UC helps pumpkin farmers produce pumpkins without pesticides

Every October, thousands of delighted children on school field trips or family outings carefully select pumpkins at the Satterstrom Pumpkin Patch near Reedley, Calif. After a hayride and a mug of hot cider, they’ll go home to carve their jack-o-lanterns never knowing a groundbreaking technique developed by University of California scientists was behind their fun.

The pumpkins they picked were grown using reflective mulch, a polyethylene sheet covered with a thin layer of aluminum that is spread out on the growing bed at planting time. The reflection of sunlight repels aphids, which then fly over the field and land someplace else, sparing the pumpkins the plant diseases aphids spread. The growing technique was developed by entomologist Charles Summers and plant pathologist James Stapleton, both based at the UC Kearney Research and Extension Center near Parlier.

The scientists found that reflective mulches decreased the incidence of aphid-borne viruses by 75 to 85 percent. In addition, if the pumpkin plants are eventually infected with viruses, the symptoms are delayed up to four weeks, a time when many plants have matured and can better tolerate disease.

“Early on, we did a one-acre research project with Charlie Summers,” farmer Mike Satterstrom said. “There was such a big difference, we decided to do more the next year. Now, we do all the pumpkins this way.”

Satterstrom said the reflective mulch costs about the same as the pesticides he used to use for aphid control on his 20-acre pumpkin farm. However, effectiveness is not comparable.

“The production difference is pretty dramatic,” he said. “Our production is probably triple, on average, to what we were before. My plants are incredible.”

Summers said the technique is applicable to many crops, including squash, cucumbers, melons, corn, eggplant and tomatoes. In addition to aphids, the reflective mulch repels whiteflies, leafhoppers, thrips and leafminers.

“On pumpkins and cucumbers, whitefly density on plants growing over reflective mulch was reduced 10- to 14-fold compared to plants growing on bare soil,” Summers said.
Reflective mulch also reduces the amount of irrigation water required, suppresses weeds and promotes improved soil nutrient absorption.

“This is a technique that can be used in large commercial production, on small farms or in the home garden,” Summers said. “It is an especially valuable insecticide-free vegetable production method for organic farmers.”

Said Mike Satterstrom, “This is the best thing we’ve learned.”

(October 2003)

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