Leaf Miners - Sevin Dust as soak/spray?
 

I have been having problems all summer with a lot of leaf miners defoliating my plants leaf by leaf. I bought the 3 pack of Sevin dust but I can't seem to get a good dusting on my plants. It's too thick in some places and not thick enough on other places. It is also very difficult to try to dust over 40 plants. My question is, if I mix some Sevin dust with water in a hose attached sprayer and soak 100% of each plant with the milky mixture do you think it would hurt my plants?

Any other suggestions for dealing with leaf miners would be appreciated. Please keep in mind that the solution will have to be for over 40 plants. Thanks!

Mark

Mark,

Sevin is ineffective against leafminers in vegetables as it doesn't penetrate the outside of the leaf to the interior where they feed. The fly doesn't feed on the foliage either but lands to penetrate the leaf with its ovipositor to lay their eggs, so it likely doesn't come into enough contact with Sevin dust to kill it. Even if it did it would have already laid its eggs by the time the Sevin had an effect.

Other than row covers to prevent the fly from reaching the plant, there isn't a chemical I can think of for the home gardener to use. Kaolin clay sprayed may work but you would have to apply it at the right time and it is difficult to get an even distribution because it is hard to keep in suspension.

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BT also has little effect on leafminers and Sevin is not poison, it is sold over the counter and carries a caution label - just like BT.

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I've never had leaf miners in tomato plants, but usually see some damage to my Swiss Chard and other greens. For a small infestation, so I just cut off the leaves and destroy them.
Leaf Miners are very small larva of some insects that live inside the leaf, so they are difficult to control with insecticides, especially broad-spectrum insecticides in powder form like Sevin. Another problem with Sevin is it is very toxic to other insects like the natural predators of leaf miners that attack adults and pupa. The leaf miners exit the leaf and drop to the soil where they pupate. You may be helping the leaf miners more than hurting them by using Sevin.
You might be better of trying an oil based, more organic approach like Neem Oil, Pyrethrin or Spinosad that sticks to the leaf surface where there is a greater chance of the larva ingesting it and as a deterrent to the insects laying the eggs on the leaf to begin with. I've done this with leaf pests like Miners and Beatles and it seems to work just fine. A soil drench with the same would be helpful to kill larva and pupa in the soil.

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Ray,

Whether oil based or not, organic or synthetic, it is a waste of time and money to apply an over the counter insecticide on your plants (or on the ground) to control leafminers. As I said above, leafminers feed inside of the leaf, not on it.

Mark,

I've had pretty good luck using a dusting of garden sulfur on dahlias to decrease the leafminer damage, but have never tested its effectiveness on tomatoes. Unfortunately, if sulfur is used during hot weather, it can cause almost as much damage as the leafminers. Leafminers are difficult to control with any pesticide - even the systemic pesticides require frequent application, and you wouldn't want to use systemics on food plants anyway. You might try a light dusting of sulfur on the lower portion of the plant (on a couple of plants) as a test.

Please don't use Sevin unless it is absolutely necessary. As mentioned above, it is [B]not[/B] a safe pesticide, and will not be of much, if any, help for leafminer control.
Besides being deadly to bees, if you apply Sevin frequently you are at a much higher risk of getting deadly skin cancer. The tip of the iceberg:
[URL]http://www.environmentalhealthnews.org/ehs/news/farm-pesticides-linked-to-deadly-skin-cancer[/URL] As a commercial farmer I would never consider using Sevin, and can't believe it is still approved for use by the general public.

Steve

I never argued that killing the larva inside the leaf was easy or that anything would be highly reliable in doing so, but I don't think its a waste of time or money (within reason) to reduce the spread of a severe infestation as Mark seems to have.
It is possible to kill some larva inside the leaf, Dow Chemical has shown that Spinosad can penetrate a few layers into leaf tissue and although not really a reliable systemic compound it can be taken up by roots.
Azadirachtin, the active anti-feedant compound in Neem has also shown to have similar capabilities.

"[URL="http://mrec.ifas.ufl.edu/lso/Manual/insect-text-only.htm"]Chemical Control[/URL]. The larvae is inside the leaf and the pupae is in the soil making it difficult to reach these stages with pesticides. The insecticides that are effective usually have some transluminar or systemic activity allowing penetration of the leaf tissue. The insecticides in this category are abamectin (Avid), azadirachtin (Azatin), cyromazine (Citation), and spinosad (Conserve). The insecticide novaluron (Pedestal) was recently registered for suppression of leafminers. No foliar insecticide can reach the pupae in the soil so repeat application is necessary to make sure the life cycle is broken. Three applications at 7 day intervals are required to make sure that control is achieved, especially with a heavy infestation."

I know mileage may vary depending on the type of plant and the species of pest, but breaking the life cycle of the pest is more effective than trying to kill every visible pest itself.

Ray,

I've been meaning to try spinosad, it looks like a promising control for leafminers. I spray a lot of Avid on flowers for leafminer control, but I won't/can't use it on tomatoes. Spinosad looks like its worth trying.

Steve

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ACT or Activated Compost Tea. Remarkable how that stuff can be used with impunity on a whole host of insect pests. I used it on my Honeysuckles which were being devastated by leaf miners, all gone.
Go Green, forget the chemicals.