Tom Carey: Nematodes are everywhere

As life forms go, nematodes are found in every possible habitat on Earth (they even survived the Shuttle Columbia disaster). The thousands of species perform numerous biological functions necessary to maintain the natural world as we know it. Most are microscopic in size, many are parasitic, some are beneficial to our needs, and a few are the bane of my existence. For the limitations of this treatise (and the variety that is most commonly experienced by Central Florida gardeners), we will focus on Tylenchida Meloidogyne species, better known as root-knot nematodes (RKN).

RKN are tiny soil ‘worms’ that thrive in warmer climates. Their three-month life cycle experiences several phases starting with sexual reproduction. Upon hatching from the hundreds of eggs laid each generation, the juveniles experience unfettered life in the soil until they burrow into a plant’s roots. The irritation of the elongating root areas cause cellular enlargement, resulting in recognizable galls or knots. RKN most commonly survive unfavorable seasonal cycles as either eggs or cysts in the soil.

Once a susceptible plant is infected by RKN, moisture and nutrient functions of the roots are damaged, resulting in decreased crop yield. Some plants, including many weed varieties, compensate by over producing leaf mass and appear to be growing normally. I have noticed this effect in my garden. But when the summer heats up, the damage leads to a tendency to wilt, and eventually wither. The RKN are discreetly reproducing at a fervent pace, and if a ‘green manure’ crop of compliant weeds was the intention, a future of crop failures is inevitable. New garden spaces that have not yet accumulated this pest may avoid numerous problems, temporarily basking in a case of beginner’s luck.

Soil fumigant chemicals, which are a major contributor to the atmospheric ozone hole over Antarctica, are so environmentally toxic that they are banned in most countries (Florida and California strawberry growers still go begging for exemptions). Luckily, there are a few cultural controls that we can practice at a gardening scale of farming. Not all plants are compliant hosts; marigolds, sunnhemp, or rye grass grown in seasonal rotation between our regular food crops will starve out a generation. Some tomato varieties are listed as nematode resistant or cherry tomatoes will produce before the damage reduces crop productivity. There are naturally occurring soil fungi that will devour this pest, best encouraged through natural, organic soil husbandry or a purchased soil amendment. Or take it easy for the summer and leave the garden soil fallow and hermetically mulched for a few months.

Tom Carey is the owner of Sundew Gardens, a you-pick gardening business in Oviedo. Visit the Sundew Gardens Facebook page and email him at [email protected]