How can I best manage nematodes?
First step is to carry out a nematode test in our laboratory to know the population and type of nematodes in your soil. Based on the results a combination of the following control Carry out a nematode analysis
(i) Avoid introduction: In nematode management, it is important bear in mind that nematodes are mainly spread through movement of infested soil, seedlings, soil working implements and plant debris. It is important to avoid introduction of nematodes into the greenhouse by planting nematode-free seedlings and using nematode free media especially for propagation. This can be achieved by inspection of nurseries by experts before the seedlings are transferred to greenhouse i.e. implement a certification programme. Equipments and tools used on soils should be properly cleaned before use in another greenhouse. Soil conservation measures to check soil erosion also limit nematode spread and introduction.
(ii) Balance soil fertility: Soils that have poor fertility, including low calcium levels (low oxygen conditions), will be more prone to nematode infestation. Balancing of your soil fertility through soil testing in our laboratory, will provide a better environment for beneficial soil organisms to compete with plant parasitic nematodes, reducing the threat to crop yields. A balanced crop nutrition program serves to reduce adverse effects of nematodes by improving plant health and making them more tolerant to nematodes.
(iii) Resistant/tolerant varieties: If the greenhouse is infested, it is highly recommended that the farmers use nematode resistant varieties. Nematode resistant varieties of many vegetables are sold locally in most leading seed stockists and are ideal for replanting in heavily infested hot spots.
(iv) Weed control: Control of all weed hosts in the greenhouse. Weeds such as Gallant soldier and black/African night shade (Solanum spp.) can habour very large populations of nematodes.
(v) Organic amendments: Incorporation of organic matter and residues into soil including manures and crop residues not only improve soil characteristics, moisture availability and plant nutrition, but also stimulate microbial antagonism to nematodes by predacious mites, springtails and earthworms. High organic content in soil servers as a substrate for proliferation saprophagous nematodes that help in nutrient cycling. Sandy soils, with lower than optimum organic matter, when fertilized with high nitrogen fertilizers, are very susceptible to nematode attack.
(vi) Antagonistic cover crops: Intercropping vegetables with crops that are non-host or with antagonistic properties to nematodes in alternate seasons reduce their numbers by depriving nematodes of food and releasing nematicidal properties. Popular cover crops for nematode management include; cabbage, mustard, velvet bean (Mucuna pruriens), hyacinth bean (Dolichos purpureus), Mexican marigold (Tagetes spp), Sorghum (Sorghum bicolor) and sorghum-sudan grass (Sorghum bicolour subsp. drummondii) among others. When establishing a greenhouse, the antagonistic/cover crop can be harvested before maturity and be mixed or incorporated into the soil (bio-fumigation) to the reduction or detriment of the nematodes.
(vii) Biological Nematicides: Biologically based nematicides, also known as bio pesticides, include neem based products, Trichoderma sp., nematophagous fungus such as Paecilomyces lilacinus and Myrothecium verrucaria, which allwork to reduce nematode numbers without concern of environmental hazards. Bio pesticides are now becoming increasing available in Kenya, with some being produced by locally based IPM companies, whilst others are being imported.
(viii) Chemical nematicides may be used when nematode population are severe and resulting in crop yield losses. These products can also be used to manage nematodes by spot treatment. It is always advisable to follow use of chemical nematodes with good quality compost to repopulate t6he soil with beneficial micro-organisms. Long term use of chemical nematicides is not recommended due to the negative effects on soil biological activity; we advise adopting an integrated management approach, which although more demanding to implement, will be far more affordable and sustainable for your farm.
(ix) Integrated nematode management and monitoring: To effectively manage nematodes, greenhouse farmers need to employ the above nematode management strategies using an integrated approach. You need to note that specific farming practises have different effects on nematode populations either in general or at species level. Therefore, the most successful farmers in controlling nematodes are those who implement an integrated approach that includes good soil fertility management, maintaining adequate soil calcium levels, the use of organic amendments, adopting biological control (IPM) and crop rotation with non-host crops.