Aphids

Myzus persicae, Aphis gossypi, Macrosiphum euphorbiae, Phorodon cannabis,
Rhopalosiphum rufiabdominale, Aulacorthum solani

There are many species of Aphids (green peach aphid, cotton aphid, potato aphid, cannabis aphid, rice root aphid, foxglove aphid), while some are host specific (monophagous), others feed on many plant species (polyphagus). There are different traits which help identify aphids: head shape, siphunculi (a pair of tube like protrusions at the posterior side of the body) size and angle and cauda (a sort of “tail” at the posterior of the body through which honeydew is secreted) size and length. Aphids come in many colors (white, black, brown, gray, yellow, light green, or even pink) and can also vary considerably within the species.

Thrips

Thysanoptera

There are approximately 6,000 species of thrips and they are worldwide pests with a wide range of host plants. The main plants being vegetable crops, field crops, flowers, fruit trees, citrus and many ornamental plants. Some thrips are predators of other insects or mites.

Adults and nymphs feed on plant sap reducing the chlorophyll content, thus causing yellowing of foliage, accompanied sometimes by dehydration and defoliation. If the infestation occurs early enough in the season it will cause the young plants to die. It typically appears as light spots on the petals with the blackening of the margins of the petals and discoloration of the flowers.

The indirect damage is caused by the transfer of harmful viral diseases which may penetrate via feeding sites. The typical signs of damage are: silvering in sweet pepper, bronzing in strawberry, malformation in cucumber, and small perforations in tomato. In addition, there is a decrease in yield as a result of the falling off of fruit.

Spider Mites

Tetranychidae

There are around 1,200 species of spider mites all belonging to the family Tetranychidae. They prefer living in the undersides of leaves. They spin silk webs which are also used as a means to protect their colonies as well as to travel from plant to plant. Spider mites can be difficult to spot but if unchecked, move to the upper leaves.

Spider mites feed on the plant cells, and this initial damage will appear as small yellow-brown spots on the leaves. This results in reduced photosynthesis, plant growth reduction, or the death of young plants.

Fungus Gnats

Sciarids

Fungus gnats (Sciarids) are small, dark, delicate-looking flies that infest soil, potting mixes, and sources of organic decomposition. Adult fungus gnats have light gray to clear wings and slender legs with segmented antennae that are longer than their head. Females lay tiny eggs in moist, organic debris or potting soil.

Adult fungus gnats don’t damage plants, however, their larvae can damage roots and stunt plant growth. Significant root damage can cause plant death. Serious fungus gnat damage is more common in greenhouses and nurseries than in open fields.