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Protect Leafy Vegetables From Summer Pest Threats in CA

May 29, 2018

Downy mildew in lettuce.

As conditions warm up and crops start to mature, recognizing, understanding and managing potential yield threats is crucial to maximizing marketability. Leafy vegetables in CA are particularly susceptible to the following insect and disease pests.

Insect Threats

Leafminers: Adult leafminers are small, black flies with a prominent yellow triangle on their thorax. As the weather warms up, these insects become more active. Eggs are inserted into leaves, with larvae feeding beneath leaf surfaces and creating “mines.” Heavy damage can slow plant growth and cause leaf drop.

Thrips: Adult thrips are tiny, slender insects with narrow wings and range in color from translucent white/yellow to brown or black. Females lay eggs on plant leaves, where larvae begin to feed. Feeding causes scar formation and stunted growth, damaging leaf development. Thrips also transmit viruses that can cause discoloration or dead spots on leaves.

Disease Threat

Downy Mildew: Downy mildew prefers cool, moist conditions. Infection starts as irregular yellow patches on leaves, with fungal growth and internal black streaks later forming along the leaves and stems. This disease can cause serious damage to young seedlings and mature plants, and can make the crop unmarketable.

Keep these identifying characteristics in mind as you monitor your leafy vegetable crops for signs of damage and infestation. When insects like leafminer and thrips reach threshold, use an insecticide like Minecto® Pro, which controls a wide range of difficult-to-control sucking insects as well as lepidopteran pests. Diseases like downy mildew are best tackled with Orondis® Ultra fungicide, which protects the crop when it is most actively growing to maximize marketable yield.

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