread to a lesser degree than in 1997.

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WCR adults generally lay their eggs in maize and their larvae feed almost exclusively on maize roots (Smith,1966,Branson and Ortman,1967,1971,Branson and Krysan,1981,Levine and Oloumi- Sadeghi,1991).For this reason,farmers have accepted growing maize in rotation with soybean to manage WCR larval populations without the use of soil insecticides.Recently,in Northwest Indiana and East Central Illinois in the USA,western corn rootworm has adapted to the above management system (Gerber et al., 1997).A portion of WCR eggs is laid in soybean and in other crops like alfalfa.This behavioral change increases the potential for survival of WCR larvae the following year since most soybean fields are rotated to maize.During the summers of 1996,1997,and 1998 field studies related to this behavioral shift were conducted in northwestern Indiana.Eleven pairs of maize/soybean fields were selected for the study.During these sampling periods,WCR beetles were present in both maize and soybean.Empirical observations show that there were higher numbers of females in soybean when compared to maize.

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Fusarium langsethiae, a toxigenic fungus known to contaminate small-grain cereals with type A trichothecene mycotoxins, HT-2 and T-2 was described as a new species in 2004. HT-2 and T-2 are some of the most potent Fusarium toxins in eukaryotes, capable of inhibiting protein synthesis. The epidemiology of F. langsethiae is not well understood and with the intent of the European Commission to set maximum levels of contamination of cereals with these toxins, importance is currently placed in trying to understand the fungal infection process and its favorable growth conditions. A field study was carried out to investigate the effect of artificially inoculated oats straw, ploughing and minimum tillage with and without incorporated crop debris (straw) on infection and mycotoxin production by F. langsethiae on oats cultivar Gerald. The results indicated that cultural field practices had effects on the infection of oats by F. langsethiae. Fusarium langsethiae DNA was quantified in significantly larger amounts (p<0.05) in minimum tilled with incorporated straw plot samples than in other plot samples. It was also shown that inoculated straw had no significant effect (p>0.05) on oat infection by F. langsethiae as quantified by DNA concentration. HT-2+T-2 quantification and analysis, gave no good evidence that either inoculation or cultural practice had any significant influence on the concentration of mycotoxins in the samples (p>0.05), but samples from minimum tillage with incorporated straw plots resulted in 2.5 times more HT-2+T-2 toxins than samples from ploughed with removed straw. These findings indicate the importance of tillage and crop debris management in the mitigation in an effort to prevent F. langsethiae infection, colonization and possible contamination of oats with HT-2 and T-2 toxins.

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A Food and Agriculture Organization of the United Nations Technical Cooperation Programme (TCP)was undertaken on the western corn rootworm (WCR)in 1997 –1998 to establish a permanent moni- toring network,evaluate a containment and control program,test the feasibility and effectiveness of using a Slam ®-based areawide pest management program,develop training materials,and conduct a risk assessment of the potential for WCR spread and establishment in other areas of Europe.TCP countries were Bosnia-Her- zegovina,Croatia,Hungary,and Romania.Bulgaria and Yugoslavia cooperated as unofficial TCP members. The data from the permanent monitoring network showed that the WCR had spread over an area of about 105,600 km 2 in Central Europe and that economic populations had developed on 14,000 km 2 in Yugoslavia through 1998.The containment and control trapping program,although designed to determine the feasibility of restricting the establishment of WCR beetles in an area,did not prove to be successful due to the number of WCR beetles encountered and their rapid movement into previously uninfested areas.The areawide pest management activity showed that the semiochemical Slam was highly efficacious against WCR beetles with residual activity for up to 2 weeks,thus making it a cost-effective alternative to other controls.Also, investigations showed that WCR will continue to spread and establish in other parts of Europe.

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