Review on Verticillium Wilt and Organic Weed Management

Review on Verticillium Wilt and Organic Weed Management

Verticillium Wilt.

Soil borne and spread through the soil can hang around in the soil for a long period of time, which makes disease management difficult. Wilt is showing up as one-sided yellowing, wilting, and scorching on eggplant and then spreads to the whole plant. In contrast, other diseases like Pythium and Phytophthera will manifest affecting the whole plant right away. Crop rotation is helpful in managing this disease, but most families or crops are affected by Verticillium Wilt. Rotation may help the most susceptible crops in the Salanaceous Family, but disease resistant varieties have proven to be the most helpful. Soil sterilization has also proven effective in ridding the soil of the disease.

Soil Sterilization – UC Davis has a helpful article on soil sterilization.

 

Organic Weed Management.

Notes from Langwater Farm (North Easton, MA) Twilight Meeting

Leaf Mulch

  • Leaves must not have come in contact with any prohibited substances to be used on organic production.
  • Spread at 3”-4” deep in walk rows and chopped if that’s possible.
  • An estimated 150-200 yards of leaves per acre provided minimal acceptable coverage.
  • Harrow immediately after field harvest perpendicular to the direction the crop had grown so that leaves are incorporated evenly. Cover crop is applied afterwards.
  • Any nitrogen loss from the leaves recovers with the cover crop by the next season.
  • Leaves add organic matter to the soil without adding too much additional other nutrients such as phosphorous.

Flame Weeding

  • Most effective on broadleaf weeds and less effective on grasses and sedges that are most often spread through cultivation.
  • Direct seeded crops that may benefit from flame weeding: slower germinating crops like carrots and beets. Landwater Farm has had success flame weeding crops like beans and sunflowers, as well.
  • Prep the bed 3-4 weeks before desired sowing, after a rain/irrigation the first flush of weeds will emerge and these can be flame weeded, sow the crop, and then 2-3 days before expected germination of crop do one more round of flame weeding.

Vinegar Injection

  • 10% acetic acid is injected into the weeds root zone. Foxtail, horse nettle, and other perennial weeds have shown positive results from this treatment.
  • An injector is equipped out onto a backpack sprayer and then the vinegar solution is injected directly into the weeds root system.

Tarping

  • Create a stale seed bed by laying clear plastic (solarization) or lay black/dark plastic or tarps for killing weed seeds in the upper most layer of the soil.
  • Useful technique for reduced till or no-till systems.
  • Based on trials, both plastics killed a substantial amount of weed seed. Additionally, used clear plastic (such as old greenhouse plastic) was more effective than new clear plastic.
  • Microbial activity in the soil reduced for approximately 5 days after the plastic was removed. However, by 14 days post plastic, the microbial activity returned to normal.
  • Tarped soil held more available nitrogen in the soil compared to uncovered soil.

 

Courtesy of UMass Veg Notes, Vol. 30 No. 16: https://ag.umass.edu/sites/ag.umass.edu/files/newsletters/july_26_2018_vegetable_notes.pdf