Whitish specks on the upper surface of leaves and dark spots varnish-like on the bottom are symptoms of Rhododendron Lace Bugs, Stephanitis rhododendri, and Azalea Lace Bugs, Stephanitis pyrioides, small insects with transparent wings on under-surface of leaves.. This insect hatches early in spring as the new foliage begins to mature and its numbers may build to damaging levels with successive generations. Lace bugs reach their peak in late summer and do their worst in sunny, exposed sites. Spiders are important predators of lace bugs and since they shy away from sunny, hot places, plant your azaleas where there is some shade. Insecticidal soap, horticultural oil, or a systemic insecticide may spare your azaleas the damage if applied in spring when the first hatchlings are noticed. Care must be taken to spray the lower surfaces of the leaves where the lace bugs live. Moving a plant to an area with more shade may alleviate the problem. Lace bugs are more prevalent on certain varieties. The following azalea cultivars have resistance to azalea lace bug: Dawn, Pink Star, Ereka, Cavalier, Pink Fancy, Dram, Seigei, Macrantha, Salmon Pink, Elsie Lee, Red Wing, Sunglow and Marilee. Rhododendron Lace Bugs, Stephanitis rhododendri, and Azalea Lace Bugs, Stephanitis pyrioides adults are about 1/8-inch long. The body is pale yellow. The lacy wings (very distinctive) are held flat over the back and are transparent with two dark spots present. The nymphs are black, spiny and smaller than the adults. The eggs overwinter partially embedded in leaf tissue. The eggs hatch in May. The nymphs mature into adults in June and lay eggs during late June and July. The second generation of nymphs appears in August. The overwintering eggs will be laid when these nymphs become adults. Lacebug adults and nymphs feed on the undersides of leaves by piercing the leaves with their mouthparts and sucking the plant juices. This causes a mottled, silvery or white discoloration, known as stippling, on top of the leaf where the chlorophyll has been removed. The undersides of leaves are covered with dark brown to black, sticky spots of excrement. Plant rhododendrons in shade to maximize the activities of beneficial insects. Varieties that are attacked by lacebug will recover if moved to shadier areas. They only get lacebugs in full sun. The National Arboretum warns: "Excess nutrients (fertilizer) may promote larger than normal populations of azalea pests like lace bugs Thrips, Thrips imaginis: This insect is a seasonal pest, causing most damage in mid to late summer. Signs of damage include silvering of the foliage and distortion of growing points and flower buds. The underside of leaves may be covered with excreta of the insect, which are like brown tar droplets. There are no effective specific biological controls and thus control can be difficult to achieve. Thrips are preyed upon by ladybirds and lacewings but these predators cannot control thrips in plague situations.

Michaelg, I appreciate your knowledge, which helps me to understand the role of soluble vs. insoluble nitrogen. And BellaL, thanks for presenting your problem which helps me in Illinois. I read that tree bark deprives the soil of nitrogen as it breaks down, so we always need to add nitrogen to the soil if tree bark mulch is used. Composted grass clippings and leaves are far superior to tree bark mulch in supplying nitrogen. I mulched my tomato bed with grass clippings, and don't have to water my tomato garden this year, since it retains moisture well. Another way to know if your soil is deficient in nitrogen is the presence of nitrogen-fixation plants, such as clover, and those annoying stringy weeds with white flowers. I got sick of pulling those long stringy weeds up, so I dumped bloodmeal around my Norway Spruces - and no more stringy weeds afterwards. Plants can extract phosphoric acid (good for blooms) easily from clay soil, but have a hard time extracting nitrogen. My white pines are yellowish in new growth, - so I dumped blood meal on them, and the growth is deeper green, with less pine cones. The good result of horse manure on my roses can be verified by this sentence from the reference book, Botanica's Roses "High alkalinity can be reduced by the addition of peat or manure, or by applying suplphate of ammonia." The best instruction for growing roses is from Pat of Rosesownrootunlimited, which I erred and learned from my mistakes: 1) Dig hole at least 18" deep and wide 2) Plant rose slightly raised (esp. in clay with poor drainage) 3) Per planting hole: 2 cups of alfafa meal, 1/4 peat moss, 1/4 compost, 1/4 top soil, and 1/4 clay. The other stuff, such as 1 cup superphosphate, 1 cup lime, 1 cup gympsum are NOT necessary for clay soil in Illinois, heavy in dolomite lime. The 2 cups of alfafa meal are important. Out of my 10 baby roses planted this year, 2 are underperformers (Eglantyne and William Shakespeare in a pot - and both these don't get the 2 cups of nitrogen like others, so the leaves are more yellowish).

I don't know enough to be sure what it is, mustgarden. If you planted out within the last week or so and the plants weren't gradually exposed to full sunlight ("hardening out"), they can get light patches. But in my experience those patches are usually light tan or white, not yellow. You can see similar damage when water droplets on the leaves magnify the sun's rays. And it does resemble the photos of magnesium deficiency, but I don't know if it's that or something else. Meanwhile, here's how to post photos from Photobucket; presumably it's fairly similar in imageshack: http://forums.gardenweb.com/forums/load/hosta/msg0513322013993.html?14 The important thing is that whatever you copy from imageshack should provide the kind of html that begins with the is-less-than sign (above the comma on your keyboard) and ends with the is-greater-than sign (above the period). When you go to Preview Message, you should see the photos, or if you're posting a link, the link should work. What you see in Preview is what you'll get in the actual post. [And yes, for some reason it took me four tries to get them all to show up.] Just to save time, here are your photos: I use a free Firefox add-on, BBCodeXtra, which provides the right code. [Still sincerely thanking GW member justaguy2 for recommending this add-on which lets me do fun format stuff!]

Hi Marnie...I too have terrible rust on my plants where last year only the pink one had it, this year the red is covered with it also the pink and white though the fruit salad one is ok that one is in the sun all day, what surprised me was the new yellow one I bought mid January only 60 cms tall and with its first bud also has the same problem its in sun most of the day also with not much around it.. Have a look at the link below it more or less states the same thing as ..My book "What garden pest or disease is that" it gives this Organic control method for rust problems on other plants...The prompt removal of the first infected leaves may solve the problem.. Improve air circulation..Clean up infected leaves and burn.. So till next year when I will start as soon as possible .......Cheers..MM. Here is a link that might be useful: Plumeria 101