Secondary pests of stored grains

In relation to stored grains, there are primary and secondary pests. The first are those that have the capacity to damage grain that is healthy, whole, while the second are those that require the presence of flour and damaged grains derived from primary attacks. Within the group of secondary pests, woodworms are undoubtedly the most present and relevant.

FAMILY TENEBRIONIDAE Tenebrio molitor (L.) (Woodworm or yellow mealworm) They are characteristic of regions with climates

temperate, since they are very resistant to cold. Apparently they do not adapt to tropical areas. Adults range in size from 14 to 20 mm. , making it one of the largest insects that infest stored grains. It is very dark brown to slightly shiny black without bristles or pubescence, firmly stippled prothorax and elytra with longitudinal striae. They have well-developed functional wings, they fly at night and are attracted to light. They are slow moving. The female lays between 80 and 550 white, shiny, oval or slightly kidney-shaped eggs. They are then covered by a sticky substance that allows them to quickly adhere to the food particles on which they were deposited. They can lay up to 40 eggs per day and oviposition lasts almost 4 or 5 months. They complete their maturation in 7 to 10 days depending on the temperature. The bright yellow larvae hatch and complete their development between 3 and 6 months. They spend the cold season immobile and without feeding, so the larval period can extend up to a year or more. They undergo between 9 and 20 molts, and when fully developed they measure up to 40 mm. Shortly before pupating, they migrate to the surface of the material on which they feed. They remain there for a few days. The pupa is white and changes to yellowish brown. The pupal period can last 6 days in the summer and up to 18 in the winter. Presents a

Tenebrio molitor (L.)

generation per year, or two with favorable temperatures. Adults live between 6 and 9 months without feeding. They feed mainly on flour, ground foods, grains in poor condition, and are capable of feeding on a wide variety of materials of plant and animal origin such as cookies, bread, meat scraps, skins, dead insects and decaying trees. Infestations frequently originate in the nests of pigeons and other birds that are installed in sheds and similar structures, or in garbage accumulated in gutters and other parts of the roofs. The larvae are nocturnal and prefer dark and humid places. They infest warehouses, basements, cellars, mills and grain tanks in nooks, corners, crevices and places where ground food materials accumulate for a long time. It is considered a secondary pest of grains and stored products, although the larvae are capable of damaging whole grains that have remained for long periods without movement, but they are not of major importance due to their low reproductive rate. Its presence indicates lack of cleanliness and hygiene. The larvae, due to their large size, are used as food for aquatic animals and, known as “golden worm”, are marketed as fishing bait, highly appreciated by many fishermen. Tribolium confusum (D.) (Confused tribolium). It is a cosmopolitan insect that in warm places is found in all stages of development throughout THE LOSSES CAUSED BY PESTS IN THE AGRI-FOOD CHAIN ARE OVERWHELMING, ESPECIALLY IF WE ANALYZE THE DIVERSITY OF MITES, INSECTS, RODENTS AND OTHERS, WHICH ARE PRESENT FROM THE IMPLEMENTATION OF THE CROPS TO THE PRODUCT The year is over. As it perfectly resists low temperatures, the southern climate is not an impediment to its proliferation in wheat mills. It measures between 3 and 4 mm. long, the body is elongated and slightly flat. It is bright reddish brown in color. The antennae gradually widen from the base towards the apex. The eyes are small, round and the distance between them is three times the diameter of the eye. Prothorax densely covered with tiny black dots. The elytra have longitudinal bands that are difficult to see with the naked eye. It is not capable of flying. The female lays up to 500 eggs or more, among the flour or grain residues, they are covered with a sticky secretion that allows them to adhere to

the surface and facilitates infestation. The eggs incubate between 5 and 12 days, giving rise to small, thin, cylindrical larvae that reach 6 mm in length, white in color tinged with caramel yellow, with the appearance of a wireworm. The number of larval stages according to the authors ranges between 6 and 11. The confused tribolio pupates in the environment in which it is found without any protection. The pupa is white at first, gradually changes to yellow, then brown, and finally transforms into an adult. The complete cycle takes 6 to 8 weeks and adults live 12 to 18 months. It is a secondary pest of cereals since it is unable to damage healthy, clean and dry grain. Both the adult and the larvae feed on Tribolium confusum (D.)

