Question

The insect inducing gall formation in apple roots is:

• A. Eriosoma lanigerum
• B. Quadraspidiotus perniciosus
• C. Brachycaudus helichrysi
• D. Dorysthenes hugelii

Hint:

The woolly apple aphid (Eriosoma lanigerum) is a major pest of apple trees. Its root-feeding colonies inject salivary toxins that induce diagnostic gall-like swellings on the roots.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Certain sap-feeding insects inject specialized salivary secretions into plant tissues during feeding.
These secretions contain plant growth regulators or enzymes that induce localized cell division (hyperplasia) and cell enlargement (hypertrophy).
This abnormal growth results in the formation of galls, which provide shelter and nutrition for the insect.

Step 2: Detailed Explanation:
Eriosoma lanigerum, commonly known as the woolly apple aphid (WAA), is a destructive pest of apple orchards worldwide.
The aphid is covered in a white, cottony, waxy secretion that protects it from predators and weather.
WAA attacks both the aerial parts (twigs, branches, and trunks) and the subterranean root system of apple trees.
When the aphids feed on the roots, their salivary secretions induce the formation of characteristic gall-like swellings and knots.
These root galls disrupt the transport of water and nutrients, weaken the tree, and make it more susceptible to secondary fungal pathogens and root rot.
Control often requires using resistant rootstocks (such as Northern Spy or MM series) that prevent WAA colonization.
For comparison:
- Quadraspidiotus perniciosus is the San Jose scale, which causes red spots on bark and fruit but does not form galls.
- Brachycaudus helichrysi is the leaf-curl plum aphid.
- Dorysthenes hugelii is the apple root borer, which physically devours roots rather than inducing galls.
Therefore, Eriosoma lanigerum is the correct choice.

Step 3: Final Answer
The insect that induces gall formation in apple roots is Eriosoma lanigerum.