Nematodes, the demon hidden beneath
By Scott Mathew, Senior Solutions Development Lead @HortApplication
They’re tiny, microscopic, and hidden in the soil but despite their size they can cause significant yield damage and loss in quality.
Establish your infestation level
The first step in managing these pests is to establish if you have a significant infestation of one or more of the types of nematodes that can cause damage. Often the effects can be quite discrete, such as plants lacking vigour, from their root system being impeded by the nematode feeding sites. Nematodes are parasites which means they rely on keeping the plant alive to a sufficient state whereby it continues to provide an ongoing source of food for them to multiply. Their speed of multiplication can be staggering when they are provided with a good host.
Key nematode species & host crops
One of the key nematode species that damages many vegetable crops are root-knot nematodes, Meloidogyne javanica and Meloidogyne incognita. Key host crops in vegetables are beans, carrot, celery, capsicum, cucurbits, ginger, lettuce, potatoes, pumpkin and tomatoes as well as over 2000 weed species.
Crop rotation will not eliminate root-knot nematodes, it will however significantly reduce crop losses when a susceptible crop is planted again. Winter cereals are useful because they are generally poor hosts, root-knot nematode reproduction is also slower during the cooler winter months. Summer crop options include sorghum-sudangrass hybrids (particularly cv. Jumbo).
When it comes to cultivation & fallow, ensure you remove plants as soon as the crop is harvested to prevent further multiplication (if possible remove the roots as well). Repeated cultivation kills nematodes in the upper soil layers by exposing them to mechanical abrasion, and the heating and drying action of the sun. Eggs can last up to a year and populations will persist on a range of weeds (control the weeds). If the area is maintained weed free, nematodes will die of starvation. A 4-6 month fallow may reduce nematode populations by up to 95 percent.
If there is good market acceptance for root-knot nematode resistant varieties they can provide a very good level of protection. For susceptible varieties, chemical control options are fewer in number than in recent years with regulation causing this decline of registered products. Certain options for fumigation of the soil do still exist but application can be very expensive and relies on moisture, application technique and soil type. Syngenta has recently registered TERVIGO® for controlling root-knot nematodes with application through trickle irrigation in fruiting vegetables and cucurbit crops. Other products are available however some can be restricted to certain states only. Always check with your customer for acceptance of the nematicides you are considering.