Molybdenum Roles in Plant Health

June 12, 2023

Molybdenum is an interesting trace mineral that has some interesting effects on plant health.

We all know that nitrogen is important. Molybdenum helps stabilize nitrogen, especially by converting soluble forms, such as nitrate, into complete proteins. This is important for many reasons but several key points are that plants are much more energy efficient when their nitrate has been converted into amino acids and complete proteins. This is important for all plants. Secondly, when the nitrate is converted in amino acids and proteins, plants become much more resistant to insect pests. For example, using molybdenum with potassium may improve resistance to cucumber beetle, because the molybdenum helps convert the soluble nitrates, while potassium helps convert soluble sugars.

We also know that some plants produce their own nitrogen, such as alfalfa, peas, clovers, etc. But in order to produce or fix their own nitrogen, these plants need a healthy, pink, nitrogen fixing nodule. And molybdenum is an essential ingredient for that. Without this healthy nodule, plants that normally produce nitrogen and fix it into the soil will become almost powerless for producing their own nitrogen. So from that perspective, molybdenum has an important impact on regenerative crop production.

In addition to nitrogen fixation and metabolism, molybdenum also has some interesting effects on diseases. In some recent cases, applications of molybdenum, combined with other traces, almost completely shut down rust and other diseases of wheat and squash. It also has a suppressive effect on bacterial infections and many other diseases as well. For instant, Mineral Nutrition and Plant Disease mentions its suppressive effect on phytophthora. Other disorders associated with molybdenum deficiencies are verticillium wilt, angular leaf spot, powdery mildew, and Xanthomonas which causes black rot, etc.

Molybdenum is also effective in helping control viruses. While all trace minerals seem to impact virus resistance, Molybdenum is particularly effective at deactivating viruses by denaturing their protein coat.¹

Mineral Nutrition and Plant Disease also mentions its suppressive effect on nematodes. This is something that I cannot verify from personal experience, but it sounds really interesting and you would expect some interesting results if you combined this knowledge with what we know about natural nematode control; utilizing a mustard cover crop as a bio-fumigant.

The flip side to all this is that molybdenum can also be toxic, just like every other trace mineral. When used at excessive rates, it will antagonize copper and make it ineffective.

In summary, Molybdenum is an important trace mineral from a plant-health perspective. It is often deficient if not being addressed from a soil and plant perspective. The first thing to do is test and then address if needed.

References: ¹ Mineral Nutrition and Plant Disease, page 203.