Hibiscus: This was too die for, a must must must have., 1 by Michael_Ronayne

Michael_Ronayne wrote:
I just discovered that Hibiscus mutabilis (Confederate Rose) is extremely vulnerable to whitefly (http://www.google.com/search?q=whitefly) infestation. My three Hibiscus mutabilis had been doing very well until about two weeks ago when I started noticing that the stems were no longer standing as upright has they had been. I had noticed small whiteflies and a small black fly flying around the racks where I keep my plants for the winter. In the last week the deterioration of the Hibiscus mutabilis was noticeable and I had started loosing Hibiscus seedling of several species which had been doing very well until then.

When I inspected the Hibiscus mutabilis I discovered a massive whitefly infestation on the leaves and stems of the plants. The Hibiscus seedlings which were in trouble had small black flies congregating about the roots which were withered. I did try rescuing some of the distressed seedlings by planting them deeper in the ground to increase the area of the stems in contact with the soil.

I had Spectracide Malathion on hand for my last insect problem and had already recalibrated the formulation which came on the bottle label from gallon quantities to small batches of 0.5L and 1.0L which can be loaded into a spray-bottle. The attached graphic contains the recalibrated formulations which I did in Excel. I used 2.9ml of the concentrate in 500ml of water.

The spray was applied to all my plants and the soil for two consecutive days. I am seeing reappearance of whiteflies and the black flies in small numbers which are quickly killed by the Malathion spray. I suspect that I will have to be vigilant for the next few weeks but I appear to have the problem under control for now. Obviously I don’t what to overdo Malathion indoors.

One DG member had commented that they don’t keep Hibiscus mutabilis in Florida because of the whitefly problem. I suspect that my whiteflies were hitchhikers on one of the shipments from Florida. I have no idea where the small black flies came from but they or their larvae appear to go after the roots of Hibiscus seedlings, with the smaller plants being most vulnerable. One Internet BLOG (http://blog.nola.com/dangill/2008/07/carefree_color.html) suggested that whiteflies can be eradicated for the year by applying the systemic insecticide Imidacloprid at the beginning of the growing season. I will have to look into that before spring, assuming that I can keep the whiteflies under control until then.

My Excel spreadsheet of recalibrated Malathion formulations is available to anyone who wants it.

Mike