Citrus mealybug

General

In a nutshell: Most common mealybug; many, diverse host plants; sap suckers—cause leaves to deform and yellow, excrete sticky “honeydew”; waxy strands around the body are roughly the same length; overwintering occurs underground during the nymph stage.

What are citrus mealybugs?

The citrus mealybug is the most important pest mealybug, and it appears frequently on ornamental plants. It probably originated in China but is now distributed worldwide. In temperate regions, like Canada, the citrus mealybug is mostly a greenhouse pest, but it’s an outdoor crop pest in warmer parts of the world.

What kinds of plants do they attack?

The citrus mealybug attacks mainly fruit trees and ornamentals. It’s not only a pest of potted plants such as ficus, palms, schefflera, croton and kalanchoë, but also of roses and gerbera. This mealybug can also attack cucumber, melon and eggplant.

What do they look like?

Adult females are 2.5–4 mm long and 2–3 mm wide. They appear oval shaped from above and move very little. Citrus mealybugs are soft and covered with a fine waxy substance through which the light yellow to pink body is visible. Often, a darker stripe running the length of the body can also be seen.

It has 18 pairs of short, wax rods sticking out from the edge of its body. It also has two slightly longer “tail strands” that are less than 20% of its body length. These characteristics distinguish the citrus mealybug from other mealybug species.

Adult males are short-lived and can be hard to spot. They are smaller than the females (only around 1 mm long), have two pairs of wings and two long tail filaments. They fly around only in the early morning, have no mouthparts for feeding and exist only to mate. As soon as a male emerges from its cocoon, it goes in search of a female.

Nine to fourteen days after she mates, the female mealybug lays several hundred eggs in an elongated cottony egg sac made of white, waxy threads. The eggs are oval or round, light yellow in colour. Once she lays her eggs, the female shrivels up and dies.

The first-stage nymphs, called “crawlers”, emerge from the eggs. They’re around 0.6 mm long by 0.2 mm wide and actively search for a new feeding spot. During this stage, they’re able to move around the plant or across other surfaces.

The male nymph attaches itself to the plant, then it forms a dark brown “pre-pupa." This quickly develops into a pupa inside a white, cottony cocoon. The female remains mobile throughout her entire development and changes form very little. After completing the third nymph stage, the female becomes an adult and starts releasing a chemical that attracts males.

How do I know if my plants are under attack?

Mealybugs can be found on all parts of the plant, but they prefer growing tips and the areas where leaf stem and plant stem intersect.

Nymphs and adult females feed on the plant’s vital sap. This stunts growth, causes leaves to become deformed or yellow, and sometimes leads to defoliation. This has the general effect of reducing photosynthesis and yield. Often flowers and fruit will drop off the plant.

Excess sugar from the sap is excreted on leaves and fruit surfaces as a sticky “honeydew”. Black fungal moulds will often grow on this substance, further reducing photosynthesis and contaminating fruit.

Growth of black mould and the white, waxy secretions left behind by the mealybugs ruin the ornamental value of plants.