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Tomato growers: Butterflies should not be a problem

Gene Miyao, UCCE farm advisor in Yolo, Solano and Sacramento counties, reassures processing tomato growers that the yellow and white colored butterflies migrating out of alfalfa this time of year are not a problem for tomato fields.

Miyao says UC Entomologist Frank Zalom “assures us that alfalfa caterpillars are a minor nuisance of tomatoes that do not feed on fruit.”

Unlike armyworms and the tomato fruit worm that damage fruit, Miyao said these velvety-green appearing, worms are foliage feeders. “We often see high number of yellow and white colored butterflies migrating from alfalfa, a preferred host, as it is being cut,” he said. “The butterfly phase of the cycle is not a problem.”

Extensive foliage feeding would be needed in tomato fields before a treatment would be justified. Insecticides like BT or Entrust would be the preferred choices since they are not disruptive of beneficials. Tomatoes are not a preferred host.

“As we hope our extreme heat spell is over, some thought it might be placed on soluble solids management by manipulating irrigations,” reminded Miyao.

As a reminder, UC Veg Crops Specialist Tim Hartz demonstrated that an evaluation of the brix level of the earliest maturing fruit could provide a relative gauge of how to manipulate late irrigations to improve soluble solids while balancing fruit tonnage yield. Select very pink fruit as early as a gallon-volume batch can be collected. As some of the fruit can be collected about five weeks before harvest, this early indicator can determine if further irrigations should target boosting fruit yields or if irrigation should be decreased to elevate fruit sugars. A PTAB inspection station or perhaps a local canner can help determine the Brix sugar level.

Blackmold reduction as a preventive fungicidal treatment has been effective as a single-timed application six to four weeks prior to anticipated harvest. Fruit rot levels compared to non-treated controls have been reduced by about 50 percent in Miyao’s tests.

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