General Pest Information Common Pest Identification Price: $0.00 Shipping: $0.00 Part Number: Qty: CONTENTS: 1. Indentification of Common Pests of Interiorscape Plants IDENTIFICATION OF COMMON PESTS OF INTERIORSCAPE PLANTS CalScape Expo '93 Irvine, CA April 1993 Prepared by: Ann I. King University of California Cooperative Extension 625 Miramontes, Suite 200 Half Moon Bay, CA 94019 (415) 726-9059 The insects and mites listed in this publication are the most common, but not the only, pests of interiorscape plants. Additional species of the pests listed below may occasionally be found. Proper identification of the pest species is critical for control, particularly when biological control is used. Pests described here include: 1. Mealybugs 5. Fungus gnats & Shore flies 2. Soft scales 6. Thrips 3. Armored scales 7. Two-spotted spider mites 4. Green peach aphids 8. Greenhouse whitefly There are several good sources for getting pests identified. The Agricultural Commissioner's office in each county should have biologists on staff who can help you or the University of California Cooperative Extension office in each county may have someone who can help you. The University of California has good written information on pest identification - check with your U.C. Cooperative Extension office for a free catalogue of their publications. Other good written sources for pest identification include: 1. Lindquist RK, TJ Roll, HK Tayama. 1991. Identification of Insects and Related Pests of Horticultural Plants: A Pictorial Guide. Ohio Florists' Association, (614) 487-1117, $21. + $ 5 shipping. 2. Steiner MY, DP Elliott. 1983. Biological Pest Management for Interior Plantscapes. Alberta Environmental Centre, Vegreville, AB TOB 4L0 Canada. 3. Flint ML. 1990. Pests of the Garden and Small Farm: A Grower's Guide to Using Less Pesticide. Publication #3332, ANR Publications, University of California, (510) 642-2431, $ 30, 286 p. REFERENCES FOR THIS ARTICLE 1. Ah AD, J Newman, D Hodel. Pests in the Interiorscape, I: Spider Mites. PIPA News, August 1987. 2. Ah AD, J Newman, D Hodel. Pests in the Interiorscape, II: Mealybugs. PIPA News, September 1987. 3. Ah AD, J Newman, D Hodel. Pests in the Interiorscape, IV: Soft Scales. PIPA News, November 1987. 4. Flint ML. 1990. Pests of the Garden and Small Farm: A Grower's Guide to Using Less Pesticide. Publ. #3332, University of California, ANR Publications, 286 p. 5. King Al. Is it a Shore Fly? Or a Fungus Gnat? Greenhouse Grower, October 1990. 6. Lindquist RK. A Guide to Mites and Thrips Control. Grower Talks, August 1991. 7. Pfadt RE. 1971. Fundamentals of Applied Entomology, 2nd edition. MacMillan Publishing, 693 p. 8. Steiner MY, DP Elliott. 1983. Biological Pest Management for Interior Plantscapes. Alberta MEALYBUGS The two most common mealybug pests on interior plants are the Citrus Mealybug (Planococcus citri) and Longtailed Mealybug (Psuedococcus longispinus). They can be distinguished by the length of the caudal (tail) filaments; the Longtailed Mealybug has much longer tail filaments. Longtailed Mealybug produces live young, while the Citrus Mealybug lays eggs. Citrus Mealybug - This is the most common species found on interiorscape plants. It has an extensive host range and thrives on soft-stemmed succulent plants. Damage - Mealybugs are sap-sucking insects, typically distorting, stunting and yellowing foliage, but they also excrete honeydew which attracts sooty mold and ants. Occurrence - Citrus mealybugs are found on all parts of the plant, including the roots, but typically are clustered on stem tips and new growth. They are often found on the underside of leaves, especially along the midrib. They have a broad host range. Life History and Appearance - The citrus mealybug is soft-bodied, oval, and pink. The adult body is covered by a white, waxy material, forming short filaments radiating from the margins of the body. Females lay up to 600 yellow eggs over 8-10 days, placing them in a light cottony mass. They hatch in about 10 days and the crawlers migrate in search of feeding sites. Generation time takes 1-2 months under greenhouse conditions. Cultural Control - Dislodge mealybugs by hosing down plants frequently unless biological control agents are present. This also washes away honeydew. Choose plant