Boxwood Psyllid

The Boxwood Psyllid (Psylla buxi) is a tiny, sap-sucking insect primarily affecting boxwood plants (Buxus species).

Host Plants

The Boxwood Psyllid is a specialist insect that primarily affects boxwood plants. Its host plants are exclusively members of the Buxus genus. This includes common boxwood (Buxus sempervirens), Korean boxwood (Buxus sinica var. insularis), and other species and hybrids within the Buxus genus.

Regions impacted

It occurs across North America, Europe, and other parts of the world where boxwoods are cultivated.

Description

In its adult form, the boxwood psyllid is about 3mm long. It has a delicate, somewhat translucent appearance with clear wings that extend past the tip of the abdomen. The body color varies but is often a light green or yellow-green, which allows the psyllid to blend in with the boxwood leaves it feeds on.

The nymphs, or immature stages, are also green, and they are flattened in shape. One distinctive feature of the nymphs is that they are often covered with a white, waxy secretion. This secretion, along with the curled and cupped leaves caused by the psyllids’ feeding, can be a helpful clue in identifying an infestation.

Life Cycle

The boxwood psyllid (Psylla buxi) has a life cycle that includes an egg stage, multiple nymphal stages, and an adult stage. Here’s a basic breakdown:

Egg: The cycle begins in late spring, when adult psyllids lay their eggs in the crevices of boxwood buds. The eggs overwinter in these protective areas and hatch the following spring.

Nymph: After hatching, the psyllid enters its nymphal stage. The nymphs, or immature psyllids, feed on the sap of the new boxwood growth, causing the characteristic cupping or curling of the leaves. The nymphs undergo five instar stages, each time shedding their skin to allow for growth. This phase lasts through the late spring and early summer.

Adult: By mid-summer, the nymphs have developed into adults, and they lay their eggs in the late spring, starting the cycle over again. Adults are about 3mm long, with clear wings that extend beyond the abdomen. They’re greenish or yellowish in color, allowing them to blend with the foliage.

Unlike some insects, boxwood psyllids have only one generation per year. Their life cycle is synchronized with the annual growth cycle of boxwood plants, ensuring a food source for the nymphs when they hatch in the spring. It’s during this nymph stage that they cause the most noticeable damage to the plants, with the curled leaves characteristic of their feeding. The adults, while they also feed on the plants, do not cause the same level of damage.

Damage and Detection

Boxwood psyllids cause a distinct type of damage to boxwood plants. The primary sign of their presence is the distinctive cupping or curling of the leaves. This is caused by the nymphs feeding on the sap of new growth. As they feed, their saliva causes the leaf tissue to deform, creating a protective shelter for the nymphs. These curled leaves are the most visible symptom of a boxwood psyllid infestation.

While this damage is primarily cosmetic, severe infestations can cause a reduction in plant vigor and stunted growth. The feeding by psyllid nymphs may also cause twig dieback. Despite these effects, boxwood psyllids rarely kill the plants they infest, though they can make them look unsightly.

To detect boxwood psyllids, check your boxwood plants regularly, especially in the spring when new growth is emerging. Look for the characteristic leaf curling, and try to spot the tiny, greenish nymphs or adults on the plant. A strong jet of water from a hose can dislodge the nymphs, making them easier to see.

Other signs of their presence include the tiny, white, waxy secretions left by the nymphs. Adult psyllids may also be visible in the late spring or early summer, often clustered around new growth or buds.

Remember that early detection is key in managing boxwood psyllids. The sooner you can identify and address an infestation, the less damage these pests can cause to your boxwood plants.

Prevention and Control

There are several strategies for preventing and controlling boxwood psyllids, ranging from cultural practices to biological and chemical controls.

Cultural Practices

• Plant Selection: Some species and varieties of boxwood are less susceptible to boxwood psyllids than others. If you’re planning to plant boxwoods, consider choosing resistant varieties.
• Sanitation: Prune the affected leaves during spring, before the nymphs mature into adults. Regularly remove and dispose of leaf debris and prunings, which can harbor overwintering eggs.

Chemical Control

• Insecticidal Soap or Oil: Spraying boxwoods with insecticidal soap or horticultural oil in the spring can kill the emerging nymphs without causing much harm to beneficial insects.
• Insecticides: Conventional insecticides can be used, but they should be a last resort due to their potential impact on non-target organisms. Apply when nymphs are active, but remember, repeated use of the same insecticide can lead to resistance.

In all cases, be sure to monitor your boxwoods regularly for signs of psyllids, and start control measures as soon as they’re detected. With timely and appropriate action, damage from boxwood psyllids can be minimized. Always make sure to follow the instructions on any pesticide labels, and consult with a local extension service or pest management professional for advice tailored to your specific situation.