FOR YOUR FILES: Aphid Management (PDF)
APHIDS (superfamily Aphidoidea) are small sap-sucking insects that are one of the most destructive insect pests on cultivated plants in temperate regions. They cause distortion of enlarging leaves and shoots and reduce the vigor of plants. As they feed, aphids produce sticky honeydew which drips onto leaves and fruit below. The honeydew is colonized by sooty molds, which reduce the quality of greenhouse vegetables and ornamentals. Some species of aphids also transmit plant viruses.
LIFE CYCLE: Aphid eggs over winter, and females emerge in the spring to begin quickly reproducing asexually. Aphid reproduction is usually parthenogenetic and viviparous, which means that aphids give live birth to first instar female nymphs that resemble their parents in every way except size. Aphids continue to reproduce multiple generations all spring and summer, with each generation living for 20-40 days. One female hatched in the spring can potentially produce thousands of descendants throughout the season. Some species of aphids produce winged females in the summer that migrate to start new colonies due to over crowding or low food quality and/or quantity. In autumn, the female aphids begin to parthenogenetically produce sexual females and males that then mate to develop eggs outside of the mother. Eggs over winter to hatch in the spring. In a greenhouse setting, however, aphids may go on reproducing asexually for years. Some species of aphids even have telescoping generations where the parthenogenetic, viviparous female has a daughter within her, who is already parthenogenetically producing her own offspring.
CONTROL: Sound Horticulture commonly consults on specific control methods of green peach, melon, black, and foxglove aphids in the greenhouse industry, as well as tackling a wide array of other problem areas such as aphid control in orchards and hazelnut production, and farmers using hoop houses to extend seasons for row crops and vegetable production. We offer several beneficial insects for aphid control, and many can be used simultaneously if needed. For example, the parasitic wasp Aphidius can be used along with the predatory midge Aphidoleteswhen aphid populations are high (see below for a complete list of Sound Horticulture’s aphid controls). Please contact us with your particular pest issue, and we will develop a biological control program that works for you!
Azalea lace bugs are small winged insects that cause damage primarily to azaleas, rhododendrons, mountain laurel and a few other trees and shrubs. They have piercing-sucking mouthparts that they use to feed off the plant juices. Extensively damaged leaves will become nearly white and prematurely drop from the plant. The azalea lace bugs will primarily feed on the underside of leaves, causing the tops of the leaves to form a yellow stippling or flecking color.
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Sound Horticulture offers a wide range of beneficial insects to fit your biocontrol needs. You can visit our Pest Control pages for suggestions on which predators to use, or contact us directly for assistance with pest identification and creating a treatment plan.
NOTE: beneficial insect orders usually ship on Wednesday afternoons for Thursday delivery. Please note order deadlines for each predator.
CATERPILLARS are soft bodied, segmented larvae, pale green or other colors, depending on the species. Most are the larvae of various species of moths; the imported cabbageworm is the larvae of the white cabbage butterfly. Cabbage loopers (Trichoplusia ni), codling moths (Cydia pomonella), and other caterpillars may become serious pests in both greenhouses and row crops systems if their numbers are allowed to build up. Caterpillars feed on leaves and when they are numerous can eat relatively large amounts of leaf area and damage fruit.
LIFE CYCLE: The adult female moths lay eggs on plant leaves. The young larvae do little damage at first, but as they grow to full size they chew progressively larger holes in leaves.
CONTROL: Caterpillar control is primarily needed in controlled environments like greenhouses and outdoor monocrops that lack biodiversity and create a biological vacuum. In other more diverse outdoor production areas, birds and naturally occurring predator insects will help control caterpillar populations. In these cases, we may not want to completely eradicate caterpillars because they (and the moths and butterflies they become) are crucial as pollinators and food sources for other native species. For more information on native predators and promoting their habitats see this recent publication by Washington State University.
