Preventing Mold on Pallets: A Shared Responsibility for Pallet Suppliers and Users

Markets in Transition: Preventing Mold on Pallets: A Shared Responsibility for Pallet Suppliers and Users

Identifying and preventing mold growth on pallets. These best practices are important for both pallet producers and users to follow.

By Rick LeBlanc
Date Posted: 6/1/2023

Pallet Handling Best Practices for Reducing Mold
To keep pallets dry, pallet decision-makers must pay attention to handling and storage practices not only at the pallet manufacturer but also during transport and usage.

As temperatures and humidity levels increase, fuzzy mold problems are more likely to grow and that can happen fast! Mold growth on wood can begin within 24-48 hours of getting wet. Once activated by moisture, mold can germinate and proliferate, especially in warm and humid conditions.

When things get bad, it has at times led to finger-pointing between the pallet customer and the pallet seller. Claims can result. On a few occasions, claims have been massive, involving dollar amounts not only involving pallets but the exponentially greater value of compromised goods stacked on them. Beyond that, some people have a phobia regarding the health risks of mold, which can potentially heighten emotions when mold is discovered. Mycophobia is a term that is sometimes used to describe an intense fear or aversion to fungi, including molds.

Depending on the application, the pallet vendor will be expected to deliver pallets free of visible mold. And over time, more customers have become mold-conscious. But even if pallets appear to be mold-free upon arrival at the customer’s location, improper subsequent handling of pallets can also lead to mold problems. And so the finger-pointing begins, but it doesn’t need to be that way. A collaborative approach is critical.

Preventing Mold Is a Shared Responsibility

In researching this article, I reached out to Dr. Marshall S. (Mark) White, professor emeritus – Virginia Tech, and president – White and Company of Virginia LLC. He is a widely respected expert on pallet performance and design and is consulted by major companies in the U.S. supply chain.

According to Dr. White, preventing the spread of mold is a shared responsibility between pallet suppliers and pallet buyers. He stressed, “It takes a collaborative effort to deter mold growth as pallets travel the length of the supply chain.”

“The industry should be cautious with any extended warranties,” he advised, noting that even dipped and KD pallets will grow mold in the wrong conditions. “Dipped or dry, all the pallet suppliers can do is deliver a product with no visible mold because inspections are visible,” he continued. “Is mold present that is not visible? Maybe!..It cannot be completely prevented or eliminated.”

In this article, we briefly review the basics of mold, how it differs from sapstain or bluestain, discuss handling best practices, and discuss the role of chemical mold inhibitors.

What are Mold and Bluestain, and How Can You Tell Them Apart?

Mold and bluestain result from fungal activity, but significant differences exist between them. Mold is a type of fungus that grows in the form of multicellular filaments called hyphae, resulting in a fuzzy appearance. These hyphae can grow on various surfaces, including wood, and can cause health problems such as respiratory issues, allergies and infections. Mold can also cause damage to the surface it is growing on, including wood pallets.

Bluestain, also known as sapstain, is a type of fungal infection that can affect the sapwood of various kinds of trees, including softwoods used to manufacture wooden pallets. The fungus is usually introduced to the wood through insect damage or wounds on the tree, and it can also be spread through contaminated tools or equipment used in processing and handling the wood.

Customers sometimes mistake blue-stain or sapstain for mold. Unlike some types of mold, which are toxic, bluestain, on the other hand, is a non-toxic fungus, stressed Anthony Accampo, technical manager for ISK Biocides. Additionally, sapstain does not reduce the structural integrity of affected pieces, although it may make wood more susceptible to mold, he noted. Bluestain is more of an appearance issue. Here are some things to watch for:

Color: Bluestain tends to cause a blue or gray discoloration of the sapwood, while mold can cause a range of colors, including black, green and white.

Texture and odor: Mold often has a fuzzy or powdery texture and may produce a musty or earthy odor, Bluestain is typically less fuzzy or powdery in texture and does not produce a strong smell.

Location: Sapstain usually affects only the sapwood of a tree, while mold can grow on both the sapwood and heartwood of the tree.

What Does Mold Need to Flourish?

Mold needs four things to survive and grow: moisture, nutrients, a suitable temperature and oxygen. Moisture is the most critical factor for mold growth, as it needs water to germinate and spread. Therefore, it is essential to keep the surface moisture content of wooden pallets below 20%. In the case of pallets, wood is the nutrient source for mold. Temperature and oxygen levels are also significant, with most molds growing best in temperatures between 60 and 80 degrees Fahrenheit and requiring oxygen to grow.

