Food & Climate 

Basics

Weeds, Diseases, and Pests

Climate also affects pests and diseases. The distribution and proliferation of insects and weeds is influenced by climate, because temperature, light, and water are major drivers for their growth and development.

Climate also affects the pesticides used to control or prevent pest outbreaks. In a changing climate, pests may become even more active than they are currently, and, even though there are alternative ways to fight them, farmers would have to use more agricultural chemicals that carry health, ecological and economic costs.

 Response to climate variables

In general, most pest species are favored by warm and humid condition, however, a weak crop during a drought is more likely to become infected by fungi than when it has enough water to be strong and healthy.

Precipitation – whether optimal, excessive, or insufficient – is probably the most important variable that affects the way in which plants are affected by pests or diseases. In these circumstances, you can never be sure if the drop in yeild is caused by the pest or by the change of conditions.

Pink rot, sometimes called water rot, occur sporadically wherever potatoes are grown. This disease is most serious when warm, wet soil conditions persist during tuber formation and at harvest. Major problems with this disease are usually associated with excessive rainfall or irrigation either early or late in the season, especially on poorly-drained soils.

Insects

Insects flourish in all climates, their habitats and survival strategies are also dependent on local weather, and are particularly sensitive to temperature because they are cold-blooded.

Insects respond to higher temperature with higher reproduction rates. Warmer winters reduce winterkill, and increase insect populations in spring and summer. Abnormally cool, wet conditions can also bring on severe insect and plant infestations, although excessive soil moisture may drown soil-residing insects.

The Desert Locust is an international problem due to the frequent migration of swarms across borders. Since earliest recorded history, this pest has been considered a serious threat to agricultural production in Africa, the Near East and Southwest Asia and often requires large-scale control operations

Weeds

Weeds compete with crops for soil nutrients, light, and space. Drought conditions increase competition for soil moisture between crops and weeds, while humid conditions increase the proliferation of weeds.

High temperature and humidity result in the spread of diseases and influences the lifecycle of soil worms called nematodes. Some disease causing agents survive in hot, dry conditions as long as there is dew formation at night.

As fall approaches and corn begins to mature and dry for harvest, weeds take advantage of the available sunlight and resume growth at full speed. Here you can see one of the most common weeds in corn in Mississippi, it is called Hosenettle, and it is also one of the most troublesome as it is quite hard to eliminate.

Author:  Marta Moneo and Ana Iglesias- Universidad Politécnica de Madrid - España
1. Scientific reviewer: Alex de Sherbinin - CIESIN, Columbia University - USA
2. Scientific reviewer: Lily Parshall - Goddard Institute for space studies, Columbia University - USA
Educational reviewer: Emilio Sternfeld - Colegio Virgen de Mirasierra - España
Last update: 12/05/2004