Key factors in integrated pest management are crop rotation, variety, seed quality/treatment, agronomics, seedling health, crop scouting, and cultural/chemical controls.
Unfortunately, even when we do everything right, plant disease can still rear its ugly head. That is because weather conditions may be highly favourable for fungal growth/sporulation, infection, and spread. According to Saskatchewan Agriculture’s final Crop Report for 2010, most of the province received 115 to 150 per cent of average precipitation in 2010. Since most of our common pulse crop pathogens prefer moist conditions, diseases thrived this season.
Reports of isolated cases and/ or widespread incidence of pulse diseases in Saskatchewan in 2010 included: ascochyta blight, anthracnose, sclerotinia white mould, botrytis grey mould, and stemphylium blight on lentil crops; the ascochyta complex on pea crops; ascochyta blight on chickpea crops; and sclerotinia white mould on dry bean crops.
These diseases will have a resulting potential impact on pathogen levels and disease risk for next year.
Many lentil crops suffered as a result of thick canopies and excess moisture in 2010. Poor crop rotations caught up to some farmers. Overall, the impact of the wet weather was the challenge for almost everyone. The disease spread, lentils sprouted, and the crop could not beharvested in a timely fashion.
A small, informal survey of 29 lentil fields was conducted by the Saskatchewan Ministry of Agriculture in west-central and southwest Saskatchewan in August. Disease assessments were made by observing plants in a few sites in each field, noting the presence or absence of disease symptoms. Stemphylium blight was observed in 83 per cent of the crops surveyed; sclerotinia white mould in 59 per cent; botrytis grey mould in 41 per cent; anthracnose in 52 per cent; and ascochyta blight in 24 per cent.
Mouldy lentils (sclerotinia and botrytis) caused the most devastating impact, as the effects were highly visible. While we know there are fungicides that can control these fungi, it was virtually impossible to get the products through the thick canopy, rendering farmers helpless by the time the disease hit late in the season.
The key to preventing a fungal disaster in 2011 will be to break the moulds’ disease cycle through proper crop rotation. This means diversifying and avoiding other hosts of sclerotinia, such as canola in problematic fields. In other words, canola on lentil stubble or lentil on canola stubble is not recommended. To provide the best chance for crops next season, it is critically important to implement recommended agronomic and IPM strategies outlined in crop production manuals, disease guides, and fact sheets. We cannot control the weather, which impacts all aspects of production. However, due diligence in the areas that we can control will make a difference in the long run.
ASCOCHYTA COMPLEX ON PEA
In the second annual pea disease survey conducted by the Saskatchewan Ministry of Agriculture, the University of Saskatchewan’s Crop Development Centre, and Agriculture and Agri-Food Canada, mycosphaerella blight was once again the most prevalent disease observed. Symptoms were found in 100 per cent of crops surveyed in all regions of the province except for the southwest, where it was found in 96 per cent of the crops.
Severity ranged from trace to severe, but on average one-third of the crops surveyed had moderate to severe symptoms in the upper canopy, while two-thirds had moderate to severe symptoms in the lower canopy. Mycosphaerella blight is common enough that we can expect similar disease prevalence each year, however, there will not necessarily be an economic impact every time, so a fungicide application is not always warranted.
Another member of the ascochyta complex on pea, ascochyta leaf and pod spot was most prevalent in the southwest. Symptoms were observed in 52 per cent of pea crops surveyed in that region. Ascochyta leaf and pod spot was also fairly common in the west-central region (20 per cent) and southeast region (17 per cent), but was not observed in any of the crops surveyed in the northeast or east-central regions of the province. The disease was observed in only one crop surveyed in the northwest.
Regional differences coincide with previous disease surveys in Saskatchewan, as well as pea seed testing data. More research is required to determine whether the occurrence of ascochyta leaf and pod spot is related to varietal or environmental differences.
INTERPRETING SEED TESTING RESULTS
Seed quality is expected to be an issue going into 2011 and therefore testing is recommended. Thresholds for seed-borne disease levels will help determine whether the seed can be used and under what circumstances a seed treatment should be considered. To interpret your seed-testing results talk to your seed analyst, agronomist, or local Ministry of Agriculture Regional Crop Specialist. You can also visit the Ministry’s website at www.agriculture.gov.sk.ca and search for “seed-borne diseases,” or contact the Agriculture Knowledge Centre at 1-866-457-2377.
2011 DISEASE FORECAST
There is a framework for anticipating disease and considering what to do about disease. This framework is called the disease triangle and the factors are as follows:
1. The presence of a virulent pest (inoculum in seed, soil, and crop residue from 2010 and previous years).
2. A susceptible host (crop rotation and variety selection).
3. Weather conditions (that are conducive for disease and have the potential for other impacts on the crop).
When approaching the 2011 season, it is important to remember that integrated pest management should receive due attention each year — not just following a year of high disease.
ArticlecourtesyofPulsePointmagazine. FayeDokken-BouchardistheProvincial Specialist,PlantDiseasewiththe SaskatchewanMinistryofAgriculture.She canbereachedatFaye. [email protected] or306-787-4671