New data on the biology of the red spotted bug (spilostethus [=lygaeus] equestris L. het, lygaeidae) causing the achene greening in confectionery sunflower hybrids

Western European and especially German-based multinational food processing companies tend to grow confectionery sunflower hybrids and varieties in Hungary. This commercial product is highly preferred as substitute for walnuts, as filling in chocolate, bread and other bakery products, or as seasoning. In the early 1990s, German companies rejected several trucMoads of confectionery sunflower due to "greening of the kernel in the achene". Almost 90% of the rejected consignments originated from a sandy terrace in the region between the rivers Danube and Tisza, which at the time was severely infected with the Asclepias syrlaca L. Field investigations revealed unambiguously that the greening of the kernel in the achene had been caused by the red spotted bug (Spilostethus [=Lygaeus] equestris L). This species is able to cause extensive damage and discontinuity in the so-called shoulder part of the achene with its powerful stinging-suctorial mouth organ. Intensive chlorophyll synthesis begins in the damaged area due to the solar effect, which is undoubtedly the cause for the greening of the kernel in the achene. In this investigation, we studied confectionery sunflower fields in two neighboring areas (Bâcsalmâs and Katyrnâr) for extent of damage caused by Spuostethus !=Lygaeus! equestris L. While in Bâcsalmâs (that district less infected with the Asclepias syriaca L) we found a damage of decreasing intensity (8.85 damaged achenes per sunflower disc) as advancing towards the centre of the field, this value was almost three times as high, reaching 31.71 of damaged achenes per disc, in the area of Katymâr (the area severely infested with Asclepias syriaca L). Though the numbers are not very high in themselves - assuming that a well-developed disc contains 1100 to 1200 seeds - the damage may result in significant reduction of kernel quality. Our extensive research into the causes of the greening of the sunflower kernels made it clear that Spilostethus [=Lygaeusl equestris L. had a significant influence on the chemical composition of the damaged achenes: it Increased the proportion of linoleic acid (C-18:2) by about 2.5%. That affects the lasting quality of the achene unfavorably (Horvâth and Bujâki, 1991). For this reason, a comprehensive study of the biology of Spiloslethus [=Lygaeus] equestrls L. was undertaken in order to develop effective protection methods. This study was a pioneer investigation of exogenous and endogenous factors that might obstruct the use of confectionery sunflower hybrids and varieties In food industry.