Study on the STOP effect of fungicide combinations to control late blight in potato

The effectiveness of different fungicide combinations to control late blight and the STOP effect of these fungicide combinations for the control of foliar and tuber blight under high infection pressure was investigated. Last summer late blight development was arrested in July due to high temperatures and lasting drought. In August the weather was cloudy, rather cold and a lot of rain. These weather conditions were very favourable for late blight. Due to the heat waves of June and July the foliage started to die allready in August and P. infestans developped very fast in the second part of August. Because of that no incidence of foliage blight was scored. No significant differences in yield were observed for the different treatments applied. The combination cyazofamid + heptamethyltrisiloxaan (Ranman) + propamocarb + chlorothalonil (Tattoo C) had the highest yield. The percent diseased tubers fluctuated between 14,9 and 45,1 % for the different treatments tested. The amount of blighted tubers was lowest for fluazinam (Shirlan) + cymoxanil +chlorothalonil (Mixanil) and fluazinam (Shirlan) + benthiavalicarb + mancozeb (Valicarb)

Study on the curative and eradicant action of fungicide combinations to control late blight in potato

Commercial fungicide combinations were tested in the field for efficacy on foliar late blight caused by Phytophthora infestans in substitution of tin. When the first disease symptoms appeared, the tested fungicide treatments for late blight control were applied 3 times at 3-day intervals. The effect of the fungicide treatments on epidemic development, tuber rot and blight incidence and tuber yields were determined. Last summer late blight development was arrested in June due to high temperatures and lasting drought. August was characterized by rather low temperatures and high rainfall. These weather conditions were very favourable for the development of late blight. The foliar protection against P. infestans was comparable for all the tested fungicide combinations. The effect of combinations with dimethomorph + mancozeb (AcrobatC, 2.5 kg/ha) was less suppressive for P. infestans than the other fungicides tested. Lowest foliar disease severity was recorded in plots treated with fluazinam (Shirlan, 0.4 l/ha) + cymoxanil + chlorothalonil (Mixanil, 2 l/ha). Furthermore, highest tuber yield was noted in plots treated with fluazinam (Shirlan, 0.4 l/ha) + cymoxanil + chlorothalonil (Mixanil, 2 l/ha). The percentage blighted tubers fluctuated between 5 and 11 %. No fungicide combinations completely arrested epidemic development under the environmental conditions of the trial. However, fluazinam (Shirlan, 0.4 l/ha) + cymoxanil + chlorothalonil (Mixanil, 2 l/ha) controlled P. infestans most effectively

Effects of therapeutants and temperature on pollen germination, pollen tube growth and fruit set in fruit crops : a thesis presented in partial fulfilment of the requirements for the degree of Master of Horticultural Science at Massey University

