12^th Agro Bangladesh Expo 2024

Pests and Pathogens

Plant pests include the arthropods (such as insects and mites), slugs, snails, sowbugs, and pillbugs. Only a small proportion of insects are plant pests with the most conspicuous being the butterflies and moths. The larvae (caterpillars) of butterflies and moths cause severe damage by feeding on foliage until they pupate. The adults rarely feed on foliage. The most common butterfly pest in North America is the cabbage white, which is seen in great numbers in the summer. Beetles also damage plants as both larvae and adults chew on plant tissue. The Colorado potato beetle is the most notorious of these pests. Juvenile (nymphs) and adult grasshoppers are also foliage-eating insect pests. Larvae of flies feed and burrow into roots, bulbs, and stems of plants and thus cause considerable damage.

The least conspicuous insect pests are those that pierce the stem or leaf and suck nutrients from the plant. Nymphs and adults of aphids, leaf hoppers, stink bugs, and plant bugs cause extensive damage in this manner and, as well, they carry plant pathogens, especially viruses, from plant to plant. Insects called thrips also pierce plant parts and are important in transmitting viruses.

Mites differ from insects, as the adults have four pairs of legs (versus six for insects) and lack an antennae. Larvae of mites feed and molt to form six legged nymphs before becoming adults. The mites that feed on plants have rasping and sucking mouth parts that damage plants and they also transmit plant pathogens as they feed. Both thrips and mites are very small and, as a result, often avoid detection until the plant growth is visibly affected.