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Agricultural entomology: Nocturnal harvest

Agricultural entomology: Nocturnal harvest


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Classification and host plants

Class: Insects
Order: Lepidoptera
Suborder: hetoneuri
Family: Nocturnes
Genus: Agrotis (= Scotia)
Species: A. segetum Den. et Schiff.

Bibliographic reference:
Phytopathology, agricultural entomology and applied biology” – M.Ferrari, E.Marcon, A.Menta; School edagricole - RCS Libri spa

Host plants: Chard, Corn, vegetables and others.

Identification and damage

Scotia segetum is a medium-sized butterfly (about 40 mm wingspan) with front wings varying in color from brown to brownish-gray; the livery also has dark patches, rounded and irregularly scattered on the wings.
The larvae, typically terricolous and about 40-45 mm long, are greyish and dotted with dark; they also often have darker longitudinal bands. The damage is determined by the larvae that are located below the surface of the ground, near the host plants.
The larvae cause initial erosions on the leaves of the young plants and, subsequently, attack the hypogean area, on which they cause erosions to the collar and to the root system in general, including the fleshy underground organs.
In arable crops, on young seedlings, attacks can cause serious failures, due to the destruction wrought by the larvae. In this case the attack becomes evident because the young seedlings collapse quickly and easily detach themselves from the root system that remains in the ground, due to the erosion of the collar.

Biological cycle

Scotia segetum survives the winter, in the ground, at the larval stage (mature larva), or as a chrysalis. In the spring, the wintering larval stages can resume their activity which is very short (with the exception of rare cases in which it overwinters as a young larva), and then becomes incriminated.
Adults flicker from late spring to early summer; flights generally start in April. These adults lay in the ground or on the basal parts of the host plants or the weeds adjacent to the fields.
The newborn larvae begin their activity on the young leaves, then descend into the rhizosphere where they cause the greatest damage.
These larvae mature in midsummer originating a 2nd generation; adults of this generation appear from late June to the end of July and beyond.
These adults oviposition and originate a second larval generation; this generation of larvae can:
- winter;
- originate a 3rd generation and sometimes even a 4th generation (very rare); these last generations close in autumn.
In some rare cases migrations can occur. Scotia segetum therefore makes 2-3 (rarely 4) generations per year.

Adult of Nottua of the harvest - Agrotis segetum Den. et Schiff. (photo www.scarboroughwildlife.org.uk)

Larva of Nottua of the harvest - Agrotis segetum Den. (photo www.hdc.org.uk)

Fight

The fight against Scotia segetum is chemical and follows the criteria of guided and integrated struggle; interventions must be performed, in a timely manner, on the larvae of about 2 cm.
The fighting technique involves monitoring which can be carried out both with traps and with direct surveys.

Use of sexual traps
Population monitoring with sex traps can be performed using both typical monitoring traps and massive (trapping) traps.
The traps are to be installed in late March, generally on the edge of the field.
There is no precise intervention threshold for both the ubiquitousness and the great phytophage polyphagia; however, following the flickering and eventual presence peaks is an important parameter for the timely detection of the first massive attacks.

Direct detection
The direct detection consists in the careful control of the cultivation, especially in the early stages of development and in the flight periods, to signal the first attacks on the seedlings.
The indicated threshold of intervention corresponds to the presence of 1-2 larvae of the 3rd or 4th age or 1-2 plants with detectable damage per square meter (up to the stage of 8-10 leaves). The fight can be made both with treatments on vegetation and with poisoned baits, depending on the type of larvae present.
The fight in the open field is performed on young larvae that do not exceed 2 cm in length, with insecticides.
To have a better treatment efficacy, these products can be mixed with sugary products (molasses or sucrose). The treatment must be carried out at dusk, with moist soil and with a lot of carrier liquid, to allow the insecticide to percolate also to the collar.
Poisoned baits are used against larvae already developed and already buried; these baits are prepared with molasses or sugar and vegetable or bran residues. The baits should be distributed in the evening, with moist soil and placed in sectors and not across the board.


Video: Agricultural Entomology-1 Nemraj Sunda (May 2022).