Thursday, May 28, 2015

A Proper Diagnosis for my Pepper Problems?

I think, I hope, that I've finally solved the mystery of what has been infecting my pepper plants. My poor plants suffer every year. They develop wrinkly stunted leaves and I always think that I'm going to have a crappy year for peppers. I've been thinking for the last few years that my plants are picking up some sort of virus transmitted by aphids. But then, the plants usually pull through and produce a decent crop. It's been a mystery but I haven't really pursued the problem because I do end up with more than enough peppers to keep me happy.

Many of my plants are looking particularly bad this year, here's one of the worst. I set the best looking plants out in the garden and was pretty much resigned to the wait and see tactic again.

And then I noticed that my eggplant seedlings were suffering from mites, there was that very distinct silvering on the undersides of the leaves. And then I had one of those lightbulb moments. Maybe it's mites attacking the peppers too! I searched the UC IPM site and found little help, just some general information on the home gardener part of the site about spider mites and even the information aimed at big ag producers claimed that  "Mites are not a major problem on peppers and treatments are generally not required."

Bummer, really?

But I couldn't get the idea out of my head. So I went ahead and just did a general web search for "mites on peppers". Lo, I found photos of what could have been my plants. Whoa. I love the internet.

It turns out that the likely culprit is not a spider mite, the common pest mite around here (there's good mites too), it's a Broad Mite. UC has information about Broad Mites on citrus and cyclamen, but nada about them on pepper plants. But Broad Mites do major damage to peppers in Florida, as I found here (along with a photo of a pepper that looks like my poor things). The mites are also problematic on many greenhouse grown plants, including tomatoes and basil. Hmm, some leaves on my tomatoes are a bit silvery in spots and the young little basil leaves are looking a bit distorted. Greenhouses seem to be hot spots for Broad Mites and I've been giving my seedlings lots of TLC with something akin to greenhouse conditions. I think that what has been allowing the plants to recover every year is that my garden conditions are too cool and dry to favor the mites, they prefer warm and humid.

The biggest problem with identifying a Broad Mite infestation is that the little boogers are really little, you need a good hand lens or better yet a microscope to properly identify them. Usually the first sign of a problem is distorted growth. So having never heard of a Broad Mite before and having no reason to suspect them, nor being able to see them with my wimpy hand lens, I've been placing the blame on an aphid vectored virus (there's always an aphid or two to be found). Apparently that's not an uncommon misdiagnosis, I found a number of references to suspected virus problems in greenhouse grown crops of a certain type of, shall we say, recreational and/or pharmaceutical nature, that turned out to be the Broad Mite. The mite seems to have found refuge in green houses around the world and can escape into gardens in the warmer months even in places like Canada and Northern Europe.

Here's more information from the University of Florida about Broad Mites. And an excerpt from the site about treatments

While a number of miticides are labeled for control of this pest, insecticidal oils or soaps are usually just as effective and less toxic to the environment. For large area or greenhouse control, biological control agents are available, including several species of predatory mites (Wilkerson 2005, Peña and Campbell 2005, Fan and Petitt 1994, Peña et al. 1996). In addition, hot water treatments may be used to control the mites without injuring the plants. This involves lowering the plant into water held at 43 to 49° C (109.4-120.2°F) for 15 minutes.

So I've given my plants a good spray of 70% extract of Neem (not to be confused with a product called Neemix which would be ineffective against mites). I think I'll have to do a few more treatments every few days because the mites can reproduce in just 2 to 3 days.  And perhaps next year I'll try the warm bath treatment if I spot symptoms in my potted seedlings.

What I really need to do is get a few specimens off to UC for confirmation, but I don't have the time right now to do the 2 hour round trip to the nearest Master Gardener office. Maybe next week, it would be nice to know for sure.


  1. Michelle, put "pepper leaves calcium deficiency" in your search engine and at the look at the images. What do you think?

    All 15 of my peppers got wrinkled leaves in the center in the last two weeks. Never had it before. We had cool, cloudy, foggy weather (like yours!). I wonder if that contributed to the problem?

    Alas, poor eggplants, spider mite and flea beetle. Beside they taste terrible, bitter and tough skins. Unusual for this type. These are 'Millionaire'; 'Nubia' and 'Kermit' haven't set fruit yet.

    1. I considered and eliminated the calcium deficiency possibility long ago, along with other micro-nutrient problems. Cold isn't the problem either, my plants sit in a mini greenhouse with a heat mat to keep them warm at night and on cold foggy days. I'm thinking the mite is the likely culprit. A few doses of neem won't hurt. But I think I finally have to get a sample to UC.

  2. At least mites can be controlled. Good luck with them.

  3. I'm actually really surprised that this has been a problem for you in the past - never would have guessed considering the baskets of peppers coming out of your garden last year!

    It's great that you have the ability to get the plants analyzed - then you will know, once and for all, who the likely culprit is & be able to deal with it head on.

  4. Good news if it is the mites. And like you say, a little neem won't hurt anything. Hopefully you can get them to UC for a positive determination.

  5. Maybe the wrinkled leaves could also be the result of weedkiller contamination in compost, like that which affected me last year? Do you use any commercial compost or potting-mix?

    1. I had considered that too because I use purchased potting soil for all my seed starting, I don't think that's the problem because it's just the peppers with those symptoms, other than just a bit of distortion in some of the basil. My tomatoes are are huge and beautiful, but as I mentioned, they do have some signs of a minor mite infestatiion.

  6. I usually have a terrible time with pepper plants ... to be honest, your unhealthy plant picture looks better than most of what I thought were my healthy plants. Guess I have more problems than just the climate here. :)

  7. Interesting. I remember you commenting about curled up leaves. A lot of my pepper starts looked that way but once I potted them up to a 4" pot, the leaves flattened out and turned a darker green. Still, it wouldn't hurt to give mine a spritz of neem oil. Will be interesting to see if the neem helps your plants.


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