The red-billed quelea,
Quelea quelea
, a major pest of cereal crops in Africa, has been ‘controlled’ in many countries for over 20 years. Yet its numbers do not appear to have altered significantly in consequence. Low rainfall, which adversely affects the supply of the birds’ natural food (wild grass seeds), can be held responsible for the temporary decline in numbers in South Africa between 1955 and 1963, and for the currently reduced population in the Sahel states. Attempts to make the population reduction strategy effective by increasing the control effort are likely to be unsuccessful and costly. Instead, other crop protection strategies should be selected, each appropriate to particular damage situations. Where damage is caused to irrigated crops in the dry season, or to wet season crops grown along the birds’ migration routes, an alteration of crop phenology strategy is appropriate. But where damage is caused by newly independent young, the destruction of nearby breeding colonies is required. Such destruction should aim to give local and temporary relief and not attempt overall regulation of the pest’s population. Neither scaring techniques (including chemical repellents), nor so-called birdproof varieties, offer much hope, since damage is largely caused by birds which have no alternative, natural, food source at the time. Other bird pest species require substantial biological research before logical decisions on strategy can be made.
Cross-kingdom RNA trafficking and environmental RNAi — nature's blueprint for modern crop protection strategies
