Thrips on onion plants

Disease name: Thrips on onion plants

The scientific name: Thrips tabaci

Type of disease: insect

Disease family: Thripidae

(Appearance of yellow thrips nymphs on onion leaves)

• The causes of disease:

Onion thrips are small insects that range in color from yellow to black. Adults overwinter in crop residues and weeds found in the field.

• Symptoms of the disease:

The initial symptoms of the infection appear on onion leaves in the form of silver lines or white spots, and the onion leaves are wrinkled or curled. As the severity of the infection increases, the tips die and the growth of the leaves slows down.

(The appearance of the initial symptoms of thrips infection on onion leaves)

• Disease development cycle:

Thrips have rough mouth parts that they use to tear apart plant cells. Adults and nymphs also penetrate the epidermis of onion leaves to feed on plant sap. Thrip damage can also lead to an increase in the appearance of purple spots, as the fungus can penetrate the plant through wounds caused by feeding.

• Conditions suitable for the spread of the disease:

Thrips prefer hot, dry weather to reproduce and spread in crops, as heavy rain can cause them to fall from trees and die.

(Wounds left by thrips on onion leaves)

• Losses resulting from the spread of the disease:

Neglecting the infestation leads to an increase in the number of thrips, which contributes to a decrease in the size of the bulb. It can also lead to the death of the plant and a decrease in crop productivity.

• Control:

1. Organic control: Removing the remains of plants and harmful weeds found in the field and using straw mulch reduces the severity of the infestation, and the small numbers present on the plant can be eliminated by spraying them with water.
2. Chemical control: Use systemic insecticides containing dimethoate when the infestation is severe.

• preventive measures:

1. Monitor the crop closely especially between the leaf blades to find light yellow thrips nymphs or dark colored adults.
2. Use healthy seedlings free of disease.
3. Avoid planting onions near alfalfa or wheat because these crops can harbor large numbers of thrips.
4. Sterilize agricultural tools before use.

(Development of symptoms as a result of thrips infection)

• Sources:
• https://ag.umass.edu/vegetable/fact-sheets/thrips-onion