Spinosad is a novel insect control agent derived by fermentation of the Actinomycete bacterium, Saccharopolyspora spinosa. Spinosad controls many caterpillar pests in vines, pome fruit and vegetables (including tomatoes and peppers), thrips in tomatoes, peppers and ornamental cultivation and dipterous leafminers in vegetables and ornamentals. Application rates vary between 25 to 100 g of active substance per hectare (g as/ha) and 4.8 to 36 g of active substance per hectolitre (g as/hL) depending on the crop and target pest. It is important that plant protection products are authorized for use only in ways that do not pose an unacceptable risk of harm to honeybees. For this purpose testing was performed to enable the safety of spinosad to be evaluated. The effects of spinosad to honeybees have been extensively researched. Testing has been performed under a variety of conditions in a range of countries globally. Studies to determine the acute toxicity of spinosad under laboratory conditions were conducted to generate LD50 or LC50 values for oral and contact routes of administration. These demonstrated that spinosad was highly toxic to worker honeybees under worst case laboratory conditions and that the oral route of exposure provided the greater risk. Residue tests conducted under laboratory, semi-field and field conditions on worker honeybees foraging on treated foliage indicated that dry product residues were harmless. Therefore the effects seen in the laboratory acute toxicity tests did not translate to a more realistic exposure scenario indicating that safe use patterns for the product can be developed. Semi-field cage studies have also demonstrated that spinosad was safe to bees when applied to flowering crops during periods of bee activity. The majority of studies conducted have indicated that spinosad does not adversely affect honeybee behaviour, brood or queen. It can be concluded that spinosad when used according to the approved product label recommendations, would be safe to foraging worker bees, queen and brood. Additional levels of safety could be achieved by avoiding situations where bees would forage primarily on aphid honey dew.
In the Flemish horticulture Pythium spp. is an important pathogen of tomato plants (Lycopersicon esculenthum) in soilless growing media. Therefore some experiments were conducted to evaluate the possibility of decreasing the damage caused by Pythium spp. by Trichoderma spp. In a tray with several growing media, a suspension of Trichoderma conidia (10(6)/ml growing medium) was applied two weeks before sowing. On some objects, a compost extract (Biostimulus) was added. The growing media used in the experiment were rockwool, recycled rockwool and recycled coconut fibre. After sowing, the trays were covered with perlite. Three isolates of Trichoderma spp.: T. asperellum (Biofungus), T. harzianum (Tri 003) and Trichoderma sp. (KHK) and two isolates of Pythium spp.: P. ultimum (MUCL) en P. aphanidermatum (HRI, UK) were used. Propamocarb was used as a chemical standard. The use of coconut fibre growing medium resulted in a higher percentage (36%) of germination than the rockwool media when only Pythium spp. was used. The presence of the spontaneous developing microflora in the coconut fibre medium gave probably also a suppression of Pythium spp. For that reason the results of the suppression by Trichoderma spp. are not easy to explain and very variable on the different objects. Pythium ultimum was more suppressed than P. aphanidermatum on all the growing media and the application of all the Trichoderma isolates increased the germination percentage of tomato seeds. T. asperellum (Biofungus) gave on rockwool also a good result for the suppression of P. aphanidermatum (increasing of germination with 48%). This effect was comparable with the propamocarb treatment (48%). T. harzianum (Tri 003) gave a small suppression (22%) and Trichoderma sp. (KHK) gave almost no suppression of P. aphanidermatum (7%). When less Trichoderma conidia were applied the germination percentage decreased. The adding of a compost extract (Biostimulus) had no influence on the results. This experiment shows that application of Trichoderma conidia in the presence of Pythium spp. increases the germination percentage of tomato seeds, sowed in the used soilless growing media.
NeemAzal PC (0.5% Azadirachtin) is a new standardised powder formulation from the seed kernels of the tropical Neem tree (Azadirachta indica A. Juss) with an inert carrier. First experiments with beans--as a model-system for hydroponics--show that active ingredient is taken up by the plants through the roots and is transported efficiently with the plant sap to the leaves. After application of NeemAzal PC solution (0.01-1%) to the roots sucking (Aphis fabae Hom., Aphididae) and free feeding (Heliothis armigera Lep., Noctuidae) pest insects can be controlled efficiently. The effects are concentration and time dependent.
