Fungicides use against potato late blight. Rolot Jean-Louis

Transcription

1 Fungicides use against potato late blight. Rolot Jean-Louis Armstatehydromet and Ministry of Agriculture Yerevan, March 2012

2 Introduction. -Potato production in the world: 320 million tons -4th place in the world food production (after wheat, corn and rice) -China is the leading potato producer with > 4 millions hectares -In comparison, Belgium, ha and 3 millions tons -Late blight (Phytophthora infestans, oomycete), one of the most important disease through the world: can devastate the potato crops at a high speed if conditions are favourable -Was introduced in Europe (Belgium) with a shipment from America in 1845 and then spread quickly through Europe -Was responsible for great population migrations (Irish Potato Famine in the mid of 18 th century, with the death of one million of people) -Today still a very important issue ant threat: global damage estimated by CIP in developing countries is a production loss of 15%. In the Netherlands Haverkort estimates the cost for controlling late blight at 115,5 million of euro)

3 Introduction. Fighting against Late blight is very important and necessary especially because most of the varieties are susceptible One of the tools we have at our disposal is the use of fungicides As fungicides are costly and harmfull for the people and environment, they have to be used carefully knowing that there are basic measures to be taken at first: Use of tolerant or resistant varieties (not easy) Country and fields survey to detect the first attacks in spring Fight against early infections in waste potato piles (inoculum) Adopt good sanitation practices like the use of certified seeds Use of Decision Support Systems in order to increase the efficacy of the struggle (application of fungicides in the right time) A good understanding of how they are working

4 Potato Late Blight Fungicides Classification (Euroblight group: ) Mobility: Do they move in the plant? How? Mode of action: Preventive Curative Anti-sporulant Effectiveness: On which part of the plant are they active Very important to know in order to make the good choice at the right time! Rainfastness: Are they washable by rains?

5 Potato Late Blight Fungicides Classification Mobility Contact fungicides: fungicides which are not entering in the plant form a layer of active substance on the surfaces of the plant Translaminar fungicides: fungicides which are entering in the plant but not circulating in the plant can cross the leaf thickness Systemic fungicides: fungicides which are entering and circulating in the plant generally, they move to new formed parts of the plant

6 Potato Late Blight Fungicides Classification Mode of action Preventive: must be present on the plant before a possible infection process generally, all the fungicides have such an action Curative: fungicide active against P. infestans during the immediate post infection period, but before symptoms become visible (active during the early latent period) can stop the infection immediately after its starting Anti-sporulant: P. infestans lesions are affected by the fungicide by decreasing sporangiophore formation and/or decreasing the viabilitity of spores and sporangia formed

7 Potato Late Blight Fungicides Classification Effectiveness On leaves: can be measured by field tests (% of destruction when the fungicide is applied and/or relatively to a control not protected) On new growth : are the new leaves formed after the fungicide application protected or not? On stems: stems can be attacked some fungicides are better than others to protect stems On tubers: tubers attacked by P. infestans can develop big problems when stored some fungicides are better than others to protect tubers

8 Potato Late Blight Fungicides Classification Rainfastness Rains can wash the fungicides applied on plants: some fungicides are not washable, some fungicides do resist more better to the rain action than others

9 PRODUCT EFFECTIVENESS MODE OF ACTION RAIN MOBILITY LEAF BLIGHT NEW GROWTH STEM BLIGHT TUBER BLIGHT PREVENTIVE CURATIVE ANTI SPOR. Copper ž 0 0 Conta ct Dithiocarbamates ¾ Conta ct Chlorothalonil Ÿ ¾ Conta ct Cyazofamid Conta ct Fluazinam 2.9 ž 0 0 ¾ Conta ct Zoxamide + mancozeb ¾ Conta ct + Conta ct Famoxadone + Cymoxanil Ÿ N/A ¾ Conta ct + Translam. Mandipropamid 4.0 ž ¾ Translam Benthiavalicarb + mancozeb 3.7 ž ž ž ¾ Translam. Cymoxanil + mancozeb Ÿ 0 Translam. Cymoxanil + Metiram Ÿ 0 Translam. Cymoxanil + Copper ž 0 Translam. Dimethomorph Ÿ ž ¾ Translam. Mancozeb Fenamidone + Mancozeb Benalaxyl + Mancozeb Metalaxyl + Mancozeb Metalaxyl + Fluazinam Propamocarb + Mancozeb Propamocarb + Chlorothalonil Propamocarb + Fenamidone Propamocarb + Fluopicolide 2.6 ž Ÿ 0 ¾ Translam. N/A Ÿ Ù ¾ Sys temi c N/A ž ¼ ¾ Sys temi c N/A Ÿ Ú ¾ Sys temi c Ÿ Ÿ Sys temi c 3.4 ž Ÿ Sys temi c 2.5 ž Ú Sys temi c + Translam 3.8 ¾ Sys temi c + 0 : no effect : reasonable effect : good effect : very good effect N/A : not recommended Source:

10 Potato Late Blight Fungicides Use in Practice Contact fungicides Copper, Dithiocarbamates good fungicides, cheap in case of rapid development of the plants (emergence to flowering), think that the new formed leaves are not protected in case of favourable conditions for infection processes need a good application (all the parts of the plants have to be covered) susceptible to the washing action of the rains: need to be applied again in case of rainfall up to 20 mm no or poor protection against tubers infection no curative effect, have to be applied before the begining of an infection process (preventive mode of action) generally used in case of low infection pressure

11 Potato Late Blight Fungicides Use in Practice Contact fungicides Cyazofamid, Fluazinam, Zoxamide: good tubers protection: can be used after the setting of tuberization, after flowering Very good resistance against the wash action of the rain (> 50 mm), especially cyazofamid No curative effect, have to be applied before the begining of an infection process In case of rapid development of the plants (emergence to flowering), think that the new formed leaves after treatment are not protected (except cyazofamid) More expensive

12 Potato Late Blight Fungicides Use in Practice Translaminar fungicides Cymoxanil, Mandipropamid, Benthiavalicarb, Dimetomorph Fenamidone: Not washable by rains: very interesting products in case of frequent rainfall episodes Some of them provides good curative effects: cymoxanil gives good results in fighting infections just installed in the plants, gives also good results to diminish the importance of fructification (sporangiophore, sporangia and spores) Mandipropamid has a good additional effect on newly formed leaves, on the tubers protection More expensive

13 Potato Late Blight Fungicides Use in Practice Systemic fungicides Benalaxyl, Metalaxyl, Propamocarb: Not washable by rains: very interesting products in case of frequent rainfall episodes The systemicity provides a protection of the whole plant: systemicity from downside to upside of the plant The new formed leaves will be protected provided that the fungicide concentration in the plant will be high enough (take care of plants in intense growth) Good curative effects: can fight infections already installed in plants, before the fructification phase, significative action on the sporangiophores, sporangia and spores Metalaxyl and Benalaxyl can favour the selection of late blight resistant strains in the field: have to be used not more than 2-3 times in the season For an optimal effect, have to be used when the plant growth is maximum (before the flowering)

14 Potato Late Blight Fungicides Use in Practice Important things to be respected in fighting potato late blight: The struggle must be PREVENTIVE: don t wait the first symptoms before to begin the application of fungicides Once late blight is installed in the crop, it will be difficult to eradicate it, even in the case of curative and anti-sporulant fungicides use Be sure that spraying machines are in good working conditions (nozzles, pressure, ) Develop good spraying practices: don t spray if wind is too hard, be sure that all the plants are treated (crop borders, joins between two spraying routes, ) Make observations in the crop, be aware about the situation in the neighbourhood