Pests, Diseases & Plant Problems

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July 3, 2024


The Searles Gardening Team

Understanding nematodes is crucial for every gardener. Contrary to popular belief, not all nematodes are harmful; some are actually beneficial. However, there are a few types that have earned nematodes a bad reputation. One such nematode is the root knot nematode, a parasite that feeds off the roots and produces the growths or knots you may notice when removing a plant. These knots restrict the plant’s ability to absorb water and nutrients, leading to weakened plants and reduced productivity.

Home gardeners play a crucial role in managing nematodes. In the past, nematicides, which are products designed to kill nematodes, were available.  However, these have been withdrawn from the market, placing the responsibility of nematode control on cultural practices.

It’s often too late when you finally see the reason for your plants’ decline. The symptoms of nematodes can be mistaken for many other causes, such as wilting, yellowing, or even death. Since nematodes are hidden underground, they often go unnoticed until the damage is severe. The warmer months are when they are most prevalent, and so to avoid disappointment, it’s crucial to take preventive measures.  

Crop rotation is a key strategy in nematode control. This involves planting a different crop in the same area consecutively. The eggs of root knot nematodes can live in the soil for up to a year. Crops commonly attacked by nematodes, such as tomatoes, should not be planted in the same garden each year, but they should have two or three beds and be moved around. This way, the soil has had other crops in it, and the root knot nematode eggs have failed by the time the next crop of the susceptible is planted. If you haven’t got the garden space, grow the crop in containers in fresh potting mix for a season. Companion planting will also help to deter nemotode activity.

Incorporate manures, compost, or organic fertiliser into the soil before each planting and always use a mulch. These organic materials not only provide essential nutrients for your plants but also improve soil structure and promote beneficial soil organisms, including nematode predators.

Look for varieties of plants bred to be nematode-resistant. Consider plants that are not as suspectable to root knot nematodes such as broccoli, leaks, spring onions, corn, etc. When you do see bumps on roots, do not jump to the conclusion of root knot nematodes. Peas and beans have small bumps on their roots to store nitrogen from the soil, which is necessary for the plants.