Aphids - Pests & Diseases
What are aphids in short
- What are aphids?
- When we refer to aphids, or plant lice, we usually mean a super family of insects which includes over 4,000 species of plant-specific parasites.
- What can you see?
- Aphids can cause decreased growth rates, mottled leaves, yellowing, stunted growth, curled leaves, browning, wilting, low yields and death in plants.
- What can you do about aphids?
- There are several cultivation techniques that we can use to prevent or minimize an attack of aphids.
Biological cycle of aphids
Aphids can be winged or wingless. Usually the first generation to emerge from the winter egg are wingless. However, after several generations there can be a lack of space on the host plant. This triggers the birth of a generation of winged aphids, which can migrate to other hosts. All the aphids born from the winter eggs are females. Several more generations of female aphids are born during the spring and summer. A female can live for 25 days, during which time she can produce up to 80 new aphids. Spring and summer reproduction occurs asexually – without males.
Symptoms of aphids
The removal of phloem sap for food weakens the plant and causes a metabolic imbalance, twisting of the leaves and, in extreme cases, leaf loss. Leaf loss affects the quantity and quality of the final harvest. They also introduce toxins into the plant, systemically altering its development.
The honeydew secreted by the aphids is an ideal culture medium for various fungi which form a barrier on the leaf, stopping it from taking in all the light that hits it.
But the most harmful consequence for the crop is the transmission of viruses. Aphids can transmit dozens of viruses from a diseased plant to healthy in few seconds, especially through the winged generation. The biggest problem with viruses is that there is no remedy for them, so that the infection of a plant that is not tolerant or resistant to the virus leads inevitably to a decline in the final production.
How to prevent aphids?
There are several cultivation techniques that we can use to prevent or minimize an attack of aphids. These include:
- Eliminating weeds that can serve as a reservoir of eggs and adults.
- Using insect nets (sometimes insecticide-impregnated) to cover crops.
- Avoiding the excessive use of nitrogenous fertilizer.
- Removing crop residues
- Establishing plant species that can serve as a reservoir for predators (banker plants).
Solutions to control aphids
The natural enemies of aphids are predators such as ladybird beetles (or ladybugs) and lacewings. Green lacewing larvae (Chrysoperla sp.) are voracious predators of aphids.
