Gordon Johnson, Extension Vegetable & Fruit Specialist; firstname.lastname@example.org
Harvest of high tunnel plasticulture strawberries is well underway in the region and field harvest is beginning on plastic. Matted row strawberry harvest is still a few weeks off in most areas.
We have had several days in the mid 80s recently and this should remind growers that while the danger from frost should be over, effects of high temperatures can also greatly reduce strawberry productivity.
When daytime high temperatures reach a certain critical level, strawberries reproductive development will be affected. Flowering will be reduced or will stop altogether. The critical high temperature where flowering is affected and overall impact on flowering will vary with variety. Of the common strawberries being grown on plastic mulch in the annual system, ‘Camarosa’ is the most sensitive and will stop flowering and grow vegetatively when temperatures are above 86°F. ‘Chandler’ will handle somewhat higher temperatures. In matted row strawberry culture, it has been shown that strawberry size in ‘Earliglow’ is greatly reduced once temperatures reach the high 80s.
Growers wanting to maintain fruiting in years where May temperatures reach the high 80s or 90s should consider irrigating with overhead sprinklers during the day to cool plants (direct cooling and evaporative cooling). Use low volume sprinklers and set them to come on when air temperatures are above 85°F and come off when temperatures drop back below this level.