Star Jasmine: Pest versus disease (or both)

Asked April 20, 2018, 12:55 PM EDT

I either have a pest and/or a disease effecting my star Jasmine. There looks to be something eating the new growth of leaves from both plants I have. Also in the area of new growth the leaves are looking a bit yellowish with purple spots scattered over the leaves in different sizes. Another thing I noticed was that the tips of the vines that are growing up the latus has turned dark and withered (look dead). Trying to figure out what’s going on and what I can do to help my plant friends that we really want to grow up a trellis. I have pics I can send. Thank you for your time.

Multnomah County Oregon cold damage star jasmine root weevils

1 Response

Thank you for including the nice images.

The red blotches on the leaves reveal environmental damage such as may have occurred during one of this past winter’s cold episodes. Remove the unsightly leaves.

The dead growing tip may have occurred during cold weather, too. Another possibility is that plant went too dry.

The feeding damage on the leaves is old. It is most likely from root weevil adults feeding last summer.

If you have only a few affected leaves, you can remove them and ignore the weevils.

But if many leaves are damaged – as in a majority – you should consider management. Because the life cycle is in both the soil and aboveground, you have two different targets. The larvae (youngsters) feed on the roots during the fall, winter and early spring. The adults feed on the leaves during the summer, often beginning in May.

Although this publication describes the damage on rhododendrons, it also has good images of both the adults and the youngsters. “Root Weevil Control on Rhododendrons” is at http://cru.cahe.wsu.edu/CEPublications/eb0970e/eb0970e.pdf. You might be able to d=find the youngsters in the soil right now. They’re often beneath the plant’s canopy and about a half inch under the soil. When you find them, drop into soapy water.

Adult feeding occurs at night, often 10pm or latter. A cultural method here is to spread a light-colored fabric – perhaps an old sheet – under the plant. When you jostle the plant, the weevils drop and play dead. You can easily gather them up and dispatch them in slightly soapy water.

Another management choice is to add beneficial nematodes to the soil while the larvae are present.