It Was Back to School for Pumpkins

2/2/2013 7:00 AM
By Bill Persson N.J. Correspondent

WESTAMPTON, N.J. — This year’s Mid-Atlantic Pumpkin School was filled to capacity with growers who came not just for the pumpkins but also to learn more about gourds, winter squash, melons and cucumbers — all members of the same plant family with similar growing requirements.

Occurring every two years for about the past 10 years, the all-day class was held in mid-January at Rutgers Cooperative Extension office in Burlington County.

Andy Wyenandt, vegetable pathology specialist at the New Jersey Agricultural Experiment Station, talked about disease control.

“Cucurbit powdery mildew is a major disease factor on all cucurbit crops in the U.S.,” he said. “From first infection to early symptoms can take from four to 12 days, so follow the reports” to know when it has reached the area.

Growers can sign up for notifications at http://cdm.ipmpipe.org/index.php.

“Typical lesions can continue to sporulate for up to three weeks,” Wyenandt said.

He suggested that growers start with cucurbit cultivars that are powdery mildew resistant.

Another disease, downy mildew, is becoming more prevalent.

“In the last few years, downy mildew has become much more serious in the Mid-Atlantic and Great Lakes regions,” Wyenandt said. “It comes up from the south with the weather, and possibly with transplants grown in the south and brought north.

“Downy mildew used to favor cold, wet weather, but now tolerates hotter, drier conditions,” he said. “Only cucumbers show some resistance to downy mildew, but not other cucurbits. It also requires a living host to survive over winter.”

Wyenandt reviewed six additional cucurbit diseases, along with the current thinking about prevention and treatment.

He also talked about the North American Fungicide Resistance Action Committee, which publishes an annual list of codes for most fungicides, grouping their chemistries according to class, mode of action and resistance risk.

The guide explains, for example, that “fungicides with a single mode of action are often considered high-risk fungicides because the chances for fungal resistance to develop are much higher than fungicides with multiple modes of action.”

Recommendations for the use of fungicides that have a high-risk of resistance include rotating their use with other fungicides. Fungicides that are not systemic also need to be applied to the underside of the leaf, where both powdery mildew and downy mildew sporulate. Rotation of crops also continues to be recommended.

Joseph Heckman, soil fertility specialist at the experiment station, talked about silicon nutrition in plants.

“Silicon is now approved as a plant beneficial substance and will be listed on fertilizer labels. Silicon is helpful with powdery mildew — at least it delays the onset,” he said. And “there is some suppression of the corn boring worm with silicon.”

According to Heckman, silicon benefits many crops, especially cucurbits and cereals. It reduces the need for fungicides, suppresses disease and helps reduce insect damage.

Silicon is added to the soil, it is not a foliar application.

Kristian Holmstrom, experimental station program associate in integrated pest management for vegetables, talked about the importance of insect identification.

“Some insects are not a problem. The arthropod on the plant might not be a pest — it might be eating the pest,” Holmstrom said.

“You do not want to treat for beneficials,” she said, adding that fortunately, “insecticide and miticide chemistries have evolved, and continue to do so, to be highly specific in what they target.”

The squash bug, for instance, is a pest of pumpkins, while the similar looking pine leaf footed bug and the brown stink bug are not.

Squash bugs feed only on cucurbits and can vector cucurbit yellow vine disease.

“Squash bugs can kill very young plants, but generally the local timing of pumpkin plantings avoids the early generation,” she said.

“Another example of why insecticide choice is so important is the melon aphid. Spraying a broad spectrum on the melon aphid — usually a pyrethroid — induces melon aphid build up,” she said.

This can occur because melon aphids are resistant to pyrethroids while many beneficial insects are not.

Additional presentations during the day covered variety evaluations, spray trials, cover crops and no-till practices.

For copies of Fungicide Resistance Management Guidelines for Vegetable Crops Grown in the Mid-Atlantic Region — 2013, contact Wyenandt at 856-455-3100, ext. 4144, or wyenandt@aesop.rutgers.edu.


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