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IPM Treatment Protocols
Claire Cooney, 1999
McGill University Phytotron
The McGill University Phytotron practices IPM (integrated pest management) in its pest management program. IPM is an established system whereby a combination of cultural, physical, mechanical, biological and chemical techniques are employed to effectively combat pest infestations. The following protocols have been developed from experience with pests encountered within the Phytotron and consultation with other phytotrons, university plant research growth facilities and IPM specialists. All protocols rely upon sanitation, plant health, monitoring and treatment as a basis of effective control. See Part A - Responsibilities of Research Users and Phytotron Staff for detailed descriptions of these areas.
Western flower thrips (WFT), Frankliniella occidentalis, are tiny insects about 1mm long that feed on flower and leaf tissues by biting into cells and sucking out the contents. When the cells die, conspicuous silver scarring is seen often with small black dots that are excreta. Young thrips larvae frequently feed within developing flower buds and stem tips resulting in severe deformation of flowers and foliage. WFT carry many viruses including tomato spotted wilt virus (a broad spectrum virus attacking many plants). Plants that become infected with viruses must be destroyed. The mature thrips has two pairs of fringed wings and varies in color from yellow, orange tan, reddish brown to black.
Thrips are capable of both sexual and asexual reproduction, a feat that adds to the difficulty in controlling them. During asexual reproduction an adult female undergoes facultative parthenogenesis producing only male offspring (Brodsgaard, 1989; Immaraju et al, 1992). During sexual reproduction mainly female offspring are produced. Adult females make a small hole within plant tissue with their saw-like ovipositor and deposit their eggs. The eggs develop within the tissue forming larvae. The larvae emerge from the leaf tissue, feed for 8-10 days and undergo three more changes in development before pupating. Depending upon the species the pupa either remains on the leaf or falls to the ground. Within 7 to 10 days an adult appears and flies to the upper portion of the plant to feed and lay eggs repeating the cycle.
Predators include the minute pirate bug (Orius insidiosus), a voracious predator that attacks larval and adult thrips, Hypoaspis miles and Amblyseius cucumeris. The latter are predatory mites. H. miles is a small brown soil dwelling mite that attacks thrips pupae while A. cucumeris dwells in the plant canopy, preying upon newly emerging larvae.
Parasitoids include the nematode Steinernema carpocapsae and the tiny wasp Thripobius semiluteus. Steinernema applied to the soil is a good prophylactic measure for species pupating in the soil. The nematode attacks thrips pupae by entering the body through natural openings. Once inside, the nematode releases a bacterium (Xenorhabdus spp.) that paralyzes and kills the thrips within 24 to 48 hours. T. semiluteus oviposits its egg within the larva of greenhouse thrips (Heliothrips haemorrhoidalis). The parasitoid feeds off the body contents of its host, eventually killing it.
In greenhouses, asexual reproduction is commonly encountered. Adult females
become parthenogenic and give birth to live young that are genetic clones. These
in turn give birth to more live young in as little as 7-10 days. In certain
instances each individual can produce between 40 to 100 offspring. Within a few
days under optimal conditions, an aphid colony can become established. When the
aphid colony becomes too populated, winged females develop that migrate to other
plants and areas. Sexual reproduction sometimes occurs during the autumn. Male
and female forms appear and mate. Eggs are produced that over winter and develop
into nymphs in the spring.
The aphid midge, Aphidoletes aphidimyza, is a predator whose larvae attack and paralyze their victums before feeding on digested body contents. Adult midges are active at night and feed on the honeydew left by the aphids. Aphidoletes enters diapause (a type of dormancy) with cooler temperatures and shortened days. Supplemental lighting should be used in autumn or winter months.
Aphidius matricariae is a small Braconid wasp that parasitizes green peach aphids and closely related species. The female wasp deposits her eggs through an ovipositor into the abdomen of the aphid. As the egg develops the aphid swells and changes color becoming more reddish. Continued growth of the larva results in the death of the aphid. At this point the aphid body forms a golden leathery pupal casing called a mummy. Adult parasites exit the mummy by chewing a round hole through the dorsal wall and seek new hosts. Aphidius colemani is another parasitoid that can be incorporated to control Aphis gossyppii.