Identifying the species of caterpillar you are seeing in your farming system is key. Try using traps to monitor and identify the pest – Sound Horticulture offers over 300 specific traps and lures, many of which are designed for the Lepidopteran family (see Lures & Traps). Knowing your crop system and the pest problems you experience annually will help you take preventative measures. Talk to your IPM advisor, know what pest you are coming after, and enhance habitats for natural predators. For more information on caterpillar identification, see the University of California’s Key to Identifying Caterpillars (search by crop).
If needed, there are several microbial pesticides that can be used early on (ask us about Dipel). At the first sign of pest moths in the vicinity, planned releases of Tricogramma spp.can be considered. Trichogramma spp. is a minute parasitic wasp that attacks the eggs of over 150 species of moths, including cabbage looper, codling moth, oriental fruit moth, twig borers and fruitworms (see Tricogramma spp.). Repeated applications of Tricogramma early on in the infection period will be necessary to build adequate populations of the parasitic wasp. Please discuss your strategy with Sound Horticulture and ask us for ideas about how to pre-hatch Tricogramma and increase efficacy.
Compost Tea is a liquid compost extract used around the world as an organic alternative to chemical fertilizers. Sound Horticulture offers premium Compost Tea Brewing Systems and Catalysts from Growing Solutions, which aerate and activate the beneficial microorganisms of compost so it can be used in liquid form to feed roots, or be applied directly to foliage for disease control. Compatible nutrients include kelp, ThermX, and Azomite. Ask us about compost sourcing!
Read more about the benefits of compost tea here.
For your files: Fungus gnats (PDF)
IDENTIFICATION: Before using biological control, it is important to correctly identify the pests as either fungus gnats or shore flies. Adult fungus gnats have long, bead-like antennae, long legs, clear wings with a Y-shaped vein, and are poor flyers that tend to run along the soil surface when disturbed. Larvae have dark head capsules. Adult shore flies have short, bristle-like antennae, short legs, smokey gray wings with 5 clear spots, and are good fliers. Larvae do not have a dark head capsule.
FUNGUS GNAT (Bradysia spp.) larvae damage plants (particularly seedlings) by feeding on fine roots. They can also spread root rot diseases, such as Pythium, Phytophthora, and Fusarium. Their presence may be indicative of a greater problem, like over watering, rot, or fungus growing in saturated topsoil. Adult gnats are a nuisance to greenhouses workers and the public.
LIFE CYCLE: A complete fungus gnat life cycle takes about 5 weeks at 68°F (20°C). There are usually continuous overlapping generations in greenhouses. Females lay eggs near the soil surface. They lay 100-200 eggs over their lifetime. The eggs hatch in 4-6 days. Larvae feed for 2-3 weeks, mostly on decaying plant material, algae, and soil fungi as well as on fine root hairs and tender lower stems. The larvae pupate in the soil and adults emerge after 4-6 days.
CONTROL: There are several measure you can take to control fungus gnats. First, eliminate wet spots that produce algae and become breeding sites. Cover floors or treat under benches with a floor spray of hydrated lime to alkalize. Monitor with yellow sticky traps 1 foot (25 cm) above the soil or media surface or using yellow traps placed above the crop (see Lures & Traps). If needed, release Stratiolaelaps scimitus (formerly Hypoaspis miles) on seedlings and as soon as transplants are set out to establish it in the greenhouse before fungus gnats appear. Another approach is to apply insect parasitic nematodes and/or various bacterial products to reduce high fungus gnat populations (see Beneficial Nematodes). Please contact Sound Horticulture to determine which approach is suitable for your particular situation. Release rates may need to change throughout the season as pest pressures rise and fall, so continual monitoring and evaluation is key.
SHORE FLY (Scatella stagnalis), like fungus gnats, live in moist environments and feed on algae and decaying organic matter. They are not known to feed on healthy plant tissue.
