10 June 2011

The Colorado Potato Beetle


Colorado Potato Beetle

The farmers of New England should bear in mind that an enemy to the potato crop, more destructive and more too be dreaded than the fatal disease with which they are already familiar, is gradually, but surely approaching from the west. This insect, the ten-lined Doryphora, was first discovered in the Rocky Mountains, upon the wild species of the potato, and has worked its way eastward on the advance of civilization towards the west, till it has nearly overrun the Western States, and gained a foothold in some points of Western New York and Pennsylvania, making a progress on an average of about sixty miles a year.

In the season of 1871 the falling off of the potato crop in the west as compared with the previous year was estimated as fully twenty percent in consequence of the ravages of this destructive beetle. In some states it was much more than that, being, in Illinois, thirty-five percent, in Michigan, thirty-four percent, and so on.

In 1870, the northern column of this great army of invasion reached the borders of Canada, and gained a foothold some distance inland. In the spring of 1871, the beetles literally swarmed across the Detroit River, and crossed Lake Erie on ships, on boards, on chips, and shingles, or whatever else would afford them a passage, and in the course of the year they invaded the whole country between the St. Clair and the Niagara Rivers, and the islands in the western part of Lake Erie. 

They have not yet reached new England, probably, though reports were circulated last year that they had been observed in some points in Western Massachusetts, on the borders of New York. This was doubtless the Trilineata, an allied species, but an old, and comparatively harmless enemy, that was mistaken for the genuine Colorado beetle, as it was the year previous, when found in several parts of Worcester county, where it gave rise to the report that we had at last been reached by that greatest of all potato destroyers.

The ravages of this beetle are very complete. It destroys the vines, attacking them soon after they appear above the surface of the ground. The mature beetle lays its eggs, from seven hundred to twelve hundred in number, on the young leaves of the potato, attaching them at the end to the under side of the leaf in clusters. The larvae hatch out in a few days, and feed on the leaves fifteen to twenty days, when the burrow in the earth, and change into pupae, in which state they remain ten to twelve days, when they emerge as full-grown beetles, to lay more eggs for a second generation. There are three broods annually, the last remaining in the ground all winter, to come out as perfect beetles when the spring opens, and the potato comes up to supply the food and the place to deposit its eggs. 

As all its transformations occupy less than fifty days, it has been estimated that a single pair, allowed to increase unmolested, will produce over sixty millions in a single season.

Though this destructive insect spreads, it does not leave a district where it has once gained a foothold. So far as now known, it holds the ground which it has once gained in spite of all efforts to eradicate it. When it first appears in a new district, if every farmer would unite in the work, and pick it by hand, it could, perhaps, be kept down for a time. Paris green appears to be the only effective remedy, but many pieces have been kept clear by persistent and laborious hand picking.


Colorado Potato beetle Eggs (photo link)

Feeding Larvae of the Colorado Potato Beetle

Anyone who has ever grown potatoes is familiar with this wicked little pest, but did you know the history of where it came from and how it became established throughout the United States? Now you do.

The "fatal disease" mentioned at the beginning of this excerpt, that the farmers of New England were so familiar with, was the potato blight that hit Ireland beginning in 1845. In Ireland, it was known as The Great Famine. Approximately one million people died as a result between 1845 and 1852. Another million people fled Ireland, many of them settling in New England.

Please note that this beetle was separated from the eastern parts of America by the vast prairies of the west. Only when pioneer farmers plowed up the prairies and planted potatoes did the beetle find favorable conditions for moving eastward.

The excerpt mentions Paris Green. This chemical insecticide was one of the first to be used by American farmers. I'll have more to say about it in an upcoming excerpt here.
Personally, I deal with Colorado potato beetles by "persistent and laborious hand picking." But I only have a few rows of potatoes in my garden to care for. Every day (sometimes twice a day) I go down the row crushing beetles and smearing their clusters of orange eggs. For the family-scale gardener, hand picking works just fine.


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1 comment:

W said...

Spinosad, a bacteria (listed as an organic OMRI-A pesticide) first discovered by a vacationing soil scientist in the earth near a deserted rum factory in the Caribbean
is remarkably effective at killing the little devils. It is marketed under a few different names, both as a powder, a liquid concentrate and ready to use liquid.
We spray a few times per season, and they die within hours. Be careful in its use though, for it also can affect bees. Read the label...but it sure beats picking and squashing the little buggers for hours and hours!