Pro­tect­ing sea­son’s new pota­toes

The Tribune (NZ) - - GARDENING - WALLY RICHARDS

Now is a good time to buy new sea­son seed pota­toes and sprout them for plant­ing out.

While plant­ing out is mostly gov­erned by frosts and the dam­age they can do to an early crop, there is an even big­ger dan­ger.

The potato psyl­lid in some ar­eas has caused to­tal crop loss.

An early crop of fairly quick ma­tur­ing pota­toes will suf­fer only mi­nor dam­age in most gar­dens.

Later in the sea­son when pest num­bers build, there is a no­tice­able in­crease in dam­age and crop fail­ure.

Potato crops planted in Novem­ber or De­cem­ber will need a lot of pro­tec­tion to pro­duce good spuds for stor­age.

In the worst af­fected ar­eas of New Zealand, Oc­to­ber plant­ings will also need plenty of pro­tec­tion.

The fol­low­ing in­for­ma­tion is taken fromMAF New Zealand’s web page:

‘‘The adult tomato/potato psyl­lid is about the size of an adult aphid but looks like a tiny ci­cada un­der mag­ni­fi­ca­tion.

‘‘The fe­male lays yel­low eggs that are at­tached by stalks to plant leaves, usu­ally to the leaf edges.

‘‘Psyl­lid nymphs hatch from these eggs and af­ter five moults, be­come adults.

‘‘The nymphs are flat scale-like in­sects which are mostly in­ac­tive but move when dis­turbed.

‘‘Later in the sea­son when pest num­bers build, there is a no­tice­able in­crease in dam­age and crop fail­ure.’’

‘‘Nymphs and adults feed by suck­ing plant juices, which is how they are thought to spread a sub­stance called liberib­ac­ter - the toxin that does the dam­age.

‘‘Nymphs and adults se­crete plant sap as white gran­ules called ‘psyl­lid sug­ars’ vis­i­ble on the leaves.

‘‘On toma­toes, symp­toms of psyl­lid yel­lows dis­ease are the yel­low­ing and stunt­ing of the grow­ing tip and a cup­ping or curl­ing of the leaves.

‘‘Many flow­ers may fall off the trusses of in­fected plants and fruit may be small and mis-shaped.

‘‘On pota­toes, psyl­lid yel­lows causes a stunt­ing and yel­low­ing of the grow­ing tip, and the edges of the curled leaves of­ten have a pink blush.

‘‘The stem may have swollen nodes and show a brown­ing of the vas­cu­lar tis­sue.

‘‘Af­ter a while, in­fected pota­toes de­velop a scorched ap­pear­ance and plants col­lapse pre­ma­turely.

‘‘Potato plants that are in­fected at an early stage de­velop nu­mer­ous small tu­bers.

‘‘Other host plants of the tomato/potato psyl­lid in­clude ap­ple of peru, cap­sicum, chilli, egg plant, ku­mara, poro­poro, tamar­illo, pepino and thor­nap­ple.’’

‘Psyl­lid yel­lows’ in toma­toes and pota­toes, and ‘ze­bra chip’ symp­toms in potato tu­bers can dras­ti­cally re­duce crop qual­ity and yield.

The prob­lem is greater than just pro­tect­ing toma­toes and pota­toes. Other plants and weeds, com­mon con­volvu­lus for in­stance, also host the pests, which means they can re-in­fest your crops.

If you leave any ma­ture pota­toes in the ground, cut the tops off and cover the stub­ble.

PHOTO: DAVID UNWIN/FAIR­FAX NZ

To en­sure a de­cent crop of spuds, home gar­den­ers need to adopt com­pre­hen­sive pys­llid pro­tec­tion strate­gies.

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