Eurygaster integriceps (sunn pest)

Eurygaster integriceps attacks wheat from April until harvest. All parts of the plant are attacked. The overwintering adults, installed in the crop at the end of March or in early April, feed exclusively on vegetative plant organs from spring start up to flowering. The new generation (nymphs and young adults) feed only on the grain within the ear. The overwintering adults mainly feed on the zone of growth cone position, showing clear organotropicity (Shapiro and Vilcova, 1973). In the spring, the leaves and stem base are attacked. As a result, the leaf zone above the eating level dries, while the central leaf and the stem, yellow and dry. After stalk shooting, E. integriceps mainly attacks the stalk and lower leaves.If the stalk is in a more advanced vegetative phase when it is attacked, damage will occur above the last internode, as well as during ear formation, causing yellowing, drying boot and ear abortion. When the ear emerges from the boot it is sterile and white. If the attack occurs after booting, the ear can be totally or partially aborted, depending on the location of the damage, at the ear base or within it. The appearance of attacked ears is characteristic. They are sterile, white and have rigid, diffuse awns.After flowering, the overwintering adults of E. integriceps are uncommon, and the nymphs of the new generation feed exclusively on the growing grains. If the plant ovaries are attacked before or shortly after fecundation they are destroyed and the grain ceases formation. Attacks on grains in the early phases of formation result in grain shrivelling. Grain attacked in a more advanced ripening phase does not shrivel, but the site of attack is marked by a black point in the centre of a discoloured spot, with yellow-whitish marks. E. integriceps can continue to feed on fully ripened grain, even after harvesting, in ears that have fallen on the ground.

The earliest evidence of damage caused to wheat crops by Eurygaster integriceps is in the first millennium, at the time of Harun-al-Rashid (Safavi, 1968). In the eighteenth century, Nedershah burnt the vegetation on the Persian mountains in an effort to eliminate the insect (Vodjdani, 1954).The impact of E. integriceps attack is particularly high (FAO, 1956, 1958, 1959, 1961, 1963, 1966, 1969; Skaf, 1996). The attacks are caused by the overwintering adults in spring, and by the nymphs and young adults in the period of grain filling and ripening (Radulescu and Gruitã, 1942; Fedotov, 1947-1955; Vodjdani, 1954; Starostin and Burov, 1976; Zakharenko et al., 1986; Popov et al., 1988; Volodichev, 1991).The damage caused by the overwintering adults is quantitative. It leads to destruction of the plant before earing or abortion of the spikes due to injection in the boot stage or before flowering. In years when spring is dry and warm, an attack by only a few adults per square metre can lead to important losses.Grain spoilage following E. integriceps attack is manifested by reduced weight and lower value of the seeds and lower bread-making qualities (Radulescu and Gruita, 1942; Paikin, 1961; Beratlief, 1964; Irodova, 1964; Vinogradova, 1965; Boldea et al., 1966; Lazarov et al., 1969; Paulian and Barbulescu, 1970; Cseresnyes, 1972; Banita, 1980; Cseresnyes et al., 1985; Popov and Popov, 1998). Enzymes excreted by E. integriceps into the grain during feeding lead to flour degradation and a reduction in the bread-making properties. The gluten is spoiled, changing its composition and leading to loss of its most valuable properties, such as extensibility. The gluten becomes soft and gluey making the dough difficult to handle. Depending on cultivar, and other factors, including soil and crop management procedures, 2-3% of attacked kernels do not significantly affect the bread-making qualities, however, above these levels, gluten spoilage is pronounced (Shumakov and Vinogradova, 1958; Irodova, 1964; Banita, 1980; Paulian and Popov, 1980; Cseresnyes et al., 1985; Popov and Popov, 1998).