Welcome back to this weeks installment of the Vegetable Crop Report!
Brassica Crops – Lepidopteran pests continue to be an issue across the province. Refer to the June 15, 2023 VCR for management thresholds for diamondback moths, cabbage loopers and imported cabbageworms. With all this moisture, be on the look out for Sclerotinia / white mould (Figure 1). The mould tends to start near the ground on plants and as it infects it creates dark, water-soaked areas on the lower leaves near the base at the soil line. As the pathogen progresses you may see white mycelial growth. These water-soaked lesions enlarge and can cause the leaves to wilt. Infected cabbage heads will retain their shape but will be filled with a soft, watery rot. If conditions are favourable for the Sclerotinia, you will see the white mycelial growth followed by small, black spots/spores that look like mouse droppings within the fluffy white growth. These black spores can overwinter in the soil for up to 8 years and the best preventative management strategy is to rotate with non-susceptible crops such as beets, onions, spinach, corn, cereals or grasses. It is also helpful to decrease the plant density of the field to allow for adequate air circulation. Allow the top inch of soil to dry out between irrigation events and incorporate residue from harvested areas as deep as possible.
Garlic – Harvest has started in some fields. Allow the crop to reach at least 40% yellowing/senesce before harvesting for better yields and increased storability. The ideal time for optimum yields is to harvest porcelain cultivars (such as Music) when 50% of the leaves have senesced or turned yellow. Since it takes several days to harvest, many growers start at 40% and by the time the crop is fully harvested it may have reached 70%. Always avoid leaving harvested bulbs in direct sunlight after they have been pulled. Curing / drying is often associated with an increase in temperature, however, when it comes to curing garlic, relative humidity should be the primary focus. Heating air increases the amount of moisture that the air can hold per cubic metre. A cubic meter of air can hold ~17 grams of water vapour at 20°C, while at 30°C it can hold ~30 grams. In most years, when the ambient air’s relative humidity is low, increasing the temperature greatly increases the water holding capacity of the air. This year, the air has been humid, and already close to being saturated. Therefore, increasing the temperature of the air will not add much more water holding capacity. As a result, it will take a longer amount of time to remove excess moisture from the crop. Read more about how curing can affect Fusarium and mite populations in storage here: https://onvegetables.com/2021/12/09/stored-garlic-might-have-mites/
Onions – Many direct seeded fields are at the 6-7 leaf stage. Despite the rain, the levels of thrips are climbing quickly in many fields. Play close attention to fields bordering hay and wheat as the levels of thrips will generally start to increase as hay is cut and wheat is harvested. Apply no more two applications of the same insecticide targeting thrips for resistance management. Older leaves are turning yellow in fields that received excess moisture over the past two weeks. Stemphylium is starting to colonize these wilted leaf tissues in many fields across the province (Figure 2). Be on the lookout for Botrytis (Figure 3), onion smut (Figure 4) and bacterial rot (Figure 5). Damage from rain may leave leaf bruising on the leaf with similar halos as seen with Botrytis.
Pest Degree Day Forecasting
|County||Carrot Rust Fly||Onion Maggot||Carrot Weevil||Aster Leafhopper||Tarnished Plant Bug||Cabbage Maggot||Seedcorn Maggot||European Corn Borer|
|THRESHOLD||329-395, 1399-1711||210-700, 1025-1515||138-156, 455+||128+||40+||314-398, 847-960, 1446-1604||200-350, 600-750, 1000-1150||See legend below|
*- Bivoltine region for ECB. First Peak Catch: 300-350 DD, Second Peak Catch 1050-1100 DD
**- Overlap region for ECB. First Peak Catch: 300-350 DD Second Peak Catch 650-700 DD, Third Peak Catch 1050-1100 DD
***-Univoltine region for ECB. Peak Catch 650-700 DD
Use these thresholds as a guide, always confirm insect activity with actual field scouting and trap counts.
Select a region below for the latest weather, crop and pest degree day information: