Maja Čačija

Ecomorphological Variation of the Wireworm Cephalic Capsule: Studying the Interaction of Environment and Geometric Shape

Studying the association between organismal morphology and environmental conditions has been very useful to test hypothesis regarding the influence of climate on shape. It has been long recognized that different environments produce dissimilar stress levels in insects, which can be reflected on the ability of an individual to overcome these pressures and spread further. Agriotes (Coleoptera: Elateridae) species infest agricultural fields in different parts of Croatia, inhabiting different climatic conditions. Previous biological studies have indicated that there is a relationship between some Agriotes biological parameters such as density and climatic conditions such as soil moisture and temperature. However, it is still unknown how these environmental properties influence the wireworm morphological structure. This is highly relevant because the head of this species is directly involved in the mobility in the soil, thus affecting the invasive capacity of this insect. Therefore the aim of this study was to assess the association between different climatic conditions and the morphological variation of Agriotes cephalic capsule. Advanced multivariate analysis and geometric morphometric tool were applied to study the covariation between shape and environmental variables. Partial Least Squares methods were used in order to analyse the association between the wireworm head shape and three different climatic conditions: soil type, temperature and rainfall. Our results showed that there is a high covariation between the wireworm head shape and the climatic conditions. It was suggested that the observed shape–environment association could be result of the high plasticity of this species in relation to its invasive capacity.

Seasonal Flight, Optimal Timing and Efficacy of Selected Insecticides for Cabbage Maggot (Delia radicum L., Diptera: Anthomyiidae) Control

In order to describe seasonal flight activity of the cabbage maggot Delia radicum (L.) adults in relation to Julian days (JD), degree-day accumulations (DDA) and precipitation, flight dynamics were followed weekly with the use of yellow sticky traps (YST). Climatic data were collected and DDA were calculated using the lower developmental threshold of 4.3 °C. The efficacy of four insecticides applied either as standard foliar treatment or through dipping the seedlings before transplanting was determined. Seasonal flight activity during the cultivation season of a mid-early variety of white cabbage was correlated with DDA and JD and was characterized by having two peaks. The first peak occurred between 119 ± 7.5 JD and 125.5 ± 8 JD when DDA was 471.35 ± 74.97 °C. The second occurred between 172.8 ± 6.1 JD and 179.3 ± 6.7 JD when DDA was 1,217.28 ± 96.12 °C. The DDA, cumulative capture of flies and JD are suitable for predicting the timing of insecticide application. Spraying with insecticides should be applied when the cumulative capture of flies reaches 100 flies/YST and when DDA reaches 400 °C. If only one parameter reaches the threshold, additional visual surveys should be employed to establish the level of infestation. Insecticides were able to ensure only partial control. In the future, alternative control tactics which employ seed treatments and nonpesticide measures should be investigated in Croatia.

Comparative Efficacy of Classical and Biorational Insecticides on Sugar Beet Weevil, Bothynoderes punctiventris Germar (Coleoptera: Curculionidae)

Bažok R., Satvar M., Rados I., Drmic Z., Lemic D., Cacija M., Viric Gaspari c H. (2016): Comparative efficacy of classical and biorational insecticides on sugar beet weevil, Bothynoderes punctiventris Germar (Coleoptera: Curculionidae). Plant Protect. Sci., 52: 134–141. The contact and ingestion activity and the potential of the insecticide spinosad for the control of sugar beet weevil were evaluated and compared with commercially used insecticides lambda-cyhalothrin and chlorpyriphos + cyper methrin. Results of three laboratory trials proved very good efficacy of spinosad applied at the dose of 72 g a.i./ha. Its efficacy was similar to chlorpyriphos + cypermethrin and significantly higher than that of lambda-cyhalothrin. Due to its favourable eco-toxicological properties and good ingestion activity, spinosad is a good candidate to be introduced in the integrated pest management strategy against beet weevil.

Endogaeic ground beetles fauna in oilseed rape field in Croatia

The abundance of ground beetles (Coleoptera, Carabidae) in oilseed rape field can be an important indicator of different agricultural measures in arable land fauna. Surveys about ground beetle fauna in Croatia are generally very scarce and only few research on oilseed rape were conducted. The aim of this study was to determine the endogaeic ground beetle fauna in oilseed rape field and to determine species abundance and frequency. The study was carried out in Podravina region of Croatia, from the end of May till the mid-September in 2015. Ground beetles were collected using endogaeic traps incorporated in the soil. Altogether, 487 individuals classified into 8 species were collected. Species with the highest abundance and frequency was Brachinus (Brachinus) psophia Audinet-Serville, 1821, which was classified as eudominant and constant species. The highest ground beetle abundance was observed in summer period. All of the species found were spring breeders, except for species Trechus (Trechus) quadristriatus (Schrank, 1781) which breeds in autumn.

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 ; Camprag, Keresi & Sekulic, 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 (Majic et al., 2010). It fed soybean seeds causing damages in yield quantity and quality. The appearance of N. viridula was in literature (Majic 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.

Linking climate change and insect pest distribution: an example using Agriotes ustulatus Shall. (Coleoptera: Elateridae)

Agriotes ustulatus (Schaller, 1873) (Coleoptera: Elateridae) is an economically important agricultural pest. Recently, changes in the distribution and abundance of this species in Croatia have been established. The present study aimed: (i) to determine the abundance and dominance of A. ustulatus in four regions in Croatia; (ii) to test the effect of temperature and rainfall on dominance and distribution; and (iii) to determine the flight activity of the A. ustulatus adults (peak and swarming period). From 2001 until 2010, five Agriotes species were captured by pheromone traps placed in 17 fields within four counties. Differences in air temperature and rainfall were determined between regions. The highest dominance of A. ustulatus was recorded in the warmest eastern county and the species was classified as eudominant. High dominance was also observed in the western county, confirming that A. ustulatus occurs in higher population in this area. Species was subdominant where the mean air temperature was the lowest. The increase in dominance in the west could be explained by the significant positive correlation found between air temperature and dominance. The seasonal activity of the adults was from June to mid‐August, with peak flight at the end of June.