Powdery Mildew Fungus on Japanese Honeysuckle

Diseased plants are normally a disturbing sight.  My initial reaction when I saw pale, shriveling plants in this jungle of greenery was dismay.  That feeling dissipated quickly as I realized that all of the sickly plants were Japanese Honeysuckle.  Anything that weakens an invasive plant species has got to be good.

Closer examination revealed a velvety covering of mold on leaf and stem.  The condition is commonly referred to as Powdery Mildew and is the result of a fungus growing on the surface of the plant.  Powdery Mildew is an affliction shared by many species of plants, but for most plant species, there is a specific fungus that produces the condition.  Spores produced by the fungus on the Japanese Honeysuckle will only grow if they happen to land on another honeysuckle vine. 

Powdery Mildew definitely weakens the plant and it can cause death in severe cases.  Shade, humidity and temperature are the three factors affecting the growth of the fungus.  Spores ride the wind and blanket the countryside.  I’m certain that all honeysuckle has been in contact with the spores.  When conditions are favorable, the fungus thrives and the plants suffer. 

The fungus is only present in a few small patches of Japanese Honeysuckle at Blue Jay Barrens. The plants probably won’t die, but I’m hoping to see a significant reduction in competition between honeysuckle and the desired native plants.  Powdery Mildew has long been known to people who cultivate Japanese Honeysuckle.  Those people are happy to share methods of saving the plants, but I haven’t found any who have recommendations on how to encourage the fungus.

I’ll be keeping a close eye on this honeysuckle area as the summer progresses.  I would love to discover a method of growing the fungus on all of the Blue Jay Barrens honeysuckle.  Since the fungus growth is more a function of weather conditions, there’s no way that I can control its spread.  About the best I can hope for is the elimination of honeysuckle in these small areas.  I’ll certainly keep hoping for the best.

Japanese Honeysuckle

It’s a shame that some invasive exotic plant species have to be so attractive. These Japanese Honeysuckle fruits almost sparkle in the sunlight. The glossy skin easily reflects the silhouette of the photographer’s head. The honeysuckle would be a joy to see, if it was a native plant. As it is, I’m just aggravated by the showy display.

Japanese Honeysuckle seems to be a replacement plant for other invasives. As I remove Multiflora Rose, Autumn Olive and Bush Honeysuckle, the Japanese Honeysuckle jumps up and takes over that space. The bushier invasives seem to out compete the Japanese Honeysuckle vines. Once the bushes are gone, the spindly vines are free to grow with abandon. If a fruit eating bird eats from one type of woody invasive, it seems to eat from them all, so it makes sense that the seeds from all of these invasives would be dropped in the same general area frequented by the birds.

The key to slowing the influx of invasives onto a site is to eliminate the berry producing individuals. If no fruit is being produced, there is no reason for the fruit eating birds to concentrate in that area. Most of the bird flocks feeding on the invasive fruits seem to concentrate on a single type of fruit until it’s gone. I’ve watched huge flocks of Starlings or Robins come through an area and feed on Bush Honeysuckle that was growing alongside fruit laden Eastern Red Cedars. All honeysuckle berries were consumed, but the cedar fruits were left untouched. Weeks later, the same flocks came through feeding on cedar fruits. My goal is to eliminate fruit production by invasive species and the Japanese Honeysuckle is my next target. If the birds are feeding on native fruit, they will be dropping native seeds. I know that eliminating fruit production won’t stop the influx of invasive species, but I believe it will significantly reduce the amount of new seed coming onto the property.

Japanese Honeysuckle vines growing along the ground don’t seem to produce fruit. It’s not until they ascend some type of structure that you see flowers developing. My first priority will be to cut back all climbing vines and eliminate fruit production. With luck, this will be my last opportunity to photograph Japanese Honeysuckle fruits.

Once I’ve beaten the honeysuckle back to the ground, I can work on ways to kill it completely. Mowing the vines every couple of years keeps them under control, but it doesn’t stress the plants enough to kill them. If I have to live with Japanese Honeysuckle, I’d rather it was in this form than draped over the trees and fences.

Japanese Honeysuckle

This is Japanese Honeysuckle, Lonicera japonica, one of those invasive plants that can really hurt native plant populations. It doesn’t look like much of a threat at this stage.

Japanese Honeysuckle is a vine and given a chance will begin to look like this. Quite a tangled mess and not at all what I have in mind for Blue Jay Barrens woods.

The vine gains altitude by spiraling around any nearby vertical object. Small trees and shrubs cannot expand their trunks when bound by the honeysuckle vine. Eventually, the flow of sap is stopped and the shrub dies. Even if the vine is removed, a weak spot is left that will eventually allow the trunk to break.

The vine grows as high as it can reach and then branches out. The mass of honeysuckle leaves shades the supporting tree. The added weight of the honeysuckle often causes the already stressed tree to fall.

The vines are not limited to aerial growth. Ground hugging vines will travel for long distances. This allows the plant to cover large areas in a hurry.

Each node along the stem can send more roots into the ground and more vines into the air. This strategy allows one plant to become a major infestation without ever producing the first seed.

Vines that receive enough sunlight produce masses of blooms in the early summer. The flowers and their sweet scent make this plant a favorite among many people and it angers some when they see me killing Japanese Honeysuckle. I often make people angry, so it’s not a new experience for me.

Those blooms eventually become berries full of seeds. Sprawling vines are wonderful for infesting a small patch, but it takes seeds to really get out and conquer new territories. Each berry contains several seeds that are easily spread by the birds.