Penny Woodward on pest-repellent plants and pest control in gardens. Penny is the horticultural director of the ABC’s ‘Your Garden’ magazine, the author of seven books on gardening and the co-author of a book on tomatoes.
• Healthy gardens are less likely to have pest problems. The start of a healthy garden is healthy soil, containing abundant microbial life, worms and fungi. Compost – preferably home-made – is very important.
• To maintain a healthy balance:
o Avoid using chemical pesticides, which may kill the beneficial micro-organisms in the soil.
o Avoid over-watering and over-feeding plants, which can encourage rapid, sappy growth. Sappy growth produces pheromones, which attract pests.
o Avoid monoculture: grow many different plants together, both flowers and vegetables.
o Practice 3-year crop rotation.
o Encourage predators, especially spiders. Don’t destroy their webs. Ants can also be beneficial, although they do farm aphids, which can be controlled by banding the trunks of susceptible trees. Plant native plants and strongly-scented flowers to encourage birds; have water to encourage frogs and microbats.
o Don’t be in a hurry to destroy bugs. Wait and see, tolerate a little damage, and nature will often work it out for you!
• Chemical-free pest control:
o Snails and slugs: use short lengths of poly pipe banded with copper tape around newly-emerging seedlings
o Birds: use exclusion net bags or waxed paper bags or flywire sleeves to protect fruit. (Not perfect, as our native birds are very smart!)
o White cabbage butterflies: Buy or make imitation white butterflies to place amongst brassicas. The real butterflies will not lay eggs on plants that appear to be already occupied.
o Scented plants can be grown near vulnerable plants so that pests are less likely to find them: sages (especially purple salvia officinalis and pineapple sage, salvia elegans), artemisia, rosemary, scented pelargoniums, dogbane (plectranthus ornatus), bronze fennel, lavenders, tree marigold, thymes, alliums, lemon grass, lemon verbena, bayleaves, winter savory. Many of these can also be made into sprays and have other uses such as in pot pourri, as teas, embrocations, etc.
o Beware! Not all pest sprays on sale as ‘organic’ or ‘natural’ are suitable. Pyrethroid sprays are not. Even some sprays derived from plant-based pyrethrins may have toxic additives. Penny recommended ‘ Yates Nature’s Way Citrus and Ornamental Spray’.
o Further assistance: Renaissance Herbs is a wholesale nursery which can give information about retail plant supply. Eco-Organic is a useful supplier of organic pest control