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Monday, October 29, 2012

Summer Pruning of Eggplant and Tomato Eliminates Whiteflies and Produces Fall Crop


Ash whitefly on pomegranate.
Q. Because of an overwhelming whitefly infestation in summer, I cut down my eggplant in the heat when it no longer had blossoms. Cut it flat to the ground. Left it to rot so removal would be easier in a week or so. Well, what do you think? It came back like all get out and blossomed in late September and set eggplants. Some whiteflies remained but with the cool nights they are giving up. This is similar to advice about keeping tomatoes until fall and getting a late crop in December.

            It never worked for me...until this year. In late summer, I let the tomato plant just be. It was an Early Girl, indeterminate in growth. I figured I would remove it with the eggplant corpse. Well, it started to blossom in late September and is setting tomatoes. Has some whitefly boarders but not too bad. My question is: The success of trying to prolong summer tomato plants for a second crop in fall is dependent on whether or not the tomato growth is determinate or indeterminate? Thanks for all your help.

Eggplant Thai Purple grown for evaluation
at the UNCE Orchard. Probably 4 on a
5 point scale.
A. Those are some great observations that you made in your garden. That was pretty radical to cut the eggplant down to the ground and still have it come back. I realize that was not your intent but I am sure you could see, with an already established root system, how quickly that eggplant grew back to the point where it could begin flowering again. This one advantage of cutting plants back and letting them regrow.

            Of course once it started to flower and set fruit the energy was taken away from new growth and focused into reproductive growth thus slowing its vegetative growth. So, ideally if someone were to do something like you did and wanted a fall crop they would cut it back about 30 days before temperatures dropped back into the mid-90's, probably about the first of August or thereabouts.

            Also your thoughts of determinate vs. indeterminate was something I really had not mentioned. Both will work but certainly indeterminate types will give you more growth to work with.

Cutting back tomato in midsummer can lead to sunburn
of remaining fruit (cream color on the green fruit on the left
and cream color on ripening fruit on right) or even sunburn
on stems that were previously shaded.
            For early flowering and fruit set you usually want determinate types. They typically will set fruit earlier than indeterminate types. The other option of course is to replant in mid-July for a fall harvest. But transplants are hard to come by that time of year so you have to grow them yourself or grow plants from seed directly in the garden which is easy to do that time of year.

            A major problem when cutting them back is sunburn. After cutting them back you have a plant with a canopy that is shading the stems. The canopy is cut back and if it is cut back too far, the stems will sunburn. This is why I usually try to have people cut them back to some side branches along the stems so that there is canopy left to shade the stems and help reduce sunburn or shade the plants until new growth begins.

            In your case though I could see why you would want to cut them back just to eliminate some pest problems. Remove the food and you remove the pest problem.

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