One of the most serious seed-borne diseases of flax is anthracnose or seedling blight caused by Colletotrichum lini (West.) Toch. This disease affects flax seedlings, leaves, stems, and fruit bags. It causes reductions in linseed germination power, stand density, stem and linseed yield, fibre output and quality. During 1999-2001 experiments were carried out at the Lithuanian Institute ofAgriculture Upyte Experimental Station to test the efficacy of seven fungicides used for seed dressing against flax anthracnose and other seedborne diseases. Experimental findings indicated that 19.0% to 34.0% of flax seeds were annually infected with C. lini (West.) Toch. causing flax anthracnose. As the disease can spread through the soil, on control plots sown with untreated with fungicides seeds 33.0% to 79.5% of seedlings showed symptoms of anthracnose. Seed treatment with Sportak 45 EC used at the dose 0.8 l f1 and Maxim Star 025 FS used at the dose 1.51 t-1 gave the best control of seedling blight causal agents. Their biological efficacy was as follows: against seed anthracnose 97.3% and 96.3%, at seedling stage, 76.5% and 76.3%, at 'fir-tree' stage - 67.8% and 60.4%. Biological efficacy of the other seed treaters was lower. The highest straw yield increases resulted from seed treatment with the Maxim Star 025 FS and Sportak 45 EC - 0.5 and 0.3 t ha" or 11.0% and 6.2%, respectively. The effect of fungicides used for seed treatment on linseed yield was similar. Maxim Star 025 FS increased the yield on average by 22.1%, and Sportak 45 EC and Premis 25 FS by 13. 7% and 13.3%. The other fungicides, except for Raxil 2 WS and Rovral FLO, also had a positive effect on flax straw and linseed yield, however, in all experimental years the increases were not higher than the least significant difference.

Soybean [Glycine max (L.)], one of the most important crops in Argentina, is commonly infected by Colletotrichum truncatum, the causal agent of anthracnose. Tagetes filifolia essential oil (EO) is presented as a natural approach to minimize the dose of chemical fungicides applied to the crop. The fungus Trichoderma harzianum is used as a biocontrol agent because of its ability to produce secondary metabolites that destroy cell walls of phytopathogenic fungi. However, its performance can be affected when it is exposed to chemical fungicides. The objective of this work was to evaluate the antifungal activity of T. filifolia EO both individually and combined with chemical fungicides against C. truncatum, and its effect on T. harzianum. Fungi were isolated from soybean crops. The following pesticides were assessed: carbendazim (F1), difenoconazole (F2) and trifloxystrobin + cyproconazole (F3). The EO was obtained from native plants and its chemical composition was analyzed by gas chromatography–mass spectrometry (GC–MS). The minimum fungicide concentration (MFC) was determined for each compound. Fungicides were combined with the EO to look for combinations that allowed a reduction of pesticide doses. Among fungicides, F1 showed the strongest antifungal activity against C. truncatum (MFC = 0.25 μl ⋅ l–1) and T. harzianum (MFC = 1.5 μl ⋅ l–1). The sensitivity of both fungi to the EO was lower than to fungicides. The EO presented MFCs of 6,000 and 9,000 μl ⋅ l–1 against C. truncatum and T. harzianum. The EO and F1 affected the growth of T. harzianum at concentrations that controlled C. truncatum (31 and 10%). Eight combinations of fungicides and the EO allowed fungicide concentration reductions of up to 80%, although the growth of the biocontrol strain was also affected. The results demonstrated that T. filifolia EO can be used to control anthracnose and reduce doses of chemical fungicides applied to soybean crops. Its effect on T. harzianum should be considered in the design of integrated pest management strategies.