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Monday, June 21, 2010
In organic gardening, prevention is often more effective than treatment, and leaf miners are no exception. Because leaf miner pupae overwinter in the soil, the maintenance of diverse soil microbial activity can prevent leaf miner outbreaks, because beneficial nematodes in the soil feed upon insect larvae and pupae. Interestingly, avoiding the use of broad spectrum chemical pesticides can also help keep leaf miner fly populations in check, because such pesticides kill parasitic wasps that can decimate larvae populations.
In organic gardening, prevention is often more effective than treatment, and leaf miners are no exception. Because leaf miner pupae overwinter in the soil, the maintenance of diverse soil microbial activity can prevent leaf miner outbreaks, because beneficial nematodes in the soil feed upon insect larvae and pupae. Interestingly, avoiding the use of broad spectrum chemical pesticides can also help keep leaf miner fly populations in check, because such pesticides kill parasitic wasps that can decimate larvae populations.
Pesky Pests
Leaf Miners
Note: this article is set to appear in the upcoming issue of our newsletter, Bountiful Harvest. If you like what you read here, you should subscribe to our newsletter by clicking the "Quick Contact" link on the top right above.
It's summertime in Los Angeles. Summer gardens mean squash and melon plants. Unfortunately, squash and melon plants mean leaf miners arrive as pests, leaving behind their signature squiggly white lines on cucurbit leaves.
The term "leaf miner" can refer to any number of species of insects, particularly flies and moths, that lay eggs on plant foliage. Leaf miner flies are particularly active during the hot weather of the summer, and the giant leaves of squash and melon plants are attractive targets in southern California gardens. About two days after they are laid, larvae emerge from their eggs and bore holes in plant leaves, a behavior that provides them with food and protection from predators. After about two weeks, the larvae drop on the ground and enter the soil, where they overwinter as pupae.
For the most part, leaf miner damage is cosmetic; though your melons might not appear quite as robust and green, their growth and production won't be seriously limited. In the case of extremely severe infestations, leaf miner tunnels can limit plants' ability to perform photosynthesis and stunt growth, but such outbreaks are rare in home gardens (I certainly have never seen a garden with that problem). In conventional agriculture, leaf miner damage is of greatest concern to spinach and swiss chard farmers, who have difficulty selling greens with such damage.
Given the limited nature of leaf miner damage, Farmscape does not usually use organic pest control products on plants infested by leaf miner larvae; in severe cases we might prune affected leaves. Neem is commonly listed as an organic control for leaf miners, but it's a bit difficult to use because you must apply the spray while larvae are still inside the leaf. Given the speed of the leaf miner life cycle, the likelihood of catching such a pest in the act is low. If you do catch a leaf miner inside a leaf, you can simply pinch the larvae between your fingers to control it in such circumstances.
In organic gardening, prevention is often more effective than treatment, and leaf miners are no exception. Because leaf miner pupae overwinter in the soil, the maintenance of diverse soil microbial activity can prevent leaf miner outbreaks, because beneficial nematodes in the soil feed upon insect larvae and pupae. Interestingly, avoiding the use of broad spectrum chemical pesticides can also help keep leaf miner fly populations in check, because such pesticides kill parasitic wasps that can decimate larvae populations.
While leaf miner damage may be unsightly, worrying about how a couple leaves look can distract you from your most important mission: enjoying your harvest.
Leaf miner damage image from Eran Finkle, "Leaf Miner tunnel," June 21, 2010 via Flickr, Creative Commons.
Leaf miner fly image from Whitney Cranshaw, Colorado State University, Bugwood.org, "Spinach Leafminer," June 21, 2010 via Forestry Images, Creative Commons.
Note: this article is set to appear in the upcoming issue of our newsletter, Bountiful Harvest. If you like what you read here, you should subscribe to our newsletter by clicking the "Quick Contact" link on the top right above.
It's summertime in Los Angeles. Summer gardens mean squash and melon plants. Unfortunately, squash and melon plants mean leaf miners arrive as pests, leaving behind their signature squiggly white lines on cucurbit leaves.
The term "leaf miner" can refer to any number of species of insects, particularly flies and moths, that lay eggs on plant foliage. Leaf miner flies are particularly active during the hot weather of the summer, and the giant leaves of squash and melon plants are attractive targets in southern California gardens. About two days after they are laid, larvae emerge from their eggs and bore holes in plant leaves, a behavior that provides them with food and protection from predators. After about two weeks, the larvae drop on the ground and enter the soil, where they overwinter as pupae.
For the most part, leaf miner damage is cosmetic; though your melons might not appear quite as robust and green, their growth and production won't be seriously limited. In the case of extremely severe infestations, leaf miner tunnels can limit plants' ability to perform photosynthesis and stunt growth, but such outbreaks are rare in home gardens (I certainly have never seen a garden with that problem). In conventional agriculture, leaf miner damage is of greatest concern to spinach and swiss chard farmers, who have difficulty selling greens with such damage.
Given the limited nature of leaf miner damage, Farmscape does not usually use organic pest control products on plants infested by leaf miner larvae; in severe cases we might prune affected leaves. Neem is commonly listed as an organic control for leaf miners, but it's a bit difficult to use because you must apply the spray while larvae are still inside the leaf. Given the speed of the leaf miner life cycle, the likelihood of catching such a pest in the act is low. If you do catch a leaf miner inside a leaf, you can simply pinch the larvae between your fingers to control it in such circumstances.
In organic gardening, prevention is often more effective than treatment, and leaf miners are no exception. Because leaf miner pupae overwinter in the soil, the maintenance of diverse soil microbial activity can prevent leaf miner outbreaks, because beneficial nematodes in the soil feed upon insect larvae and pupae. Interestingly, avoiding the use of broad spectrum chemical pesticides can also help keep leaf miner fly populations in check, because such pesticides kill parasitic wasps that can decimate larvae populations.
While leaf miner damage may be unsightly, worrying about how a couple leaves look can distract you from your most important mission: enjoying your harvest.
Leaf miner damage image from Eran Finkle, "Leaf Miner tunnel," June 21, 2010 via Flickr, Creative Commons.
Leaf miner fly image from Whitney Cranshaw, Colorado State University, Bugwood.org, "Spinach Leafminer," June 21, 2010 via Forestry Images, Creative Commons.
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