species least susceptible to damage and infestation. SOFT SCALES (COCCIDS) Several species of soft scale are included under this heading. They are related to the armored scales but differ by being slightly larger and lacking the hardened protective shell. Damage - Soft scales are related to mealybugs and inflict similar damage. They are sap suckers, typically distorting, stunting and yellowing foliage. They also excrete large quantities of honeydew, which is a useful indication of the presence of these often unnoticed pests. Occurrence - Soft scales generally are found on the underside of leaves and stems, but may also be found on upper leaf surfaces. Both young and older leaves may be attacked, but scales on the stems usually select new growth. Life History and Appearance - In the greenhouse, soft scales may produce 3-6 generations per year, often overlapping. The female scale lays as many as 2,000 eggs beneath her hard outer shell. These hatch into mealybug-like crawlers which migrate over the plant, looking for feeding sites. The species of soft scale most commonly encountered in interiorscape locations are: 1. Black Soft Scale (Saissetia olene) - prefers woody plant hosts, including weeping fig, citrus, banana and olive. Black or dark brown in color, oval and convex, it is recognized by a raised H-shape on the upper surface, and a somewhat roughened appearance. 2. Hemispherical Scale (Saissetia coffeac) - a smooth, and strongly convex shiny brown scale, roughly circular in outline. Immature scales are white and have the H-pattern typical of the black scale. Host plants include ferns, Schefflera, asparagus fern and many non-woody evergreen plants. 3. Brown Soft Scale (Coccus hesperidum) - is oval and more flattened than the black and hemispherical scale. It is pale brown, dirty white or greyish, mottled, with dark brown on the back. The shell is pliable. Females produce living young. The soft brown scale excretes copious amounts of honeydew. It feeds on a wide range of hosts, including Schefflera, weeping fig, ferns, and citrus. 4. Nigra Scale (Parasaissetia nigra) - can vary in size, shape and color. On thin stems it is slim and elongate; on leaf blades it is more oval. Its hard outer shell is shiny black or dark brown. Woody plants are its common hosts, including weeping fig, citrus, ivy, and holly. Cultural Control - Soft scales are often introduced on infested plants, so careful inspection is essential to preventing infestations. Prune heavily infested branches before crawlers hatch. Mist or spray with water to wash off honeydew and dislodge crawlers. ARMORED SCALES (DIASPIDS) Less commonly encountered in interiorscapes than soft scales, the armored scales can be a problem where chemical spraying is not used in a biological control program. Damage - Armored scales are sap-sucking insects which cause further damage by injecting toxins into the plant while feeding, resulting in yellow to brown areas around the feeding sites. They do not excrete honeydew. Occurrence - Armored scales are found on both leaves and stems where they may form thick crusts. They normally occur on the lower leaf surface, but may be found on both surfaces. Life History and Appearance - Eggs are usually laid under the scale cover, and hatch into crawlers which are similar in appearance to mealybugs and soft scales. They wander until they find a feeding site and settle down to a sedentary existence. In protected environments there may be 3-6 generations per year. The following species may occur on interiorscape plants: 1. Ivy or oleander scale (Aspidiotus nerii) - Grey or dirty white, circular and flattened scale with an off-centered 'nipple'. It infests many indoor plants. 2. False Florida red scale (Chrysomphalus bifasciculatus) - Also a circular scale with a central 'nipple'. It is dark red to nearly black in color. It feeds on leaves and fruits of palms, rubber plant, banana, and figs. A similar scale is the California Red Scale (Aonidiella aurantii). 3. Boisduval's scale (Diaspis boisduvalii) - The female is circular, white and flattened, while the male is elongate with three powdery ridges along the back. This scale is found on the leaves and bark of palms, banana, cacti, and orchids. 