Natural pest control: will garlic keep bugs at bay?

OUR gardening expert answers your questions about garlic as a pest deterrent, wisterias, grasshoppers and borers.

Garlic and garlic chives have a low repellency rating, needing regular cutting for any effect.

RESEARCHING natural pest control methods, I read that planting garlic is a great organic alternative. Is this effective? Does it work on flowering plants and vegies? — Kathleen Willes, by email

Jackie French’s recently updated Guide To Companion Planting (Manna Press, $18.95) is your go-to book. She gives garlic and garlic chives a low repellency rating, needing regular cutting for any effect. Both are useful foods; garlic chives are attractive and the flowers attract beneficial insects, but I can attest aphids adore garlic chives. Effectiveness is the same around any plants.

Could I grow a white wisteria in a west-facing position in Brisbane? How long would it take to reach 2m and what soil is required? — Samantha Bilton, Brisbane

Wisterias prefer areas with cold winters. They grow as far north as Brisbane in the right position but west facing might be too exposed. Ideally the roots should be shaded to keep cool, but it still might not flower well. They’re not fussy about soil, but the better it is the faster the growth. With optimum care yours could reach 2m in its second year. Alternatives for your climate are climbing frangipani (Conemorpha fragrans), Mandevilla ‘White Fantasy’, Pandorea ‘Lady Di’ or white bougainvillea.

What can decimate all our newly planted cucumber and zucchini seedlings? There are no snail trails. We have seen some grasshoppers on nearby grasses. — Helen Dawson, Perth

Grasshoppers could be responsible, or caterpillars, earwigs, slaters or possums. Physical protection against most of these is easiest by covering each seedling with half a clear soft drink bottle until they’re big enough. For caterpillars, use Dipel, a biological control, or Success Ultra. Eco-neem will treat grasshoppers on nearby plants but is not registered for food plants.

This season we’ve noticed borers in our macadamia crop. How can we treat a huge, 20-year-old tree? — Rosina Owen, Gold Coast

Macadamia nut borers are the larvae of a moth. They also affect lychee, longans and some ornamentals. Although intended for commercial use, Trichogramma wasps, which seek out and parasitise the eggs, are available, with excellent information, from bioresources.com.au. A pump sprayer with Dipel or Success Ultra might reach the lower parts of the tree; you must spray after hatching but before caterpillars enter the nuts.

Flora

Dedicated amateur and professional growers of Australian native plants will be thrilled by Pests, Diseases, Ailments and Allies of Australian Plants, co-written by David L. Jones, Rodger Elliot and Sandra Jones (New Holland, $45). This triumvirate of esteemed experts has fully revised and updated a classic, first published in 1986 and reprinted several times. It’s the authoritative reference, with meticulous coverage and detail including host plants, feeding habits and climatic regions. It’s made highly usable by excellent colour photographs and line drawings, and useful shortcut sections to help identify problems. The emphasis is on natural rather than chemical controls to minimise ecological interference. For home gardeners wanting a more general pest and disease reference, I’ll be reviewing the book for you in coming weeks.