Kitchen gardens may seem easy to maintain until invaded by pests. When that happens, it’s time to take effective actions

KITCHEN gardens are popular for various reasons. People may start a kitchen garden perhaps to supplement the food budget, to get high quality food, or simply to experience the joy of watching plants grow. However, gardeners are disappointed when diseases or other pests become such a problem that the yields are reduced or non-existent.

Nematodes are one of the more serious pests of vegetables and are often responsible for reduced yields. Nematodes are worm-like animals visible only under the microscope. It is for this reason that nematodes have been termed as “hidden enemies” or tiny but mighty enemies of the crops. There are many kinds of nematodes that attack all types of plants. Some nematodes are specific to a particular crop, whereas others are polyphagous i.e. attacking several crops. They need food for survival which they obtain by sucking the roots of plants with an organ known as stylet. In this way, they cause direct mechanical injury to the plants and disturb its systems biochemically. When roots are punctured by nematodes, other micro-organisms present in the soil attack the roots and cause damage to them. This is called secondary invasion.

The most common nematode problem in vegetable gardens is that of root-knots. As a result of the feeding activities of these nematodes, plant roots become swollen and form root galls. Nematodes are also known as endoparasitic nematodes. Due to heavy root-knot nematode infection, plants become more susceptible to drought stress, root-rots, and the yields are very low and below standard. These nematodes attack nearly every vegetable grown in Pakistan.

Root-knot galls distort the tissue that conducts food and nutrients to the upper part of the plant. Various kinds of nematodes damage and interfere with the growth of the plants as well as the supply of food and water that the plant gets from the soil. The easiest of the nematode diseases to recognize is root-knot, caused by nematodes of various species of the genus Meloidogyne. They are called root-knot nematodes. The typical simple galls are best observed on younger roots, giving an appearance of beads on a string. Galls have several short adventitious roots that rise from the upper part and make the root appear bushy.

On larger roots, compound galls may be an inch or more in diameter. Severely infected roots show a clubbed appearance. Often there is considerable rotting of the roots, particularly late in the season. Identification of the galls is made by breaking them open and looking for the nematodes. Usually the adult females are found, that are pear-shaped, white and are large enough to be seen with the naked eye. The egg masses of root-knot nematodes are also fairly easy to see. They are brown in colour, often as large as the nematodes and are found clinging to the side of the roots. Sometimes the male, a slender worm quite different from the female, can also be found in the egg mass.

There are several methods that can be used to control nematodes and to minimize the damage they cause in vegetable gardens. Some of these methods are more effective than others and quite often it takes a combination of methods to optimize the results.