In this category we will look at common parasites which affect chillies.

Nematodes

Nematodes are round worms that belong to the family Nematoda. These parasitic worms range in size from microscopic to around 7 meters and habit soil, water, plants and animals. In fact they are all around us.

We are going to focus on just two of these that concern us, the pepper grower. Namely, Root-knot Nematodes and Stubby Root Nematodes. The chances that we will be able to tell the two apart is slim. So for sake of simplicity, we will call them Root-knot Nematodes. And this is really one of the best descriptions for these parasites. They live in the soil and feed on roots.

Nematodes are most active during summer months (peak temperatures). Which is unfortunate for the pepper grower, as this is our peak season. The good news is that most pepper home growers are predominantly container growers. But, if you are growing peppers in the open field, you will want to read on.

If you are a container grower and are using commercial potting mediums, it is unlikely that you will encounter Nematode issues. There is a proviso here though and that is unless you have mixed any garden soils with your potting medium. Nematodes are soil living organisms and primarily an issue for those growing in open fields. But having said this, if you have composed your potting mediums with some garden soil, or used tools that were previously in contact with garden soil, or you have boots or gloves that have handled garden soil that have come in contact with your potting medium, or used compost that is made up of Nematode infested plant material. Nematodes could also be a factor.

The name is derived from the knot like growths (galls) that manifest in the roots of infested plants. Being microscopic and living under the ground, these tiny parasites pose quite a substantial problem for the pepper grower. Firstly they are not visible. Secondly, the symptoms that manifest above ground are not easily diagnosable.

Symptoms can also be very slight at first. As the infestation grows, symptoms will become more severe. The damage sustained by the plants roots will progressively get worse until the root of the plant is totally dysfunctional. Roots loose all their fine secondary growth and are stripped down to just the primary roots. This means roots will no longer be able to avail themselves of nutrients and moisture in the soil. Ultimately, plants will be stunted, struggle with yielding fruit and if the infestation is bad enough, die. Any lesion on plants can also be an entry point for pathogens, so plants very often also succumb to disease once attacked by Nematodes.

Diagnosis is virtually impossible above ground. Infested plants will display signs of wilting, nutrient deficiency and disease which are not a clear indicator of Nematodes. So, Nematodes are very often not diagnosed as the root cause (excuse the pun).

The best way to diagnose Nematodes is with an inspection of the roots. Even better is doing a soil test to establish Nematodal activity. A root inspections can reveal visible signs, but this does involves digging up the plant. Poorly developed roots that are lacking in volume and have galls (knots) will be a good indication of Nematodal activity.

Nematodes can survive in plant material and soil and can be transferred from infested soil to un-infested soil by gardening implements carrying infested soil, even boots that have been in contact with infested soil. So, infested plant material should be disposed of safely and not thrown on the compost heap. Tools and boots that have been used in an infested area should be cleaned properly.

There are several options available to the grower when tackling Nematodes. None are totally conclusive unfortunately. Soil infested with Nematodes needs to be managed and navigated as best as one can.

Knowing that you have an issue with Nematodes in your garden, start with buying crops (peppers) that are known to be Nematode resistant such as Carolina Cayenne and Charleston Hot.

Certain types of Marigolds are known to be Nematode suppressive. Garden growers often plant Marigolds in among their vegetables as they are not only great attractors for pollinators, but also keep many of the sap sucking insects at bay too. We can’t vouch for the effectiveness of Marigolds with respect to Nematodes, but we are led to believe that they will suppress them in areas where the plants are grown.

Nematodes are more prevalent in sandy soils and do not enjoy rich loamy soils high in organic material. Plants in poor soil, plants that are weak or plants that are stressed are more likely to perishing from Nematods.

So, as a first port of call, ensuring plants are in soil that is rich and loamy is a plus. Keeping plants healthy and unstressed is another – watering is a big key to this.

Fallowing is a good option on combating Nematodes in the field. Fallow fields should be kept weed free. Tilling will help expose soil to the sun which can further aid combat Nematodes in soil.

Soil Solarization can be used for small patches of soil or small batches of soil that are known to be infested. This involves wetting and covering soil with black plastic sheeting and baking the soil in the sun in peak summer temperatures for a good 4-6 weeks. Raising soil temperatures in excess of 50°C for extended periods of time will kill Nematodes and eggs. In the open field, solarization will give temporary reprieve as only the top 20cm of the soil that reach this temperature will be Nematode free. Nematodes below this level will eventually rise to the surface again.

Solarization in conjunction with Crop Rotation can be an even more effective way to combat Nematode infestations. Every species of Nematode will have its preferred host plant. Rotating crops with crops that are Root-Knot Nematode resistant, can help suppress Nematodes in the field.

With regards to pesticides, we are advised that there are currently no Nematicides or fumigants available to home growers. But this is certainly something larger farming operations could take into consideration.

Other options might include beneficial organisms, but we have not experimented with this and can not give any advice with regards to the efficacy of these organisms.