Thrips, the Bane of my existence
by R. Scudder
2002

Thrips is the one pest that occurs in unacceptable numbers in my otherwise "balanced" garden. Hence my recent obsession with implementing a management program that will reduce their population to acceptable levels, i.e. to a level that limits their aesthetic damage to 5-10% of current experience. It is my belief that augmentation with the parasitic wasp, Thripobius semluteus will provide the reduction in my Greenhouse Thrips problem necessary to achieve this goal. However, this wasp, as previously reported is not available from insectories on a casual call up basis. Currently there is not enough demand for agricultural/greenhouse releases so they are simply not in production. After repeated calls to various insectories, I chanced to reach one of the principals at Rhincon-Vitova, she described a possible solution to the lack of availability, "Contract Rearing".

"Contract Rearing" would entail setting up a prepaid tareted delivery of a set number of starter populations. The size of these populations is generally not specified for this type of contract. It should, however, be specified that the population be free of Hyper-parasites. To be successful over the long haul, a consortium for the purchase of hard-to-get beneficial starter populations for initial or annual augmentive releases could be formed of individuals, small horticultural companies (gardeners, etc.), horticultural associations, schools, other public agencies such as Rec. & Park, Presidio Trust, etc., and other entities such as Pier 39. A system of shares of starter po;ulations would provide the structure for larger groups with greater needs to secure more colonies for their needs while providing the opportunity for small groups or individuals to participate in a program that would otherwise be beyond their means.

It is was my hope that such a consortium could be formed in time to contract for release populations of Thripobius semiluteus and perhaps other beneficials for the spring of 2003. This did not happen. I still believe that this is a valuable strategy. If you have an interest in this opportunity please contact me at e-steward@pacbell.net.

