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Arthropod fauna associated to soybean in Croatia

Soybean (Glycine max (L.) Merr.) is today’s leading oil and protein crop with exceptional chemical composition of grain and important agro technical properties. It has an important role in world production and processing. Lately, soybean is also gaining more importance in Croatia. Soybean was introduced into Croatia in 1878 but until 1971 it was not present as an important field crop. Significant cultivation of soybean started in 80-ties. In 1981 soybean was sown on an area of 3.381 ha. Since that time the area sown by soybean has increased considerably, and productivity has also risen steadily. Today the area on which soybean is cultivated is approximately 30.000 to 40.000 ha. The subject of pest control is rarely discussed without the reference to the concept of integrated pest management (IPM). IPM is essentially a holistic approach to pest control that seeks to optimize the use of a combination of methods to manage whole spectrum of pests within particular cropping system. IPM relies heavily on naturally and biological controls with a perspective chemical input only as a last resort. For effective control, there needs to be an understanding of a pest’s interaction with its environment. This is so called concept of “life system” which was initially conceived by Clark et al. (1967) to reinforce the idea that population cannot be considered apart from the ecosystem with which interacts. The life system consists of the pest population plus its “effective environment”. Most ecological pest management concentrates on the agro-ecosystem, defined as “effective environment” at the crop level (Altieri, 1987). Monitoring in insect pest management can be used to determine the geographical distribution of pests to assess the effectiveness of control measures, but in its widest sense monitoring is the process of measuring the variables required for the development and use of forecast to predict pest outbreaks (Conway, 1984). Such forecasts are an important component of pest management strategies because a warning of the timing and extent of pest attack can improve the efficiency of control measures. For successful pest control according to the principles of IPM it is of great importance to have deep knowledge in harmful and beneficial arthoropods in particular agro-ecological conditions. Comparing to weeds and diseases, pests are of somewhat less importance for soybean production in Croatia. But, with any increase in soybean production they could become a problem. In different agro-ecosystems, the arthropod fauna of soybean contains a great number of damaging species (Hygley & Boethel, 1994 ; Čamprag, Kereši & Sekulić, 1996). Soybean pests have not been investigated completely in Croatia. Maceljski (2002) listed possible pests which could be associated to soybean but he reported only few of them as serious threat (Tetranychus urticae Koch. and Vanessa (Pyrameis) cardui L.). Therefore, in this chapter a literature review of possible pest and beneficial in soybean will be given. Also the results of the study aimed to identify the harmful and beneficial arthropod fauna during the soybean growing season, based on their dynamic of occurrence and abundance will be presented. In order to determine the soybean beneficial and pests, a research was conducted on soybean field sown by variety “Zlata” in Zagreb in 2010. Investigation was carried out between June 24 when plants started to flowering and Septemebr 9 when plants reached maturity. Entomofauna was collected using the standard entomological net, by visual inspection of the plants and by sampling and inspection of leaves under the stereomicroscope. Entomological net was used once a week with 50 randomized cuts from the investigated areas. Visual inspection of ten plants was done once a week and at each inspection ten leaves were collected for determination of spider (Acari) incidence. All inspections (sweeping, visual inspection and leaves collection) were repeated four times. Collected individuals were classified into orders using the determination keys, and where possible into families and species. Cenological values (dominance and frequency) were defined at the level of orders. The total catch was 1357 specimens which belonged to six orders: Thysanoptera, Hemiptera, Coleoptera, Lepidoptera, Diptera and Acarina. Using the entomological net, 759 individuals were collected, whereas 598 individuals were gathered by visual inspection. In total catch the eudominant orders were Hemiptera (60.3%) and Acarina (28.5%), while subdominant were orders Thysanoptera (4.7%), Coleoptera (3.3%), Lepidoptera (1.8%) and Diptera (1.4%). Out of all collected individuals beneficial were presented with 5% while pest species were presented with 95%. The most numerous beneficial species (62 individuals) was identified as Nabis ferus L. The species which belongs to the genus Anthocoris was represented by 11 specimens, and three individuals belonged to family Coccinelidae were found. Out of all captured species two pest species, Tetranychus urticae and Nezara viridula L. have been found in significant population. While T. urticae is well known pest of soybean in Croatia, N. viridula is relatively new pest which outbreak was reported few years ago (Majić et al., 2010). It fed soybean seeds causing damages in yield quantity and quality. The appearance of N. viridula was in literature (Majić et al., 2010) connected with higher temperatures and drought, what was not the case in our investigation. Obtained results indicate that the increase in pest population has occurred recently and that one existing species became significant pest of soybean. It is realistic to expect even more pest outbreaks since soybean became more and more abundant crop in Croatian cropping system.

arthropods, soybean, pests, Croatia

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