By Scott Ockey
The thought of nematodes might send shivers down your spine, and many of them definitely send shivers right down to your roots.
There are thousands of nematode species, which are tiny worm-like creatures that exist under the soil, and they’re not all bad, but plant parasitic nematodes are the enemies we need to be aware of to prevent long-term damage to crops.
Harmful nematodes cover a wide spectrum, including migratory or sedentary types, and they feed on the outside or inside the roots of plants with a needle-like mouth that penetrates root tissues, which causes loss of vigor and yield in crops. Many crops could potentially recover after a season of plant-parasitic nematode damage, but permanent specialty crops including berries (blueberries and strawberries), citrus, tree nuts, tree fruit, and wine grapes run the risk of long-term damage that can inhibit growth, yield, and revenue to the detriment of growers.
Know What’s Below Your Soil
Unfortunately, many harmful nematodes love permanent crops because the roots act as long-term room and board for them.
Perennial crops often have increased numbers of nematodes associated with their root systems more specifically as the plants age. For example, nematodes such as Pratylenchus spp. (lesion nematodes) can reach such high numbers that replanting following removal of older trees or vines can result in a reduced vigor, stunting or even death of the replant because of the excessive damage by the high population of nematodes in the soil.
For this reason, growers should regularly test for nematodes during the life of trees and vines. A great way to do this is by approaching your testing results with a presence or absence mindset. If plant parasitic nematodes are present, set up a control program to reduce their damaging effects. If they are not currently detected, continue with a consistently scheduled soil testing program to ensure you can catch them early before they start to damage roots.
In cases where plant parasitic nematodes are present, it is best to apply an effective nematicide at key timings during plant growth. For perennials, you should target applications during root flush. This timing is when soils are warm enough for nematode activity and 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, and knowing their lifecycles is an important aspect that directly relates to successful 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 will not be effective. However, 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, so apply at regular intervals according to label instructions.
- Sedentary endoparasitic nematodes are nematodes in which female adults are attached to the plant root and do not relocate. In the case of root-knot nematodes, the female is found sedentary within the root tissue, and in cyst and citrus nematodes, females are attached to the root with a large portion of the female exposed outside the root.
It is important to choose a nematicide that is effective on all life stages because egg and juvenile nematodes can be controlled with effective applications, but some types, like the root-knot nematodes as adults, are protected by the root once they are inside.
When It Comes to Nematode Control, Timing Is EverythingTiming is imperative when considering biological nematicides for nematode control.
Nematodes in 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 since roots are constantly growing and nematodes are likely migrating in the soil. In particular, focus an application timing in the late fall and spring to reduce nematode populations for spring planting and to protect new root flush before the nematodes go deeper in the soil for the winter.
These methods provide added flexibility and opportunity to control nematodes in annual crops and reduce the long-term effects of nematode damage in perennial crops.
Looking for a natural, effective and flexible solution to control nematodes at all life stages?