Information

Agricultural entomology: True wheat moth

Agricultural entomology: True wheat moth

Classification and host plants

Class: Insects
Order: Lepidoptera
Suborder: hetoneuri
Family: Gelechidae
Genre: Sitotroga
Species: S. cerealella Oliv.

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

Host plants: Wheat Caryoxides, Corn, and other Cereals (in warehouse and in the field).

Identification and damage

The Sitotroga cerealella is a small butterfly, about 15 mm in wingspan; the wings are narrow and long fringed, with yellowish livery with dots or brownish streaks.
The larvae that are pinkish-white with a brownish head have short legs and pseudo-legs; they are about 5-6 mm long.
The damage occurs on the kernels and is determined by the trophic action of the larvae; these penetrate the kernels emptying them and they also deteriorate the foodstuffs with excrements and exuvies. We also remember the Tinea species (= Nemapogon) grain of 10-15 mm wingspan, with front wings of a sooty gray-ocher color, whose larvae live at the expense of seeds, flours, dried fruit and other preserved foods.
It is frequent in central-northern Italy where it takes 2 to 4 generations.

Biological cycle

Sitotroga cerealella overwinters at the larva stage, inside the caryopsis.
In spring, adults (1st flight) flicker and lay eggs in small groups:
- on kernels, in stock;
- on the ears, on the field.
The newborn larva immediately penetrates the caryopsis (one larva per bean) and feeds inside; when he reaches maturity, about a month after entering the karyoxide, he prepares the exit hole, without however puncturing the integument and becomes pupated. 2nd generation adults flicker in early summer; from these adults there is a new oviposition which is carried out in the warehouse.
In fact, the wheat harvest has already taken place.
The number of generations varies according to the environmental conditions; in our environments you can also have 5 generations, one in the field and the other in the warehouse.

Wheat moth adult - Sitotroga cerealella Oliv. (photo agspsrv34.agric.wa.gov.au/ento)

Real wheat moth - Sitotroga cerealella Oliv. (photo agspsrv34.agric.wa.gov.au/ento)

Fight

The fight against food insects follows the criteria of the guided and integrated fight and also makes use of a whole series of constructive measures of insulation which have a preventive function.
In the specific case of Sitotroga cerealella, the fight is carried out with population monitoring, made with sexual traps; the technique involves the installation of traps in April, both for field and warehouse surveys. The means of preventing and combating food insects are common and therefore the general criteria are described once and for all.

Prevention and fight techniques
Prevention and control techniques must follow the following basic rules:
- the rooms intended for the warehouse must be perfectly impervious to insects. Doors and windows must have measures that allow their hermetic closure. The same building must also be isolated in the foundations, to allow any disinfection fumigation, even under pressure; the windows must be equipped with metal or nylon nets, with fine mesh, to prevent the entry of adult insects;
- in warehouses and processing rooms they find effective application:
• food traps;
• electric discharge light traps;
• sexual traps: these are particularly effective against Lepidoptera. With these traps you can get different results:
+ massive capture: in this way the numerical consistency of the population is reduced, by capturing the males who can no longer carry out mating;
+ monitoring capture: in this way the size of the population is identified and the development cycle is followed in order to determine the intervention threshold. This allows to identify the most propitious moment to intervene with pest control products and only when the population is slow enough to cause real economic damage. The threshold varies from 1 to 2 insects per trap depending on the phytophagous considered;
- disinfestation is carried out with fumigants or with residual action insecticides; it can be done both with current infestations and with empty rooms, for preventive purposes.

The fumigation
The fumigation must be carried out by specialized personnel, with the authorization of the Police Headquarters, the A.S.L., or the Harbor Master's Office.
The doses and periods of exposure must be strictly respected to prevent the stored product from taking on odors which are then also transmitted to bread and other derivatives.

Residual insecticides (contact action)
The application of the doses must be rigorous to avoid the onset of resistance phenomena, it is also advisable to alternate the use of the active ingredients, to reduce these phenomena.

Other conservation methodologies
Preservation of foodstuffs is currently focusing on the use of two new technologies: controlled atmosphere and refrigeration; these new techniques that tend to replace chemicals allow to limit infestations and to obtain products preserved without chemical residues.
These techniques involve specially built and naturally watertight environments.
The controlled atmosphere technique is carried out with the use of nitrogen or carbon dioxide to replace oxygen.
The best results are obtained with carbon dioxide which requires shorter application times, compared to nitrogen, even in the presence of a certain% of oxygen.
Insects die from suffocation and the toxic effect of CO2 at the cellular level.
The refrigeration technique allows you to effectively store products for long periods as insect metabolism is blocked.
Refrigeration times vary according to the chosen temperature drop, which depends on the species of insects present and their stage of development.
Conservation could also be integrated, i.e. using both techniques: low temperatures associated with a controlled atmosphere.


Video: Entomology Part 5 Stored Grain Pests for AFO, JRF, NABARD or any other Agricultural compitive exam (January 2022).