LIFE CYCLE: Shore flies lay their eggs singly on the surface of algae. Larvae have eight pairs of short legs and a breathing tube with two dark colored openings called spiracles at the posterior end. Pupation occurs at the edge of the algae mats. Breeding takes place in stagnant and strongly saline water found in greenhouses as a result of excessive irrigation and soil leaching.
CONTROL: There are several measure you can take to control fungus shore flies. First, eliminate wet spots that produce algae and become breeding sites. Cover floors or treat under benches with a floor spray of hydrated lime to alkalize. Monitor with yellow sticky traps 1 foot (25 cm) above the soil or media surface or using yellow traps placed above the crop (see Lures & Traps). If needed, release Dalotia coriaria (formerly Atheta coriaria).
GENERALIST PREDATORS are the creatures, by definition, that feed on a wider array of pests or even pollen resources throughout their life cycles. Many insects do this to a minor degree, including certain beneficial predator mites, but for the sake of this listing we will start with just a few common generalist insects and spark the conversation.
Most generalist predator insects are not commercially available from insectaries. For field production we suggest building habitat to encourage free biocontrol, and augmenting where you need to. We offer a few helpful creatures here that might be of interest, especially when integrated together with your more specific Aphid predators and Thrips predators (see Aphids and Thrips). We find that sometimes adding a layer of periodic generalist predators to the system can enhance greatly the control a grower can achieve.
A great example of seriously ravenous generalist predators are the native ground nesting beetles, which consume a wide variety of prey as they scavenge through their soil environment. In field production it is strongly recommended that farmers do everything that they can to create stable, undisturbed habitat for beetles, spiders and other beneficial predators who will work to keep pest populations in check. Taking a wider ecological view, we would of course also want you to consider birds (swallows, wrens, robins, etc.) as very important aspects of your biological system. Bats would also be encouraged, as voracious feeders of flying insects.
Look forward to additional postings on this important topic, and if you need further information, we strongly recommend the following publication: Farmscaping to Enhance Biological Control, published by ATTRA. The Farmscaping measures that we like to discuss with farmers have many benefits:
Generalist predators in greenhouse production are viewed a little differently. As opposed to more specific predators and parasitic wasps, they will feed on a variety of pests. Predators like Green Lacewings are good examples of generalist predators that will work well for growers in the greenhouse environment, gravitating to aphids and other “large” juicy prey first, and then only later, after exhausting those resources, move on to other smaller prey. Orius, also known as Minute Pirate Bug, will feed on Western Flower Thrips but also requires a nice source of pollen. There are many things that the greenhouse grower, in a more protected environment, can still do to encourage a natural diversity of predator insects in this “closed system”. We can add additional forage and fodder and protection to lure natural aphid predators like hover and syrphid flies into the operation, by adding pollen producing plants, or even add banker plants which can help establish their presence and sustain them. We can provide more information about these ideas and options.
FOR YOUR FILES: Leafhopper tech sheet (PDF)
LEAFHOPPERS get their name from their tendency to take short, ‘hoppy’ flights when disturbed or sense danger. They feed on a variety of hosts and consist of many different species. They are easily seen, often resting on foliage, and often cause little or no damage. However, when they do find a crop they savor, they can cause significant feeding damage. Stippling (white spots), yellowing leaf edges, curled or mottled young leaves, and dark excrement left on the underside of the leaves are all examples of leafhopper damage. This damage alone could be attributed to a number of different pests, leafhoppers molt several times during their nymphal stage leaving papery castings. Pests and casts are typically found on the underside of the leaves where they are more likely to find shade and higher humidity environments. A leafhopper’s unique flight ability can be a good indication of their presence when scouting.
LIFE CYCLE: Adult leafhoppers overwinter in areas where there is ample plant debris, established weed patches and other areas where there is little chance of disturbance. In the spring, adults (generally up to a half-inch long) emerge and lay up to 6 eggs per day in plant stems and veins. It generally takes a week for eggs to hatch and about two weeks for the nymphs to complete their molting process and become adults. Multiple, overlapping generations can occur each year.
