Potato moth: how to fight it (photo)

Diseases and pests

The potato moth (Phthorimaea operculella Zell), better known as the potato moth, is a destructive insect that can ruin an entire potato crop. To combat this pest, it's important not only to know how to combat it but also to implement timely control measures and preventative measures, both before and after the potatoes are planted.

The absence of natural enemies allowed it to reproduce unhindered, and its narrow specialization (Fthorimea prefers potatoes, tobacco, and wild nightshades) made it a real scourge for both gardeners and those involved in the transportation, storage, and retail of this sought-after vegetable. Potato exports from the Americas, where the crop is grown in central regions, led to the pest, originally thought to originate in Africa, spreading throughout virtually the entire world.

For the potato moth to thrive and reproduce rapidly, it requires a geographic range with an average annual soil temperature of 100°C and the presence of nightshade crops. The southern regions of the Russian Federation and the countries of Central Asia are the predominant distribution zone for this voracious pest.

Methods and techniques for combating it are being sought not only in America, where farmers and the government are expending considerable physical and material resources to save entire fields infested with Phthorimea. Crop growers in many countries are developing measures to combat this pest, which can cause damage comparable to the Colorado potato beetle in fields and gardens. Preventative measures taken in advance to prevent the emergence of pest populations help ensure the safety of harvests stored in warehouses. Without the necessary chemical control, the moth can render tons of finished products unfit for consumption.

Appearance and dimensions

The photo clearly shows that the potato moth, unlike the Colorado potato beetle, is equipped by nature with camouflage:

flattening of the body;
inconspicuous grayish-brown color;
a smooth transition of halftones of the body from pale brown on the body to gray-brown with yellowish scales on a pair of wings;
wings with a span of 14 to 16 mm, which fold and make the insect relatively small (6-8 mm when at rest);
uneven, fuzzy-terry edges of the wings;
with long, thin antennae.

Please note: The ability to mimicry, which Phthorimea acquired in its original habitats, from which it began to spread, has also come in handy in its new areas of settlement: they are as similar in color as possible to the halftones of the soil and sand.

Its distinctive features, compared to the brightly colored Colorado potato beetle, include camouflage and the ability to remain unnoticed. The Colorado potato beetle's bright coloration serves as a warning to natural enemies, highlighting the insect's unique characteristics and its unsuitability as food. The potato moth, a broad-winged butterfly in its adult stage, is a target for many birds and insectivorous predators. Its main threat to crops is its ability to reproduce rapidly. It cannot feed because its mouthparts are reduced, and its lifespan ranges from three days to two weeks.

For reference: Each female lays 150-200 eggs and is active both day and night during the summer. They are able to reproduce year-round in warehouses because the temperature there is just right for reproduction and egg laying.

Such fecundity is beneficial for the insect, which maintains its population despite external enemies. However, it also poses a danger to those who grow nightshade crops, particularly tobacco and potatoes. The potato moth, in terms of danger and damage potential, is on par with the Colorado potato beetle, and tens of thousands of people are searching for treatments and technologies, conducting scientific research to discover how to combat it with maximum effectiveness.

Important: The main danger is missing the adult butterfly, which hatches from a chrysalis hidden in a secluded spot, ready to lay hundreds of potential caterpillar eggs. Once hatched, it is ready to mate.

Stages of development and lifestyle

In late April and early May, the potato moth begins its mass flight in the wild. Adults hatch from pupae that have overwintered in suitable locations and become active when the air reaches a certain temperature. Enhanced control measures during storage are necessary because the stable temperature maintained in industrial warehouses using special equipment not only ensures the preservation of potatoes but also the possibility for year-round reproduction of the pest. Caterpillars, which hatch from the moth's eggs, pose a particular threat.

The butterfly itself does not feed on the potato, but merely carries a future threat in the form of a clutch of eggs. The hatched caterpillars are incredibly voracious. They enter the potato tuber through the eye, creating winding, black tunnels in its flesh, reminiscent of intricate labyrinths.

The caterpillar fills the tunnels it makes with secretions and webbing, but its negative impact doesn't end there. An experienced gardener can identify a potato moth infestation by several signs:

perforated, gnawed leaves, on which the passages made are clearly visible, and small bulges filled with caterpillar excrement;
cobwebs and small cells on the inside of the leaf;
withered or dried bush tops on which no flowers appear.

Fact: The potato moth causes colossal damage to vegetable crops. Damaged leaves and stems are unable to photosynthesize sufficiently to support fruit set and tuber development. Potatoes burrowed and excreted by the pest become unfit for consumption. Before harvesting time, approximately 80% of the resulting crop will already be destroyed.

Caterpillars are colored according to the food they consume. They can be green if they feed on leaves and stems, or translucent-whitish when feeding on the flesh of the tuber. The larva (or caterpillar) goes through four molts, sometimes called instars, during which time it intensively consumes the crop it has chosen to attack. After the potato harvest, the moth can switch to other food sources, such as wild nightshade crops or other cultivated species.

Interesting: After molting, it pupates and matures in a cocoon until it emerges again as a butterfly. The natural cycle of reproduction begins anew, and it goes through its stages again: butterfly (moth), ovipositor, caterpillar (larva), pupa.

Control measures for plantings and storage, prevention in the garden

Pest control is systematic and consistent throughout the season, beginning with planting. Only healthy, properly inspected and treated potato tubers are selected for planting. To prevent larvae from overwintering in the soil and reappearing in the spring, infected tops and roots are destroyed rather than discarded in a compost pit. Sprinkler irrigation kills most egg-laying moths. Planting the seed at a depth of 15 cm and double hilling prevent caterpillars from penetrating the tubers.

Advice: Systematic and regular weed control will deprive the potato moth of food when the tops dry out. Weeds not only provide a haven for this dangerous pest but also weaken potato crops.

Early-ripening potato varieties are least susceptible to pests, a fact that small-plot owners successfully exploit. In commercial cultivation, mid-season varieties are treated with insecticides, with Danadim, Bi-58, Ditox, Di-68, and Rogos-S considered the most effective. Warehouses are disinfected, including containers, and low temperatures and humidity are maintained, slowing the moth's development cycle to 150 days.

If signs of infestation are detected, fumigators and insecticides are used. Early control and preventative measures will help prevent pest infestations and ensure a healthy harvest.