Morphological aspects


The adult has an oval body, long, with dimensions between 4,4 - 6,6 mm the male and 4,2 - 6,8 mm the female. The body’s color is yellow-greenish. The male has brown wings with their posterior part lighter. On the female’s wings three longitudinal black strips are well marked. Watched from the lateral, the female’s abdomen is larger and sharper than the male’s, who has a smaller and rounder (blunt) abdomen. This is representing an important characteristic in determining the gender at the adults.
The egg is pale yellow when it is deposited, then becomes yellow – brownish, oval shaped, having 0,5 mm. The larva is long, thin, having the color white, with the cephalic capsule darker. It measures 10-18 mm in length. The dorsal part of the 9th abdominal segment presents a dark spot, where is located the darker anal plate. It comes through three larval ages.
The pupa is free type, white, having soft consistency, fine, having de 12 - 14 mm. It can be found in the soil.


Development


In our country’s conditions there is a generation yearly (mono-voltine) and is hibernating in the stage of egg in the soils cultivated with corn. The apparition of the larva is divided during some weeks (middle of May – beginning of August) and depends of the depth where the eggs are located, of the soil’s type and temperature. Immediately after the apparition, the larva spread in the soil, searching for food. These have to install in an interval of 72 hours on the corn roots, otherwise they won’t survive. The optimum development temperature for the larva is 22°C (30 days). The mature larva are moving towards the superior layers of the soil, transforming in pupa (nymph). The spreading of the pupas takes place form the middle of June until the end of August. The adults are coming out at the end of June- beginning of July and will redraw at the end of September. The largest number of adults exists in July and August, when the temperatures are between 23 - 27°C. The adults’ longevity (63 - 98 days) is influenced by the length of the photo-period and of the quality of the food. After the apparition, the adults are remaining in field for feeding themselves. The copulation takes place at one week after apparition. The eggs are deposited in the corn cultivations, starting with the second decade of July, until the second decade of September. The embryonic development last for 3 weeks. A female is depositing in soil between 90 – 335 eggs, in groups of 10 – 20.

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Adult damages

 

Damages


At the apparition, the adults feed themselves with the foliar limb, perforating it as longitudinal stripes in the long of the veins (attack similar to that produced by the Oulema melanopa). At the beginning, the freys are superficial, only on one epidermis, later extending on the other epidermis. Around the perforation, the leaves are getting yellowish and dry. In the period of the blooming, the adults are feeding themselves with silk and pollen. They are partially or even totally eating the corn’s silk, when they are present in a large number. After the disappearance of the pollen and of the silk, they are migrating on the corn cultivations, seeded later. They are also consuming the seeds from the top of the corn hob, being in the "milk phase". The larva are feeding themselves with the corn roots, causing their shortening. As a result of this way of attack, the strength of the roots is diminishing, they are not able to sustain the plant anymore, in consequence the plants have the tendency of bending to the soil. The larva are completely damaging the secondary roots, as well as the main ones. The plants with the roots damaged in percentage of 50%, are presenting a stem characteristically bent, as "goose neck". The roots are weekly griped in the soil and they could be easily pull out. The mature larva are hiding in the cortical parenchyma of the roots and are digging channels in the central vascular tissues. The tunnels from the corn roots are representing an characteristic aspect of the attack, although these could be also made by other species.

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Larva damages



Where do we meet them and to where are they heading?


According to the information published by the Central Laboratory for Phito-Sanitary Quarantine from Bucuresti, the species is present in the counties: Arad, Timis, Caras Severin, Mehedinti, Bihor, Satu Mare, Salaj, Hunedoara, Cluj, Alba, Sibiu, Gorj, Dolj, Vâlcea, Olt, Bistrita Nasaud, Mures, Harghita, Maramures, Arges, Brasov, Prahova and Teleorman. The orientation and speed of moving at national level is not known until the present, but it still can be observed a preference towards N-E. In the neighboring countries, the moving speed of the adults is 30-40 km/year.

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Some strategies for the population reduction

The agrarian phito-technical methods: avoiding the single cultivation, fertilization with nitrogen, the soil’s works (part of the deposited eggs are transferred in improper places ), early harvesting, etc.
Mechanical methods: use of yellow traps, pheromonal traps.
Chemical methods
Against the larva: the treatments at the seed, with products based on clothianidin or imidacloprid, tested also in our country.
Against the adults: for a number of 5-6 adults/plant (in the maximum period of apparition) it is recommended a treatment using products based on tiacloprid. The maximum period of apparition of the adults is similar with the apparition of the silk and formation of the corn cob (during July). For a maximum efficiency is compulsory to mix the chemical treatments against the larva and adults.
Perspective methods, less used in Romania:
Biological methods: protecting the natural enemies Argiope bruennichi (Araneae: Araneidae), Speira diademata (Araneae: Araneidae), Theridion impressum (Araneae: Theriidae) and Pseudophomus rufipes (Coleoptera: Carabidae).
Genetic methods: corn lines resistant to the larva’s attack, MON 863, NG72317, NG72312 NG72227, SD30, A251, synthetic populations: H225Syntetic, H55SynteticB and varieties : Midland Yellow Dent, Hays Golden and Golden Republic (recommended by the American specialists)

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