The soil on plot may be non-optimal at start of the gardening year. The most common problems are lack of nitrogen and soil alkalinity. Typical diseases and pests found at the garden include gray mold, powdery mildew, red spider mites, coccidae, mealybugs, sciaridae flies, thrips, and aphids. More complete information about plant diseases can be found here. Potatoes are known to be prune to disease especially if they’ve been grown on the same spot for multiple years. Gardening stores and some bigger general stores sell pesticides if needed.
Self-made pesticide recipes
Add 2-5dl of liquid mäntysuopa to 10l of water. Mix and spray for example on aphids.
100g crushed garlic, 10l of water. Mix the crushed garlic into boiling water. Set it aside and let it be for 24h. Remove the garlic, and the liquid can be sprayed on top of plants. Works on weevils and mites, and also helps keeping mold away.
1kg fresh or 250g dried nettles, 6l of water. Pour the water on nettles and leave like that overnight. Remove the nettles from water and spray the liquid on plants. Helps keeping aphids away, but also works as a fertilizer that contains nitrogen.