The Dangers Of Nematode Damage

Nut trees infested with nematodes experience reduced growth and yield, according to the University of California. These microscopic pests feed on plants’ roots, prohibiting the plant from absorbing the nutrients and water out of the ground. With nematode pressure, trees cannot grow and produce at their full potential. Growers cannot see the nematodes, but the damage and gradual reduction in production that occurs with nematode pressure are both hard to miss.

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Tim Weststeyn, a pest control advisor (PCA) with Crop Production Services out of Vernalis, CA, consults on 4,000 to 5,000 acres of tree nuts. Weststeyn is currently treating for high ring nematode pressure in some of the almond crops.

Nematodes reduce the vigor of trees by attacking their root systems, making the tree more vulnerable to disease. Damaging diseases such as bacterial canker can be transmitted by nematodes. Weststeyn explains that the disease not only impacts the trees with nematode damage, but it is also highly contagious, posing a threat to previously healthy trees.

“You’ll have dieback in a tree, gumming, oozing, the limbs will suddenly die, buds will fall off the tree, they will look like they got burnt, and they pretty much die.” Weststeyn explains, “That’s the type of nematode damage and bacterial canker pressure I’m dealing with in almonds.”

Experience With Nematode Management

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Many growers fumigate at planting to reduce nematode numbers, but Weststeyn explains that the fumigation only lasts for so long. Eventually, the nematode populations return, causing issues in the established crops.

“We don’t have many post-plant treatments that are reliable,” explains Andy Dugo, a PCA from the Escalon branch of Mid Valley Ag Services. “I see Movento as being one solution we’ve got that looks like it’s going to work.”

Movento (spirotetramat) from Bayer CropScience is an insecticide that can be applied as a foliar spray after crops are established. It is systemic throughout the plant to provide protection. The product’s two-way action allows it to move from the leaves to the roots, where it manages nematode populations.

Weststeyn and Dugo are both in their third year of treating established almond trees with Movento for nematode management. The biggest differences they’ve noticed? New growth and healthier trees.

“The tree has a lot of vigor,” says Weststeyn. “The tree doesn’t stress as bad.” Weststeyn also saw a better yield in the established orchards where he used Movento to treat for high nematode pressure. He explains that although it is too early to tell exactly how much larger the yield will be, he expects an improvement from 900 pounds of almonds last year to around 3,000 pounds this year.

“I see a healthier tree. It’s a greener tree,” says Dugo. “We are in our third year and we are seeing a big difference this year.”

Dugo attributes the healthier tree to a stronger root system, which he believes Movento allows the plant to establish. His experience has taught him that stronger roots grow healthier trees, which are more resistant to diseases.

Answers For Growers

“These field observations confirm what we have seen in our research and the research from Dr. Mike McKenry, a recently retired nematologist with the University of California-Riverside Department of Nematology,” explains Kevin Adam, Movento product manager. “Research has consistently shown Movento provides a 50% reduction in nematode populations for five to six months after application.

“Nematode damage is often overlooked because foliar symptoms from nematode infestations are not as dramatic as leaf loss due to mite feeding or nut damage from navel orangeworm, but the damage can be just as severe,” says Adam. “As growers manage their nematode populations, they will see a stronger, larger, healthier crop.”

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