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Integrated Pest Management Program

Department of Plant Science and Landscape Architecture, Department of Extension

Fact Sheets > Greenhouse > Herbs

Scouting guidelines and biological control options


How To Monitor

Signs and Symptoms

Biological Control Options


Monitor weekly. Look on the underside of leaves and along stems on tips of new growth for small (1/16 inch long) aphids with 2 cornicles or “tailpipes” at the rear of their bodies. Identification to species is needed to determine which host specific aphid parasite to release. If uncertain, mixes of different species are available.

Distorted young growth (will vary depending upon type of aphid).

Shed white skins of aphids that have molted. Honeydew and sooty mold.


Adalia bipunctata (ladybird beetle larvae)

Aphidoletes aphidimyza (aphid midge, predator)

Aphelinus abdominalis (aphid parasite)

Aphidius matricariae (aphid parasite)

Aphidius colemani (aphid parasite)

Aphidius ervi (aphid parasite)

Chrysoperla carnea  (green lacewing, predator)

Hippodamia convergens (lady bird beetle)

Bacterial Diseases


Bacterial Fasciation 



Pseudomonas Leaf Spot




 Bacterial Blight



Look for abnormal branching near the base of scented geraniums.


Inspect basil and other small plugs during routine scouting.



Test plants prior to use as stock plants. Grower friendly test kits for Xanthomonas are available from Agdia



Plants are stunted with short, swollen, fleshy and misshapen leaves.


Look for water-soaked, dark-brown to black leaf spots especially on young plugs. Confirm diagnosis through a plant diagnostic laboratory.


Scented geraniums may be carriers of disease without showing typical symptoms: wilting, small leaf spots and v-shaped angular lesions.




During routine inspection, look for chewed holes or pinholes in leaves especially on herbs grown outdoors.

Chewed holes or pinholes in leaves.


Botrytis Blight

Concentrate scouting in areas where crop is closely spaced with poor air circulation, and on tender crops. Look for dieback, stem cankers (especially near a wound), and powdery gray fuzzy appearing spores during humid conditions. 

Leaf blights, stem cankers, damping off and occasionally root rots.

Biological fungicides:

Bacillus subtilis

Streptomyces griseoviridis

Streptomyces lydicus



If adult moths or butterflies are seen in the greenhouse, look for eggs and young caterpillars. Look for fecal droppings and bites taken out of leaves.

If damage is observed, look under pots or in planting medium just around the base of the plants. Many caterpillars hide during the day and feed at night.

Bacillus thuringiensis subsp. kurstaki

Trichogramma spp.(egg parasite)

Crown and Root Rots

Inspect plants weekly for signs of disease: wilted off-colored plants with discolored root systems. Pay particular attention to media that stays wet. Monitor fungus gnats and shore flies, especially in propagation houses. Monitor soluble salt levels.

Leaves turn yellow and wilt. Plants are stunted and off-color. Roots are discolored and may turn brown or black.

Biological fungicides:

Bacillus subtilis

Streptomyces griseoviridis

Streptomyces lydicus

Trichoderma spp. (soil applications only)



Downy Mildew

Inspect basil leaves, especially underside of leaves during humid conditions.

Look for yellowing between the veins. (Maybe confused with nutritional deficiency). Look on underside of leaves for dark purple-brown sporangia (fungal sporulation).



Damping Off

Monitor weekly. Scan flats for signs of seedlings that do not emerge or collapse at the soil line. Disease often spreads from a central point.  Discard heavily infected flats to avoid future problems.

Seeds do not germinate or collapse with dark, necrotic stem canker at soil line.  Infected plants may later develop crown and root rots.

Trichoderma spp. (soil applications only)


Fungus Gnats

Use sticky cards to monitor for adults. Place cards at base of plants at soil line.  Place potato chunks on soil surface to monitor for larvae.  (Check every two days.) Scout favorable habitats including areas with standing pools of water, dirt floors or spilled media and weeds.

On cuttings, fungus gnat larvae may feed on callus, slowing down rooting. Larvae feed upon roots and may tunnel into stems causing plants to wilt and die.

Atheta  (Dalotia) coriaria (rove beetle, predator)

Hypoaspis (Stratiolaelaps) miles (mite predator)

Steinernema feltiae  (nematodes)



Fungal Leaf Spots

Scan the crop for leaf spots.  With a hand lens, look for small, fungal fruiting bodies. To confirm, send sample to diagnostic laboratory.

Alternaria leaf spots are generally dark brown to black with a yellow border.

Septoria leaf spots are small, grayish-brown with a dark brown edge.

Biological fungicides:

Bacillus subtilis

Streptomyces lydicus

Fusarium Wilt on Basil

Scan the crop for symptoms. The first symptom is a downward bending or cupping of the leaves. May be confused with water stress, root rot diseases or Botrytis stem canker.  To confirm, send sample to diagnostic laboratory.

