Problems reported in Ontario tobacco greenhouses over the last few weeks include chill injury, nitrogen deficiency and harvester ants. The stand unevenness reported on April 24 also continues to be observed. Additionally, the Blue Mold Forecast Centre has reported that they will not be issuing forecasts in 2012. Read more for additional details.
A sudden drop in greenhouse temperature over a short period of time can cause chill injury in tobacco seedlings. Even if the greenhouse is heated, chill injury can occur from venting in cold air. When determining whether seedlings have suffered from chill injury, younger leaves are narrower than normal, possibly elongated, slightly pointed and cupped upwards. The youngest leaves in the growing point may be yellow or almost white in colour. The leaf tissue can be puckered with a yellow colour around the outside of the leaf. Typically, seedlings can recover from chill injury and develop normally, although growth may be set back for a few days after the injury occurs.
Nitrogen deficiency often occurs in early May, especially in over-watered seedbeds. Typical nitrogen deficiency symptoms are when areas of the seedbed remain small and seedlings appear to have stopped growing. The plant stand in these areas is often normal, but the seedlings are pale in colour. The roots of these seedlings are usually well developed and white in colour without any signs of discolouration or injury. See OMAFRA Publication 298, Chapter 4 – Seedling Production for fertilizer suggestions for tobacco greenhouses. Remember that fertilizers should be applied before the greenhouse reaches a high temperature. These practices will reduce the risk of injury to the seedlings.
Blue mold update for 2012
We have been informed that North Carolina State University’s Blue Mold Forecast Centre will not be posting forecasts for tobacco blue mold in 2012 due to a lack of resources. They will still be posting disease reports, but there will be no predictions of spore movements. The OMAFRA specialty crop report will continue to post any disease reports from theUnited StatesorOntario. Ontariogrowers are reminded to monitor tobacco plants regularly for this disease, both in the greenhouse and after transplanting to the field, and are asked to report any suspected cases to the OMAFRA office in Simcoe at 519-426-4434.