VCR – Vegetable Crop Report – July 29th, 2021

Temperature – Daytime temperatures are forecasted to range from low thirties to low twenties for most regions over the next week.

Nighttime temperatures are forecasted to range from low to mid-teens based on region. Carrot Rust Fly is at its threshold in Essex, Chatham-Kent, Norfolk, Huron, Simcoe, Durham, and Kemptville. Onion Maggot is still at its threshold in all regions monitored except Essex. Cabbage Maggot and Seedcorn Maggot are at their thresholds in Sudbury. European Corn Borer is at its threshold in Huron, Wellington, Simcoe, and Kemptville. Degree Day data for each region is shown below.

Rainfall – Most regions are forecasted to have some rainfall over the weekend with partial cloudiness on Monday and more rain following throughout the week. All regions except for Huron and Kemptville are well above their respective 10-year averages by about 20-40mm with Simcoe County being ahead by roughly 100mm. Precipitation data for each region are shown below.

Crop Updates

Beans – White mould has been reported in some soybean crops. Fields are susceptible to infection if extended periods of leaf wetness occur during the bloom period. Fields with lush, dense foliage are most susceptible to infection.

Brassica Crops – Bacterial rots and nutrient disorders are becoming more common. Cabbage aphid and Swede midge populations are increasing. Alternaria is starting to show in some fields. Burying residue after harvest will help manage Swidge midge and Alternaria levels. Given the high humidity and colder mornings, be on the lookout for downy mildew. We are currently looking for Brassica downy mildew samples. If you are finding downy mildew in your field, please call 519 835-3382 or E-mail travis.cranmer@ontario.ca.

Celery – Celery leaf curl and bacterial rot is becoming more common. Continue to dig up stunted plants weekly to examine the roots for nematodes, the hearts for carrot weevil damage or blackheart.

Cucurbits – Scout fields for signs of two-spotted spider mites (Figures 1 – 2). These small mites are very difficult to scout for and a 10x hand lens may be needed to confirm their presence. Affected fields may appear off colour; yellow to slightly bronze. Severely infected leaves may become yellow, with green veins. Symptoms are easily confused with magnesium or manganese deficiency. Miticides can be slow-acting, so it is important to take action before populations become damaging.

**Figure 1.** Two-spotted Spider Mite damage to cucurbit plant

**Figure 2.** Two-spotted Spider Mite damage viewed from afar

Wet conditions have been conducive to the development of Phytophthora crown rot (Figures 3 – 4). Rots will extend well beyond the known wet zones or low-lying areas. On higher ground, the pattern of rot in the crop will appear random, with diseased plants next to apparently healthy ones. Once established phytophthora will spread from plant to plant via the root system, as well as through soil water.

**Figure 3.** Phytophthora crown rot damage to cucurbit stem

**Figure 4.** Phytophthora crown rot damaged cucurbit plant

Garlic – As garlic cures, check bulbs in the middle of pallet boxes or totes regularly to get a good sense of how the entire crop is drying out. Thinking of planting a new cultivar for 2022? Test any new planting stock for bulb and stem nematode before planting in your field. Low levels of nematodes can be found in planting stock that otherwise looks great.

Onions – Continue to scout for downy mildew given the high humidity, heavy dews and colder mornings. The 2017 Muck Crops Research Station Greenbook Report summarizes downy mildew product efficacy on page 66: Click here to visit page 66 of the 2017 Greenbook Report. We are currently looking for Botrytis samples. If you are finding botrytis in your onion field, please call 519 835-3382 or E-mail travis.cranmer@ontario.ca.

Sweet Corn – Western bean cutworm adult populations continue to climb. Researchers expect peak activity in Southwestern Ontario within the next week. Moths are most attracted to pre-tassel field corn. Once the corn has tasseled, populations may move into sweet corn or beans. Scout sweet corn fields for the presence of eggs.

Pest Degree Day Forecasting

*NOTE: Data as of July 28th, 2021

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
Essex*	1683	1554	1183	970	701	1301	1554	876
Chatham-Kent*	1559	1432	1082	878	578	1192	1432	784
Norfolk**	1546	1421	1073	868	572	1184	1421	773
Huron***	1424	1305	977	783	495	1079	1305	694
Wellington**	1384	1262	932	738	459	1036	1262	649
Simcoe County***	1421	1297	958	763	485	1064	1297	674
Durham***	1456	1334	987	799	515	1095	1334	711
Peterborough	1323	1198	859	670	405	965	1198	583
Kemptville***	1410	1290	945	745	465	1055	1290	656
Sudbury***	1219	1110	818	653	396	909	1110	574