By Clint Thompson
Alabama Extension is researching “outside the box” with regards to whitefly management. The pest is a threat to vegetable production not just by feeding on the plant but also by transmitting multiple viruses.
It has forced scientists like Andre da Silva, Alabama Extension vegetable specialist, to research alternative ways of managing the insect.
“You need to think outside the box if you want to remain sustainable. You can still control whiteflies having spray programs, but at the same time you might create resistance,” da Silva said. “You need to just think outside the box, literally.”
One outside the box method involves tomatoes and potentially breeding varieties that better repel whiteflies than others.
“What we’re trying to do now as far as research is we’re investigating wild material of tomatoes. Tomatoes’ leaves have trichomes and some sugars that work as repellant. We’re trying to identify those wild tomatoes that have those larger numbers of trichomes and larger production of those sugars so our breeding program can cross commercial varieties with those wild varieties and release new hybrids that will be more repellant to whiteflies,” da Silva said.
The Alabama Extension scientist has also studied the effectiveness of using different colors of plastic mulch, comparing white to silver in zucchini and squash.
“What we identified was that if you use silver plastic, the silver will reduce your whitefly population in yellow squash and zucchini,” he said. “If you were a grower and wanted to plant those two crops during the whitefly season, I’d strongly recommend the silver plastic instead of the simple white plastic. You’re going to have a reduction in the whitefly population.”
Using row covers also helps suppress the populations. The challenge, though, is knowing when to remove the cover. If row covers remain on the plants too long, they will interfere with pollinators trying to make contact with the plants.
“You need to remove it the correct time to allow for pollination. We identified the window to remove the plastic is 15 to 20 days after transplanting. That’s when the plants are starting to flower,” da Silva said. “That’s enough (time) to keep the whiteflies out.
“Whiteflies in yellow squash and zucchini, it’s a problem because they will cause the silver leaf by sucking the plants, but they will also transmit the crumple virus. Crumple is a virus that will damage the plants mostly in the early stage of crop development.”
Whiteflies migrate from winter vegetables to spring vegetables to agronomic crops, like cotton, to fall vegetables and back to winter vegetables. The buildup of whiteflies is concerning since growers have planted their fall crops. Whiteflies can cause feeding injury issues in vegetables and transmit two viruses: cucurbit leaf crumple virus and cucurbit yellow stunting disorder virus. Vegetables like squash, zucchini, cucumber, cantaloupe and snap beans are most susceptible to these viruses.