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Using a Steamroom To Sterilize Pallets of Styrofoam Seedling Container Blocks

Tests at Lucky Peak Nursery

Filling the room to capacity and heating it to 160°F for 6 hours tested the sterilization room's ability to kill harmful fungi on reused styroblocks. Ten test styroblocks were placed randomly throughout the room in the center of styroblocks stacked on pallets. Results (table 6) indicate that the treatment is very effective.

Fusarium levels were reduced from almost 90 percent to 5 percent. After treatment, 80 percent of the styroblocks had no fungal growth.

Further work could determine the minimum amount of exposure time required for sufficient sterilization. The less time required, the lower the energy costs of heating the room. However, it costs just $3 per hour to heat the room, so it's best to make sure that the styroblocks are heated long enough to sterilize them.

Table 6—Test results for treating styroblocks at the Lucky Peak Nursery sterilization room. Styroblocks were treated at 160°F for several hours.
Fungus PERCENT COLONIZATION
Before After
Fusarium 90 5
Trichoderma 15 2
Penicillium 42 3
Other fungi 0 10
No fungi 0 80
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