VCR – Vegetable Crop Report – July 18, 2024

vegetablecropreport

2 years ago

Welcome back to the next VCR of 2024!

Many counties have continued to experience heavy precipitation over the last week. Counties such as Durham, Lambton, Middlesex, Norfolk, Peterborough, Simcoe, and Wellington Centre have already received more precipitation this July than their ten-year average for the month.

Almost all counties continue to trend above their 10 year average GDD, with the exception of Thunder Bay which is on trend with its 10 year average.

Crop Updates

Beans – prolonged leaf wetness, accompanied by lush, full crop canopies provide the ideal environment for white mould (sclerotinia) (Figure 1). Apply a preventative fungicide at early bloom and again 7 days later. Keep an eye on the pre-harvest interval as many products have a 14-day PHI. Spent blossoms are usually the main point of entry for this disease. Thorough spray coverage into the canopy is important.

Brassica Crops – Given all the precipitation over the past couple of weeks, some fields are showing symptoms of nutrient imbalances which have resulted in tip dieback, leaf edema and/or sun scorch. The conditions have also been favourable the past month for Alternaria and Sclerotinia white rot and they have shown up in multiple fields at various stages of crop development. Sclerotinia will start as white mycelial growth followed by small, black spots/spores that look like mouse droppings within the fluffy white growth (Figure 2). 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. Once the crop is harvested, incorporate residue as soon as possible to reduce inoculum for future years. Managing chewing insects will also reduce the spread of Sclerotinia.

**Figure 2.** Sclerotinia white mould on cabbage.

Cucurbits – consider the next few weeks a peak disease management period for all cucurbit crops. For cucumbers, the key disease is still downy mildew. Unless foliar symptoms of other diseases begin to appear, there is not a strong benefit to adding additional fungicides to the program. For pumpkins and squash the primary target is powdery mildew. Keep in mind that there is documented powdery mildew resistance to the group 11 (QoI) fungicides. Scout fields regularly for signs or symptoms of other foliar diseases such as alternaria, anthranose or gummy stem blight. Ontario Crop IPM is a great resource for scouting and identification information. https://cropipm.omafra.gov.on.ca/

Garlic – Harvest continues across the province in areas that are dry enough for machinery to enter the field. Remove bulbs from direct sunlight as soon as possible and be mindful of how long garlic is sitting in wagons/crates when there is no forced air present. Remove excess moisture from the crop as soon as possible as a slow cure will make it easy for pathogens to colonize wounds / bruises from harvest which will lower quality and the length of time the crop can be kept in storage. Be vigilant about reducing mechanical injury during harvest.

Onions – Many fields are still green to the tip, but most fields are showing some Stemphylium lesions by now (Figure 3). Onion downy mildew is spreading to new fields and a protective fungicide should be applied if one has not been applied already. Past work by the Ontario Crops Research Centre – Bradford has shown that Orondis Ultra (groups 40/49), Zampro (groups 45/40) and Orondis Gold (Groups 4/49) are effective at protecting the crop against downy mildew. A full list of products registered for onion downy mildew can be found on the Ontario Crop Protection Hub. More onions are showing symptoms of bacterial rots, especially in fields that have seen excessive amounts of rainfall over the past week.

**Figure 3.** Stemphylium lesions coming in on older leaves senescing due to excess moisture.

Sweet corn – western bean cutworm activity is on the rise. Adults will typically select pre-tassel field corn fields in which to lay eggs. Sweet corn is less attractive to them. However, it is a good idea to scout for egg masses (Figure 4) in fields of pre-tasseling stages. Reports out of the US have indicated a low to moderate risk of corn earworm moth flights into the Great Lakes region at this time. Take note of any weather patterns originating in the SW United States and protect corn at the silking stages.

**Figure 4.** Western bean cutworm eggs.

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
Bruce***	1174	1060	758	578	348	853	1060	497
Chatham-Kent*	1506	1385	1049	851	571	1155	1385	754
Durham***	1331	1213	891	703	453	993	1213	614
Essex*	1628	1502	1152	944	654	1264	1502	845
Huron***	1269	1152	831	644	410	933	1152	558
Kemptville***	1363	1245	937	752	503	1032	1245	665
Lambton**	1472	1353	1018	819	554	1126	1353	725
Middlesex**	1424	1304	973	779	518	1079	1304	689
Norfolk**	1436	1313	971	773	508	1079	1313	680
Peterborough	1254	1138	827	642	404	926	1138	557
Renfrew	1360	1244	937	758	513	1033	1244	673
Simcoe***	1275	1160	847	660	420	945	1160	571
Sudbury***	1093	992	720	557	344	806	992	480
Thunder Bay	879	782	525	382	200	604	782	316
Timiskaming***	1074	979	716	558	353	800	979	484
Wellington Centre**	1290	1172	857	671	425	955	1172	584
Wellington North**	1272	1157	844	661	423	943	1157	575