What is San Jose Scale? How to Control it.
The San Jose scale is a tiny insect pest that attacks apple trees and many other fruit plants. It is one of the most dangerous pests in orchards because it sucks sap from trees and can kill them if not controlled.
The scientific name is Comstockaspis perniciosa (earlier called Quadraspidiotus perniciosus). It belongs to the armored scale insect family.
It attacks:
- Apple
- Pear
- Peach
- Plum
- Cherry
- Apricot
- Ornamental plants
The insect attaches itself to:
- Fruits
- Leaves
- Branches
- Bar
- and sucks plant juice continuously.
It got its name from San Jose because it was first discovered there in the United States around 1880–1881.
Although discovered in California, scientists believe it originally came from:
- China
- Northeast Asia
- Korea region
It likely entered America through imported plants from China.
Who Found It?
The insect was discovered and scientifically described by entomologist John Henry Comstock in 1881.
Because of his work, the insect species name includes “Comstock”.
How Does San Jose Scale Occur?
The pest spreads mainly through:
- Infected nursery plants
- Wind
- Birds
- Farm tools
- Transport of infected fruits or branches
The young insects are called crawlers. They move around until they find a suitable place on the tree. Then they:
- Attach themselves
- Insert needle-like mouthparts
- Start sucking sap
- Form a hard waxy covering (“scale”)
After settling, females usually never move again.
Life Cycle of San Jose Scale
1. Crawler Stage
Tiny yellow young insects move on the tree looking for a feeding spot.
2. Nymph Stage
They develop under a waxy shield.
3. Adult Stage
- Females remain fixed under the scale cover.
- Males become tiny winged insects.
A female can produce thousands of offspring in one season.
Damage on Apple Trees
San Jose scale causes:
- Red spots on apples
- Weak branches
- Dry twigs
- Poor fruit quality
- Reduced yield
- Tree death in severe infestation
On apples, a red ring often forms around each insect feeding site.
Treatment in Apple Orchards (Kashmir)
1. Dormant Spray (Most Important)
Spray during:
- Late winter
- Before bud break
- Usually February–March in Kashmir
Recommended:
- Horticultural mineral oil (dormant oil) 2–3%
This kills overwintering scales hidden on bark.
Farmers often combine oil with insecticide for severe infestation.
2. Control During Crawler Stage
The crawler stage is easiest to kill.
Usually appears:
- May–June
- Sometimes second generation in July–August
Common insecticides used in apple orchards:
(Use according to local agricultural department recommendations and label instructions.)
3. Pruning
Remove:
- Heavily infected twigs
- Dead branches
- Dense canopy areas
This improves spray penetration and reduces spread.
4. Orchard Sanitation
- Destroy infected plant material
- Use clean nursery stock
- Avoid overcrowding
- Monitor regularly
5. Biological Control
Natural predators help:
- Ladybird beetles
- Parasitic wasps
Avoid unnecessary pesticide overuse because it kills beneficial insects too.
Important Advice
- Do not spray during full bloom.
- Rotate insecticides to avoid resistance.
- Severe infestation may require 2–3 years of management.
- Consult local horticulture officers for approved doses in your district.
For Kashmir-specific recommendations, Also check these government sites:
- Sher-e-Kashmir University of Agricultural Sciences and Technology (SKUAST-Kashmir)
- Department of Horticulture Kashmir