4. Fern scale (Pinnaspis aspidistrae) - Has an oystershell shape. Females are pale brown, males have white upper surfaces, parallel sides and three longitudinal ridges. They prefer ferns and aspidistra. 5. Purple scale (Lepidosaphes beckii) - Dark brown or purple and oystershell-shaped. It is an important citrus pest but attacks many other plant species also. Cultural Control - Same as for Soft Scale. GREEN PEACH APHID (Myzus persicae) Green peach aphid is not the only aphid found on interior plants, but it is the most frequently encountered and most difficult to control with conventional pesticides. Another aphid found on interiorscape plants is the Melon aphid. Damage - Aphids cause direct damage by sucking sap, which results in wilting, deformation and retarded growth of the host plant. They also excrete sticky honeydew. Occurrence - Aphids are usually clustered in large colonies on new growth, at the base of buds, and on the underside of leaves. Because of the honeydew production, the presence of ants may indicate that aphids, or other insects that excrete honeydew, are present. Life History and Appearance - Wingless nymphs vary in color from pale green to yellow to pink. Winged adults are usually green. In indoor plantings, all adult aphids are winged or wingless unfertilized females which give birth to living young. A single female may give birth to 60-100 nymphs during her 20-30 day lifetime. The young may then begin to reproduce 6-10 days after birth so colonies can build up very rapidly. They thrive over a wide temperature range and in moderate humidity. Cultural Control - Prune heavily infested branches and hose off aphids with water unless predators and parasites are present. FUNGUS GNATS & SHORE FLIES Fungus gnats (Bradysia spp.) and shore flies (Scatella spp.) are two distinct pests which are commonly (and mistakenly) called "fungus gnats". Damage caused by the two pests is quite different, and biological control agents are different for the two pests. Damage - Both pests are nuisances as adults, because of their flying and swarming activity above the soil. The larval stage of the fungus gnat feeds on roots in the soil and car result in wilting and stunting of plants. Additionally, feeding by the fungus gnat larvae creates wound sites which allow for pathogen entry into the plant. Shore fly larvae, also found in the soil, are not known to feed on plant roots. Occurrence - Larvae are typically found in the top inch of the soil or growing medium, while adults are found on the soil surface and flying, running, or hopping at the soil level. Fungus gnat larvae feed on decaying organic matter and young roots. Life History and Appearance - Fungus gnats and shore flies are small black flies, about 1/8-inch long. Fungus gnats look a bit like mosquitoes, with longer, spindlier legs than shore flies, and longer antennae. The clear wings of fungus gnats have a Y-shaped vein at the tip, while shore fly wings are dark gray and have about 5 clear spots on each wing. Fungus gnat larvae are up to 1/4-inch long, and are white with a distinct black head capsule. Shore fly larvae are brownish-yellow and indistinct in appearance. Cultural Control - Avoid overwatering and use of growing media high in organic matter. THRIPS Several species of thrips are troublesome in indoor plantings, particularly during the summer months They often go unnoticed until damage to plants is evident. Damage - Both adults and larvae feed by scraping and rasping on plant tissue and sucking up the plant juices. This causes silvering, flecking and distortion of growing points, fruit, and flowers. The surface may also be fouled by small black shiny drops of excretory material. Western flower thrips also transmit Tomato Spotted wilt Virus, a damaging virus which is being found in increasing frequency in ornamental plants. Occurrence - Leaves, flowers, flower buds, and leaf sheaths all harbor thrips. Life History and Appearance - Thrips are tiny, slender insects. They are the smallest of the common insects on interiorscape plants. Winged adult females lay 25-200 eggs in the plant tissue. Nymphs resemble adults except that they are wingless, smaller, and paler in colon They feed for 7-10 days before pupating, either in the ground or on the leaf. Adults emerge 4-14 days later There are many overlapping generations a year. The greenhouse