So mainly from cereals cracked or damaged by other insects, cereal milling products, flours, oilseeds and their products, biscuits, cracked nuts and other soft or ground products. It is considered a primary pest for milling products of cereals, legumes and oilseeds. It is very common to find it in wheat mills and various factories that work with ground cereals. It is generally found in empty bags with flour residue, in pellets and wheat bran meal. Its eating habits are broad, so it is common to find it in factories where cleaning is not very frequent. There is another species of the same genus Tribolium called castaneum, its biological cycle has practically no differences with confusum. Regarding morphology, it is important to highlight that T. castaneum has the same color but is not bright. Furthermore, in the latter case, the distance that separates one eye from the other is equal to the width of each eye. T. castaneum is usually found in the field since it is an excellent flyer. The chestnut tribolio comes from India, it is cosmopolitan and is found in warmer places than the confused tribolio.

FAMILY SILVANIDAE

Insects belong to this family and are characterized by having antennae with 9 to 11 antennae, typically filiform, ending in a club. They have a length that ranges between 1.5 and 5.5 mm. Generally elongated, parallel-sided, flattened and pubescent. Oryzaephilus surinamensis (L.) (Toothworm) It is an insect that owes its common name to the peculiar structure of its thorax, which is provided with six teeth on each side. This woodworm measures 3 to 3.5 mm. long, it is pubescent, reddish brown to dark brown in color and has two longitudinal depressions on the pronotum. The elytra are narrow and striated and although the membranous wings are developed, it rarely flies. Females lay between 45 and 375 eggs scattered in the food or in the cracks of the grains. The larvae hatch and measure 2.5 to 2.8 mm. in length, they are pale yellow with darker bands on the back of the thorax and abdomen. The larval period lasts 15 to 20 days. Before pupating, the larvae build a cocoon by joining food particles with a special secretion and attaching it to a solid element on the caudal part. This remains the case for a week to 20 days, after which the imago emerges. The cycle in this way can be completed in 22 days up to 108 days. There are between 2 and 5 generations per year. Adults of this species can generally live between 6 and 10 months, with cases having been recorded

Oryzaephilus surinamensis (L.) with up to 3 years of longevity. The larvae and adults live in grains of wheat, rice, oats and barley broken or attacked by other insects and also in pasta, flour, bran, sugar, tobacco and many other plant products used in human nutrition.

FAMILY BOSTRICHIDAE This family is characterized by having individuals with an antenna of 9 to 11 segments and ending in a club or club of 2 or 3 segments. The body length is between 2 and 20 mm. They have thin elongated and also cylindrical shapes. They generally have a dark brown or black color and a cylindrical body. The pronotum is shaped like a hood that covers the head. The larvae are cylindrical, C-shaped, white or yellowish, with a brown head. They are rounded, sometimes with few hairs, they do not have legs. It is common to find them in stored grains. There are also some large Bostrichidae found in the

wood, such as furniture. Rhizopertha dominica (Grain drill) It is native to the tropics and is widespread in warm regions of the world. Both larvae and adults attack all types of grains including rice, oats, barley, corn, wheat and rye. The larvae have been found feeding on flour. It can also be made of cardboard and wood. It generally does not develop in seeds of oilseeds and legumes. The adult has a cylindrical, elongated body,

with the back rounded and slightly truncated. Head large, retractable within the prothorax. Antennae whose last three segments are markedly larger than the others, forming a serrated club. Prothorax more or less circular, rough due to the existence of small protuberances. Capable of flight, the elytra have thick longitudinally aligned scores. It is 2.5 to 3 mm long and brown to dark brown in color. The female lays 150 to 500 white or pink eggs in isolation or in small packets, which can be found loose or attached to the grains. The incubation period ranges from 5 to 14 days. The larvae are very agile, curved, hairy and dirty white in color, they make their way inside the grains on which they feed. The larval period lasts 20 to 35 days. They generally pass the pupal phase inside the grains. The entire cycle lasts 4 to 10 weeks. The adult has a lifespan of 4 to 6 months. The number of annual generations ranges between 3 and 5.

Rhizopertha dominica