Pests of Sugar Beet

Carrion beetles

Species Spectrum

Carrion beetles (Coleoptera: Silphidae) represent a relatively small family, with only 186 members worldwide and 23 members in the Czech Republic. The individual species can be distinguished by their external appearance. Their size ranges from moderate to large, they have flattened bodies, elytra very often not covering the whole abdomen. Eleven-segment antennae are ended with a club (subfamily Nicrophorinae) or are of a more gradual club shape (Silphinae). When touched, they fake death, releasing foul-smelling liquid from their rectum. Black-coloured larvae with pointed edges of tergits resemble terrestrial crustaceans woodlice. Based on their relationship to food, carrion beetles can be predators, e.g. four-spotted carrion beetle (Dendroxena quadripunctata), omnivorous (members of the Silpha genus), necrophaguos (burrying beetles) and phytophaguous (members of Aclypea genus). Larvae and adults of phytophaguous species gnaw at aerial organs of plants and can also cause damage to beet (Šustek, 1981; Růžička, 2005; Šefrová, 2006). Beet carrion beetle (in German Brauner Rübenaaskäfer, in Slovak zdochlinár hnedkastý) is considered as a more important pest in Western Europe. In our territory, it is mostly Aclypea undata causing damage to plants.(in German Runzeliger Rübenaaskäfer, in Slovak zdochlinár vlnkovaný). This beetle is also listed in the Red list of threatened species of the Czech Republic. The following species are commonly found on beet: Silpha obscura L., 1758 and Thanatophilus rugosus L., 1758. They develop mainly on dead bodies of various animals and their harmfulness to beet is negligible (Šustek, 1981; Farkačet al., 2005, Šefrová, 2006).

Morphology

For carrion beetles of the Aclypea genus is typical a wide head, not pinched behind the eyes. Adults of A. opaca are 9 – 12 mm long, black with spotted longitudinally ribbed elytra, with dense yellow – golden hairs, these being longer on the head (Fig. 16). Outer ribs on the elytra are noticeably raised. There is a sizeable protuberance at the end of each elytra. The pronotum is spotted. Eggs are white or yellow-white, almost spherical, 1 – 2 mm in diameter. Black larvae (Fig. 17) grow up to 11 – 15 mm, their antennae are rusty red and legs yellow-brown. The tips of tergits are yellow. Body surface is covered with sparse short cilia, finely grained. Mesothorax and metathorax are one third shorter than prothorax. Anal segment is two times wider than its length.Adults of A. undata are 12 – 15 mm long, matte black, almost glabruous, with irregular transversal lines on the elytra. The pronotum is more finely spotted in the middle than around the edges. Larvae are longer than those of A. opaca, they grow up to 12 – 17 mm, are all black, covered by short bristles. The front edge of pronotum is incised.

Bionomics

A. opaca and A. undata have a similar bionomics, form a single generation during the year, adults hibernate in different sheltered places (in compost, fallen leaves, under stones, in forest litter). A. opaca is better examined, its adults leave their winter habitat from early April, depending on the weather, they are active during the day and sometimes fly. They copulate usually in late April, afterwards the females lay eggs in the soil 7 – 8 cm deep. Every female lays approximately 120 eggs. The period of egg – laying is quite protracted and lasts until mid-July. Eggs are susceptible to drying out. Larvae hatch after 5 – 9 days. They are very voracious and timid, hiding under leaves and pretending to be death. In 11 – 21 days, larvae go through three instars. Before pupating, they crawl in the soil in the depth of 1 – 5 cm, and pupate after 2 – 7 days. New adults hatch after 7 – 9 days in late July, most abundant in July. Adults hibernate, becoming sexually mature after their maturation feeding in the following spring. Adults of A. undata enter a diapause in summer (Miller, 1956; Šustek, 1981).

