leaf miners

The white, squiggly lines on your leaves are highly likely caused by 

leaf miners. This damage is a result of insect larvae (typically from flies, moths, or beetles) feeding on the internal tissue between the leaf surfaces. 

Identification and Impact

• Appearance: The serpentine or winding trails are dead tissue left behind as the larvae tunnel through the leaf.
• Cause: Adult insects lay eggs on the leaf surface, and when the larvae hatch, they burrow inside where they are protected from most topical sprays.
• Impact: While a minor infestation is mostly cosmetic and unlikely to kill the plant, a severe case can reduce the plant's ability to photosynthesize, weaken it, and lower its yield. The damaged areas can also create entry points for secondary infections like fungi or bacteria. 

Recommended Actions

• Remove Affected Leaves: The simplest and most effective solution for a small garden is to immediately pinch off or remove the affected leaves and dispose of them far away from your garden (not in compost). This eliminates the larvae before they can mature, drop to the soil to pupate, and start the cycle over.
• Use Neem Oil: Applying neem oil can help disrupt the leaf miner's life cycle by deterring adults from laying eggs and acting as an anti-feedant. Apply it in the early morning or evening to avoid plant damage from sun exposure.
• Encourage Natural Predators: Beneficial insects like parasitic wasps are natural enemies of leaf miners. Avoid using broad-spectrum pesticides which can harm these helpful predators.