Many potato diseases are difficult to treat, making prevention the key. Hilling the soil around plants, crop rotation and clearing away night-shade plant debris are among the many strategies available for minimizing disease risks.
Fungus issues to consider in cool wet climates include black scurf (Rhizoctonia solani) which causes leaf lesions and stem cankers with firm tissue; and late blight, which produces dark-brown spots on leaves and corky bumps on tubers, leading to dark-blotched foliage and corky bumps on tubers if left unchecked; in both instances use antifungicides if required.
Aphids
Aphids are an increasingly prevalent threat to potato crops. Feeding on young leaves, they can weaken and stunt growth as well as spread plant diseases like Potato Leafroll Virus (PLRV). Afflicted plants produce small, misshapen tubers unsuitable for sale due to this virus as well as experiencing phloem net necrosis– a brown discoloration inside of tuber that reduces quality – further diminishing quality and quality levels overall. Although PLRV can also spread by Green Peach Aphids as well, potato aphids tend to be more harmful.
Potato aphids can be either winged or wingless and spread more than 40 plant viruses. They tend to congregate on the lower third of potato leaves when sampling; be mindful to observe whether wingless or winged aphids appear; this will indicate their status and population size; because these insects feed off various sources, regular monitoring is vitally important.
Utilize multiple approaches to prevent and control aphids. Spraying insecticides can be effective; however, this approach could disrupt natural enemies like lady beetles and lacewing larvae, so when possible it would be prudent to use alternative products such as horticultural oils, insecticidal soaps, and neem seed extracts instead of spraying insecticides directly.
Crop rotation and bed coverage are essential in managing aphid populations. Checking and replacing straw as necessary ensures a comfortable, well-covered bed that protects from disease caused by rot and prevents potatoes from sprouting prematurely. It is also wise to establish and implement an effective weed management program as these may compete with aphids for water and nutrients.
Leaf Roll
Potato Leaf Roll Virus (PLRV) infection produces stunted, erect foliage with stiff leathery texture that often rolls upward at its edges. PLRV affects potato plants as well as nightshade family plants like pepper, tobacco, tomato and eggplant and leads to necrotic netting on tuber vascular tissue of tubers.
PLRV infection can be difficult to prevent or control; however, effective ways of reducing its incidence include early planting with certified seed potatoes, garden sanitation and the removal of volunteer tubers before planting can reduce its occurrence significantly. Aphids serve as the main vectors for PLRV transmission – green peach aphids typically pick up and carry it throughout their lives, becoming infected at long distances exceeding 100 feet.
Aphicides such as pyrethrins and methyl ethyl parathion are an excellent way to manage aphids effectively, particularly during the spring when their numbers increase dramatically. When applying insecticides with this wide spread pattern sprayer ensure that all plant parts are covered, including interior foliage as well as ground surfaces.
Sulfur can be added to topsoil to slightly acidify it, which will help lessen the severity of many diseases like Fusarium and Verticillium wilt. Weed control should also be kept to a minimum while potato plants are growing, since competing weeds compete for water and nutrients that could otherwise go towards harvesting potatoes. Regular hoeing or raking with hoe or rake rather than cultivation with tiller will prevent tubers or roots being pulled up accidentally and polluting soil contamination.
Verticillium Wilt
Verticillium Wilt can cause significant crop losses in potato and other nightshade family plants (tomatoes, peppers, tomatillos and eggplant). Its symptoms include the leaves wilting or fading away along with discolored vascular tissue; verticillium wilt fungus may restrict water flow into plants which stunt their growth reducing yield significantly. Verticillium Wilt symptoms can be difficult to spot; if foliage shows brown discoloration with rapid wilting it could indicate presence of verticillium Wilt.
Fumigation with metam sodium can be effective at eliminating soilborne inoculum of V. dahliae and should be done prior to planting higher value crops such as potatoes. Fields can be treated with herbicide or fungicide sprayings or rotated with other crops in order to decrease inoculum build-up in soil, while decreasing frequency of potato planting can reduce disease severity while rotation with non-host crops reduces both nutrient depletion and disease pressure in soil.
Hilling your potatoes – piling soil around each plant to keep its tubers submerged during growth – is one way to help combat verticillium wilt in your crop. Simply pile several inches of dirt or mulch at the base of each plant until all but the top few rows of leaves have been covered by soil, then check on them periodically during their season for signs that the tubers remain buried under soil.
Watering too frequently after harvest could result in rot. Instead, try watering deeply once every week to maintain even moisture levels in the plant’s root zone and keep its leaves uniformly moist.
Beetles
Colorado potato beetles (Leptinotarsa decemlineata) not only feed upon potatoes but can also wreak havoc with other members of the nightshade family, such as tomatoes and eggplants. Adult beetles emerge each spring to lay eggs on leaves before larvae feed beneath the leaf surfaces and rapidly increase in size before pupating 10 days later – an individual female beetle may lay 500+ eggs during just one growing season! Two generations may occur within one growing season.
Potato beetle infestation can be difficult to prevent without chemical pesticides, so commercial growers have developed various strategies for mitigating it, including planting non-host plants in the area as trap crops; this practice has been shown to increase tomato yields by 61-68%! Alternatively, planting a cover crop of corn may disorient or confuse beetles and prevent an infestation occurring immediately.
Mulching with 2 to 3 inches of clean straw or hay mulch is an effective method for protecting potatoes against beetles, while deterring and repelling other common garden pests such as beetles. Additionally, this barrier acts to deter and repel many other garden pests as well.
One natural way of dealing with beetles is introducing beneficial insects into the garden. Ladybugs, spined soldier bugs and lacewings all feed off of egg masses and larvae left by beetles in your soil; adding nematodes that attack immature beetles could also prove effective.
If these tactics fail to control Colorado potato beetles effectively, spraying with pyrethroid insecticide is another option. Select products with high selectivity for Colorado potato beetles while not being harmful to mammals such as cyfluthrin, permethrin or esfenvalerate are suitable; should the beetles develop resistance, organic insecticides such as Btt (Bacillus thuringiensis tenebrionis) may provide some control – please keep in mind that managing pests successfully will require multiple steps and frequent applications over time.
Cutworms
Cutworms, moth larvae of various moth species that feed along the ground by cutting off seedlings and stems before burrowing down into roots, tubers and fruit to feed, are an ongoing threat to most vegetable crops, particularly potatoes. When present they have the power of wiping out up to 75% of your crop!
Protecting and controlling cutworms will help ensure a healthy harvest. Their larvae overwinter as eggs in the soil or garden debris and once temperatures warm up in spring they hatch and begin feeding at night while remaining hidden during the daytime hours. After several molts they eventually pupate in the soil when fully grown – producing one to five generations of moths every year.
Protect delicate transplants from cutworms by placing collars made of tin cans or cardboard (cutting slits in toilet paper rolls and extending them two inches out of the soil will also work), into the soil around their bases; this provides protection from caterpillars reaching stems; another effective strategy is inserting sticks or coffee stirrers into the ground around each plant so cutworms cannot wrap themselves around these objects.
Hilling — regularly layering layers of soil or mulch around potato plants during growth — helps prevent cutworm damage to tubers by keeping them underground throughout their growing season. To make sure this happens without damaging their flavor and making them unsuitable for consumption by sunlight-sensitive organisms like cutworms. It’s essential that tubers remain covered and not exposed to direct sunlight, which could turn them green and inedible.
Biological controls such as parasitic wasps and tachnid flies can help combat cutworm infestation, while deep tillage in late summer or early fall also helps decrease the amount of eggs laid by cutworms on soil surfaces.
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