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Agronomic Crops Network

Ohio State University Extension


Harvesting Corn Fields with Moldy Leaves and Stubble

Dark Dust Clouds during Harvest: There have been reports of huge dust clouds blowing up behind combines during harvest. It is certainly not uncommon to see dust during harvest as fragments of dead, dry plant parts and soil particles are usually suspended into the air as the combine drives though the field. However, the concern this year is that the dust seems excessive and particularly darker in color than usual. One possible explanation for this could be the fact that leaves in several corn fields died prematurely as a result of mid- to late-season diseases such as tar spot, gray leaf spot, and particularly, northern corn leaf blight. These leaves were then exposed to wet, humid conditions which caused them to produce lots and lots of fungal spores. For instance, under wet conditions, northern corn leaf blight lesions produce large amounts of dark-colored spore that are easily suspended in the air once the plants are disturbed by the combine. In addition, saprophytic fungi such as Alternaria, which also produce dark-colored spores, may also grow on dead plant tissue exposed to wet, humid late-season conditions, adding to the amount of dark particles in the dust cloud during harvest.       

Respiratory Alert – Harvesting fields with dry, moldy leaves may expose farmers to dust. Dust in grain harvested from fields that were severely affected by foliar disease contain a mixture of tiny pieces of diseased leaves and fungal spores, all of which may cause irritation and allergic reactions. Breathing dust can have adverse effects on the human respiratory system. For field with ear rots, dust (pieces of moldy cobs and husks) may also be contaminated with mycotoxins.

Wearing a disposable, 2-strap N95 mask (respirator) helps protect the worker from breathing in dusty, moldy and toxic substances. This type of personal protection equipment will filter out at least 95% of the dust and mold in the air. The 1-strap mask does not have this level of protection, and is basically worthless in agricultural environments.

How to wear the N95 correctly

Make sure you wear the N95 whenever working in dusty and moldy environments, especially at the grain storage and handling bins.

  • The mask should have a tight fit over your nose and mouth, and requires contact with smooth skin. Facial hair, eyeglasses and certain dental appliances can prevent the mask from making a seal around your face.
  • The N95 respirator is available in many sizes and various configurations, making sure the proper fit can be made.
  • Always use both straps to hold the mask in place and prevent air from leaking in around the edges.

How to test your respirator for proper fit

Ideally the N95 should be fit-tested for each worker. Once a fit-test is performed, the worker will know which type provides the best fit. Then before each use, perform a seal test to be sure the mask fits snugly

  • Negative pressure check: Place both hands completely over the mask and inhale sharply. The mask should pull into your face. If you feel any air leaking around your face or eyes, adjust the nosepiece and straps for a tighter fit.
  • Positive pressure check: Place both hands completely over the mask and breathe out sharply. Be sure to cover the exhalation valve if your mask is equipped with one. No air should leak out of the mask if it fits properly. If air leaks, adjust the nosepiece and straps for a tighter fit.

When to throw out the N95 mask

Consider the N95 respirator similar to the air filter in your vehicle.

  • When the mask gets clogged beyond a comfortable condition, replace it with a new mask. Likewise, if the inside of the mask becomes dirty, dispose of it.
  • Replace masks if they become wet, torn or have stretched out straps
  • N95s are made to be disposable, they cannot be cleaned or disinfected.

There are no recommendations for how many minutes or hours a mask will last in agricultural environments. A face mask filter is rated to absorb a total mass of 200mg, however on the farm, the time to reach this level is not known. Each respirator will be affected by personal hygiene, breathing resistance and density of the air contaminants. Each job will vary - as will the heat, humidity and other environmental conditions while performing the job.

A 2-strap N95 respirator is the best form of protection from moldy and dusty grain dust. Protect yourself and all workers exposed to grain dust during the Ohio c harvest.

For more information on respirators for farm use, consult the OSU Extension Factsheet: Dust and Mold, AEX 892.2.11

Crop Observation and Recommendation Network

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.