To study the gene persistence in the soil environment, soil samples were collected from sugar beet (Beta vulgaris) and chicory (Cichorium intybus) experimental fields just before harvest. They were homogenized, mixed and stored at constant humidity in a non-heated room. Sub-samples of soils were subsequently collected at regular intervals, dried and sieved through a 1.8-mm mesh before DNA was extracted. Specific primers were then used for the detection of plant DNA by hot start PCR. Results reveal that, under laboratory conditions, transgenic and non-transgenic sugar beet DNA was still detected after 25 days incubation in the soil taken from a sugar beet experimental plot while detection of chicory DNA was still possible after 50 days incubation in soil taken from the chicory experimental plot. This might be in correlation with the stronger resistance of chicory radicles to decomposition as compared to radicles from sugar beets.
The preventive activity of 1:8 mixture of cymoxanil and mancozeb against Phytophthora infestans was higher than that of either the two single ingredients or the other nine mixtures. The synergistic interaction existed (synergy ratio 2.01) between the two at the mixing ratio of 1:8, whereas additive interaction (synergy ratios ranged from 0.73 to 1.34) existed at the mixing ratios ranging from 1:1 to 1:7, from 1:9 to 1:10, 1:8 was the optimal ratio. The preventive activity of 1:8 mixture was higher than the curative and the eradicative. In addition, the eradicative synergism of inhibiting sporangia production on lesions was stronger than the eradicative synergism of inhibiting lesion extension and suppressing infection of sporangia, and than the curative synergism of inhibiting lesion sporulation on detached potato leaflets.
In vitro, isolates resistant to metalaxyl (M) and oxadixyl (O) of Phytophthora infestans were 11.2% of 62 isolates from potato and tomato in Hebei Province, mean resistance factor was 15,022 fold and 24,733 fold, respectively, no isolates resistant either to cymoxanil (C) or to dimethomorph (D) were detected. On the other hand, in vivo, isolates resistant to M and O were 29.0% and 32.7%, respectively, among 217 isolates from potato plants in Weichang and Chongli, Hebei, only one isolate resistant to M and O was found among 88 isolates from tomato plants in Xushui, Hebei. Among 73 isolates from potato in Weichang and Chongli, 6 isolates with A2 mating type were 8.2%, 3 A2 isolates resistant to metalaxyl and oxadixyl. 3 A2 isolates were 6.8% of 44 isolates from tomato in Xushui. Cross resistance in Phytophthora infestans was confirmed between M and O, but no cross resistance between C or D and M or O. The field isolates resistant to M and O were outstandingly fitter than sensitive or intermediate ones, mainly due to stronger sporulation capacity of the field isolates.
The pulse beetle, Callosobruchus maculatus (F.) is a destructive pest of pulses in both storage and field. It is well known that diatomaceous earth (DE) kill the insects by locally absorbing the epicuticular lipid layers leading to high rate of water loss through the cuticle. However, the effectiveness of DE depends on its ability to kill the adults before copulation and egg-laying. Newly emerged virgin males and females of Callosobruchus maculatus (F.) were exposed to the DEs, Fossil-Shield and Silico-Sec on 30 treated mungbeans (Vigna radita (L)). Fecundity, number of beans used for egg-laying and beans without eggs were evaluated after four days; the number of unhatched eggs was evaluated after ten days. It was determined, that the fecundity of female insects decreased sigmoidely with increasing rate of DE content. Percentages of unhatched eggs and seeds without eggs increased with increasing DE dosages. However, the maximum egg densities (eggs per used secd) occurred at 1200 mg DE/kg for Fossil-Shield and Silico-Sec. The reason for such DE-stimulated behaviour of egg laying expressed as a number of seeds with eggs of C. maculatus is not known, but it may be related to the stress caused by the inert dusts or to the reduction of both chemical and physical (tactile) stimuli. Treatment with DEs altered the surface texture of the beans and caused less cohesion between eggs and the seed surface. Only few larvae managed to penetrate into the grains, possibly due to increased grain roughness and repellent effect of DE. A relatively high number of eggs were laid on the surface of those beans where the amount of dust had been locally reduced by adults' movement and their pick up of DE. Therefore, several larvae tried to penetrate into these treated beans, causing a high larval density per partially cleaned bean. All these reasons lead to a progeny decline.