thrips (Heliothirips Haemorrhoidalis) is a large, slow-moving, dark brown thrips with yellow legs. It is a foliage feeder and pupates on the leaf. Larvae are glassy white with red eyes. The flower thrips (Frankliniella tritici and F. occidentalis) are tiny yellowish species which attack flower. They pupate on the ground. Onion thrips (Thrips tabaci) ranges in color from pale yellow to dark brown; the larva is white or pale yellow; it has several hundred hosts and feeds on both leaves and flowers. Cultural Control - Mist plants frequently. Soils high in organic matter seem to favor those thrips which pupate in the soil. TWO-SPOTTED SPIDER MITE (Tetranychus urticae) Also called red spider mite, the two-spotted spider mite is a common pest on interiorscape plants. It has a broad host range, short generation time, continuous reproduction and is resistant to many miticides. Spider mites are not technically insects - they have 4 pairs of legs on the adults, and they lack wings. Damage - Mites feed by piercing plant cells with the mouthparts and sucking up the cell contents, causing white specking on the leaves. Browning and drying of the foliage may occur; as may leaf drop, and fine webbing on the underside of leaves may sometimes be seen. Occurrence - Two-spotted spider mite can be found on all areas of the plant, most often on middle--aged leaves unless infestation is severe, then it occurs at the tips. Usually the lower leaf surface is favored over the upper surface. Life History and Appearance - Adult mites are very small, oval-shaped, and yellowish-green, with two dark spots on the back, one on each side. Males are slightly smaller than females. Eggs are small, circular, and pearly white, and are laid among the webbing on the leaf. Young mites resemble adults and pass through three growth stages before reaching adulthood. In warm interiorscapes mites usually remain active year-round. At 30 C (86 F), a female mite lays 50 - 100 eggs singly on the underside of leaves, and lives 30 days. A new generation is produced every 8 days. At 21 C (70 F), a generation is produced every 14 days. Cultural Control - Mites are often introduced on infested plants, so careful inspection with a hand lens is essential before moving new plants into an area. Mist plants frequently to slow spider mite dispersal. Avoid high temperatures which favors mite reproduction. Some plant species may not be suitable for interiorscape use if they are highly susceptible to spider mite infestation. Water-stressed plants often develop high spider mite populations, so proper irrigation and plant health can curb spider mite populations. GREENHOUSE WHITEFLY (Trialeurodes vaporariorum) The greenhouse whitefly is a common pest in interiorscapes where flowering plants are present. Sweetpotato whitefly (Bemisia tabaci) is a new pest of greenhouse crops and will likely be found in interiorscape settings soon. Damage - Whiteflies are sap-sucking insects in both the adult and juvenile stages. Heavily infested plants may wilt, turn yellow and grow poorly. Whiteflies excrete honeydew which covers leaf surfaces and allows the growth of black sooty mold. Occurrence - Adults are generally found on the under surface of the top leaves of actively growing shoots. Nymphs or immature stages are found on younger expanded leaves. Older leaves generally bear empty pupal 'skins' left behind by emerging adults. Life History and Appearance - Adult greenhouse whiteflies are tiny white fly-like insects which fly when disturbed. The female lays 200-400 eggs on the underside of the leaves. The young nymphs resemble tiny mealybugs or aphids when first hatched. After the first molt, they lose their legs and resemble small white oval scales. They molt through four stages to a pupa-like stage, from which the adult emerges. The time from egg to adult is approximately 26 days at 21 C (70 F), and 18 days at 27 C (81 F). Cultural Control - Select plant species least susceptible to whitefly infestation. Misting may be necessary to remove honeydew and sooty mold on leaves. Use yellow sticky traps where practical to monitor populations and to trap the adults. SouthWest Plantscape Products 265 Durley Ave Camarillo, Ca 93010 Telephone: (800) 333-7977 (SWPP) Fax: (805) 988-4975 E-Mail: sales@SouthWestPlantscape.com