CONTROL: Leafhoppers can be challenging to control since they are considered secondary pests in many crops. As a result, effective biological and biorational control options have not been widely developed. To overcome this apparent lack of options, it is best to apply the principles of integrated pest management to YOUR particular crop system. The products below are either labeled for leafhoppers or can be used as part of a broader pest management program. For more information on the modern paradigm of IPM, see Surendra Dara's article below.
MEALYBUGS are segmented, soft-bodied insects, covered with white waxy hairs. They are usually found on the growing tips of plants. They damage plants by sucking their sap, usually in roots or other crevices. Their feeding causes distortions, stunting, and yellowing of foliage. They also produce honeydew, which supports the growth of unsightly sooty molds on leaves and attracts ants. Some mealybug species can also transmit viruses.
Of the approximately 15 species found in ornamentals in greenhouses, the most common species are citrus mealybug (Planococcus citri) and long-tailed mealybug (Pseudococcus longispinus). Their host range is extensive and includes most foliage plants grown in plantscapes, and they have even been found on vegetable crops such as cucumber. Citrus mealybug prefers soft-stemmed plants, but can also be a problem on woody plants. Other species that may occur are obscure, citrophilus, grape, and ground mealybugs.
LIFE CYCLE: A complete life cycle takes from one month up to a year, depending on temperature. Females of most species lay eggs in a cottony white mass. These hatch into crawling nymphs that migrate over the plant in search of feeding sites. The female nymphs develop through 3 growth stages. Long-tailed mealybugs give birth to live young and do not produce this cottony material. Male mealybugs develop wings and resemble fluffy gnats or wasps, flying to fertilize females.
CONTROL: Before releasing biological controls, prune out and destroy infested foliage, and hose plants with a strong stream of water to reduce mealybug numbers. Ant control may be necessary when implementing beneficial insects, as ants are attracted to the honeydew produced by mealybugs, and they may disrupt the oviposition of beneficials. Sound Horticulture offers Cryptolaemus montrouzieri (see Cryptolaemus) as well as the mealybug parasitoids Anagyrus pseudococci and Aphytis melinus (see Aphytis) as biological control of mealybug. Stratiolaelaps scimitus ‘Womersley’ can be used to control root mealybug (see Stratiolaelaps). Green and brown lacewings are also effective in controlling mealybug (see Green Lacewings). Check the progress of biological controls by inspecting the new growth for signs that mealybugs are disappearing.
SCALES suck plant sap, attacking both old and new growth. Their feeding causes distortions, stunting, and yellowing of foliage. They also produce large amounts of honeydew, which supports the growth of unsightly sooty molds on leaves. There are two types of scale: soft scale (Coccidae) and armored scale (Diaspididae). Black scale, hemispherical scale, brown scale and nigra scale are common soft scales that attack a variety of foliage plants. California red scale and purple scale are examples of armored scales. It is important to correctly identify the scale species because some biological controls are specific to a particular species or group of scales.
LIFE CYCLE: Scales have 3-6 generations per year indoors. Each female lays up to 2,000 eggs, sheltered under her outer shell. The eggs hatch after several days into minute crawlers, which migrate over the plants looking for feeding sites. Females die once they have laid their eggs. Female scales look like circular or oval bumps (2-4 mm, 1/10th inch) on stems and the under surface of leaves. Adult males are winged and rarely seen. Scales develop fastest in warm, humid conditions, especially in the shade.
CONTROL: Close examination with a hand lens is necessary to detect scales. They often go unnoticed until the honeydew they produce is conspicuous, or until plant growth is stunted or distorted. Before releasing biological controls, prune out and destroy severely infested branches, treat infested plants with insecticidal soap sprays to reduce scale numbers (this is most effective on the crawler stage of scales), and mist plants with water to remove excessive honeydew. Scale outbreaks often occur in early January or February, which means that biological controls should be released in the summer or by late November. Sound Horticulture offers Cryptolaemus montrouzieri (see Cryptolaemus) as well as the parasitoids Anagyrus pseudococci and Aphytis melinus (see Aphytis) as biological control of scale. Green and brown lacewings are also effective in controlling scale (see Green Lacewings).