Since several years commercial cauliflower in Belgium is severely affected by a vascular wilt disease. Plants wilt and a vascular discoloration of the cauliflower stems can be observed. The pathogen causes significant yield and quality losses. The first objective of this study was to isolate and characterise the causal agent of this disease. Verticillium species could be isolated out of the vascular tissue of symptomatic cauliflower plants. Morphological and physiological characteristics indicated that the isolates from cauliflower could be identified as the new and brassica-related species V. longisporum. Secondly, the susceptibility of several cauliflower cultivars to V. longisporum was evaluated by way of field experiments in naturally infested soil. At harvest, vascular discoloration was evaluated by a visual score. These experiments pointed to considerable differences between cultivars in their susceptibility to V. longisporum. The final goal of this study was to find a way to control the wilt disease on cauliflower. A field experiment showed that vascular discoloration of cauliflower was significantly reduced when soil was incorporated with broccoli residues, two Brassica green manures (B. juncea or B. nigra) or two commercial biological products based on Talaromyces flavus or Trichoderma sp..
The rhizomania is known in Hungary since 1982. The causal agent, Beet necrotic yellow vein benyvirus (BNYVV) is transmitted by a soil-borne fungus Polymyxa betae Keskin. A field experiment was done under rhizomania infested and non-infested conditions to compare the yield parameters of five tolerant and four sensitive sugar beet hybrids. Tolerant varieties produced higher root yield under rhizomania infected conditions. The root yields of the sensitive varieties were similar to the tolerant ones on the uninfested field, but the root mass of some tolerant varieties exceeded the production of the former group. Subsoiling was carried out in two strips of a heavily infested field, while conventional soil cultivation was done on the other parts. There was not any other difference in the cultivation of the treated and control areas. Sugar beet root samples were collected at the time of harvesting from the subsoiled and control plots. Beet necrotic yellow vein virus (BNYVV) infection was tested by means of ELISA. Virus content, yield and yield parameters of samples were compared. There were no significant differences in virus infection between sugar beet roots derived from subsoiled and untreated plots. Ratio of BNYVV infected plants was about 90% in both areas. However, yield and yield parameters showed remarkable difference. Root yield of treated plots, calculated from average individual root weight and 80,000 plant/ha plant density exceeded by 140% the yield of control. Sugar content was 2.6% higher and the harmful non-sugar content was lower on the subsoiled plots. Owing to the favourable chemical and technological value of beet the white sugar content was approximately three-times higher on the treated area.
The competitive saprophytic fungus Ulocladium atrum was selected on the basis of its antagonistic potential for the control of grey mould caused by the necrotrophic pathogen Botrytis cinerea. Field trials were carried out to asses the efficacy of U. atrum as a biocontrol agent against B. cinerea in grapevine. The results demonstrated that under moderate disease pressure U. atrum had the potential to control grey mould, whereas under high disease pressure the efficacy was not sufficient to substitute the use of fungicides completely.
Since 1994 the importance of tan spot of wheat has increased in the wheat growing areas of the Netherlands. The purpose of the present study was to determine inoculum sources of this disease caused by Pyrenophora tritici-repentis. Both in 1999 and 2000, the incidence of tan spot was assessed in 40 commercial fields of winter wheat scattered over the main wheat growing areas of the Netherlands. Adjoining fields were checked for presence of stubble or crops with straw covers and the surrounding vegetation was searched for grasses with leaf spots. Straw and affected leaves of wheat and grasses were examined for P. tritici-repentis. In greenhouse experiments the pathogenicity of isolates from alternative hosts was compared with that of isolates from wheat. The possible development of P. tritici-repentis perithecia on straw of crops other than wheat was explored for barley, oat, rye grass and rape grown in fields nearby a tan spot affected wheat field. Furthermore, dispersal of tan spot was studied in a field trial in which winter wheat was sown leeward to stubble of above-mentioned severely tan spot affected wheat crop. During the surveys three cases were found of wheat crops adjoining fields with P. tritici-repentis infested stubble or straw covers. It was only after flowering that the first symptoms of tan spot appeared in the three commercial wheat crops. Couch grass (Elymus repens) was often found as host of P. tritici-repentis. In the surroundings of more then half of the wheat crops affected by tan spot this weed was also infected. Pyrenophora tritici-repentis isolates from couch grass were found to be as pathogenic to wheat as isolates from wheat to both wheat and couch grass. The observations on straw of barley, oat, rye grass, rape and wheat revealed P. tritici-repentis perithecia only on wheat straw. In the field trial with wheat sown leeward to P. tritici-repentis infested stubble, first symptoms of tan spot appeared on wheat during April and May when the release of ascospores was at a maximum. Disease severity gradually decreased with increasing distance from the side adjoining the stubble. The results of this study indicate that straw covers and stubble from tan spot diseased wheat crops and cough grass are inoculum sources of P. tritici-repentis.
