Many gardeners don't like to use lots of chemicals in the garden, but certain insects and problems tempt us to use chemical sprays to deal with pests and diseases. Thankfully nature as always has provided an organic and natural alternative to prevent and cure diseases and control and deter pests. Essential oils available from health food shops and on line can really help us to keep our garden plants healthy, attract beneficial insects and deter creatures that like to eat them, use them as a nursery or dig them up
Fungus: Black spot and mildew can affect roses, especially if they are in a damp spot or there are infected plants in neighbouring gardens. Tea tree is famous as an anti fungal oil, both on humans and plants, but be careful not to get it in your eyes or swallow it. It can prevent and control fungal issues. Add about 8-10 drops to a plant spray bottle and spray all the leaves, above and below.
Flying pests: Neem, Rosemary, Peppermint, Thyme and Clove oils all have uses in the garden as insecticides or flying insect deterrents, Simply add to a plant spray bottle and spray the whole plant. Especially when young shoots are growing. Remember to spray above and below the leaves and replenish regularly, especially after a heavy shower of rain. Shake well every time you spray. You might want to stop spraying once flowers bloom as this may deter pollinating insects.
Slugs and snails: Gastropods hate Cedarwood, Hyssop and pine essential oils. Mix a few drops in a spray bottle and spray in a ring around plants they like to munch. Do this regularly and especially after heavy rain.
Rabbits: Rabbits love new rose shoots as we often find out in our field to our cost! We hear that peppermint oil is abhorrent to those cotton-tailed rose munchers. A few drops applied to strips of cotton left around the plants may help deter them, or a few drops added to a spray bottle and frequent spraying while there are young shoots within rabbit's reach. Not sure how we do this in the field yet, but I'm working on it!
Rodents: Peppermint can deter these critters. A little oil dropped onto some scraps of material which are then placed in areas they may like to frequent can put them off.
Cats: usually don't like Rosemary or Black pepper oil.
Dogs: are put off by the strong scent of black pepper, a few drops in a spray bottle frequently applied to the areas you don't want them around can help deter them, but will be dilute enough to be almost undetectable by humans.
Attracting pollinators: certain fragrant oils attract natural pollinators to your garden. Neroli (orange blossom) is an irresistible attractant for bees, as are the essential oils of many small-blossomed flowers like Lavender, Hyssop, Marjoram, Helichrysum, Basil, Sage, and Rosemary. Also, try Lavender, Yarrow, Catmint, Fennel, Helichrysum, and Sage essential oils to attract more butterflies to your garden.
The information in this article was obtained from this website which contains more detailed information.