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Keeping Illinois Vegetables Healthy

Mohammad Babadoost Mohammad Babadoost
Assistant Professor
Department of Crop Sciences
(217) 333-1523
  Zahirul Islam Zahirul Islam
Postdoctoral Research Associate
Department of Crop Sciences
(217) 244-6181

More than 50 vegetables are grown commercially in Illinois for processing and fresh markets. Among the major vegetable crops grown are cucurbits (cucumbers, melons, pumpkins, squashes, watermelons, and zucchinis), eggplants, peppers, and tomatoes. Illinois ranks first in pumpkin production among all states, and approximately 65 percent of the total commercial processing pumpkins in the United States are produced in Illinois.

Phytophthora blight, caused by Phytophthora capsici, has become a serious threat to the production and industry of cucurbits, eggplants, peppers, and tomatoes in Illinois and the Midwest. This pathogen causes pre- and post-emergence damping-off, root rot, crown rot, foliar blight, and fruit rot. In the past three years, P. capsici caused up to 100 percent yield losses in commercial fields of the above-mentioned vegetables, particularly in pepper, pumpkin, squash, watermelon, and zucchini fields.

Phytophthora fruit rot of pumpkin
Figure 1. Phytophthora fruit rot
of pumpkin.
Phytophthora fruit rot of squash
Figure 2. Phytophthora fruit rot of squash.

No single method provides adequate control of P. capsici on vegetables. Beginning in 2000, we initiated an integrated approach for management of Phytophthora diseases of vegetables. This approach includes preventing damping-off by an effective seed treatment, induction of resistance in plants by light-and chemo-therapy, and application of effective fungicides.

Efficacy of several seed-treating fungicides was evaluated for control of seedling death of pumpkin caused by P. capsici. Pumpkin seeds were slurry treated with the fungicides and planted in naturally and artificially infested soil with P. capsici. Allegiance LS at the rate of 1.5 fl. oz/100 lbs and Apron XL LS at the rate of 0.64 fl. oz/100 lbs effectively prevented pre- and post-emergence damping-off.

Phytophthora blight of bell pepper

Figure 3. Phytophthora blight of bell pepper.

Induction of resistance in pepper, pumpkin, and tomato plants against P. capsici by light-therapy (ë = 650nm) in the greenhouse and application of acibenzolar-s-methyl (Actigard) in the field has been successful. The light treatment not only reduced the incidence of the disease significantly but also increased fresh and dry weights of the plants considerably.

Fifteen fungicides were tested in the laboratory and fields for control of Phytophthora blight and fruit rot of pepper and pumpkin. Dimethomorph plus mancozeb (Acrobat MZ) at the rate of 2.25 lbs/A was found very effective in controlling foliar blight and fruit rot. Cuprofix, Ridomil Gold/MZ, and Zoxium were also found to be effective in suppressing P. capsici.

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Department of Crop Sciences
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