Gardening - Pests: go hard, go early

By: Andrew Steen

We have had a particularly warm winter this year and MetService is predicting a warm, wet summer for the eastern North Island due to a combination of La Niña and what looks to be another marine heatwave emerging. This combination of weather events will provide the ideal conditions for pests and diseases to flourish this summer.

In a warm winter, a higher proportion of pests are able to survive their hibernation or indeed, not even go into full hibernation. This year, I’ve noticed flies coming out on warm days in midwinter; likewise, mosquitoes haven’t really stopped. I spotted the first caterpillars in the veggie garden the other day and already the citrus whitefly are multiplying. Diseases, likewise, are expected to flourish this season, with wet root diseases such as phytophthora loving the higher rainfall levels, mildews and blights having a whale of a time with the higher humidity, and regular rainfall wetting the leaves.

Spring is the time to crack out the arsenal to control these bugs and blights. To borrow a phrase, “go hard and go early”. The ideal opportunity to reduce the coming plagues is now, with preventative measures taken before the populations explode!

For mosquitos I’m sprinkling Mozzie Bits on any standing water (including bromeliads), clearing gutters and looking for any potential habitats like old buckets or upturned lids in the undergrowth. Slugs and snails are getting dealt with a monthly light sprinkle of Quash over all the gardens; with the veggie gardens getting an extra dose. As this product doesn’t seem to affect slugs as much as snails, I’m backing this up with beer traps made from old ice cream containers. Fortunately, I have a home brew left over from last summer that wasn’t the best, now providing a rather large supply of beer for the traps.

Any plants that are prone to root rot I’m dusting around the root system with gypsum and spraying with a chemical sold under various trade names such as Buxus Blight Fighter, Agri-phos 600, Aliette, Phosgard and Foscheck. This spray is also useful against various blights and downy mildew. Another product that I use a lot for leaf fungal diseases is potassium bicarbonate (sodium bicarbonate can also be used, but is not as effective), with the addition of some insecticidal soap or spraying oil to increase its effectiveness.

A combination of insecticidal soap and neem oil is my go-to solution for just about any pests. This combo is highly effective when used regularly, particularly if you focus spray any pests before they can begin their exponential population growth. It can be used on the whole garden, but do be careful on fine-leaved plants such as ferns and on hairy leaved plants like tomatoes. For some reason these tend to burn more easily. I’ll often spray everything else first, then dilute the remaining spray by half before spraying the sensitive plants.

There is no question these products are less effective than some of the chemicals that have been used in home gardens in the past, but all are quite safe to use and soft on the environment. I still shudder to think of my mother using arsenate of lead, carbaryl and mercuric chloride in the 60s and 70s.


Andrew Steens

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