A recently planted rhodie has brought infection to my garden

chester_grant(6)May 28, 2006

I have a garden which - ulike my prior property - is free from little black weevils. However I recently purchased a small rhodie from Home Depot (what an idiot) and I noticed that the flowers had all dropped overnight last night (its small so there are only three of them!).

It is clear that this plant has weevils as the liitle flower components are all cut through the stems - exactly the same tye of damage as I had in my lasat property.

More important my garden is now infected to some extent by weevils. The question is by how much? This lousy plant has been in the ground for three weeks and I wonder whether the nearby rhodies which are about three or four feet away would have been "invaded" yet? How long do this little pests take to migrate? I guess I will yank this piece of infected Home Depot trash up - maybe I should return it for a refund.

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rhodyman(SE PA, USDA Z6)

There are two weevils that attack rhododendrons and azaleas: Black Vine Weevil or Strawberry Root Weevil

They create two entirely different situations:

Adult weevils feed on the leaves at night. Leaves chewed on edges is a symptom of the Black Vine Weevil and Strawberry Root Weevil, 1/4"long black beetles. They are nocturnal feeders and can be found at night with a flashlight for identification. Foliar sprays are very effective at controlling adult weevils when leaf notching starts. Foliar sprays of Orthene should be sprayed at about three week intervals from about May to October, depending on the weather, until no adults emerge. Since weevils feed at night, you can hand pick adult weevils at night using a flashlight. Since weevils spend the daytime in the soil and come out at night to feed, you can paint the trunk with Tanglefoot to stop them, but make sure no branches are touching the ground. Foliar sprays are very effective at controlling adult weevils when leaf notching starts. Foliar sprays must be repeated until no adults emerge.

The major damage is caused by weevil larvae which girdle the roots and kill the plant. Prior to killing the plant the plant shows signs of chlorosis (yellowing of a leaf between dark green veins.) Larvicidal drenches may be used to kill them but are of limited effectiveness. A more effective approach is to use nematodes. They are very effective against weevils when applied in the fall to control the larvae. While this approach is promising, it has limitations in that the beneficial nematodes are very sensitive to temperature and moisture extremes and will not live over winter. If applied to soil that is too cold, too wet, too dry or too hot, they will die and provide no control. Best control is achieved by using both chemical and nematode methods with proper timing.

    Bookmark   May 28, 2006 at 3:19PM
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I have seen two types o weevils over the years - one type much larger than the other. The larger weevil is greyish and has a very hard shell so it is hard to squish beteeen your fingers (I always did a visual inspection using a torch at night - the easiest way to get em was to put white papaer under the rhodie and just shake the plant).
The other weevil was harder to deal with - and I suspect is the one which I have brought to my garden thanks to the grower who sells to Home Depot. This other weevil is the same shape as its larger cousin but very small and black - and very hard to catch as it doesnt drop off the rhodie. It typically snips through the stork of the flowers comprising the large bloom of rhodies. The result is an unsightly mess of a flower instead of a beautiful head. Which of your weevil examples is which I wonder?

    Bookmark   May 30, 2006 at 7:47PM
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In the past, I have used Talstar for weevils and it works but it is not available in all states. Recently, I started using beneficial nematodes and I have almost no notches in my rhododendrons leaves at all. There are a few different strains of nematodes;I use Steinernema feltiae
because they are hardy and last over winter. You can purchase them from BioLogic (http://www.biologicco.com/). Hope this helps.

    Bookmark   June 3, 2006 at 8:43AM
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