One hundred and forty microfungi (Ascomycetes and Deuteromycetes) were collected in the "Landschaftspark Duisburg-Nord" located in North Rhine-Westphalia. New hosts for rarely found fungi are recorded for the first time. New for Germany are Massaria inquinans (Tode) De Not. and Nitschkia grevillei (Rhem) Nannf. on Acer pseudoplatanus L., Pirottaea nigrostriata Graddon on Artemisia vulgaris L., Ceratopycnis clematidis Höhn. on Clematis vitalba L., Dasyscyphus aff. humuli (W. Phillips) Dennis on Humulus lupulus L. and Leptosphaeria derasa (Berk. & Br.) Auersw. on Senecio inaequidens DC. New for North Rhine-Westphalia are Chaetosphaerella phaeostroma (Durieu & Mont.) E. Müller & Booth and Phomopsis platanoides (Cooke) Died. on Acer pseudoplatanus L., Microsphaeropsis pseudaspera Sutton, Mycosphaerella osborniae D. Hawksw. & Sivan. and Phomopsis oblita Sacc. on Artemisia vulgaris L., Leptosphaeria acuta (Fr.) P. Karst. and Leptosphaeria doliolum (Pers.) Ces. & De Not. on Bryonia dioica Jacq., Ophiobolus erythrosporus (Riess) G. Winter and Pleospora herbarum (Pers.) Rabenh. ex Ces. & De Not. on Dipsacus sylvestris (Huds), Keissleriella ocellata (Niessl) Bose on Hypericum perforatum L., Dactylaria aff. graminicola on Lolium perenne L., Siroplacodium aff. atrum on Oenothera beinnis L., Diatrypella favacea (Fr.) Sacc. on Prunus spec., Hapalosphaeria deformans (Syd.) Syd. and Microdiscula rubicola (Bres.) Höhn. on Rubus fructicosus agg. L., Cryptodiaporthe salicina (Pers.) Wehm. on Salix alba L. and Pleurophoma pleurospora (Sacc.) Höhn. on Salix caprea L.
Earthworms (Lumbricus terrestris L.) were exposed to commercial formulations of endosulfan and aldicarb for 2, 7, and 15 days, and the LC10, LC25, and LC50 were determined. Worms were then exposed to LC10, LC25, and LC50 concentrations of endosulfan and LC10 and LC25 concentrations of aldicarb. The growth rate and total protein content were determined and related to endosulfan and aldicarb residues in soil and earthworms. Aldicarb was more toxic than endosulfan under the experimental conditions. The residues of endosulfan and aldicarb caused a significant reduction in the growth rate and total protein content of earthworms. The residues of endosulfan and aldicarb were monitored in soil and earthworms after 2, 7, and 15 days of exposure. The residues remaining in the soil after the experiments ranged between 37.75% and 68.54% of the applied concentration for endosulfan and between 10.13% and 67.71% of the applied concentration for aldicarb. Small amounts of both insecticides were detected in worms, and accumulation was more important for endosulfan. This study proposes the use of growth rate and total protein content as biomarkers for contamination by endosulfan and aldicarb. © 2003 Wiley Periodicals, Inc. Environ Toxicol 18: 1–8, 2003.
Adjuvants can improve the targeting of pesticides and nutrients. During the last thirty years, the use of adjuvants has become a useful tool for optimising the efficacy of pesticides. In the USA volumes of approximately 110 ML oil and 20 ML surfactant are used per year. For several reasons, the yearly volume for oils and surfactants in Europe is much lower, being approximately 10 ML per year for oils and a similar amount for surfactants. The red line in the developments is a fine-tuning between composition of adjuvants and their function plus effect in a certain application. This means that knowledge-based development of adjuvants more than the "spray and pray" approach will gain importance. This paper describes in a nutshell the different chemistries and possible functions of adjuvants. Recent developments are presented regarding adjuvants for glyphosate, waxes, alkoxylated triglycerides, calcium nitrate and adjuvant influence on drift.
