Pest Patrol: Potato Beetles

I think everyone has heard of the potato beetle! These striped beetles are pretty well known and a nusiance to all who have dealt with them. There are two types of potato beetles: the Colorado potato beetle (Leptinotarsa decemlineata) and the three lined potato beetle (Lema daturaphilia). We've actually had both of them in our garden! 

So what are the differences between these two beetles? For the most part, the Colorado beetle is more common. This beetle is larger than the three striped beetle. It is also easily differentiated by the fact that it has ten thin stripes as opposed to the three on the three striped potato beetle. Both beetles feed on the entire nightshade or solanaceae family, which includes potatoes, tomatoes, eggplant, tomatillos as well as others. Both overwinter as adults, emerging in spring to lay their eggs on suitable plants. Both also lay clusters of orange eggs, usually on the underside of a plant leaf. In warmer areas, multiple generations can be hatched out during the growing season, but further north only 1-2 generations will be hatched. After hatching, they move from the plant leaves to the soil to mature. 

How can you prevent potato beetles? If you have had problems with them in the past, you can apply a lightweight floating row cover over your plants until harvest time. This creates a barrier between the beetles and your plants! It's surprising that such a little thing as a row cover can deter them so much! Mulching around your plants also helps prevent them, because the mulch confuses the beetles and makes it difficult for them to find your plants. The mulch also is a favorable habitat to many good garden bugs which are natural predators to potato beetles. Using natural organic matter to fertilize your soil (aged manure) has been shown to also lower the number of potato beetles when compared to commercial fertilizers. 

Another preventative measure involves planting a trap crop. Plant a few plants out earlier than the rest, in a far corner of the garden. Wait for the beetles to settle in and lay their eggs, and then pull up the trap crop, immediately placing them into sealed trash bags. Leaving these bags out in the sun to bake for a few days will kill the beetles and their freshly laid eggs on the trap crop. This prevents them from attacking your main crop and hatching out another generation for further feasting. 

What else can you do later on in the season? Handpicking potato beetles is surprisingly effective! Grab your gloves and a bucket of soapy water. As you see the beetles, pluck them off the leaves and toss them into the bucket! Don't forget to check the undersides of the leaves for any clusters of their orange eggs. Additionally, growing healthy & hardy plants is very helpful. Even if you cannot keep them completely at bay, strong plants will tolerate light damage from potato beetles. 

Even in organic gardening, there are organic pesticides that can be applied. Although most tend to use them as a last resort for serious infestations, as they are still a pesticide. Some well known for their use on potato beetles are neem oil and insecticidal soap. Personally, we have found potato beetles manageable without the use of any pesticides, organic or not. 

Helpful Products:

 


Click the photo for more information. The neem oil & insecticidal soap above are both OMRI certified.

Pest Patrol Series:

Observation, Prevention, & Handpicking 

Slimy Slugs

Potato Beetles