Mold management efforts must serve to restrict at least one of the four ingredients. The first line of defense has been limiting exposure to moisture. Keeping pallets dry is important. Chemical treatments such as those offered by ISK Biocide, including FDA-approved PQ-8 and PQ-80, however, work to inhibit mold growth by cutting off the mold’s food supply, making the wood nutrient source toxic to the mold.

Pallet Handling Best Practices for Reducing Mold

To keep pallets dry, pallet decision-makers must pay attention to handling and storage practices not only at the pallet manufacturer but also during transport and usage. Even seemingly inconsequential details, such as staging pallets briefly outside on a rainy day or postponing the unloading of a trailer because of other priorities, can result in an unwanted outcome.

A failure to unload pallets in a timely manner from a hot, dark trailer can turn them into an unintended science experiment, as one industry veteran told me. Keep pallets out of the rain, elevate them off the ground to avoid uptake of surface water, and store them in a well-lit, ventilated area. Strategic placement of fans can help.

A while ago, a long-time industry sales veteran winced that pallet users too often choose to store their pallets in the darkest, most poorly ventilated area of their warehouse – the worst spot they could choose. Other steps to improve air circulation include leaving space between rows of pallets and orienting the pallet openings in the direction of prevailing winds. Some companies will even install big fans to improve airflow in the pallet storage area.

Care should also be taken to remove any obvious mold sources in the vicinity, such as stacks of moldy old pallets or lumber. Minor mold occurrences can be scrubbed with a mixture of water and bleach.

And it is one thing to establish processes, but it is another to ensure they are consistently undertaken, given high employee turnover and seasonal changes. Getting front-line processes right is enhanced by thorough training, effective supervision and mindful executive support. Both pallet suppliers and pallet users can benefit from including retraining and supervisory reminders in their seasonal operational checklists.

Chemical Inhibitors Help Minimize the Cost of Rejected Loads and Expand Material Options

When handling safeguards to keep pallets dry still fail to deter mold, the use of chemical products can help. But it can be a long sell, vendors observe. “A lot of times we will talk with somebody for years,” said Lance Johnson, vice president of sales and marketing at ISK Biocides, and then finally, they’ll get hit so bad they bite the bullet and start using our products.

“Pallet companies have very thin margins,” he continued, “and they’re not going to use our stuff until they absolutely have to.” But the unbudgeted costs associated with not treating pallets can quickly build a case for dipping, he noted. “What we usually hear is that they have gotten loads of pallets rejected and sent back.” When that happens, they must try to scrub off the mold or find another customer.

“It’s a huge cost,” Johnson said of the rejected loads. “Pallet companies come to us when they are at their wits’ end with their customers. That’s how I see it.” And once a pallet company in an area decides to buy a tank and start offering dipped pallets, Johnson has observed that other surrounding pallet suppliers also tend to purchase dip tanks to remain competitive. It is a scenario he has seen play out several times in different parts of the country.

Customers sometimes have concerns about the safety of chemical treatments. However, Johnson stresses that ISK Biocides has two FDA-approved products, PQ8 and PQ80. Additionally, an FDA Food Contact Notification was recently granted on these two for the hydro-cooling of palletized fresh produce. He called the ruling a “feather in the company’s cap” and believes it will be a big help to some of our customers in promoting treated pallet usage.

One emerging opportunity Johnson sees is that some of the company’s customers have converted from KD pine to dipped green pine to enjoy improved recovery and greater lumber sourcing flexibility. “We’ve had customers that were buying kiln-dried lumber, and they were able to switch to our product and do the same thing with green lumber and not have mold,” he said.

“When you build a pallet out of dry lumber, you’ve got a lot more losses,” he said. “Whereas if you’re using green lumber or even just partly air-dried material, you’re not going to have near as much splitting and breakage during the construction of the pallet.”

The bottom line is that mold prevention practices are a shared responsibility. “The one thing everyone needs to remember is we can do everything right; pallet manufacturers can do everything right,” Johnson concluded. “But if their customer does everything wrong, the treatment can still fail. So, even when you treat, you still have to work with your customers to not do things like leave pallets closed up in a hot van.”


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