FOR YOUR FILES: Two-Spotted Spider Mite Tech Sheet (PDF)
MITES belong to the order Acari and have four sets of legs, distinguishing them from insects, which have three sets of legs. Mites are one of the most common pests of protected crops in greenhouses and interior plantscapes. They are also found on berry and fruit crops and many woody ornamentals grown outdoors. Mites damage plants by piercing and sucking the contents of cells, which results in speckling on leaves as the cells turn yellow and die. Although most mites are on the undersides of leaves, the damage is visible on both leaf surfaces. As damage increases, the whole leaf may turn yellow and wither. 2-spotted spider mites(Tetranychus urticae), broad mites (Polyphagotarsonemus latus), cyclamen mites (Steneotarsonemus pallidus), and bamboo mites (Schizotetranychus celarius) are the most common pest mites that Sound Horticulture addresses, but we are happy to help you with whatever mite problem you are experiencing.
LIFE CYCLE: A complete 2-spotted spider mite life cycle takes about 14 days at 70°F (21°C), 33 days at 59°F (15°C) and only 7 days at 86°F (30°C). Females lay eggs on the lower leaf surface; larvae hatch from eggs in about 3 days. Nymphs pass through two more stages before becoming adults. Feeding and number of eggs laid by 2-spotted spider mite females increases as temperature rises and humidity drops. Under hot, dry conditions, 2-spotted spider mite populations can cause extensive damage and quickly get out of control. When 2-spotted spider mite populations are high, they disperse easily throughout the crop on air currents and are also carried along on workers’ clothing as they handle plants. 2-spotted spider mite diapause in response to short days, lower temperatures or a deteriorating food supply. They travel up or down the plant, away from light, searching for protected places to hibernate, such as crevices in the greenhouse structure or at the soil line at the base of posts. This phase doesn’t feed and is very difficult to control with either chemicals or biological controls.
CONTROL: Sound Horticulture offers several different predatory mites as solutions to your pest mite problem. Predatory mites feed on pest mites and sometimes on other small arthropods and pollen, depending on the species. Which predatory mite you use depends on the crop, climate, and population lever of the pest mite. Many predatory mites can be used simultaneously for greater effect and efficiency. Read the informational pages on each predatory mite listed below, and ask Sound Horticulture which one or combination is most suitable for your pest problem.
FOR YOUR FILES: Rice Root Aphid Management (PDF)
RICE ROOT APHIDS (Rhopalosiphum rufiabdominale) are cryptic and the symptoms are not always obvious. Damage will often look like a nutrient deficiency but can go unnoticed until populations are at a critical point. The aphids are olive-red in color and tend to be clustered around roots. These insects are polyphagous (hosted by many different plants) and have been associated with Prunus spp., various grasses, sedges and solanaceous crops. (Tanaka, 1961). They have been observed to be important pests in Cannabis in North America, particularly in indoor and greenhouse environments.
Coming from the same genus, rice root aphids (R. rufiabdominale) and cereal oat aphids (R. padi) look similar, though cereal oat aphids tend to have a hairier body and shorter setae on their antennae (Sunil and Poorani, 2018). Wingless and winged forms of root aphids are often present, but the winged forms will typically have darker coloration due to more sclerotization (hardening of exoskeleton) and will be present in the canopy. Keep a close eye on your yellow sticky cards as this can be an indication of their presence.
