Pest Management Weather

Fumigants and cool, wet weather

This article is from the OMAFRA Ginseng and Specialty Crop Report and relates to tobacco, but it’s good information for tomato and pepper growers, too.

Dr. Jim Todd, OMAFRA Transition Crops Specialist

The effectiveness of the chemicals used for soil fumigation is strongly influenced by weather conditions and the cool, wet spring weather we’ve been experiencing has not been ideal.  Chemical fumigants do not move as easily through wet, cool soils as they do through drier, warmer soils.  As a result, it takes longer to reach the same level of pest control and for the fumigation chemicals to dissipate from the soil.

Growers should check their fumigated fields prior to planting as tobacco plants can be killed or severely stunted by the presence of residual fumigant in the soil.  To guard against this, a week before transplanting, it’s a good idea to check several areas of the field, including a lower area, for residual fumigant in the soil.  Knock down the top of the fumigant hill and transplant about 10 plants down the centre of the row.  If a four-row applicator was used, transplant into each of the four rows to check the consistency of the fumigant application.  As a comparison, 10 plants should be planted between the fumigant rows where no fumigant was applied.  After a couple of days, check the plants early in the morning to see how they compare to the plants between the fumigant rows.  If only the plants in the fumigant row are laying down and their stems are limp below ground without any signs of insect feeding, fumigant is still present in the soil.  In this case, the hills should be opened with a single chisel or cultivator tooth about 2 to 3 days prior to planting in order to allow the remaining fumigant to escape.

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