When you notice damage on your plants, it’s natural to wonder who (or what) is causing it. Different pests leave distinct traces of their feeding, and by examining these signs, you can identify the culprit. Here’s a quick guide to identifying some common greenhouse pests—thrips, aphids, spider mites, and whiteflies—by their feeding symptoms.
1. Thrips
Symptoms: Silvery streaks, spots, and flecking on leaves; distorted or deformed new growth; tiny black specks (thrips excrement).
Details: Thrips use their rasping mouthparts to scrape the surface of leaves, resulting in a silvery or stippled appearance. They commonly target young leaves and flower buds, causing malformed flowers and leaves. If you look closely, you may even spot the tiny thrips themselves—thin, slender, and usually less than 2 mm long.
Solution: Thrips can be managed with OriLiv (Orius insidiosus) for effective predation on thrips populations. For preventative control, CucuLiv (Neoseiulus cucumeris) can be introduced to keep numbers low before an outbreak occurs.
2. Aphids
Symptoms: Curled, distorted leaves; sticky “honeydew” residue on leaves; presence of sooty mold.
Details: Aphids use piercing mouthparts to suck sap from plants, primarily on new growth. They secrete a sugary waste called honeydew, which attracts ants and can lead to sooty mold, a black fungus that coats leaves and inhibits photosynthesis. Aphid infestations can quickly spread, so early detection is crucial.
Solution: Introducing Aphidius colemani is a natural and effective way to control aphid populations, as these wasps parasitize aphids. Additionally, OriLiv can help to keep aphid numbers in check by feeding on them as they emerge.
3. Spider Mites
Symptoms: Tiny yellow or white speckles on leaves; fine webbing on the underside of leaves; leaves that turn bronze or fall prematurely.
Details: Spider mites are tiny but destructive, especially in hot, dry conditions. Their feeding creates a stippled or speckled pattern as they extract cell contents, causing a yellowish or bronze appearance. Severe infestations can lead to leaf drop, weakened plants, and even death if left untreated. Spider mites also spin fine webs on the undersides of leaves, which helps distinguish them from other pests.
Solution: PersiLiv (Phytoseiulus persimilis) is a specialist predator that targets spider mites and can rapidly reduce their population. For preventive measures, introducing CaliLiv mites can help limit spider mite populations.
4. Whiteflies
Symptoms: Yellowing leaves; leaf drop; sticky honeydew on leaves, often covered in sooty mold; visible white insects fluttering when disturbed.
Details: Whiteflies are small, winged pests that cluster on the undersides of leaves. They suck plant sap, leading to yellowing, wilting, and stunted growth. Like aphids, they excrete honeydew, which attracts ants and encourages the growth of sooty mold. When plants are disturbed, whiteflies take flight, making them easy to spot.
Solution: Introducing EncaLiv (Encarsia formosa), a parasitic wasp, is an effective way to keep whitefly populations under control. Combined with SwiLiv (A.swirskii), you can establish a natural predator-prey balance to manage whiteflies over time.