In a lab setting, rice root aphids were observed to produce 53-58 generations in one year (Hsieh, 1970), or one generation every 6-7 days. The nymphs mature in 9-10 days and each adult can live for about a month (Cranshaw, 2018). Reproduction can continue through winter on various crops including tobacco, wheat and grasses (Hsieh, 1970). As a result, it’s best to avoid harboring pet plants in your grow rooms, and to always manage weeds and volunteer plants in the area surrounding your crop.
The winged adults migrate between May and June to colonize new hosts (Tanaka, 1961), so pay extra attention to incoming plants and ensure that your screening is adequate to prevent aphids from entering your grow rooms. Living soils with a layer of mulch provide favorable conditions for root aphids (Kindler et al, 2004), which means careful monitoring and quarantine of incoming plant material becomes even more imperative.
Due to government regulations, little if any literature has been published on the topic of rice root aphids in Cannabis. As such, many of the recommendations are from experience and observation. At Sound Horticulture, we have found the best way to avoid an infestation is to thoroughly inspect roots of incoming plant material and reject them if aphids are spotted. Also, make sure everyone in your facility is following good sanitation practices. Root aphids are not known to produce a persistent egg stage indoors in Cannabis, so a plant free period of one week between crop cycles should be sufficient to starve the aphids (Cranshaw, 2018).
There are currently no products that will eliminate root aphids on their own. The key is population suppression until a host-free period can be established. Suppression can be achieved using periodic drenches of azadirachtin, Isaria fumosorosea, Beauveria bassiana (Cranshaw, 2018), Grandevo and Metarhizium anisopliae strain F52. Follow up the drenches with sprays around the perimeter of your pots or trays, on plant material and on the flashing around your grow room. Additionally, we always recommend dipping your incoming plant material or cuttings as per the Vineland Research and Innovation Centre protocols (Buitenhuis et al. 2016).
In 2015, Dara looked at the control of rice root aphids in celery; he found that the best control was achieved with a tank mix of Beauveria bassiana (Mycotrol-O) and azadirachtin (AzaGuard), compared with the other products tested.
The soil mite, Stratiolaelaps scimitus, is generally used for control of fungus gnats and thrips but may also provide some suppression of root aphids. However, more research needs to be done on this topic and beneficial insects and nematodes should not be relied upon alone for control.
Cranshaw, W. (2018) [Pest management of hemp in enclosed production: Rice Root Aphid.] Hemp Insects, Colorado State University.
Dara, S. (2015) [Reporting the occurrence of rice root aphid and honeysuckle aphid and their management in organic celery.] E-Journal of Entomology and Biologicals, UCANR.
Hsieh, C.Y. (1970) [The aphids attacking rice plants in Taiwan (II). Studies on the biology of the red rice root aphid, Rhopalosiphum rufiabdominalis (Sasaki) (Aphidae, Homoptera).] Plant Protection Bulletin, Taiwan. 12: 68-78.
Kindler, D., L. Hesler. N. Elliot, K. Shufran, and T. Springer. (2004) [Cereal and grass hosts of the rice root aphid, Rhopalosiphum abdominalis (Sasaki), and a description of an efficient greenhouse rearing technique.] J. Agric. Urban Entomol . 21: 51–59.
Sunil, J. and Poorani, J. (2018) [Aphids of Karnataka.] URL: http://www.nbair.res.in/Aphids/index.php (accessed* on October 9, 2019).
Tanaka, T. (1961) [The rice root aphids, their ecology and control.] Spec. Bull. Coll. Agric. Utsunomiya 10: 1-83.
Two-spotted spider mite (TSSM), also known as greenhouse red spider mite or carmine mite, is one of the most common pests of protected crops in greenhouses and interior plantscapes. It also occurs on berry and fruit crops and many woody ornamentals grown outdoors.
Adult TSSM are minute, 0.5 mm (1/50 inch) long, and a pale tan color with two greenish-black spots, one on each side of the abdomen. They have 8 legs and, under magnification, 2 red eyespots can be seen. Male TSSM are half the size of the females. Diapausing adults are orange-red with dark side spots. The carmine strain of TSSM found on tomatoes is a brick-red color in the adult stage. Immature and larval mites have 6 legs and the spots are less visible.
