The Long-Term Effects of Nematode Damage on Permanent Crops

By Scott Ockey

The thought of nematodes might send shivers down your spine, just as some send shivers down to the roots of your crops.

There are thousands of tiny, worm-like nematode species that can exist under the soil. They’re not all bad, but those that are plant-parasitic feeders can cause long-term crop damage and big problems for growers.

Harmful nematodes feed on the outside or inside of plant roots (depending on the type of nematode) with a needle-like mouth that penetrates root tissues and causes loss of vigor and yield in crops. 

Some crops can recover after a season of plant-parasitic nematode damage, but permanent specialty crops like blueberries, strawberries, citrus, tree nuts, tree fruit and wine grapes run the risk of long-term damage. This can inhibit growth, yield and revenue to the detriment of growers.

Know What’s Below Your Soil

Harmful nematodes love permanent crops because the roots stick around, providing a potential long-term living situation.

Many perennial crops have increased numbers of nematodes associated with their root systems as a plant ages. For example, some lesion nematodes can reach such high population numbers in the soil that replanting following removal of older trees or vines can result in a reduced vigor, stunting or even death.

For this reason, growers should regularly test for nematodes throughout the life of the plant, approaching soil testing results with a presence or absence mindset. If plant-parasitic nematodes are present, you can set up a control program to reduce their damaging effects. If they are not detected, continue with a consistently scheduled soil testing program to ensure you can catch any latecomers before they start to damage roots.

In cases where harmful nematodes are present, it is best to apply a nematicide at key timings during plant growth. For perennials, target applications during root flush can be more effective. While soils are warm enough for nematode activity, you have the greatest opportunity of protecting the more vulnerable roots.

Determine Nematode Types to Protect Perennial Crops

There are numerous species of plant parasitic nematodes that can damage perennial crops. Knowing their lifecycles is a great way to inform effective control efforts.

• Migratory ectoparasitic nematodes are nematodes that spend their life outside of the plant roots, so you need a nematicide that can attack and kill all life stages – from eggs to juveniles and adults.
• Migratory endoparasitic nematodes are nematodes that spend a portion of their lifecycle inside the plant root, where some nematicides are ineffective. But since they are migratory, there are life stages that are susceptible to nematicides as they move outside in the soil from root to root. This group of nematodes varies with some only having adult stages within the roots, whereas others have more life stages within the protective cover of a plant. Lesion nematodes are in this category but have numerous stages outside the plant when you can control them. The best way to address these pests is to apply an effective nematicide at regular intervals according to label instructions.
• Sedentary endoparasitic nematodes are nematodes whose female adults attach to a plant root and do not relocate. In the case of root-knot nematodes, the female can be found sedentary within the root tissue. In cyst and citrus nematodes, female nematodes attach to the root only partially, with a large portion of the body exposed outside the root.
  
  

Egg and juvenile nematodes can be controlled with effective applications, but other types (like the adult root-knot nematodes) are protected by the root once they are inside. These variables make it especially important to choose a nematicide that is flexible and effective at all life stages. 

When It Comes to Nematode Control, Timing Is Everything

Timing is imperative when considering biological nematicides for nematode control.

Nematodes feeding on perennial crops have adapted to be the most mobile during the root flush stages, so in-season applications are important during the spring and fall root flush timing while roots are growing and nematodes are migrating in the soil. To reduce nematode populations for spring planting and protect new root flush before the nematodes go deeper in the soil for the winter, focus application timing in the late fall and spring.

These methods provide added flexibility and efficacy to control nematodes in annual crops and reduce the long-term effects of nematode damage in perennial crops. For extra excellent nematode defense, consider NemaClean™ for a cost-effective application rate to enhance an existing IPM strategy.

In need of an effective and flexible solution for harmful nematodes at all life stages? Learn how NemaClean can help.