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There are several different species of plants in my yard that have developed some kind of condition where the leaves get pale, tiny specks all over them (such that they look kind of sandy). Many of them have webs that seem indicative of spider mites. Are the webs from spider mites? However, I'm not sure if the speckling is caused by spider mites or something else, like maybe manganese deficiency caused by too much calcium in the soil (I did add probably too much basalt rockdust for all of these except the apple tree at the end, which has had the problem for 1-3 years now). What could be causing this (the speckling)?

It began with the apple trees and rose bushes about a year or two ago, but it seems to be on lots of stuff in the yard, now. It seems to be leaving alone the tomatoes, peppers, and muskmelons, however. It was all over the watermelons, except the Citron watermelon (which was only lightly afflicted, but it wasn't with the other watermelons). On the other watermelons, it started on the shaded parts of the plants, and slowly progressed to the parts in full sun. Eventually, it totally enveloped them, and pretty much killed them (although the pictures I uploaded only show the early stages of the condition). Thankfully, the fruits ripened at about the same time they were completely overcome. Strangely, however, Aunt Molly's ground cherry showed symptoms in stronger sun first, and then on the shaded plants. These plants also gave their fruit and eventually died.

The issue was virtually absent until about mid-summer (although it affected apple trees, rose bushes, and maybe grape vines on at least one previous year).

The pictures that follow show the issue on several different kinds of plants in several different locations. It should be noted that it also affects the fruit, however, but that's not pictured here (it speckled the outer rind of a Ledmon watermelon quite heavily).

Around the time I first asked this question, I gave some of the plants some manganese sulfate and monopotassium phosphate. The pepino melons improved quite a bit (and seem fully recovered from the problem), whether or not manganese deficiency is the visible problem. Many of the other plants improved after the weather cooled down, and perhaps with a little rain, too.

The soil here is clay loam. We have a couple large pine trees that possibly could be eating up the manganese in the yard. I understand they prefer acidic soil (and because of that they are probably used to a lot more manganese than is available to them in our yard). The soil possibly also has a higher PH, which could also cause manganese deficiency symptoms in plants.

I should note that our nieghbors fruther away from the aforementioned tree also have speckles like this on their apple tree.

The black stringy things you see on some of the plants are not related to the problem. They're just ashes from the fires that have been going on in southwestern Idaho. The speckles, however, are definitely not ashes, even where they may look kind of like them.

Pepino Melon Pepino Melon Aunt Molly's Ground Cherry Aunt Molly's Ground Cherry Aunt Molly's Ground Cherry Aunt Molly's Ground Cherry Diamond Eggplant Diamond Eggplant Garden Huckleberry Garden Huckleberry Shark Fin Melon Shark Fin Melon Watermelon Watermelon McIntosh Apple Tree McIntosh Apple Tree

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All of this damage looks like spider mites. It is odd to see so extensive an infestation outside where natural predators like ladybugs usually move in for a feast.

Spider mites like it when it is hot and dry. Plants that are stressed are favourite targets.

Indicators are:

  • webbing
  • tiny pale spots on the leaves where the mites have sucked out the plant juices
  • they normally live on the underside of the leave and can usually be seen with the naked eye. They resemble grains of salt in size and colour.

Examination with a magnifying glass is usually conclusive.

Control is by soap and water as has been discussed here. This gets much harder for trees and shrubs but persistence with multiple sprays at five to six intervals. For your purposes any of these plants that are annual should be removed and composted.

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  • It's definitely very hot and very dry here. I forgot to mention that after I asked the question and suspected spider mites, I found that spraying the plants' leaves and stems with water once in a while helped quite a bit. The ladybugs pretty much have a full scale buffet here, with lots of options. I think they're busy with the other pests, but they have been on the plants, probably eating spider mites, too. I did buy ladybugs this spring, too. There are ladybugs (we just need probably a lot more). There are lots of lacewings, too. – Brōtsyorfuzthrāx Oct 17 '15 at 2:36
  • I think the flecks on the watermelons may also have been related to Anthracnose, since the later symptoms on the leaves looked a lot like it, but I do agree with the spider mites, too. – Brōtsyorfuzthrāx Oct 26 '15 at 21:07
  • See this picture (this is what it looked like, but worse, but although the fruit didn't have spots, it did have flecks like the leaves in my picture in my question): s3.amazonaws.com/plantvillage/images/pics/000/001/696/large/… – Brōtsyorfuzthrāx Oct 26 '15 at 21:15
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    Yep. The watermelons did have anthracnose on the foliage after this. The problem seems to be due to spider mites infesting the apple trees, and the dry weather causing the apples to drop. The fallen apples eventually rot (the pathogen that makes them rot seems to be anthracnose). The spider mites probably infest the rotting apples which are squishy and juicy and then migrate to the watermelons, where they spread anthracnose to the foliage. So, yeah, don't leave fallen apples on the ground to rot (even if they're under-ripe). That's the moral of the story, it seems. – Brōtsyorfuzthrāx Dec 9 '16 at 8:48
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    Here's a link about spider mites near my region (where sugar beets are common), which you're free to add to your answer: pnwhandbooks.org/insect/agronomic/sugar-beet/… (It gives a lot of information and says some things I've found myself to be true, before I read this, such as about how to water infected plants. It mentions the speckled appearance of leaves, too.) I might add that thrips and leafhoppers can make leaves look similar, though. – Brōtsyorfuzthrāx Mar 30 '18 at 0:33

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