Del. Research Focuses on Pollinating Seedless Melons

7/15/2014 7:00 AM
By Michael Short Delmarva Correspondent

GEORGETOWN, Del. — As July’s heat settles upon Delmarva, local watermelons are beginning to show up at farmers markets.

Watermelons are the single most valuable fresh crop grown on Delmarva. An estimated 5,000 to 6,000 acres are planted on the Delmarva Peninsula, and the fruit is as sure a sign of summer as sunshine and traffic jams.

Nearly 3,000 acres are planted each year in Delaware.

At the University of Delaware’s Carvel Research and Education Center, researchers are studying ways to better pollinate seedless watermelons. Seedless watermelons cannot pollinate themselves, so researchers are always looking for ways to improve pollination and fruit set.

Gordon Johnson, Cooperative Extension vegetable and fruit specialist, and University of Delaware graduate student Donald Seifrit Jr., are studying different sources of pollination.

Unlike most of the world, Americans prefer seedless watermelons. While seeded varieties are still grown, many of those melons find their way to the international market, where seeded watermelons are still the norm.

The sandy, well-drained soils of Sussex County are nearly perfect for melon production, both for watermelons and cantaloupes. Delaware Department of Agriculture figures show that Delaware watermelon production in 2012 was 105 million pounds grown on 2,800 acres of land. Of that production, 85.1 million pounds were seedless watermelons.

Johnson said that Delmarva and Indiana produce the bulk of the nation’s watermelons.

The University of Delaware focuses heavily on melon research, including efforts to graft different melon varieties on to disease-resistant rootstock. But the core of the current two-year research project is the use of 24 different types of pollen sources planted next to seedless watermelons. The traditional method for growing seedless varieties is to plant one row of seeded watermelons next to two rows of seedless plants.

The current study includes both traditional seeded varieties and special pollinizers, Johnson said. He said some of those plants may only produce tiny fruit themselves, but that doesn’t matter because their purpose is to provide pollen for the seedless varieties.

The goal is to determine what type of pollen sources produce the best fruit set, as well as the best early fruit set and the best late fruit set. Johnson said that better pollination success can produce as much as an extra 20,000 pounds of melons per acre for farmers. A better early set means a better early crop, which can bring a better market price for producers, he said.

MarDel Watermelon Association provides funding support for the study. Seifrit’s stipend is made possible through a specialty crop block grant from the Delaware Department of Agriculture and the USDA.

It is too early to report any findings about the best pollen source, but their work has already seen unexpected results in the area of “hollowheart” prevention.

Hollowheart occurs when an area in the center or heart of the melon is cracked or hollow. Instead of the tender sweet center of the melon, there may be a large hollow area.

Johnson said that hollowheart may be associated more closely with certain varieties of melon. Their research has also shown that the distance from a pollen source and the amount of pollen present appear to be factors as well.

Hollowheart was a big problem for Indiana growers last year and there has been widespread interest in the university’s research on the connection between pollen and hollowheart, Johnson said.

In fact, Delaware researchers have been able to deliberately grow melons with hollowheart problems, which could lead to better prevention. . “We are the only program that has been able to replicate the disorder,” he said.


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12/18/2014 | Last Updated: 2:45 PM