The Pocket Book of Insect Anatomy by Marianne Taylor

Author:Marianne Taylor
Language: eng
Format: epub
Publisher: Bloomsbury Publishing
Published: 2019-12-15T00:00:00+00:00

Strict biocontrol measures are needed at docks and ports to prevent further accidental spread of invasive species.

INSECTS AS CROP PESTS

Ever since humankind began cultivating plants to harvest, we have been doing battle with a range of insects that have a taste for the same plants as ourselves.

When we set out to grow a crop of a particular plant, whether in our back garden or on a wide expanse of farmland, we are creating an unnatural habitat in the outside world. Monocultures rarely occur in nature – only where conditions are so hostile that just a few highly adapted specialists can survive. Elsewhere, plant communities are naturally mixed, and the animals that depend on those plants tend to make use of many of them. Those herbivores that feed only on one species of plant will normally have scattered populations, as individuals of their host plant will be scattered.

Creating a habitat occupied by just one plant species can encourage unusually large populations of particular insects, sometimes to the extent that they can destroy the entire harvest. A famous example is the Colorado Potato Beetle (Leptinotarsa decemlineata). These beetles and their larvae are not actually interested in the potatoes, but consume the plants’ foliage, drastically reducing yield of potatoes below ground. Crop pests can also harm plants we grow for non-food purposes, such as the Cotton Aphid (Aphis gossypii), which feeds on the stems and leaves of cotton plants (and also attacks other crop plants including coffee, cocoa, citrus trees and cucumbers).

Locusts are perhaps the most notorious of all crop-eating insects. When their numbers rise enough for them to enter a swarming phase, they can cover huge distances and entirely devastate all kinds of food crops over a wide area. Locust ‘plagues’ occur at intervals of several years, and when they do, they can cause famine, which may result in mass human migration. Careful monitoring of their numbers and decisive action when an outbreak occurs is necessary to preempt these devastating events, as occurred in western Africa in 2004 when over 50,000 square miles (around 130,000 sq km) were treated with insecticide to control an upsurge. This action stopped the upsurge, but crop losses valued at US$2.5 billion had already occurred.

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