The Una-Sana Canton (the northwest part of Bosnia and Herzegovina) abounds in large forest areas, where the self-sown sweet chestnuts Castanea sativa Mill. grow. However, the plant has been endangered due to the negative effects of disease-causing agents, harmful insects, and human factors (uncontrolled forest logging). Moreover, the chestnut weevil Curculio elephas causes significant damage to the local chestnut fruit. This study aims to analyze the emergence of the pest and the damage which it produces in the forest areas of the northwestern Bosnia and Herzegovina, precisely in Una-Sana Canton. The presence of the chestnut weevil has been examined on samples taken from 15 locations in chestnut forest in the municipalities of Cazin, Velika Kladuša and Bužim. In order to research this phenomenon more precisely, each fruit has been cut, the larvae have been separated from it and damage in the inner part of the fruit has been observed. The number of larvae has been noted per a sample. With respect to each sample, the mass of healthy and damaged part of the fruit has been measured. The number of larvae ranges from 5 to 15 per sample. The percentage of damaged fruit parts ranges from 4,2% to 13,6%. The reason for the increased presence of the chestnut weevil in the analyzed chestnut forest is in addition to the beneficial chemical composition of the fruit and the late detection of the presence of insect existing in severely large populations. The use of chemical preparations (pesticides) as a solution to this issue is ecologically unacceptable, especially in a larger area. It is mandatory to manually collect all the fruit that fells of the chestnut trees prematurely and, moreover, to stop the further development of the larvae. Considerable results can also be achieved by separating individual chestnut stands and changing the purpose of its use, as well as combining the method with the limited use of pesticides.

In 2015, wheat fields on the territory of Una-Sana Canton (northwestern Bosnia) were regularly inspected. Occurrence of Gaeumannomyces graminis (Sacc.) von Arx et Olivier (syn. Ophiobolus graminis Sacc.) was registered in a large number of localities. In vegetation period, symptoms characteristic for this fungus were observed on spike and roots. The fungus G. graminis was isolated from a large number of collected wheat samples which were analyzed in the laboratory by the conventional method. In 2015, presence of the pathogen was registered on 12.8% of the wheat acreage. Infection intensity above 15 was registered on 16 % of the infected acreage and 2% of the total wheat aceage. After harvest, infected wheat grains were measured for absolute and hectoliter weights, which were found to range from 26 to 40 g and from 63 to 68 kg, respectively. To improve the effectiveness of crop protection, it is necessary to apply the required agricultural practices (long-term crop rotation, control of volunteer wheat and grassy weeds, plowing under of harvest residues, balanced fertilization) and treat wheat seed with fungicides from the groups of benzimidazoles, triazoles and triadimenoles. Biological protection is possible with bacteria Pseudomonas fluorescens and fungi Trichoderma viridis.

In 2010. and 2011, barley fields on the territory of Una-Sana Canton (northwestern Bosnia) were regularly inspected. In addition to the common diseases, occurrence of Rhynchosporiumsecalis (Oudem.) J. Davis, (Syn. Rhynchosporium graminicola Heinsen) was registered in a large number of localities. The typical symptoms were visible on the leaves, the smaller of the branches of leaf. On the reverse of leaves emerged gray-white coating, composed of konidiofora and the conidia. The fungus R. secalis was detected on a large number of collected barley samples which were analyzed in the laboratory by the conventional method. In 2010, infection symptoms were found at 70% of the barley acreage, in 2011. at 55% of the acreage. The intensity of infection higher than 70% was registered in 20.9% of the infected acreage for winter barley, and 18.3% for spring. The computed severity coefficients of noxiousness ranged from 28 to 59. The lowest coefficient was established for the cultivar Matej, the highest for the cultivar Novosadski 313. After harvest, infected barley grains were measured for absolute and hectoliter weights, which were found to range from 25 to 43 g and from 51 to 63 kg respectively. To improve the effectiveness of crop protection, it is necessary to apply the required agricultural practices: long-term crop rotation, control of wild barley and grassy weeds, plowing under of harvest residues, balanced fertilizzation and treat barley with fungicides from the groups of karbendazimes, propikonazoles and triadimefonales.