Pest Management Guidelines

The Berlese Funnel, a Tool for Monitoring Thrips on Orchids  

By: Victoria L. Tenbrink, Arnold H. Hara, Trent Y. Hata, Ben K.S. Hu, and Ryan Kaneko

Beaumont Agricultural Research Center, University of Hawaii, CTAHR

Figures referred to in this document are unavailable at this time.

Thrips are tiny insects barely visible without magnification. This makes monitoring orchids for thrips by visual inspection difficult. Thrips are especially hard to see when the color contrast between the insect and the flower is not great, when they are not moving, and when they are deep within the blossom or hiding in crevices.
A simple apparatus, the modified Berlese funnel, separates thrips from orchid blossoms. University of Hawai'i researchers confirm the effectiveness of the Berlese funnel in recovering thrips and highly recommend its use by growers. The materials needed to construct one are available at hardware, automotive, and lawn and garden stores. Once constructed, the funnel is useful for these important jobs: monitoring thrips in the field, testing the effectiveness of field insecticide treatments, and checking harvested flowers for export quarantine security. The funnel also detects other tiny insects, such as aphids, that might be overlooked in the field.

Materials needed:
1 10inch automotive funnel (Balkamp brand, Napa Autoparts, Part
#8211 126)
1 square foot of l/4inch mesh, galvanized hardware cloth
1 4-ounce jar with screwon lid, such as a baby food jar
1 10inch brooder lamp (Woods Wireproducts brand, Ace Hardware,
Item #30715)
1 40watt incandescent light bulb (Do not substitute with bulb brighter
than 60 watts)
4 pieces of 3/4inch galvanized plumber's tape, each 41/4 inches long
8 I/8inch aluminum rivets
1 Liquid Nails brand adhesive

Tools needed:
* Electric drill with l/8inch drill bit
* Hole saw bit the same size as the funnel spout diameter
* Rivet gun
* Tin snips
* Pliers

Procedure for construction:
1. Remove the filter screen from the funnel.
2. Cut the hardware cloth to fit and place it in the funnel (Figure 1).
3. With the hole saw bit, cut a hoie in the center of the jar lid. Use
Liquid Nails adhesive to glue the lid onto the spout of the funnel
about 1/4 inch up from the bottom of the spout so that the jar can
be screwed onto the lid.
4. Bend four pieces of plumber's tape so that, when evenly spaced
around the lamp, they will hold the lamp just above the funnel. Drill
l/8inch holes in the lamp and rivet the plumber's tape to the lamp
(Figure l). Adjustmentscanbemadebybendingtheplumber's tape so
that the lamp rests just above the funnel.

The funnel cannot stand on the small jar at the bottom, therefore it needs to be supported in a box or bucket. A frame constructed from wood or galvanized pipe can be used to support one or more funnels.

Additional supplies needed include: a hand lens or magnifying glass (recommended magnification of at least lOx) and 70 percent isopropyl alcohol.
1. Pour 1 or 2 fluid ounces of alcohol into the jar. Screw the jar onto
the lid. If you plan to have the thrips identified, use a mixture of half
alcohol, half water, and add a drop of detergent. This keeps the
thrips from getting too stiff.
2. Harvest enough sprays to yield 50 to 100 blossoms. Remove
blossoms from stem. Write down the date, the cultivar, and the
number of sprays used.
3. Put blossoms into the funnel, place the lamp on the funnel, and
turn on the light. Heat from the bulb drives the thrips down and
they fall into the alcohol.
4. After 8 or more hours, tum off the light and remove the jar. Pour the
alcohol into a flat dish. Using a hand lens or magnifying glass,
inspect the alcohol for thrips. If aphids or mealybugs are on the
flowers, they will also be in the jar. Moths arld beetles may be
attracted to the light and fall into the funnel. If this occurs, check
the fit of the lamp and adjust the plumber's tape to minimize the
space between the lamp and the funnel. If the problem continues,
seal the space with tape.
5. Record the number of thrips and divide by the number of sprays.
The result of this calculation is the number of thrips per spray. This
number, when compared with the numbers from other surveys,
shows whether the population is rising or falling.
6. Finally, clean out the funnel and the jar. This is important to avoid
contamination of later samples.

Without magnification, thrips look like debris in the alcohol (Figure 2). Under a magnifying lens, the adults are usually yellow, brown, or black. They have narrow bodies that taper to a point at the tail end. Adults have wings that may be partly spread or flat along the top of the body. The wings have a hairy fringe that can be seen with a good lens.
The antennae are short and straight (Figure 3).
Juveniles are usually white or pale yellow. Their bodies are smaller and may appear chubby compared with those of the adults. Juveniles have short, straight antennae, but no wings (Figure 4).

Reference to a company or product name does not imply approval or recommendation of the product by the College of Tropical Agriculture and Human Resources, Cooperative Extension Service, University of Hawai'i, or the United States Department of Agriculture and does not imply its approval to the exclusion of other products that may be suitable. All matenals should be used in accordance with label instructions or manufacturers' directions.

Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Noel P. Kefford, Director and Dean, Cooperative Extension Service, College of Tropical Agriculture and Human Resources, University of Hawai'i at Manoa Honolulu Hawai'i 96822. An Equal Opportunity/ Affirmative Action Institution providing programs and services to the people of Hawai'i without regard to race, sex, age, religion, color, national origin, ancestry, disability, marital status, arrest and court record, sexual orientation, or veteran status.