Southeast tomato production has neverbeen an easy ride. And if weather forecasters’ La Niña predictions hold, 2012 will be no different. 

Farm Press spoke with Daniel Sherrod about the impacts of a La Niña on tomato crops, typical pests and what products are available to deal with them. Sherrod is a DuPont product development manager for insecticides. Among his comments:

On La Niña predictions…

“To frame this, we’re talking about tomato production in the Southeast — particularly in Florida.

“What has triggered interest in this topic is that, right now, it's predicted Florida will face a La Niña. There has been a lot of work done on the impact of climate on food production.

“A La Niña year is characterized by warm, dry weather. An El Niño year is cooler and wetter. So, they’re saying it will be dryer and warmer than usual this winter in Florida.”

Whiteflies and tomato yellow leaf curl virus…

“So what does that mean in terms of tomato production and insect pests? A couple of things come into play: If a grower is to plan for a dryer, warmer tomato production season what does he need to consider?

“One is the whitefly. In warmer, dryer conditions the silverleaf whitefly thrives; it’s a kind of a desert insect in that it does best in arid conditions. That means a grower is more likely to have more whiteflies to deal with this winter.

“Whiteflies — a piercing, sucking insect — can be a direct pest of tomatoes. They can just suck the juice out of the plant. But, the real problem with whiteflies is a virus they transmit: tomato yellow leaf curl virus. They vector that virus, and it’s likely to be the bigger problem.

"That’s particularly true if a plant is infected when it’s still young — the impact from the virus is pretty devastating on young plants. The virus gets its name due to its causing the plant’s leaves to curl, to remain small and take on a yellowish color.

“But, the real impact of the virus is that it can stunt the plant and reduce yields. Florida researchers have said a heavy infestation of tomato yellow leaf curl virus early in the production cycle can lead to a yield reduction of 50 percent. So, the virus can mean a substantial, devastating impact.”

How a producer can mitigate the problem…

“There are a few things a producer can consider.

“First, he/she can plant disease-resistant varieties. There are some tomato varieties that have shown some resistance — or tolerance — to this virus. They may not be the best- yielding varieties, but they are an option.

“Another thing to consider is to separate tomato crops in space and time. That means you try to create a situation where you have no tomatoes for a period of time, so there’s no host crop for the whiteflies to reproduce on. You’re breaking the whitefly cycle.

“But, that isn’t an easy thing to do, particularly in Florida.

“Another thing is good field hygiene. That means when you’re finished with the crop, the best practice is to destroy crop residue — in other words, get rid of the host.

“Many times, producers will apply a spray at the end of the season to kill off as many whiteflies as possible. Then, they burn down the crop and disk or plow it under.”

On actual insect control…

“Tomatoes normally fall into two categories: fresh market and bush tomatoes, which are usually grown for processing. Bush tomatoes end up in ketchup and spaghetti sauce.

“Tomato production in Florida is predominantly fresh market. These are basically grown for supermarkets and direct consumption of the fruit. Florida is a huge producer of fresh market tomatoes.

“Many Florida tomatoes are staked. They’re grown from transplants and as they get larger, a stake is put next to each plant. The plant is then tied to the stake as it grows.

"It’s kind of like a trellis system and these plants get tall — five feet or more. 

“So, you want to start out by protecting the tomato transplant.

"Currently, I believe, recommendations often call for a treatment of Fulfill. Then, about a week before the transplants head to the field, they’re treated with a neonicotinoid.

"This is all geared toward protecting the transplants from whiteflies as soon as they are put in the field. That carries the crop out through early stand establishment. At that point, it is recommended you step away from the neonicotinoids. That’s due to concerns with resistance management.

“So, switch to other modes of action. One product you can use five or six weeks into the production is DuPont's Coragen. It is very unique in that it can be applied to the soil — usually through drip chemigation — and it acts as a systemic insecticide. It will be translocated into the plant and provide worm control; that is, lepidopterous control.

“Mid-South producers certainly know about budworms and bollworms. One of the pests in tomatoes is the bollworm (also known as tomato fruit worm).

“Coragen will actually go up into the plant and control a number of the pest/worm species. It’s unique in that regard — I don’t believe there is another active ingredient that will do that.

“It also will provide suppression of whitefly nymphs. Plus, it has a different mode of action than the neonicotinoids or other insecticides. So, you can fulfill the resistance management/integrated pest management approach by using Coragen, one of the choices depending on the pest complex you’re facing.” 

Other products in the pipeline…

“DuPont Verimark insect control, powered by Cyazypyr, is scheduled for major market launches within 18 months, pending Environmental Protection Agency approval.

“Cyazypyr will be DuPont’s second product family from the anthranilic diamide class of chemistry, and will help foster strong, vibrant plants.

“Specifically for the situations described above, Verimark will be an ideal product. The insect control it provides will give seedlings a strong start by providing rapid cross-spectrum systemic control of sucking and chewing pests, and it will bring stronger control for whitefly, as well as reduced transmission of some plant viruses. 

“As I noted with tomato yellow leaf curl virus, it’s important to protect the tomato plant from infection while it’s still young. This new mode of action will help get crops off to a strong start and relieve seedling stress from pests and the impact of disease.”