Nematodes can wreak havoc for gardeners

Two weeks ago I pulled out the last tomato plant – a stunted cherry tomato that wasn’t recovering from the early September hot spells and wasn’t setting new flowers. As soon as the roots came out of the ground, the problem was clear. Nematodes! The worst case I’ve ever seen in my garden. The roots were swollen and deformed with large, ugly nodules caused by an infestation of the microscopic worms and so were unable to draw up sufficient water and nutrients.

This cherry tomato was a new hybrid from a Bay Area hybridizer sold at a local nursery. It’s hard to determine whether the nematodes were already in that one spot in my new garden (no signs of problems with the other two tomatoes planted nearby) or whether the nematodes were carried into the garden on the transplants’ roots.

An amateur gardener friend pulled out her wimpy, half-dead tomatoes last week and we diagnosed that they suffered from fusarium wilt caused by a soil-born fungus that plugs up plants’ vascular system. The lower leaves had died – mostly on one side – the plant had produced few fruit over the season, and when we cut the stems at soil level we saw the telltale signs of dark brown tissue just under the bark.

Nematodes and soilborne disease pathogens including verticillium and fusarium wilts live indefinitely in the soil but populations can be significantly reduced by solarizing planting beds. Soil solarization uses the heat of the sun to cook the top 8 to 12 inches of soil to high enough temperatures to kill pathogens and nematodes. But solarization must be done during the hottest summer months to be effective.

To help control for soilborne diseases and nematodes this fall, all plant debris must be cleaned up and all of the affected root systems must be pulled out and placed into the green waste bin, not the compost pile. Newer research is showing that beneficial micro-organisms feed on disease pathogens and nematodes. I’ll be digging in a few bags of mushroom compost and buckets of my own compost this week and solarizing the spots next May or June.

This a a good lesson, especially for the expert, to always check labels before buying transplants to verify that the plants are resistant to several common pathogens and nematodes.

Note: There are a couple of great gardening events coming up this weekend.

▪ Intermountain Nursery, 30443 N. Auberry Road in Prather, is having its annual harvest festival from 10 a.m. to 5 p.m. on Saturday, Oct. 15, and from 10 a.m. to 4 p.m. on Sunday Oct. 16. The festival is free; a donation of $1 is suggested to help defray parking lot rental costs.

Intermountain Nursery specializes in drought-tolerant native plants suitable for our Valley climate as wells as the foothills. Its staff is extremely knowledgeable and helpful and the nursery’s landscaping is inspiring.

▪ Also, the Clovis Botanical Garden at Dry Creek Park just north of Alluvial Avenue in Clovis is holding its annual fall Water Wise Plant Sale and Fair from 8 a.m. to 1 p.m. on Saturday, Oct. 15. Admission is free.

You’ll find food booths, vendors, a plant clinic staffed with Fresno County master gardeners, local water agencies, environmental groups, and garden clubs. The CBG is a demonstration garden and it should be at its most colorful fall best.

This story was originally published October 13, 2016 at 12:45 AM with the headline "Nematodes can wreak havoc for gardeners."