By Clint Thompson
Last week’s brief cold snap is likely to have a lasting impact on Alabama’s vegetable crops. Joe Kemble, Alabama Extension vegetable specialist, expected farmers to start seeing cold damage this week, especially on warm-season vegetables like tomatoes and peppers.
“I think there was enough hours below optimal temperatures for a lot of crops that you’re going to start seeing some damage pop up. You’re likely to see a few things on tomatoes. With low temperatures you can see some phosphorus deficiency develop. The lower leaves will get a purplish color to them. That’s simply due to the low temperatures,” Kemble said. “Phosphorus availability is dependent on microbial activity. Sometimes you’ll see this purpling develop on tomatoes and actually on corn as well. Anything that was planted a few weeks ago, you may start to see some purpling until the soil temperatures warm back up.”
Kemble said temperatures do not have to dip to freezing for cold damage to occur. Producers can expect to see damage once temperatures reach below 63 degrees or 64 degrees Fahrenheit for an extended period of time. Plants that are in low points in the field are especially vulnerable since that is where cold air accumulates.
“Any of the warm-season crops, they don’t like it when it’s below 64 degrees. Basically, the colder it gets, the fewer hours you need of cold temperatures to cause a lot more damage,” Kemble said. “A couple of hours at 35 degrees or 36 degrees can be just as bad as an extended period of time at 50 or 60 degrees.”
How Cold Was It?
Kemble said temperatures in north Alabama dropped to freezing, while central and south Alabama, temperatures stayed in the upper 30s.
He also emphasizes that growers need to be scouting their plants for potential diseases. Any stress in the plants leave them susceptible to diseases. It is important to make sure nothing gets established.
Any cold damage might leave farmers with, what Kemble terms a “gut-wrenching decision.” Do they proceed with the current crop to try to meet the market, or do they replant to try to improve any yields that were impacted?
“If they were already stressed from that earlier cold weather, this second whammy may be a real problem with some of those crops. That’s when a grower needs to sit down, look at the numbers and make a decision on, ‘If my crop doesn’t bounce back (soon), what’s my next step?’” Kemble said. “That is a gut-wrenching decision, considering how much money has been invested. Anything that went in as a transplant, the idea was earliness. You’re trying to get a jump on the market. What’s going to happen now is, anything that went in early, especially these warm-season veggies, they’re going to be held back a little bit. They’re going to be stressed.”