Ladybugs (Hippodamia convergens) are predators that feed on slow moving soft-bodied insects. They are extremely useful for outbreaks of melon aphid (Aphis gossypii). Both the larva and adult are avid feeders; larvae consume up to 400 aphids each while adults eat an astonishing 5,000.
Keys to success:
Reproduction can be either sexual or parthenogenic with only males produced. Adult females lay eggs on the undersides of leaves in a webbing. Nymphs emerge and resemble adults in form. Five stages of development occur from egg to adult and all stages feed on plants. The length of the life cycle is greatly dependent on temperature. At 21°C it is 14 days. At 30°C adult females can lay 100 eggs within 1 week and live for 30 days, producing theoretically 13,000,000 offspring.
Other species of predatory mites can withstand humidities and temperatures outside the range favored by P. persimilis. For example, when humidity is low and temperatures are high, Mesoseiulus longipes is useful or Galendromus occidentalis. When temperatures and pest population levels are lower, Neoseiulus fallacis can survive even in the absence of prey, feeding on pollen. Neoseiulus californicus survives even longer than N. fallacis in the absence of prey but is not as aggressive as P.persimilis or M. longipes.
Another biocontrol is the tiny midge, Feltiella acarisuga, whose larvae are predatory. The tiny beige maggots eat for about a week before pupating and repeating the cycle. Feltiella populations increase in proportion to prey increase and compliment P. persimilis. (Mahr, 1998).
The beetle, Stethorus punctillus, is an aggressive predator of spider mites. It is native to North America and is capable of reducing pest populations quickly. Both adult and larvae prey on the spider mite consuming between 75-100 mites (Hull, 1995).
Keys to success:
Females can lay up to 200 eggs that hatch into larvae within 4 - 6 days. Maggots remain active for approximately two weeks and then pupate in the soil 4-6 days at which time the adult emerges.
Shore flies (Scatella stagnalis) are strong flyers in contrast to fungus gnats. They are larger, have short antennae, red eyes and dark wings with five clear spots. Their larvae are up to 6 mm in length and are yellowish brown in color with no identifiable head. The life cycle is similar to that of the fungus gnat. Both adults and larvae eat algae on the soil surface and surrounding areas. Although they do not damage plants directly, they can be vectors for soil pathogens. Control is dependent on reduction of wetness and subsequent elimination of algae.
Steinernema carpocapsa and Steinernema feltiae are two nematode species that parasitize fungus gnat larvae. They are applied directly to the soil through irrigation. Reproduction is sexual with third stage larvae infecting the fungus gnat larvae. The nematode enters the host larva through openings in its body cavity and releases bacteria that digest it. The available food products are then metabolized by the nematodes that subsequently reproduce and seek out new prey.
Bacillus thuringiensi (B.t.) is bacterium that is applied to the soil through irrigation. Different strains of the bacterium affect a variety of different insects. Insects eat the bacterium that then releases toxic cystaline proteins in their guts. As the intestinal lining is paralyzed, the insect stops eating, becomes less active and eventually dies from starvation and tissue damage.
Keys to success:
The adult greenhouse whitefly, Trialeurodes vaporariorum, is approximately 1 mm in length with an average lifespan of 20 to 30 days. It has a yellow body with white wings that lay in a flat plane against its body. Whitefly females lay between 200-400 eggs on the undersides of leaves. Each egg is attached on a small stalk. The eggs hatch within 2 to 8 days forming oval larvae that resemble scales. These in turn molt during three more instar stages. In the final stage of metamorphosis, the pupa is formed from which the adult emerges after about 5 days. Both adults and young feed by inserting a stylus into the phloem and sucking sap, damaging tissues. A sticky substance, "honeydew" is secreted that secondarily becomes infected with a black mold. Infected plants show symptoms of yellowing, wilting and stunted growth. If not caught in time, entire plantings may be decimated.
In practice, it is difficult to differentiate between B. argentifolii and B. tabaci. By examining pupae, one can however, distinguish between T. vaporariorum and Bemisia spp. The pupa of T. vaporariorum is oval shaped and has a ring of wax filaments around the edge of its body. The pupa of Bemisia is pointed at one end and has no wax filaments. In side view, the Bemisia pupa looks like a squished football; the edges are tapered. The pupa of T. vaporariorum in side view resembles a hockey puck; there is a cylindrical "wall" between the parallel upper and lower surfaces. It is important to identify which species of whitefly is present to ensure successful control.