Distribution and Ecological Requirements

The distribution A. opaca is holarctic, in Europe it is common in the north, towards south, its occurrence is lower, it can also be found in moderate Asia as far as in the Far East and northwestern part of North America. In other parts of the North American continent, another very similar species is found – Aclypea bituberosa. A. undata is distributed palearctically, in southern and central Europe, in northern England and southern Scandinavia, it also inhabits a considerable part of Asia. In our territory, A. undata is more common, found in oak altitudinal zone and higher (areas of maize production), in fields, pastures and pathways. The most important antagonists are insectivorous birds (partridges, pheasants), moles, frogs and predatory ground beetles, especially large  Carabus species. Older larvae can be parasitized by Tachinidae. Carrion feeders require more humid environment and gather in places sheltered from the wind. There can be an outbreak usually after more humid years, when the weather in April was moderate and dry and warm in May and June. The eggs are highly susceptible to drought (Miller, 1956; Šustek, 1981; Anderson & Peck, 1984).

Host Spectrum and Symptoms

A. opaca as well as A. undata are polyphagous, developing on Poaceae, Brassicaceae, preferring Amaranthaceae plants. Adults gnaw at the leaves starting at the edge. The edges of feeding marks are dark, which is caused by a green liquid, secreted from the mouthpart. Larvae gnaw holes in blades, they can also start gnawing leaves from the edges. They do not colour the feed marks by green liquids.

Importance

A. opaca causes damage in Western and North Europe, in our territory, A. undata is more abundant. The greatest damage is done when the feeding takes place during singling of beet. Mainly older larvae are harmful, roughly one week before pupating, one larvae consumes up to 6 cm2 of leaf surface, one imago 4 – 5 cm2. In the case of outbreak, larvae can destroy the growth in 2 – 3 days. (Rambousek, 1931; Miller, 1956). In our territory, the harmfulness of Silphini beetles to sugar beet was first described by O. Nickerl in 1878. In the first half of the 20th century, carrion beetles were among important sugar beet pests. In 1920s and 1930s, they caused significant damage, sometimes the growth had to be ploughed in (in 1920 in exceptionally high numbers in Moravia, in 1928 more than in the previous years in Bohemia and Moravia, in 1931 they caused significant damage in Moravia, in 1932 in Třebíč and Kunovice, in 1936 and 1937 in south Moravia, in 1939 ploughing was necessary in Moravia) (Fytopathologický ústav, 19201940). In 1940, they caused damage worth millions of crowns (1946 2.75 mil. CZK, 1948 18 mil. CZK, 1949 15 mil. CZK) (Drachovská-Šimanová, 1951). In the second half of 20th century, they caused only local damage, especially on fodder beet (1964 Kolín, Kutná Hora, Přerov, Bruntál, 1969 Jičín, 1974 Vyškov, 1976 Žďár nad Sázavou, 1977 Kolín, Příbram, Liberec, Pelhřimov, Svitavy, 1978 Pardubice, 1979 Svitavy, Semily, 1980 Blansko, Žďár nad Sázavou, 1981 Brno, 1982 Pelhřimov, Písek, Plzeň, Žďár nad Sázavou, Nymburk, 1983 Pardubice, Břeclav, Žďár nad Sázavou, 1985 Kolín, 1986 Nymburk, Jičín, Pardubice, 1987 Nymburk, 1993 Pardubice, 1994 Pardubice (ÚKZÚZ, 1955 2000). In recent years, their harmfulness to beet has not been registered.

Detection of Occurrence and Pest Control

Adults can be caught using sweep nets after sunset (Baudyš, 1935). In order to capture saprophaguous species, ground traps with lure are used (Růžička, 2005). Critical number of adults is 2 – 3 per m2. There no registered insecticides against carrion beetles. The protection lies in preventative measures, eradication of weeds, especially goose foot and orach, timely seeding, following crop rotations and deep ploughing (Miller, 1956; Ackermannet al., 2013).

Fig. 16: Adults of Carrion beetle (photo by Šefrová)

Fig 17: Larvae of Carrion beetle (Benada et al., 1985)



 

The document was created: 26. 03. 2019 05:49:40
Source: http://web2.mendelu.cz/af_291_projekty2/vseo/