What’s Bugging You? Colorado Potato Beetle

The Colorado Potato Beetle ( Leptinotarsa decemlineata) is a wylie pesticide resistant bug that emerges from the ground during late May to early June.

If you have ever grown potatoes, you will be familiar with the Colorado Potato Beetle.  If you have not encountered this voracious potato leaf snacker consider yourself lucky; but do read on.  As the old saying goes “an ounce of prevention is worth a pound of cure”! 

The Colorado Potato Beetle ( Leptinotarsa decemlineata) is a wylie pesticide resistant bug that emerges from the ground during late May to early June. They have been sleeping over the winter in grassy areas near your potato patch or in an area where you have grown potatoes the previous year. I think it is worthwhile to mention here that they also like tomatoes, eggplant, peppers,  petunias and nicotiana.

The adults are a rather impressive looking beetle and once out and about in your garden will wander the potato patch looking for potato plants and a mate.  In mid June to early/mid July females will each lay up to 500 yellow-orange eggs in groups on the undersides of the leaves.  Ladybug egg masses are similar in color but much smaller eggs.  

Larvae will hatch in approximately 9 days.  The hatched eggs will progress through 4 larval stages, from very tiny up to ½ inch long after the last molt. The larvae are voracious potato leaf eaters and along with the adults can quickly decimate a potato crop.   They have orange-red bodies with black legs and heads wtih two lines of black dots on either side of their body.    The larval stage lasts 14-21 days.  In the last stage they will burrow into the ground and pupate into an adult in 7-14 days.  The new adults will prepare for winter by feeding and then will burrow into the ground to wait out winters extreme cold.  Fortunately, in Saskatchewan there is only one generation of Colorado Potato Beetle a year.

As previously noted, Colorado Potato Beetles have built up an immunity to most pesticides.  Chemicals are never safe to use on plants we eat and will also kill the good bugs.  This is where becoming proactive and taking some preventative measures really is the best way to get rid of these bugs.

Photo: Colorado Potato Beetle Larvae ( Pixabay)

If you have the luxury of space, rotate your potato crop yearly. 

A two- three inch layer of straw mulch actually confuses the newly emerged adults in spring and they wander aimlessly through the straw until they starve. 

Check your new potato plants for adults and egg masses every two to three days in the early morning. Throw them into a bucket of hot soapy water to kill them.  Make this an educational and fun job for the kids as well!

Other control and kill methods include nematodes, diatomaceous earth and BT (Bacillus thuringiensis) BT should only be used on the first and second larval stages – it will not kill the older larvae or the adults.  All are nontoxic to humans and animals. 

Lastly if you are growing potatoes in the same spot every year, rototill the area in late fall.  This will expose the burrowing beetle to winter’s freezing temperatures. 

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