The following tools and techniques provide some examples of organic pest management (IPM) tactics for Colorado potato beetle (Leptinotarsa decemlineata) using the “Four T” method.
Our target for the Colorado potato beetle (CPB) changes. The adults are the first (1st) to emerge from their overwinter places. The second (2nd) target will be the eggs that are laid by the female adult Colorado potato beetles. The third (3rd) target will be the young larvae that emerge from the eggs that are most vulnerable to treatments.
General calendar time: Adults emerge between late April and late May (in Minnesota)
Biofix: When eggs are first scouted
Degree days: For CPB, the emphasis is on taking action when the larvae are young and vulnerable. Degree days for Colorado potato beetle are counted as soon as the eggs are first observed. 1st instar larva @ 185 DD, 2nd instar larva @ 240 DD, 3rd instar larva @ 300 DD, 4th instar larva @ 400 DD, Pupation occurs @ 675 DD
Tool #1: Yellow sticky trap cards (Type: Mechanical/Monitoring)
For all-sized plots: Place yellow sticky cards at regular intervals. around perimeter and within plot area at least 1 day before earliest expected emergence. Note: Yellow sticky cards are not as effective for trapping “larger” insects like CPB; the aim here is to monitor so that you are detect the early instances of CPB so that you know when to take additional action(s).
A. Space traps geometrically
- For a very small (12×12 sq. ft. or less) plot, place at least one trap at each corner, and one or two within the plot to monitor for CPB.
- For a small (24×24 sq. ft or less) plot, place one trap every six feet around the perimeter of the plot and at least three to four at selected intervals within the plot to monitor adult CPB.
- For a moderate (48×48 sq. ft.) plot, place one trap every six feet around the perimeter of the plot and place additional sticky traps within the plot area to monitor for adult CPB.
B. Adjust angle + placement of yellow sticky cards to anchor them firmly
- Attach yellow sticky cards on long (8 to 10-inch wooden craft/popsicle sticks) using hot glue gun.
- Place the yellow sticky card at least three-to six inches from the plants you intend to monitor, but far enough so that leaves are not easily blown into the yellow sticky area.
- Place stick at least 3-4 inches into the soil so that the stick is planted firmly in the ground and not easily blown away. Press down around the stick so that it remains firm in the ground.
Tool #2: Plant a “trap crop” (Type: Cultural)
Plant a trap crop that is attractive to CPB than potatoes, such as the elongated Italian or Japanese eggplant, ‘Vittoria’. This particular variety has been determined to be preferred by CPB and can be used as a perimeter trap crop.
- Border trap crop plants can be sprayed with a one-time treatment of azadirachtin (neem oil) or rotenone/pyrethrin spray when CPB arrives to provide initial interference or knockdown of adults.
- You may, if you like, use a propane torch to “flame” the CPB adults on the trap crop OR if the adults are numerous enough you may elect to apply a one-time treatment of a botanical insecticide with a short half-life / approved for organic production) such as Pyganic to effectively knock down their numbers on the trap crops.
Tool #3: Release the egg parasitic wasp Edovum puttleri (Type: Biological)
The parasitic wasp species Edovum puttleri is a commercially available parasitic wasp that lays its eggs inside of CPB eggs.
- Release after adults are seen. Release adult parasitic wasps between 1-2 weeks after observing your first Colorado potato beetle adult.
- Release during a cool time of morning or evening. Ideally, the ambient average daily temperature should reach at least 62-65 degrees and night time temperatures should not fall below 50 degrees for more than a couple hours overnight for the parasitic wasps to emerge safely after they are released.
Tool #4: Apply Bt or Beauvaria bassiana on (Type: Biochemical)
If you are not able to suppress a certain number of adults, reduce their egg lay, then the next thing to do is to apply a biological insecticide such as Bt or Beauvaria bassiana. These formulations, when ingested by young larvae, kills them as they ingest plant material with Bt enzymes or Beavaria bassiana spores.
- Treat plants as soon as possible after eggs are observed.
- Treat plants during periods when rain is not forecasted.
Tool #5: Use row cover material to protect crops
Row cover material may be time intensive to setup, take down, and store, but its effectiveness is guaranteed to protect against Colorado potato beetles is guaranteed. In addition to protection from insects, row covers may also provide additional protection from sun/wind exposure, heavy rains, hail, and other weather-related pressures.
- Setup row covers before adults are observed. Continue to observe plants to ensure that adults are not emerging from under plants.
Control measures outside of the season
- Preserve habitat such as around your growing area so that beneficial insects who may feed on adult CPB might have something to eat.
- Consider releasing beneficial nematodes in soil areas where you think the CPB are overwintering.
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