Eretmocerus californicu is a tiny yellow wasp that parasitizes Bemisia spp. Its mode of action is similar to that of Encarsia. Parasitized scales are yellowish in color.
Delphastus pusillus is a predatory beetle that attacks all three species of whitefly.
Keys to success:
Leptomastix dactylopi is a parasitic wasp of citrus mealybug, Planococcus
citri. Adults are yellowish brown in color, about 3 mm in length. Females
lay their eggs within third stage larvae of the mealybug. Larvae develop within
the mummy and completely devour their host. After pupation, the new wasp cuts an
exit hole and emerges, feeding on honeydew. Adults are strong flyers and can
search out prey in low numbers making them excellent control agents for low
density populations. Other parasitic wasps include: Anagyrus fusciventris and Pseudoaphycus angelicus for longtailed mealybug and Leptomastidea
abnormis for citrus mealybug.
Keys to success:
Soft shelled scales have no covering shell even though their skin becomes sclerotized with age. It cannot be removed without killing the insect. Soft shelled scales feed from phloem and produce copious amounts of honeydew that subsequently becomes infected with black sooty mold. Examples of this type of scale include, brown soft scale (Coccus hesperidum), hemispherical scale (Saissetia coffeae) and black scale (Saissetia oleae).
The female brown soft scale (Coccus hesperidum) keeps its eggs within its body till giving birth to live crawlers. The young mobile crawlers are yellowish with a mottled rounded shell. They begin to feed immediately after birth and molt twice. Older second stage nymphs are sessile. Males are rare and undergo four stages of metamorphosis before emerging as winged adults.
Adult female California red scale (Aonidiella aurantii) have a round cover underneath which they lay 100 -150 eggs during their life time. Newly hatched crawlers are mobile for only a short period before settling and molting to the adult sessile form. Within the second instar differences are seen between male and female nymphs. Males develop an elongated form, while female continue in a circular pattern. Adult males are winged and live for only 6 hours during which time they mate.
Aphytis melinus is a parasitic wasp of California red scale and oleander scale. The adult female lays her eggs within host scales. Larvae develop within the mummy destroying the host before exiting. One Aphytis can kill 30 scales. Adults live for 26 days and feed on honeydew.
Lindorus lophanthae, Chilocorus nigritus and Harmonia axyridis are predatory beetles that feed on both armored and soft shelled scale. Adults and larvae of both are voracious feeders.
Keys to success:
The above protocols address individual pests. What happens when there is more than one pest present? The more pests present, the more complex the system becomes, the more balancing is required. The use of a chemical when two or more pests are present has to be carefully decided. When choosing a pesticide to knock back a pest population increase, look at what effect it has on the biocontrol agents present. For example, if green peach aphids and western flower thrips are both present, and the aphid population booms, spraying with Pirliss (an aphicide) would not be a good choice. It will kill the biocontrols of the aphids (Aphidius and Aphidoletes) and one of those of the thrips (Orius). The residue left will prevent their reintroduction for one to two weeks. In that time period, the aphid population may or may not increase depending upon resistance but the Thrips population will definitely increase. The biocontrol agent that targeted the adult phase of the life cycle will be gone and although Pirliss is not lethal to the other thrips controls (A. cucumeris and H. miles) some mortality will occur resulting in decreased predation. Two pesticides that could be used to knock back the aphid population and not leave lethal residues would be insecticidal soap or Enstar. The soap would have an immediate effect on the aphids and also their controls to some extent (Aphidius that are in the mummy stage would be protected but adults would be killed as would all stages of Aphidoletes). The Enstar would not affect either biocontrol but would have a slower effect on the aphid population because it is an insect growth regulator; it prevents maturation.
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http://www.nysaes.cornell.edu/ent/biocontrol/ (Cornell University)
http://www.biocontrol.ucr.edu/ (University of California at Riverside)
http://www.cips.msu.edu/biocontrol/ (Michigan State University)
http://www.biocontrol.ucr.edu/WFT.html (Thrips management)
http://ipmwww.ncsu.edu/biocontrol/biocontrol.html (North Carolina State University)
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