TSSM damage plants by piercing and sucking the contents of cells, which results in speckling on leaves as the cells turn yellow and die. Although most mites are on the undersides of leaves, the damage is visible on both leaf surfaces. As damage increases, the whole leaf may turn yellow and wither. The carmine strain of TSSM causes more serious damage to tomato. Yield losses start to occur in greenhouse cucumbers and tomato crops when about 30% of the leaf surface area is damaged. Ornamental plants attacked by TSSM show leaf damage and reduced growth.
A complete TSSM life cycle takes about 14 days at 21C (70F), 33 days at 15C (59F) and only 7 days at 30C (86F). Females lay eggs on the lower leaf surface; larvae hatch from eggs in about 3 days. Nymphs pass through two more stages before becoming adults. Feeding and number of eggs laid by TSSM females increases as temperature rises and humidity drops. Under hot, dry conditions, TSSM populations can cause extensive damage and quickly get out of control. When TSSM populations are high, they disperse easily throughout the crop on air currents and are also carried along on workers’ clothing as they handle plants. TSSM diapause in response to short days, lower temperatures, or deteriorating food supplies. They travel up or down the plant, away from light, searching for protected places to hibernate, such as crevices in the greenhouse structure or at the soil line at the base of posts. This phase doesn’t feed and is very difficult to control with either chemicals or biological controls.
Inspect leaves under 10-15 X magnification for signs of TSSM infestation. Some growers use bean seedlings or climbing runner beans as trap plants to detect the first appearance of TSSM on new crops. TSSM damage is easy to see on bean leaves, which alerts growers that there may be mites present in the crop (the bean plants also serve another purpose as they are good nursery plants for predatory mites.)
Thoroughly clean up the crop at the end of the season. Wash the greenhouse structure with a strong detergent. Dormant oil sprays applied to cracks in concrete, posts and other mite hiding spots will reduce the number of diapausing mites in the greenhouse. Do not maintain ornamental plants in vegetable greenhouses and remove weeds. Keep grass or vegetation mowed adjacent to the greenhouse. Misting TSSM infested sites with fine sprays of water will slow TSSM reproduction and increase the feeding and reproduction of predatory mites.
FOR YOUR FILES: Thrips Management (PDF)
THRIPS are straw-colored, elongated insects. Adults have narrow, fringed wings, and nymphs are wingless. They can move rapidly and prefer to shelter in crevices and folds in foliage and flowers. Thrips damage plants by feeding on leaf and flower tissue, leaving a silvery appearance. They also lay eggs in leaves and flower tissue and in young developing fruit (such as cucumbers). This damages leaves and flower petals and causes distortions in fruit and in the growing points. On tomatoes, thrips feeding causes “ghost rings” on the fruit. Western flower thrips can also transmit Tomato Spotted Wilt Virus, which is lethal to tomatoes and some ornamentals. Western flower thrips (Frankliniella occidentalis) is found in both vegetable and ornamental crops; onion thrips (Thrips tabaci) is usually a problem only in vegetable crops.
LIFE CYCLE: Both species of thrips have similar life cycles. The overall life cycle of Western flower thrips takes 21 days at 72°F (22°C). Females lay eggs in leaf tissue. Each female lays 6-10 eggs per day over her life span of 4-5 weeks. The eggs hatch in five days at 72°F (22°C). The nymphs feed on plant tissue for 8-10 days, then drop to the ground to complete development in protected sites on the floor. Thrips have an immobile stage, similar to a pupal stage (called a pseudo-pupa), which takes 7-10 days. When adults emerge they fly to upper parts of plants and begin laying eggs after a day or two.
