Main pests that attack potatoes

The potato Solanum tuberosum L.(Solanaceae) is characterized by being one of the most important sources of food in the world. In Brazil, it is the main vegetable crop, responsible for the largest cultivated area and food preference, with approximately 130 thousand hectares planted and a production of around three million tons, with an average productivity of around 20t/ha. Of the various producing states, Minas Gerais is characterized by being the largest in production, with approximately 30% of national production, followed by São Paulo (25%), Paraná (20%), Rio Grande do Sul (10%), Bahia (5%) and other producing states (10%).

Several factors contribute to potato productivity, however, the incidence of others causes opposite effects. This is the case of insect pests, which, in addition to causing damage associated with their habit and type of oral apparatus, are agents that disseminate pathogens, as they break the epidermis, exposing internal tissues to attack. In insects with chewing mouthparts (caterpillars and beetles) the damage is more evident, being generated by the jaws. For insects with sucking-biting mouthparts (aphids and bedbugs), the damage is less evident, with only necrotic spots being exposed.

 

main pests

Two classifications can be made regarding the incidence of insect pests: the first relates to insects that cause damage to the aerial part (indirect damage) and insects that cause damage to the root system (direct damage) (Figure 1). The second classification relates to the different phenological stages in cultivation and the respective incidence of pests. A summary of the main pests, the phase in which they are harmful, type of damage and respective control is presented in Table 1.

Moth

The moth [Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae)] attacks leaves and tubers, its characteristic is the opening of galleries, in addition to its damage (if present on the tuber) continuing after harvest. It is more frequent and abundant in crops grown in autumn. In certain regions of Brazil, during the harvest, it can cause total defoliation when not controlled in time.

Screwworm

The screwworm [Agrotis epsilon (Hufnagel) (Lepidoptera: Nuctuidae)], in large infestations, it even damages the tubers. First instar caterpillars begin their activities by scraping leaf tissue. They later migrate to the ground, where they bury themselves, only coming out at night to feed. At this stage, they section the stem, drastically affecting productivity.

The attack of the cutworm causes greater damage in small crops (less than two hectares), on the edge of capoeiras and mainly in areas with the occurrence of weeds such as weed and cow's tongue (Polygonaceae), main hosts of this caterpillar. When these plants bloom, the caterpillars abandon these hosts and start attacking cultivated plants. In areas where these plants occur, attacks are frequent and, if not controlled in time, they can sever stems, delaying crop development and reducing productivity. It is more common in spring crops.

Leafminer

The damage of the leafminer [Liriomyza huidobrensis (Diptera: Agromyzidae)] are caused by larvae that open mines inside the leaf parenchyma and feed on the tissues. They partially or completely destroy the leaf, causing it to dry out. In very intense attacks, it tends to harm the development of the culture. Leafminer damage reduces the photosynthetic area of ​​the plant and predisposes it to fungal diseases, in addition to reducing the weight and size of tubers.

The leafminer is more frequent in autumn, as it attacks several species of wild solanaceae and, at this time, there is generally a high local population, causing adults to migrate to cultivated areas looking for new plants for oviposition.

pinworm

The pinworm (larva)/kitty Diabrotica speciosa (Germar) (Coleoptera: Chrysomelidae)] is characterized by being one of the main pests of the crop. It is a polyphagous species, which damages the aerial part (adult) and tubers (larva). Adults do not cause significant damage, as they feed on leaflets. Larvae directly affect the product, reducing its commercial value.

The incidence of pinworm larvae is higher in spring crops. Females lay aggregates (up to 30 eggs) at the base of the stem, causing high infestation in roots and tubers. The presence of more than three galleries/tubercle (equivalent to three larvae with subsurface galleries 3cm to 4cm long) reduces the usable volume of the tubercle by more than 30%.

Aphids

Aphids [Macrosiphum euphorbiae (Thomas) and Myzuspersicae (Sulzer) (Hemiptera: Aphididae)] cause damage that is related to sap sucking, associated with the injection of “toxic” saliva (presence of viruses such as Y (PVY), mosaic A (light mosaic), leaf roll virus leaves or seed potato degeneration). However, direct losses only occur when the pest population is high. Chemical control is recommended when monitoring finds that around 10% of the plants examined are affected by aphids.

Potato kitty

The potato cow [Epicauta atomaria(Germar) (Coleoptera: Meloidae)] feeds on leaves, leaving only the veins. When the population is large, it can cause total defoliation.

The potato cow has only one annual generation, with adults emerging at the beginning of summer. As a consequence, attacks on potato crops occur in the autumn harvest. The incidence is localized, that is, the population of a place gets together and invades a field and defoliates everything in sight. It can remain for a few hours or last up to two days in the attacked area. Then, it migrates flying to another location. Due to this form of occurrence, monitoring of these pests in regions where they are frequent must be daily, because when the occurrence is confirmed, curative (chemical) control needs to be immediate.

Wireworm

The wire worm [Heteroderes spp. (Coleoptera: Elateridae)] feeds on roots and tubers. In the southern region of Brazil, species of the genus Heteroderes and in other regions those belonging to the genre are mentioned Conoderus.

These larvae open galleries in tubercles, two or three millimeters thick and up to five centimeters long. As they develop, they expel their excrement inside the galleries, which causes the tuber to rot. Attacks at the beginning of tuber formation can cause production losses of more than 50%. Its highest incidence has been observed in crops from the 2nd to 4th harvest, planted in the same location.

Corós

Potato cultivation in high-altitude soils (above 400m) in the states of Santa Catarina and Rio Grande do Sul has shown, in a sporadic and localized manner, the presence of corós or boletus insects attacking potato crops throughout the cycle. , especially in the first year's harvest on native or pasture land. The larvae (the only damaging phase) make holes up to 8mm in diameter in the tubers. The attacked tuber is not suitable for sale and is discarded during washing.

Table 1 - Pest, weed phase, type of damage and control of the main pests occurring in potato cultivation
Prague	Weedy phase	Type of damage	Control
Moth	Larva	Galleries in leaves and tubers.	Pulverization.
Screwworm	Larva	Section the plant stem. Pierces tubers.	Pulverization.
Leafminer	Larva	Gallery on the leaf, especially on the leaves closest to the ground.	Pulverization.
pinworm	Larva	Attacks roots and tubers.	Preventive. Tuber treatment.
aphid	Nymph/Adult	It sucks sap from leaves and buds.	Up to 10% of plants with Aphids.
Potato kitty	Adult	Defoliate	Pulverization.
Wireworm	Larva	Roots and tubers.	Preventive. Tuber treatment.
Corós	Larva	Roots and tubers.	Preventive. Tuber treatment.

Table 1 - Pest, weed phase, type of damage and control of the main pests occurring in potato cultivation

Prague

Weedy phase

Type of damage

Control

Moth

Larva

Galleries in leaves and tubers.

Pulverization.

Screwworm

Larva

Section the plant stem. Pierces tubers.

Pulverization.

Leafminer

Larva

Gallery on the leaf, especially on the leaves closest to the ground.

Pulverization.

pinworm

Larva

Attacks roots and tubers.

Preventive. Tuber treatment.

aphid

Nymph/Adult

It sucks sap from leaves and buds.

Up to 10% of plants with Aphids.

Potato kitty

Adult

Defoliate

Pulverization.

Wireworm

Larva

Roots and tubers.

Preventive. Tuber treatment.

Corós

Larva

Roots and tubers.

Preventive. Tuber treatment.

 

 Click here to read the article in issue 78 of Cultivar Hortaliças e Frutas.