How to Manage Thrips in your Garden
Thrips in the home garden are best managed with cultural practices and natural biological control.
The following are generally adequate to keep thrips from noticeably reducing onion growth and bulb size in the home garden:
add compost to enhance organic matter and soil tilth; use mulches;
plant onions and garlic in small plots surrounded by a diversity of other plants, including garden crops, herbs, and cultivated and wild flowers;
apply a stiff spray of water from a hose to wash thrips from plants when they are observed;
and avoid using broad-spectrum, toxic insecticides to preserve natural enemies that keep onion thrips populations low.