This study involved assessments of therapeutant effects on pollination and fruit set; of temperature effects on pollen germination and pollen tube growth in apples, peaches and kiwifruits; of flowerage effects on pollen germination and pollen tube growth in kiwifruit styles; and of hand pollination effects on fruit set, fruit weight and seed numbers per fruit in kiwifruit vines. From the point of view of their in vitro effects on pollen germination therapeutants can be listed in order of decreasing inhibitory effect as follows: (a) for apples - mancozeb plus dinocap, triforine, dichlofluanid, bupirimate, bayleton, citowett R captan and mancozeb; (b) for peaches - triforine, vinclozoline, streptomycin plus triforine, mancozeb, captafol, iprodione, dichlofluanid, streptomycin and benomyl; and (c) for kiwifruits - dichlofluanid, captan and vinclozoline. However, it appeared that while in vitro a therapeutant was very inhibitory, the application of a spray to anthers in an intact flower did not affect the germination of pollen subsequently released by those anthers. Fungicides proven to be toxic to pollen in vitro did not necessarily produce similarly toxic effects in vivo. Reasons for such varying effects of fungicides on pollen germination and pollen tube growth in vitro and in vivo are suggested. At 24 hours after pollination the number of pollen tubes growing more than 1/2 the style length of kiwifruit (Hayward) flowers one to two days old were 38% and 27% higher than in flowers less than one day old and more than three days old respectively. In apples 5 sprays of either bayleton or captan, 3 sprays of either of the therapeutants mancozeb, mancozeb plus dinocap, and triforine and a wetting agent citowett R applied during bloom period caused no effect in fruit set in Golden Delicious trees; and 3 bupirimate sprays during bloom period had no effect on the fruit set in Splendour trees. In peaches 6 sprays of either captafol, or benomyl or iprodione, 5 sprays of either mancozeb or vinclozoline or streptomycin or triforine during bloom period caused no effect on fruit set in Golden Queen trees. Three sprays of streptomycin or dichlofluanid caused no effect but 3 sprays of triforine, triforine plus streptomycin or of ethephon caused 50%, 70% and 90% reduction in fruit set in Red Haven peach trees. In kiwifruits 3 sprays of either dichlofluanid, captan or vinclozoline reduced seed numbers per fruit by 37% but did not affect fruit set or fruit weight. Thus in vitro and in vivo studies were useful in determining therapeutant effects on pollen but did not necessarily provide information on their effects on fruit set in apple, peach and kiwifruit and on fruit weight and seed numbers per fruit in kiwifruit. The germination of both apple and peach pollen was higher at 24°C than at 16°C, 20°C, 28°C and at 32°C. After 18 hours incubation pollen tubes were longer at 28°C and at 32°C than at 16°C, 20°C and 24°C. In vivo studies with kiwifruit (Matua) pollen showed that pollen germination at 14°C, 18°C, 22°C and 26°C did not differ significantly. Temperatures both higher and lower than the temperature range 18 to 22°C were found to be inhibitory to pollen tube growth in kiwifruit (Hayward) styles. Hand pollination of flowers did not influence percentage fruit set but increased fruit weight and seed numbers per fruit in kiwifruit (Hayward) vines. Because fruit weight was positively correlated with seed number per fruit in fruits from both bee pollinated and bee plus hand pollinated flower clusters, supplementary pollination may play an important role in the production of fruit in kiwifruit orchards

Effect of adjuvants on the efficiency of benthiavalicarb plus mancozeb (Valbon 1.6 kg/ha) on the control of late blight in potato

Industrial adjuvants were tested in combination with benthiavalicarb plus mancozeb (Valbon 1.6 kg/ha) in the field to investigate their efficacy on foliar late blight caused by Phytophthora infestans. The tested adjuvant-fungicide treatments for late blight control were applied 6 times at 7-day intervals. The effect of the adjuvant-fungicide treatments on epidemic development, tuber blight and tuber yields were determined. Because of the favourable weather conditions a high disease pressure could be observed. The incidence of foliage blight was scored and at the end of the growing season the disease level was lower in plots sprayed with the Valbon-adjuvant combinations than in plots treated with only Valbon. The addition of an adjuvant had a clearly positive effect on the tuber yield although the differences were not significant. In the plots treated with Valbon 6.9 % infected tubers were observed. The mean tuber infection of plots sprayed with the Valbon-adjuvant combinations fluctuated between 2.3 and 15.6 %

Soil and water pollution in a banana production region in tropical Mexico

The effects of abundant Mancozeb (Mn, Zn— bisdithiocarbamate) applications (2.5 kg ha-1week-1 for 10 years) on soil and surface-, subsurface- and groundwater pollution were monitored in a banana production region of tropical Mexico. In soils, severe manganese accumulation was observed, wheras the main metabolite ethylenethiourea was near the detection limit. Surface and subsurface water was highly polluted with ethylenethiourea, the main metabolite of Mancozeb (22.5 and 4.3 lg L-1, respectively), but not with manganese. In deep ground water, no ethylenethiourea was detected. The level of pollution in the region presents a worrisome risk for aquatic life and for human health

Mancozeb impairs the ultrastructure of mouse granulosa cells in a dose-dependent manner

