Almost overnight, they’ve attacked our Yukon Gold potatoes, but thankfully they haven’t found the Purple Viking potatoes, peppers, eggplants, or tomatoes. Every gardener growing potatoes is likely to run into this beetle, as it’s a devastating pest of potatoes. Both the yellow, black-striped adult and the black-spotted, red larvae feed on potato leaves, and can completely consume them thereby greatly reducing tuber yields and even killing plants. The potato beetle can also be a serious pest on tomato, eggplant, and pepper; and the damage is so severe, the beetle must be controlled.
Adult potato beetles overwinter in the soil and emerge in late spring as temperatures rise. They establish themselves on early or volunteer plants, mate, and the females lay orange-yellow eggs on the underside of the leaves. They lay the eggs in bunches of about two dozen, but can lay up to 500 eggs over a month. Eggs hatch in approximately a week, and the larvae begin to feed on the potato foliage. Because they’re laid in bunches, the larvae tend to be found in clumps, and the damage they do can be quick and severe. The larval stage lasts approximately two weeks, and then they burrow in the ground to pupate. In about another week, the adult beetles emerge, and the process starts all over. Depending on where you live, there are typically two to three generations of beetles per year.
Organic Methods of Control
A variety of strategies are generally necessary to control potato beetles, particularly if organic control is desired. Crop rotation is recommended (see Crop Rotation), but it just generally delays the first beetle attack. Mulching with straw has also been shown to reduce the beetle’s ability to locate potato plantings, and it creates an environment favorable to potato beetle predators. Since we use the “lazy bed” potato method for growing potatoes, we definitely mulch. Another reliable organic strategy is to rotate the potato bed (so the overwintering beetles don’t emerge into the potato bed), and use floating row covers to prevent the beetles from reaching the plants. Hand picking and destruction of beetles is also practical for small potato patches.
Rotenone can be used, but it is quite toxic so should be used with caution. Bt is effective if the beetles ingest it early in the larval stage. Therefore, Bt must be applied when larvae are first seen, and repeated frequently to assure later hatching larvae ingest the Bt.
Potato Varieties to Consider There are genetically modified potato varieties that commercial growers are using, but I wouldn’t even consider using them. Instead, there are several varieties of potatoes that mature in just 75 – 88 days, and can develop tubers before potato beetles become serious pests. These varieties include Norland, Redsen, Sunrise, Superior, Caribe, Pungo, and Yukon Gold. Since we live in Northern Ohio, where the beetles emerge later because of cooler temperatures, using one of these varieties may be a good strategy. The beetles found and attacked the Yukon Gold patch first, so we’ll see how well that strategy worked for us.