Four surfactants Tween 20, Agral 90, Silwet L77 and Break Thru, commonly used in the formulations of agricultural products, were evaluated on their spray performance and dynamic surface tension. In a spray test the Dv 50 (micron) or the Volume Median Diameter and the percentage of droplets with diameter below 100 microns (drift sensitive droplets), were measured for different kind of nozzles varying from the classical flat fan up to the low drift nozzles. The spectra changed considerably when different kind of nozzles and different kind of surfactants were used, the concentration effect was less important. The dynamic tension of the different surfactant solutions could not always explain the changes in droplet spectrum.
Based on the morphological characteristics of the ustilospores, the geographical distribution and host preference of common bunt Tilletia foetidae and T. caries on bread wheat and durum wheat in Syria has been studied. The spore wall structure forms the most feasible and convenient method for differentiation between the two pathogens. Accordingly, T. foetidae is the most prevalent pathogen in North Syria and the predominant pathogen in the bread wheat. T. caries was widespread in durum wheat in South Syria. This phenomenon has been confirmed in artificial inoculation tests and discussed as host-preference in T. foetidae and T. caries irrespective of the geographical area in which the disease is observed and irrespective of the environmental conditions. T. foetida, however was the predominant pathogen on bread wheat, while T. caries preferentially attacks durum wheat.
Experiments were carried out with 133 bacterial isolates that were collected from soybean rhizosphere. These strains were used to investigate their biocontrol traits in vitro and their ability to suppress the soybean damping-off in vivo (soil and seed treatments). Three highly effective isolates were selected from these antagonists for subsequent studies. According to the biochemical, physiological and morphological tests, these isolates (B-2, B-12 and B-80) were identified as Bacillus spp. In soil treatment, the isolate B-3 with 70.8%, B-12 with 66.7%, B-80 with 54.2% had the highest effect on reducing the soybean damping-off. In seed treatment, the isolates B-43 with 62.5%, B-12 with 58.4 and B-80 with 45.8%, had the greatest effect on reducing the disease. These isolates produced volatile metabolites that inhibited mycelial growth of Phytophthora sojae.
Infection by Mycosphaerella graminicola (anamorph Septoria tritici) was monitored between April and July 2001 on F6 to flag leaf in 11 farmers' fields or fungicide trials. Data were analysed by mean of the decision support system "Proculture" which links an automatic weather station of the PAMESEB network to a particular field, simulates plant development with adjustment by one phenological observation during the stem elongation and analyses superposition of emerged leaves and infection events (http://www.fymy.ucl.ac.be/proculture). Several climatic events favourable for the infection and dissemination of M. graminicola occurred between October 2000 and March 2001 and allowed build up of a large amount of inoculum on the lower leaves at the end of the winter. The start of stem elongation was associated with frequent rainy periods during April, causing early infection of F5, F4 and up to F3 in some precocious fields. Dry weather with only a few local showers during most of May and June slowed down spread of infection to the upper leaves, leading to absence of M. graminicola infection of the flag leaf in 9 out of the 11 fields. Yield increase by a single fungicide spray ranged from 800 to 2200 kg/ha. A second treatment was cost effective in none of the fields. The interest and limitation of the decision support system for understanding M. graminicola epidemic and for guiding decision on spray timing are discussed.
Numbers of strains of Trichoderma asperellum are known as biological control agents of certain root pathogens of tomato (Lycopersicon esculentum). The restricted use of fungicides is sometimes useful in combination with these biological control agents. Therefore some experiments were conducted to evaluate the growth of T. asperellum in the presence of fungicides as Previcur (active substance propamocarb) and Sumico (with the active substance carbendazim and diethofencarb). The influence of these fungicides was first examined in laboratory conditions. The fungus was brought on a potato dextrose agar where the fungicides Previcur, Sumico and carbendazim were added in a concentration of 0.1x, 1x and 10x the recommended dose. The growth of T. asperellum was totally inhibited by the three Sumico and carbendazim concentrations. T. asperellum knew a small but significant decrease of growth when the 10x dose of Previcur was added. Afterwards the influence of these fungicides on the fungus was tested in field conditions in the greenhouse. The fungus was applied to the roots of the tomato plant, which was grown on a rockwool medium. Previcur and Sumico were submitted to the plants using the normal procedure. The results of the tests showed that in field conditions there was no effect of the fungicide treatment on the presence of the fungus, although the laboratory tests showed the opposite for Sumico. To explain this contradiction two other experiments were conducted to follow the migration of the Sumico after treatment. A residue analysis showed that the highest concentration of Sumico was detected in the rockwool medium, and some residues were found in the drain water and the stems. Even with a 100x recommended dose of Sumico the fungus was still present the day after the treatment.