Leaves may cup downward or the top of the stem will bend like a Sheppard’s crook. On large-leaved cultivars, defoliation may occur. In later stages, brown streaks can be seen on the stem.

None. Use resistant varieties


Inspect herbs propagated by cuttings. Look for small, oval, soft-bodied insects covered with a white, wax-like layer especially along stems, and on underside of leaves. 

White, cottony residue may be seen. 

Cryptolaemus montrouzieri (predatory beetle) is used against citrus mealybug but is ineffective against long-tailed mealybugs that give birth to living young.


Plant Bugs




Four-lined plant bugs





Tarnished plant bugs

Monitor herbs outdoors and those in greenhouses especially if weeds are nearby.


Look for signs of feeding activity - small, yellow spots on upper leaf surface. Four-lined plant bugs tend to be secretive and move to the underside of leaves or drop off the leaves.



Look for signs of feeding injury on youngest growth and buds.





Round, brown, dead leaf spots that   may be confused with fungal leaf spot disease.




Look for death of tender young, growth, dead spots and badly distorted buds.

Naturally occurring predators include big-eyed bugs and damsel bugs.






Powdery Mildew

Scout weekly. Inspect susceptible crops. Scout areas near vents, hanging baskets or any location with a sharp change between day and night temperatures.  Use a hand lens to see white fungal threads and spores.

White powdery fungal growth can occur on upper or lower leaf surfaces.  If severe, white coating can be seen on the foliage.

Biological fungicides:

Bacillus subtilis

Streptomyces lydicus


Rhizoctonia Web Blight

Scout susceptible crops, especially when they are closely spaced.  Look for cobweb-like growth that mats leaves together (web blight) especially during humid conditions.

Stems and leaves collapse rapidly and turn mushy with fine, web-like fungal strands present.



Look for yellow spots on the upper leaf surface and rusty brown spots on the lower leaf surface during routine foliage inspections.

Rusty brown spots or stripes especially on the lower leaf surface.


Scale - Brown Soft Scale

Look for yellow-brown, to dark brown scale insects along veins and stems.  

Honeydew and sooty mold are additional signs of infestation.

 Cryptolaemus montrouzieri (prefers mealybugs)

Chrysoperla carnea (green lacewing)


Look for chewed holes in leaves and shiny patches of slime.  Slugs hide under dense foliage, beneath pots and benches and in other protected locations.

Chewed, irregular holes with smooth edges in leaves and slime that dries into silvery trails on foliage.


Two-Spotted Spider mites

Look on leaf undersides, especially along the veins, for all stages of mites, empty eggshells and webbing.  Look near hot, dry areas of greenhouse near furnace and near vents. Tap foliage over sheet of white paper to look for mites and faster-moving predatory mites. Scout mite-infested areas last.

Light flecking, and discolored foliage.

Leaf drop and webbing may occur during outbreaks.

Amblyseius andersoni (predatory mite)

Amblyseius  californicus (predatory mite)

Amblyseius cucumeris (predatory mite)

Amblyseius fallacis (predatory mite)

Feltiella acarisuga (predatory midge)

Galendromus occidentalis (predatory mite)

Mesoseilus longipes (predatory mite)

Phytosieulus persimilis (predatory mite)


Rely on sticky cards (placed just above crop canopy) and foliage inspection to track population trends and to evaluate treatments.


Distortion of flowers, buds and tender young growth.

White scarring on expanded leaves and flowers.

Transmission of tospoviruses.

Amblyseius cucumeris (predatory mite)

Amblyseius swirskii (predatory mite)

Hypoaspis (Stratiolaelaps) miles (predatory mite)

Orius spp.  (minute pirate bug, predator)

Steinernema feltiae (nematodes)


Scan crops weekly. Inspect incoming plants. Look for mosaic patterns, leaf crinkle or distortion, chlorotic streaking, ringspots, line patterns and stunted plants

For confirmation, send sample to diagnostic laboratory.



Use sticky cards to monitor for adults.  Inspect plants for scale-like immature stages found on underside of leaves.

When high populations develop, honeydew and sooty mold may be seen.


Amblyseius swirskii (predatory mite)

Chrysoperla carnea  (green lacewing)

Delphastus (catalinae) pusillus  (predatory beetle)

Encarsia formosa (greenhouse whitefly)

Eretmocerus eremicus and mundus


By L. Pundt (University of Connecticut) and T. Smith (University of Massachusetts), 2005. Updated 2013.  

The information in this document is for educational purposes only.  The recommendations contained are based on the best available knowledge at the time of publication.  Any reference to commercial products, trade or brand names is for information only, and no endorsement or approval is intended. The Cooperative Extension System does not guarantee or warrant the standard of any product referenced or imply approval of the product to the exclusion of others which also may be available.  The University of Connecticut, Cooperative Extension System, College of Agriculture and Natural Resources is an equal opportunity program provider and employer.