As an aid to others facing a "Thrips Dilemma", I have included a management guide/table. This is a compilation from many sources and may contain errors. If you spot something that you feel or know is in error, please let me know so that I may review and update the materials. Thanks for your help!
Insect Name Western Flower Thrips, Frankliniella occidentalis GreenHouse Thrips, Heliothrips haemorrhoidalis (Bouche) Cuban Laurel Thrips, Gynaikcothrips ficorum (Marchal)
Notes:
  1. Most abundant & widely distributed thrips in U.S.
  2. Many overlapping generations
  3. Migrate May to June in WAshington D.C.
  4. Adults feed on flowers, flower buds and leaf buds
  1. Feeds openly on leaves
  2. Shaded Conditions preferred
  3. Hot, sunny, dry weather limit population buildups
  4. varnish-like excrement unsightly
  5. Not strong fliers
  6. 1mm dark black adults
  1. Cause rolled distorted leaves
  2. Purplish red spots on underside of leaves
  3. Severe aesthetic injury
  4. Common in California, Florida, Hawaii, and Texas
  5. Good Fliers
Life Cycle
  1. 1 Generation every 2 weeks possible
  1. 5-7 Generations/yr in CA
  2. 1 Generation/5-7 wks.
  3. Over Winter as eggs
  4. Eggs deposited in leaf tissue, hatch in 2-3 weeks
  5. Nymphs feed 2-3 weeks
  6. Resting Stage 1 week
  7. Adult
  1. 5 Generations/yr in CA
  2. 1 Generation/30 days possible
Host List (partial)
  1. Breeding Host Plants:
  2. Various Grasses
  3. Weeds
  4. Clover
  5. Alfalfa
  6. Note: This information and some in the "Notes" section are for F. tritici (Fitch) & may not be applicable to F. occidentalis, the western flower thrips
  1. Host Plants:
  2. Alligator Pear, Persea americana
  3. Azalea
  4. Citrus
  5. Croton, Codaeum variegatum
  6. Dogwood, Cornus spp
  7. Ficus
  8. Fuschia
  9. Frecian Laurel, Laurus nobilis
  10. Mango, Mangitera indica
  11. Magnolia
  12. Maple, Acer
  13. Palm
  14. Rhododendron
  15. St. Johnswort, Hypericum
  16. Toyon, Heteromeles arbutifolia
  17. Viburnum
  1. Host Plants
  2. Ficus retusa
  3. Ficus retusa nitida
  4. Note: Other Ficus may become infested when pest populations are high
Monitoring Months & Techniques
  1. Late March thru August
  2. Carbon dioxide exhalation - gentle breaths into terminals cause movement
  3. Shaking plant tips over black or white paper
  4. Yellow or Blue sticky traps
  5. Degree-day phenology
  6. Flush terminals with water, soap or pyrethrum
  1. March thru October
  2. Shaking plants over black or white paper
  3. Yellow or Blue sticky traps
  4. Degree-day phenology
  1. September to January
  2. Most abundant October thru December
Predator Release Strategy
  1. Amblyseius cucumeris, predatory mite
  2. Hypoaspis miles, predatory mite
  3. Aphytis melinus
  4. ^Chrysoperla spp., Green Lacewing
  5. ^Ladybugs
  6. ^Minute Pirate Bug, Orius tristicolor
  7. ^Praying Mantids
  1. Amblyseius cucumeris, predatory mite
  2. A. mackenziei, predatory mite
  3. $ Franklinothrips vespiformis, predatory thrips
  1. ^Chrysoperla spp., Green Lacewings
  2. ^Hemerobius spp., Brown Lacewings
  3. Amblyseius cucumeris, predatory mite
  4. A. mackenziei, predatory mite
  5. $Franklinothrips vespiformis, predatory thrips
Parasite Release Strategy
  1. $Thripobius semiluteus, nymphal endoparasitic wasp
  2. Beneficial Nematodes for soil phase (& on Turf Sp & F may help)
  3. $Thirpinema niclewoodii, a nematode
  4. $Ceranisus americensis & C. menes, wasps
  1. $Thripobius semiluteus, nymphal endoparasitic wasp
  1. $Thripobius semiluteus, nymphal endoparasitic wasp
Microbials; Always check labeling for proper use
  1. Beauveria bassiana
  2. Verticillium lecanii
  1. Beauveria bassiana
  2. Verticillium lecanii
  1. Beauveria bassiana
  2. Verticillium lecanii
Environmental Management
  1. Avoid shearing
  2. Avoid water stress
  3. Use resistan species or cultivars
  4. Avoid grouping susceptible species
  5. Reduce shay conditions by improving plant spacing & thinning
  6. Control weeds and grasses by cutting and/or removing material frequently throughout the year
  7. Aluminum foil or other disrupting mulch
  1. Reduce shady conditions by improving plant spacing & pruning (thinning)
  2. Avoid water stress
  3. Hose Off underside of foliage with strong stream of water (note: this may impact beneficials also)
  4. Avoid grouping susceptible species
  5. Use resistant species or cultivars whenever possible
valign="top"
  1. Avoid shering
  2. Prune & destroy material when only a few specimen plants
  3. Avoid water stress
  4. Planting Site preparations, i.e. a bigger hole, improve drainage, etc. are especially important for street trees
Pesticides: Note CA labeling for use of materials mentioned here may have changed, always refer to and follow CURRENT label recommendations
  1. Conserve* SC, Dow AgroScience, for exposed thrips
  2. Insecticiadal soap
  3. Sulfur Dust
  4. Merrit (systemic insecticide)
  5. Neem oil products
  6. Pyrethrin products
  7. Cinnamon Oil, Garlic
  8. Diatomaceous Earth
  9. Repellent Garlic Spray
  10. Sabadilla products
  1. Conserve* SC, Dow AgroScience, for exposed thrips
  2. Insecticiadal soap
  3. Sulfur Dust
  4. Merrit (systemic insecticide)
  5. Neem oil products
  6. Pyrethrin products
  7. Cinnamon Oil, Garlic
  8. Diatomaceous Earth
  9. Repellent Garlic Spray
  10. Sabadilla products
  1. Conserve* SC, Dow AgroScience, for exposed thrips
  2. Insecticiadal soap
  3. Sulfur Dust
  4. Merrit (systemic insecticide)
  5. Neem oil products
  6. Pyrethrin products
  7. Cinnamon Oil, Garlic
  8. Diatomaceous Earth
  9. Repellent Garlic Spray
  10. Sabadilla products
Additional Bio Controls to consider (listed under various thrips pests for conveniece, check with your supplier for appropriate use)
  1. Mallada signata - Lacewing^
  2. Franklinothrips orizbensis - predatory thrips
  3. Deraeocoris brevis, predatory bug^
  1. Orius albidipennis, predatory bug^
  2. Orius insidiosus^
  3. Orius laevigatus, predatory bug for flower thrips^
  4. Orius majusculus^
  1. Amblyseius barkeri, Mite
  2. Amblyseius degenerans, Mite


Legend:
^ - My personal preference is to avoid these predators or use tight controls for releases
$ - Potential for Contract Rearing. Not readily available from insectories at this time

Resources Cited:
  1. Hydro-Gardens, Inc. Catalog 2001/2002
  2. Insects that Feed on Trees & Shrubs. Johnson & Lyon. Cornell U. Press 1976
  3. IPM in Practice: Principles & methods of integrated pest management. UC Publication 3418
  4. IPM Practitioner, XXIII (11/12) November/December 2001
  5. Natural Enemies Handbook; The Illustrated Guide to biological Pest Control. UC Publication 3386
  6. Peaceful Valley Farm Supply, 2002 Main Catalog
  7. Pests of Landscape Trees & Shrubs; An Integrated Pest Management Guide. UC Publication 3359
  8. Pests of the Garden & Small Farm; A Grower's Guide to using Less Pesticide. Mary Louise Flint, UC Publication 3332
  9. Rincon-Vitova - Personal Communication