White Spikes on Tomato Stems: Powdery Mildew, Not Insects

A gardener with two tomato plants (one initially unhealthy) sees small white bumps on stems that become 3 mm white spikes with black tips, now spreading to the healthier plant.

Diagnosis: Powdery Mildew

This is a fungal disease (powdery mildew), not an insect pest. The "spikes" are fungal structures. It spreads rapidly in humid conditions with poor air circulation.

Treatment

• Copper-based fungicide (e.g., Soap Shield)
• Product details
• Treat both plants immediately—preventive on healthy plant
• Improve air circulation, avoid overhead watering

Urgency

Act quickly to prevent total crop loss and spread to other garden plants.