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Chestnut pests

Chestnut moth miner

Cameraria ohridella Deschke et Dimić

This type of pest was discovered in Ohrid, Macedonia and spread rapidly throughout the Balkans and many parts of Central Europe. In Croatia, it was recorded for the first time in Zagreb in 1989. It prefers to feed on the leaves of horse chestnut (Aesculus hippocastanum L.) and trees with white flowers.

The pest attacks

  • Leafs

Description of the pest

An adult butterfly grows up to 5 mm. The chest is golden ocher, and the rump is dark gray. The front wings are shiny, light brown in color with 3 thin, transverse silver-white stripes bordered by a black border. The back wings are dark gray with long tassels. Its wingspan is from 6 to 8 mm.

The eggs are dirty green in color, oval in shape and 0.2 to 0.3 mm long.

The caterpillar has a dorso-ventrally flattened yellowish-green body. It is very article-like. It grows up to 6 mm.

The pupa is 4.5 to 5 mm long, red-brown in color and cylindrical in shape.

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Biology and life cycle of pests

  • Overwinters as a caterpillar or pupa in fallen leaves. Butterflies emerge from the pupae in the spring (May), usually during the flowering of chestnuts, which copulate after a few days of flight. One female lays 20 to 40 eggs individually on the face of a leaf. Females of the first generation lay their eggs on the leaves of the lower third of the horse chestnut crown. After 2 to 3 weeks, they will develop into a caterpillar that burrows into the leaves. There they feed and go through 4 to 5 mining and 2 feeding development stages. After 4 weeks, the caterpillar pupates in the mine, and two weeks later the adult butterflies of the next generation appear. Then the described life cycle repeats itself. In years of strong attacks, when the leaves are completely destroyed by the colonies of this pest in autumn, there is a high mortality of the caterpillars due to lack of food and space, so the next year the attack is much smaller.
  • The species has 3 to 4 generations per year. In years with dry and warm weather, this pest can have up to 5 generations per year. In addition, it has been shown that the pupae are very resistant to low winter temperatures, so some studies record that they can survive temperatures as low as -23 °C, which allows the population to increase after cold winters.

Damage caused by a pest

  • The caterpillar feeds and develops inside the leaf, making, in the process, between two epidermal layers, first a round mine, and when it spreads to the first transverse vein, the mine becomes angular, bounded by veins. Usually, there is only one caterpillar in one mine, but a stronger attack can also occur. to the mutual joining of individual mines into one common one, so that it appears that there are several caterpillars inside one mine.

Protection against chestnut miner moth

  • Protection consists of hygienic measures that reduce infection, namely the thorough collection and destruction of fallen leaves in autumn. Collecting and destroying fallen leaves earlier in the fall leads to greater success, as some of the pupae eventually fall out of the fallen leaves onto the ground. This method requires a lot of time, but for now there is no alternative. This measure must be supplemented by the application of toxicologically and ecotoxicologically favorable insecticides, such as the growth regulator diflubenzuron, at the time of the appearance of the first butterflies in the spring. For the success of the spring application of the development regulator, it is most important to treat the lower third of the canopy with quality, where the butterflies of the overwintering generation mainly lay their eggs. It sometimes has to be repeated in about 15 days.
  • Wild chestnut protection is usually carried out by foliar or endotherapeutic application of insecticides. The main limiting factor in the use of insecticides in cities is the risk of contamination of humans and pets.
  • Foliar treatment is carried out with sprinklers whose vertical reach is 6 to 10 m. It is based on treating the leaves with insecticides intended for the control of the chestnut miner moth. In doing so, insect growth regulators are usually used, which are low in toxicity for humans and pets, as well as beneficial insects. The main disadvantage of this method is the limited reach and the possibility of drifting of the applied insecticides.

This shortcoming is avoided by using endotherapeutic methods of plant protection based on the application of systemic insecticides that are translocated in the plant after application. Endoterpeutic methods include watering the soil in the root zone, injecting insecticide into the soil in the plant’s root zone, and directly injecting plant protection agents into the plant – under controlled external pressure or diffusely (gravitational force).

Chestnut bender

Cydia splendana Hb.

The pest attacks

  • Fruit.

Description of the pest

  • Adult forms grow from 13 to 18 mm. The front wings are trapezoidal in shape, ash gray in color and crossed with clear lines. In the back corner, it has a silvery point bordered by brown color and with 4 small black lines.
  • The larva grows from 12 to 16 mm, with a rather plump body. It is white or pink in color with the first segment of the thorax which is dark brown in color.
  • The cocoon is white, egg-shaped and 8 to 10 mm long.

Biology and life cycle of pests

  • 24 now after the female appears, she starts laying eggs. One female lays an average of 60 eggs. He also places them on the reverse, but especially on the face of the page. Embryonic development lasts 10 to 15 days.
  • The egg will develop into a caterpillar. Its development lasts 3 weeks. Young caterpillars move along the leaves and branches to the fruits where they burrow. When it develops, the caterpillar leaves the fruit, descends to the ground where it overwinters. They pupate at the beginning of summer, and adult butterflies appear in the second half of August.
  • It has one generation per year.

Damage caused by a pest

The caterpillar burrows into the fruit, the core of which it eats and fills with excrement. Attacked fruits are unusable due to “worminess”, and their presence reduces the quality of production and requires expensive fruit sorting.

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Chestnut tap

Curculio elephas Gyll.

The pest attacks

  • fruit

Description of the pest

  • Adult taps are 6 to 9 mm long. They are yellowish to grayish in color and their body is covered with thick hairs. The rillo is thin, strongly curved and, in females, as long as the body.
  • Larvae grow up to 15 mm, they have no legs. Their body is thick, curved, cream-white in color. They have a brown head.

Biology and life cycle of pests

  • Adult taps appear at the beginning of autumn. They are fed for a week. Then the females lay one or several eggs in the fruits. One female lays an average of 40 eggs. Egg development takes 35 to 40 days. The egg will develop into a larva. It burrows into the fruit where it will develop and feed for the next 35 to 40 days. After that, it comes out of the fruit and descends to the ground, where it is buried 7 to 8 mm deep. It overwinters there and pupates during the following summer.
  • It has one generation per year.

Damage caused by a pest

  • Attacked fruits fall off prematurely. It causes “worminess” of sweet chestnut fruits. Damage varies depending on the chestnut variety.
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