Diseases of St. John’s Wort and Feverfew
Answered by: Conrad Richter
Question from: Kathy Kinter
Posted on: August 18, 1999

I’m in my second year of small scale commercial production (1/4 acre) and both my feverfew and St John’s wort are not doing well. I did spread some lime around the plants in early spring (our soil is a bit acidic) and we have not had much rain until the last few weeks (I live in central Vermont). Plants were started by seed last year and put out then. They grew very well last year.

Feverfew is small and most of the bottom leaves are dead (black/brown) with those on the flowering stems yellowed. Almost all of my plants are like this. Some were mulched over winter and some not. That doesn’t seem to matter.

The St John’s wort appears to have what sounds like fusarium wilt, despite robust growth and gorgeous, full blooms. First bottom leaves die and turn rust colored, then stem by stem the leaves all wilt and the rust moves up the stem until several stems have died. It appears systemic, as it appears to be happening a plant at a time, from the bottom up. I grow organically. There are other plants mixed in with them in the rows: motherwort, plantain, nettles, grasses, echinacea and bedstraw. They are planted close together. The wild St John’s wort in the field doesn’t seem to have the problem.

What do you think? I called ATTRA and Katherine Adam had no idea. She said more diseases are appearing in monocultures of herbs that typically do not effect wild plants.

We do not know what the problem with the feverfew is. We have not seen similar symptoms ourselves. You should consider sending a sample to your local agricultural authorities or extension specialist to have the plants examined for possible fungal or viral cause. A word of caution, though: some fungi are not causally pathogenic, rather they are opportunistic. That is, they invade a plant when it is already weakened by other causes, such as nutrition or water problems. You should ask the lab to indicate which diseases are likely to be more of the opportunistic type.

The problem with St Johnswort is almost certainly anthracnose. This has become a serious problem in St Johnswort. The extent of the problem is only now coming to light. It could be the symptoms (reddening of stems, lower leaves, followed by eventual die back) have always been present in wild populations, but as Katherine Adams has suggested, the disease may have become more of a problem when St Johnswort was moved into commercial cultivation.

We do know that the anthracnose fungus responsible is seed borne. At present there are no known strategies for seed treatments, seed screening, or plant treatment. At this point (August 1999), Richters is experimenting with several approaches of dealing with the disease, everything from seed treatment, organic and non-organic, seed screening, changes in recommended cultivation methods, and searching for resistant germplasm. All of these initiatives are preliminary and there is nothing to report so far.

What can you do? If the damage is not too great yet, probably you should consider pulling up affected plants. When doing so, take care not to infect neighbouring plants by pulling plants on a windless, dry day, and disposing material in plastic garbage bags immediately upon pulling without carrying diseased plants through unaffected areas. Do not touch healthy plants at any time during this operation. Because the disease appears to be spread by splashing water overhead irrigation should be avoided.

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