Leaf miners

[b54red]

Just what I need to start out the season. A new pest. I was doing the initial tie up on some of my plants today and found a lot of damage from leaf miners. I have never had more than a couple of leaves get them in the past but this year they started on my plants while they were still hardening off and now I have quite a few with significant leaf miner damage.

Do these miners have a major affect on plant health? If so how do you combat them? In the past I just clipped off and discarded the few leaves that were affected; but that would nearly defoliate some of the plants this year.

[ArcherB]

I've had damage from leaf miners but it has not affected the plants in any negative way that I'm aware of. When they attack my basil, on the other hand, I can't bring myself to eat the leaves that are affected, but it doesn't seem to harm the plant.

[Heritage]

b54,

I think a heavy infestation of leaf miners would eventually reduce yields, but I don't know if it would ever get bad enough to kill the plant. I've had it almost completely defoliate dahlia plants, so I try to prevent it and control it as much as possible on my tomatoes.

A pesticide containing Spinosad seems to help and a dusting of sulfur (you know the restrictions) helps to keep the flies from injecting the leaves, but sulfur is only a preventative. Leaf miner is a tough pest to control. Use of some pesticides will actually increase their population. A few pesticides that work on dahlias are not something I could/would use on tomatoes.

Good luck!
Steve

[b54red]

Thanks guys. Maybe they will only be unsightly and not affect production. I don't really mind an ugly plant but I don't care for the ones that don't make fruit.

[kurt]

Thr life cycle of the leaf miner starts as a egg injected into plant,it feeds and eventually drops onto the ground burrows 1-2 inch in then emerges as a adult fly and the process starts all over again.You can nuke the ground but make sure it is soaked to 2 inches.Do pick the leaves to stop that part of the cycle.Or as I did put plastic underneath the plants so larvae will not morph into flys again.The eggs when injected into leaf are in the leaf not topical so spraying the leaf really do not do much.

[bower]

Originally Posted by kurt

Thr life cycle of the leaf miner starts as a egg injected into plant,it feeds and eventually drops onto the ground burrows 1-2 inch in then emerges as a adult fly and the process starts all over again.You can nuke the ground but make sure it is soaked to 2 inches.Do pick the leaves to stop that part of the cycle.Or as I did put plastic underneath the plants so larvae will not morph into flys again.The eggs when injected into leaf are in the leaf not topical so spraying the leaf really do not do much.

This is the best advice I know of for leaf miners. I had the same problem with my cucumbers last year, that I hesitated to pick all the affected leaves because it would have been seriously defoliated. In the end the damage was extensive, I may as well have picked em clean.
Doing something to prevent new flies from emerging after they drop to the ground is also key to stop the cycle. Turning the soil to make sure that top 2 inches is buried is recommended as a control measure on a seasonal basis, before you plant. Evidently they will not emerge from deeper than 2 inches. If the plant is tomatoes, you might also stop them from by building up another two inches of clean soil on top of what is there now. But plastic mulch is a great idea, to stop them from dropping into the soil in the first place so they can't complete the life cycle.

[Heritage]

Originally Posted by kurt

Thr life cycle of the leaf miner starts as a egg injected into plant,it feeds and eventually drops onto the ground burrows 1-2 inch in then emerges as a adult fly and the process starts all over again.You can nuke the ground but make sure it is soaked to 2 inches.Do pick the leaves to stop that part of the cycle.Or as I did put plastic underneath the plants so larvae will not morph into flys again.The eggs when injected into leaf are in the leaf not topical so spraying the leaf really do not do much.

kurt,

Spinosad is not a systemic but it does penetrate the leaf surface so has some degree of effectiveness. There are true systemics registered for tomatoes that will do a good job (better than Spinosad) on leaf miners but they are not available to the home gardener.

I agree, plastic mulch does seem to be a logical solution. However, this study indicates that the opposite is true - plastic mulch will increase the leaf miner populations:
http://journals.fcla.edu/flaent/article/view/57060

It would make an interesting experiment to try it both ways in the home garden...

Steve

[attml]

They ruined my season last year - here is a recent thread I started

http://www.tomatoville.com/showthread.php?t=22081

[mysidx]

I have been using spinosad and it seems to be keeping them to minimal damage. Last year I would pluck out every larvae , and it seemed i could never keep up.

[mysidx]

Would a thick layer of pine needles help?