![]() In the North, as reported in the news the month of May has been very rainy with floods in the province of Romagna (Ravenna, Forlì, Cesena) that also affected tomato cultivation and mainly organic crops. The crop in the south of the country has already been harvested, while in the North-East and North-West, planting is finished for a start of the harvest in July. Hopefully more information can be provided soon. This means that the current estimates for Iran (1.3 million tonnes) are probably too low. Unfortunately, there is no data available so far now from any governmental departments for indications of tomato this year, the only indication is that this year’s crop will be similar to last year so 6 to 7 million tonnes for a tomato paste production of 600,000 to 700,000 tonnes. The total surfaces planted are 1,350 hectares for an expected production of 100,000 tonnes. The weather is good, and planting was done in time with only very short delays due to rains. The forecast remains unchanged at 440,000 tonnes. There is currently a warm spell with about 30☌ over the last two days. The weather has been quite erratic with unseasonable rains most days which has not caused any damages yet but some delays in plant development and a need for treatment against Alternaria and phytophthora development. The forecast remains 160,000 tonnes for a total of 2240 hectares. Wet conditions are starting to favour the development of blight on some localised fields. The planting is now finished in the south-west where conditions have been good, but delayed in the south-east due to rains at the start of the spring and storms most evening in the last two weeks. Due to increased surfaces planted (15,000 hectares instead of 12,500), the total forecast is now raised to 600,000 tonnes. More than in other years, however, expectations are that this volume may not be achieved due to risks linked with a late harvest in many regions following delays in planting and development of diseases because of a generally wet spring. Map showing 7-day rainfall and late blight DSV values across Ontario.As harvest is now over in the southern hemisphere and planting is finishing in the northern hemisphere, the total forecast for the 2023 season is slightly reduced to 42.5 million tonnes. WIN suggests applying fungicide at every 15 to 20 DSV since the late blight has already been reported in Ontario and neighboring states. The 7-day DSV and rainfall for this week is also very high in most of the locations as conditions are still favourable for development (Fig. The thresholds for subsequent sprays have been reached around 7 to 13 days depending on the growing conditions and locations across the province. Map showing accumulated rainfall and late blight DSV values across Ontario. The first spray threshold reached 3 to 4 weeks earlier than the first symptom of late blight reported in the province indicates that the model recommended the first spray at the appropriate time to protect tomato plants from late blight. Late blight in tomatoes was reported on July 10th in Essex County. The first spray threshold (40 to 45 DSV) was reached during mid to 3rd week of June depending on the locations (Fig. 2) creating very favourable environment for late blight infection and the pathogen dispersal. High and frequent rainfall occurred in June and early July (Fig. The 2015 growing season late blight advisory model has shown very high risks of late blight infection across tomato growing regions in Ontario (Fig.2). Comparison of late blight disease severity value (DSV) from three locations in Ontario in 2015 (Assuming that fungicides were applied at 40/20 DSV intervals). The subsequent sprays can be made at 15-25 DSV depending on the crop stages, varietal resistance, and incidence of late blight in the region. Growers can apply first fungicide application when the DSV has reached 40-45 DSV accumulating since the planting date (Fig 1). Management guidelines are also available on the website to guide fungicide timing using DSV threshold. They can update the spray dates to recalculate the DSV graph since last spray. Growers will get accumulated DSV graph since the planting date. Growers can sign up at register their fields, and add 'tomato' crop to access site-specific late blight advisory. Weather INnovations Consulting LP has been deploying several site-specific decision support tools to advise Ontario Vegetable Growers on better fungicide timing to control fungal diseases of tomatoes, leafy vegetables, carrot, and asparagus at WIN has developed a late blight advisory tool, which calculates daily disease severity values (DSV), indicating the daily risk for late blight infection. Rishi Burlakoti, Weather INnovations Consulting LP, Chatham ON Site-specific Late Blight Advisory for Ontario Tomato Growersĭr.
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