Home and Garden
August feels like life in the transit lounge. Even though it's not yet spring, I like to feel I've already left winter behind and I'm just waiting to move on.
It's the pause before the flurry of action in the spring garden, a calm anticipation hiding wild excitement, with no-one wanting to make the first move, lest they seem impatient.
Not me. Bring it on, I say. I'm always queued up at the door, keen to go catch a plane or plant my first potatoes.
As many Nelsonians know, next Monday, the first in August, marks the start of the potato-planting season.
Spade and spuds in hand, I'm ready to get amongst it and have always supported a move to make Spud Monday a public holiday, as it once was in Nelson - the perfect antidote to the post-winter blues.
But, sadly, potato growing is becoming more and more challenging as gardeners report decimated crops from the potato psyllid and the nasty little STD (sucking transmitted disease) it's reputed to spread.
Originating from North America, the tiny psyllid was first spotted in an Auckland tomato house and adjacent potato paddock in 2006, and later found in a pepper greenhouse near Taupo.
Being a strong flyer and carried on the wind, it's made a meal of spreading through the country and doing what it does best, sucking on not just potato plants, but also tomatoes, peppers, chillies, eggplants, tamarillo, kumara and our native poroporo. That's because they're all related, in either the Solanaceae family or, with kumara, the Convolvulaceae.
Just like humans, plants like to keep things in the family, and in terms of adversity, Solanaceae seem to attract more than their fair share of pests and diseases.
Remember, it's tomatoes that have been targeted in the new Draft Import Health standards by the Ministry of Primary Industries (see www.biosecurity. govt.nz/biosec/consult/draft-ihs-tomato-seed-for-sowing), which are aimed at putting tighter controls on seed importation to prevent a whole new range of nasty viruses hitching a ride to "clean, green" New Zealand and affecting similar Solanaceae crops here.
That's because once here, as the old argument goes, these nasty diseases and pests like potato psyllid are notoriously difficult to control. Annoying as controls may be, it's easier to put the brakes on them at the borders than to have the challenge of combating them here.
Just ask any kiwifruit grower how they feel about pollen importation, now implicated in the arrival and spread of the devastating BSA disease.
And, just as bees can spread diseases from flower to flower, potato psyllid spreads a debilitating bacterial pathogen called liberibacter that lives in plants.
Like the insidious pathogen spread by passion vine hopper and believed to cause the decline in our native cabbage trees, liberibacter is thought to cause psyllid yellows in tomatoes and potatoes, as well as distinctive zebra chip, causing dark rings, inside the tubers.
On top of that, liberibacter drastically reduces the quality and yield of crops.
If you've seen the symptoms but no sign of the culprit, it's probably because the potato psyllid is so small, about the size of an aphid, although it looks like a cicada. Don't be fooled by the size.
After the female psyllid lays eggs on the edges of plant leaves, the young go through five stages to adulthood, feeding and sucking the life out of your potato and tomato plants.
That's probably when you notice the effects, with stunted, yellowed plants and leaves that look distorted and scorched. Tomatoes will drop their flowers and, if infected at an early stage, potato crops can develop lots of small tubers instead of the kind of crop you expect when you dig them.
In other words, it's not until the damage is done that you're likely to notice - and then it's probably too late to do much about it.
Unfortunately, control is like trying to keep a lid on aphids.
The key is attempting to keep the damage to a minimum, especially at the start of the growing season, when your plants are most susceptible to psyllid yellows.
While Plant and Food Research and other regulatory authorities are reluctant to recommend any specific pesticide sprays, they say some insecticides - including organic ones - may work, but obviously getting at the little critters is part of the problem.
Instead, you may prefer, as I do, to follow the recommended prevention measures that might help, such as removing self-sown potato and tomato plants and keeping the garden clean to prevent the psyllids overwintering, and trying to attract plenty of beneficial predatory insects to your garden.
Plant and Food Research says several predators, including some ladybirds and lacewings, will feed on psyllids.
Which is a good reason to grow honesty Lunaria in the spring garden, to attract the predators that also feed on the early spring flowers and shallow nectarines of honesty.
And, as always, the inevitable solution to a huge problem brings you back to the need in the home garden, as well as in the paddock, to maintain the biodiversity and, as much as possible, keep things in balance.
You may not eradicate potato psyllid, but you just may be able to keep these unwanted arrivals to a minimum.
- © Fairfax NZ News