Spider mite infestation on tomatoes


Growing tomatoes successfully in Phoenix has always been a challenge. We have successfully identified varieties that work here and how to grow them. What vexes us seriously is how to deal with spider mite infestation that comes on strong around the middle of May and takes everything out by the end of June. This is our pattern every year. Now we still get substantial harvests by the end of June and its still worth growing…but I really do hate loosing healthy plants to the little bastards.

So far we have tried daily jets of water to knock them off (This helps a little) and pyrethrin (which makes things far worse). Anyone out there have a organic or non organic solution that works? When its cool enough we spray omni oil and that keeps them well in check…but around May 15th it gets too hot here to use oil.


These guys are in Tuson it might be worth a phone call.

Tomato pollen dies at high temps so you might not be able to extend the season.
We have a short season here in Alabama because it just gets too hot and humid and you can not pollinate them.
Eggplants and Peppers make it to fall but tomatoes we just pull out like you do.


You must have predators if spraying makes the problem worse. Spray is killing predators but not mites. I’m trying benefical mite predators now but don’t have a lot of hope. There are numerous highly effective miticides but not many registered for tomatoes or fruit. And you need at least two with different modes of action to rotate so mites don’t develop resistance as fast.


Ive looked into the mite predators but from what ive seen most of them are cool season insects and die at higher temperatures… Ill keep looking.

I wish I could just keep spraying the Omni oil…its works! But it also starts burning foliage about 90 degrees.


I’m going to second what David said. Tomato production declines rapidly once the temps start advancing into the 90’s, especially if the night temperatures don’t offer significant cool down. The pollen loses vitality and the photosynthesis ability decreases. They lose more water through transpiration than their capillaries are able to uptake from the roots. For some people, it’s worth it to keep them on life support until fall when they get a second shot at production, but I doubt that would be a commercially viable option.


Alright guys…I guess the message is that im doing about as well as can be. I already knew that this would be the answer but hope springs eternal. Its all good, the harvest we get before the spider mites take them out is substantial.


I’m spider mite free so far this year thanks to 7 to 10 day applications of neem oil. The details are in the following forum threads:
Pest pics?
EarthBox Tomatoes


Id happily spray neem…but doesnt it have a upper temperature limit like other horticulture oils?


This is my first go 'round with neem oil so I can’t speak to how it performs on hot or cold days. Rest assured I will find out soon enough as I grow tomatoes year round.

There just isn’t enough first hand experience out there from people who have successfully defeated full blown SM infestations (such as I’ve had). That said, I would probably spray on one plant in the evening during a hot spell and monitor closely. Right now I’m spraying first thing in the morning with great success. Speaking from experience, water spray alone isn’t enough to defeat them.


You know…I really dont have much to loose if I apply neem as a test to a few plants. I think I will pick some up and give it a shot tonight. The planting in total is about 60 plants so if it doesnt work out im only down the two I am going to test spray. Agreed that water sprays alone wont get it done. Slows them down slightly.


The Monterey 70% neem oil I’m using seems pretty dilute, and is then mixed at 2 T per G of water. I would probably shade the trial plants the day after spraying to be on the safe side. Just a portable patio umbrella should do the trick.


Oil is oil they fry up nice, bring some fries for your ketchup!
You could use a miticide. I have used malathion, worked very well. Spray a few times at 5 day intervals. Or you could use others, just Google miticide. All kinds exist.

If you try the neem do it in the morning or at night. Bonide’s neem warns about burning.

With malathion you may have the same issues as with pyrethrin. I myself did not, but spider mites are wimps here. Not really a problem. I had them on cacti, not tomatoes.



Folks in Texas say that the Monterey brand Horticultural Oils can be used at higher temps.
Something about it being mineral oil and formulated differently.

Monterey Neem or Monterey oil is worth a test on one or two plants.

Spider Mites are Especially Nasty little critters. I feel your pain…


The product label regarding leaf burn is pretty generic:
“As with other oil-based products, care should be exercised in timing applications to early morning/late evening to minimize the potential for leaf burn”

As a fungicide the mix is 2 T per G, for insecticide/miticide you can go 2 to 4 T per G. By starting at 2 T, it should be less prone to burning and gives some room to move up to 4 T if they build up some resistance.


Despite the spider mite issues the tomatoes are still producing gobs! This was one days harvest recently.


Although I don’t have mites on my tomatoes, I do have them on green beans, eggplant, peas. And Safer’s Soap kills them dead, but you have to come back and do it again every 5-7 days as eggs hatch, and to get any that you’ve missed. But it’s hard to spray the underside of leaves…I bend or twist the plant/stem/leaf with one hand and spray with the other…it can be tedious if you have many plants. You also have to spray the stems/trunks, they are the spider mite highways.

It really helps to have a hand held microscope with LED lights, you can see all the spider mites, young and old, and their eggs, so you know the effect of the spray and when you need to do it again. I’ve been buying these cheap (but very good) LED microscopes from China, on Amazon. They give a very clear view, about 10-20x (claimed to be 40x), are a bit awkward to use but once you get used to them it’s easy and quick.


JB, I’ve been using one that is probably like that for years, way before Amazon. They were $12 at Radio Shack. Work better than much more expensive devices that I’ve purchased from professional suppliers.


Good looking harvest, @amadioranch. I just sprayed neem yesterday as the sun was setting and it’s 99* here today. No sign of leaf burn at this point:


Good looking plants Clint. I never did end up spraying the neem. It turned ungodly hot, we have been around 115 all week. Its end of season for them anyway…they arent setting more fruit. Im just harvesting whats left and letting them go. The yield out of them despite the mite issues has been awesome. No regrets.


Yeah, toms are really starting to come in now. In my experience they stay vegetative until they hit some kind of stress. When grown in EarthBoxes water and fertilizer aren’t limiting factors, so it takes a heat wave for them to get busy with ripening.