CONTROL: Sound Horticulture offers several different options for biological control of thrips. You can use A. cucumeris (see Cucumeris) along with other thrips predators such as Orius insidiosis (see Orius) on flowering plants and Stratiolaelaps scimitus (formerly called Hypoaspis miles) to control thrips pupae in the growth media (see Stratiolaelaps). Read about the thrips predators listed below, and talk to Sound Horticulture about a thrips control strategy that works for you.
We offer a wide variety of traps and lures, see our full price sheet here. Below are a few of our most popular products.
WHITEFLIES damage crops by sucking plant sap, which weakens plants and causes shoot and leaf distortion. A more serious problem is the large amount of honeydew they secrete onto leaves and fruit. The honeydew is colonized by sooty molds, which reduces the quality of greenhouse vegetables and ornamentals. The main pest in greenhouses is the greenhouse whitefly (Trialeurodes vaporariorum). The sweet potato or silverleaf whitefly (Bemisia tabaci) is usually a problem on ornamentals, such as poinsettia. Sweet potato whitefly can also spread plant viruses. It is important to identify the species of whitefly correctly because the risk of spreading plant viruses differs between the two species as do treatment recommendations. It is difficult to identify whiteflies trapped on sticky traps, therefore examine adults and
immature whiteflies on leaves. Both adults and larvae are found on the undersides of leaves, the adults mostly on upper plant leaves, the larvae lower down on the plant. Larvae are flattened, legless, translucent ‘scales’, 1/30 inch (0.8 mm) long. Adult whiteflies are 1/25 inch (1 mm) long and a powdery white.
Greenhouse Whitefly (Trialeurodes vaporariorum) adults are powdery white with wings that form a triangular profile. Pupae have setae arranged in a ring around the top edge of the scale.
Sweet Potato Whitefly (Bemisia tabaci) adults are smaller, less powdery, and slightly yellowish. Their wings form a tent-like canopy over their body, and their abdomen may be seen between the wings. Pupae have setae scattered across the scale.
LIFE CYCLE: A complete greenhouse whitefly life cycle takes 28 days at 68°F (20°C). Females lay pinpoint sized, black eggs in circular patterns on the undersides of leaves. Each female lays up to 200 eggs during her one week lifespan. The eggs hatch in 7 days and the mobile larvae (‘crawlers’) move over the leaves for 5 days, then settles and molts to a sedentary ‘scale’ stage. After 7 days and another molt, the last stage larva remains where it was feeding and pupates; adults emerge in 8 days. The life cycle of the sweet potato whitefly is similar, but the development time is shorter, and more eggs are laid.
CONTROL: To monitor whitefly, hang up yellow sticky cards (3″x 5″) at the rate of 1 trap/500-2000 ft² (50-200 m²) (see Lures & Traps). Traps should be placed just above the plant canopy (if sweet potato whitefly is present, lowering the traps within the canopy may give better results.) Whiteflies tend to remain in one area and gradually move out from the initial site. Check traps weekly for adult whiteflies; traps should be replaced every 3 weeks. Using higher densities of traps helps pinpoints infestation sites more accurately. If monitoring time is limited, however, it is more important to check and record counts on fewer traps (the lower rate) and do it weekly, than to check larger numbers of traps but at longer intervals. With small plants, examining the foliage of 1% of the plants will give a more accurate count. With small plants, examining the foliage of 1% of the plants will give a more accurate count than yellow traps. At 15 traps per 1000 sq.yrd. a count of 1 whitefly per 15 traps is approximately equivalent to 0.1 individual whitefly per plant or 10/100plants. Starting levels of whitefly above 0.1 per plant can lead to hot spots and control problems. Sound Horticulture also offers the parasitic wasp Encarsia formosa and the predatory beetle Delphastus catalinae as whitefly control. Encarsia and Delphastus work well in tandem because Delphastus avoids feeding on the whiteflies that have been parasitized by Encarsia, and Delphastus adults also feed on whitefly eggs (for more information, see Encarsia and Delphastus).