Mancozeb, an ethylene bis-dithiocarbamate, is widely used as a fungicide and exerts reproductive toxicity in vivo and in vitro in mouse oocytes by altering spindle morphology and impairing the ability to fertilize. Mancozeb also induces a premalignant status in mouse granulosa cells (GCs) cultured in vitro, as indicated by decreased p53 expression and tenuous oxidative stress. However, the presence and extent of ultrastructural alterations induced by mancozeb on GCs in vitro have not yet been reported. Using an in vitro model of reproductive toxicity, comprising parietal GCs from mouse antral follicles cultured with increasing concentrations of mancozeb (0.001-1 µg/ml), we sought to ascertain the in vitro ultrastructural cell toxicity by means of transmission (TEM) and scanning (SEM) electron microscopy. The results showed a dose-dependent toxicity of mancozeb on mouse GCs. Ultrastructural data showed intercellular contact alterations, nuclear membrane irregularities, and chromatin marginalization at lower concentrations, and showed chromatin condensation, membrane blebbing, and cytoplasmic vacuolization at higher concentrations. Morphometric analysis evidenced a reduction of mitochondrial length in GCs exposed to mancozeb 0.01-1 µg/ml and a dose-dependent increase of vacuole dimension. In conclusion, mancozeb induced dose-dependent toxicity against GCs in vitro, including ultrastructural signs of cell degeneration compatible with apoptosis, likely due to the toxic breakdown product ethylenethiourea. These alterations may represent a major cause of reduced/delayed/missed oocyte maturation in cases of infertility associated with exposure to pesticides

Technological learning for innovating towards sustainable cultivation practices: the Vietnamese smallholder rose sector

Deregulation and globalisation has altered the views of public involvement in development and led to strategies focusing on private sector participation. An implicit assumption seems to be that these linkages will enhance the technological capacity of smallholder producers by way of more cost-efficient technologies trickling down through the value chain or by quality requirements inducing best practices. The argument put forward in this paper is that sustainable non traditional agricultural chain development requires more purposeful actions and institutional transitions, both in the public and private spheres, targeting improved upstream innovative capacities. Empirical findings from a Dutch-Vietnamese partnership on sustainable floriculture development are used. Research revealed that the pest and disease control solutions applied by smallholder rose growers were incremental adaptations of experiences obtained in former food crop cultivation practices. Floriculture however may require more drastic changes in cultivation practices to make the sector more environmentally benign. In the case of smallholder Vietnamese flower producers, this implies adaptation of knowledge and skills currently not present. An important hindrance in promoting this knowledge and skills appears to be the weak vertical linkages between flower growers and public and private research and development organizations

Pesticide Use on Fruit and Vegetable Crops in Ohio 1990

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Epidemiology and integrated control of Potato Late Blight in Europe

Phytophthora infestans, the causal agent of late blight, is a major threat to potato production in northwestern Europe. Before 1980, the worldwide population of P. infestans outside Mexico appeared to be asexual and to consist of a single clonal lineage of A1 mating type characterized by a single genotype. It is widely believed that new strains migrated into Europe in 1976 and that this led to subsequent population changes including the introduction of the A2 mating type. The population characteristics of recently collected isolates in NW Europe show a diverse population including both mating types, sexual reproduction and oospores, although differences are observed between regions. Although it is difficult to find direct evidence that new strains are more aggressive, there are several indications from experiments and field epidemics that the aggressiveness of P. infestans has increased in the past 20 years. The relative importance of the different primary inoculum sources and specific measures for reducing their role, such as covering dumps with plastic and preventing seed tubers from becoming infected, is described for the different regions. In NW Europe, varieties with greater resistance tend not to be grown on a large scale. From the grower’s perspective, the savings in fungicide input that can be achieved with these varieties are not compensated by the higher (perceived) risk of blight. Fungicides play a crucial role in the integrated control of late blight. The spray strategies in NW Europe and a table of the specific attributes of the most important fungicides in Europe are presented. The development and use of decision support systems (DSSs) in NW Europe are described. In The Netherlands, it is estimated that almost 40% of potato growers use recommendations based on commercially available DSS. In the Nordic countries, a new DSS concept with a fixed 7-day spray interval and a variable dose rate is being tested. In the UK, commercially available DSSs are used for c. 8% of the area. The validity of Smith Periods for the new population of P. infestans in the UK is currently being evaluated