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 2018. wheat fields on the territory North-western part of Bosnia and Herzegovina were regularly inspected. Occurrence of the causal agent of wheat powdery mildew, Blumeria graminis (DC) f. sp. tritici Speer (syn. Erysiphe graminis DC f. sp. tritici Marchal)) was registered in a large number of localities. In vegetation period, symptoms characteristic for this fungus were observed on all green plant organs, but it was most commonly present on leaves and basal leaf sheaths of wheat plants. Microscopic preparations were made from samples of diseased parts of wheat in the laboratory of the Biotechnical Faculty. Chasmothecia and conidia were observed under the microscope. Chasmothecia and conidia were registered under the microscope. In 2018, presence of the pathogen was registered on about 60% of the total wheat sowed. Disease Index (DI) was calculated using the McKinney formula. The disease index represents the percentage of the disease.The intensity of plant infection was ranged on a scale 0-9. The disease index above 35% was registered on about 56.6% of the infected plants and 40% total wheat plants. After harvest, grains from infected wheat plants were measured for absolute and hectoliter weigts, which were found to range from 25 to 42 g and from 60 to 67 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 of the family Poaceae, deep plowing, balanced fertilization, optimum sowing time and others. The main strategy to control powdery mildew is by using resistant cultivars the disease can also be controlled by fungicide treatments.