Have you noticed a decline in your pecan trees? Are the top branches dying out while leaves are smaller or chlorotic? Even worse, are some of them stunted with little foliage; while others are barren? Are there small galls on the rootstocks of your prized trees? If so, it is possible you have a disease issue such as pecan root knot nematodes.
About Pecans with Root Knot Nematodes
In addition to those described above, other symptoms that indicate nematodes on pecans are wilting and spots on the leaves. This infestation is often mistaken for a nutrient deficiency. If the health of the tree fails to improve after feedings of supplemental zinc or nickel, inspect further for nematodes.
Nematodes are microscopic roundworms found in soil, and in and on plant tissues. Pecan root knot nematodes puncture plant tissue and remove cell contents with a spear-like mouthpart, called a stylet. They begin by damaging the roots from within, creating galls and interfering with water and nutrient intake. Galls develop further up the tree. This process affects photosynthesis and nutrient uptake of new branches and nuts.
Root knot nematodes are likely present in soil and water that may move them toward your trees. They are transported by soil on tools, footwear, or infested plants. Many experts believe they overwinter in soil as eggs, waiting to hatch the next spring.
Nematode Control for Pecan Trees
Avoidance of this disease is easiest, so buy nematode resistant stock when planting. Keep drainage around the trees impeccable to prevent infected water from sitting and infesting the orchard.
If you suspect nematodes are present on your trees, there are a few means of control for pecans with root knot nematodes. You may solarize the soil throughout the orchard.
Treat affected trees with pruning of the canopy. Remove dead branches and prune thoroughly to encourage root growth. This does not control the parasite, but may keep the tree healthy enough to produce on a limited level. Encouraging a heavy crop is usually more than the infested tree can handle.
No chemical nematode control for pecans is available. When replacing trees in this area, take precautions such as soil solarization and purchasing trees on nematode resistant rootstocks. If you can let the land lie fallow for a year or longer, all the better. Pecan root knot nematodes will eventually die if no host is present.