Garden Word of the Day
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Cousin to aphids and leafhoppers, potato psyllids can be a real pain, and not just for potatoes.
Potato psyllids (Bactericera cockerelli) are disease-carrying, life-sucking plant lice. These invasive pests also feed on tomatoes and other members of the nightshade family, along with several other garden plants.
Potato psyllid description
Potato psyllids are tiny. When I say tiny, I mean that an adult potato psyllid could stretch out comfortably across the edge of an American nickel, without dangling. If you get close enough, preferably with a hand lens or magnifying glass, you would see that they look like miniature cicadas. Potato psyllid adults are black, with a white band across the first abdominal segment and an inverted “V” on the final segment. They have clear wings that are held roof-like over the body when not flying or jumping. [They jump a lot.]
Potato psyllid lifecycle
Potato psyllids start out as eggs. Each female lays approximately 200 eggs, each of which hatches in 6 to 10 days. Those eggs look like microscopic footballs held to the underside of leaves with short stalks. [Do not mistake those short-stalked eggs to the longer stalked, beneficial lacewing eggs.]
After those eggs hatch into green, fringed nymphs, they look more like whiteflies or soft scale insects. Then, they go through five developmental stages, also known as molts or instars. Under ideal conditions, all that growing can be completed in less than two weeks.
Damage caused by potato psyllids
If sucking nutrient rich plant fluids wasn’t problem enough, potato psyllids cause other problems, too. For one thing, as nymphs feed, they release a toxin that can kill young transplants. This toxin also causes upward curling of leaflets closest to the stem on the upper portions of the plant. This condition is known as “psyllid yellows” or “vein greening”. The characteristic yellowing usually starts along leaf margins and then moves inward, turning purple in some cases. As this condition worsens, nodes [bumps where leaves emerge] become enlarged and closer together, rosetted clusters of leaves emerge from axillary (or lateral) buds, and aerial tubers begin to form. Aerial tubers grow at the end of aboveground stems, as opposed to underground stems, the way proper potatoes grow. When this pest feeds on tomato plants, it can cause no fruit production or overproduction of poor quality fruits.
Eventually, the once green, bushy potato plant looks more like a pitiful yellow Christmas tree. [If chlorosis is spotty and leaf rosetting is not present, the problem is more likely to be calico virus.] If potato psyllids are removed from the plant, the condition will stop progressing.
Potato psyllids are also carriers of another condition, known as zebra chip. Zebra chip is a bacterial disease that causes potatoes to store sugar, rather than starch. That might sound like a great idea for a new dessert food, but the presence of sugars cause ugly brown lines across the length of the potato. When cooked, these brown lines turn black, hence the name. This condition reduces crop size by 20 to 50%. Healthy appearing potatoes from plants affected by zebra chip are more likely to sprout while in storage.
Managing potato psyllids
You can’t control potato psyllids if you don’t know where they are. The first step to managing potato psyllids is to use yellow sticky traps. You can buy these at any garden center, or you can make your own with some yellow paperboard and sticky barrier goo. You should also inspect the undersides of leaves, looking for nymphs. While you’re at it, you should probably check the underside of any nearby bean or pepper plants, as these may also become infested.
In commercially grown potato fields, where potato psyllid is known to occur, a type of systemic neonicotinoid neurotoxin, called imidacloprid, is applied. [While not yet noted in California, resistance to imidacloprid has been documented in Texas.] Organic growers, like myself, use spinosad.
Because potato psyllids are not native to California, our local team of predators, which include lady beetles, lacewing larvae, and minute pirate bugs, have not been very effective at controlling this pest. Not yet, anyway.
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