Sweet Chestnut Tree Pests

Identification

• The omnivorous looper is among the likely pest of the sweet chestnut tree. The pest is also called the avocado looper and has a wide range of plants on its host list including sweet chestnut. Other potential pests include acorn moth and filbertworm. These are common pests of oak acorns and also infest other nut species such as chestnut and almond.

Description

• Omnivorous looper is a green-colored caterpillar with distinct yellow, green, pink or black stripes down its back. The pest arches its body in a looping motion as it crawls. Mature caterpillars are 2 to 2 ½ inches long. Filbertworm and acorn moth are the larval stage of small, copper-, bronze- or red-colored moths. The light brown to white larvae have dark heads and three pairs of legs.

Damage

• The omnivorous looper is a foliage-feeding caterpillar that infests and feeds on the leaves of the sweet chestnut. Damage is evident in the form of skeletonized foliage with only the main veins left behind. The pests do not produce any webs as they feed. Extensive feeding is also likely to scar the fruit surface. Both the acorn moth and filbertworm primarily attack the nuts on infested trees where they eat and tunnel their way inside the nuts, destroying the kernel entirely. The insects often deposit their larvae inside the nuts. Damaged nuts are prone to bacterial infections.

Management

• Remove the omnivorous loopers manually by handpicking them off the trees. This is effective in cases of light infestation. Chemical control options include the use of spinosad or Bacillus thuringiensis. Pesticides are most effective when used on younger caterpillars. There are no effective control methods for acorn moth and filbertworm once an infestation has occurred. Pest presence is less likely on trees that are growing in areas of sun.