Ze­bra chip field tri­als

NZ Grower - - PRODUCT GROUPS - By Glenys Chris­tian

Peter Wright, who is site man­ager at the Plant & Food Re­search cen­tre at Pukekohe, led a field day for grow­ers at Pa­tuma­hoe in mid-jan­uary re­port­ing on the re­sults of field tri­als. His work looked at the ef­fect of JMS Stylet Oil fo­liar ap­pli­ca­tions com­bined with in­sec­ti­cides on the tomato-potato psyl­lid (TPP), crop yields, tu­ber dry mat­ter con­tent and ZC in pota­toes.

Al­though grow­ers gen­er­ally rely on reg­u­lar ap­pli­ca­tions of mainly broad spec­trum in­sec­ti­cides to con­trol TPP, they may not be killing TPP feed­ing on fo­liage fast enough to pre­vent Can­di­da­tus Liberib­ac­ter solanacearum (Lso) trans­mis­sion, he said. So the search had be­gun for a TPP re­pel­lent which could be used in in­te­grated pest man­age­ment pro­grammes (IPM) to re­duce in­sec­ti­cide ap­pli­ca­tions. “Min­eral oils have a re­pel­lent ef­fect to in­sect pests that dis­cour­age egglay­ing and feed­ing, and can kill in­sect eggs through con­tact tox­i­c­ity and suf­fo­ca­tion,” he ex­plained. The field tri­als were car­ried out over three sea­sons from 2012, test­ing JMS Stylet Oil fo­liar ap­pli­ca­tions both on their own and in com­bi­na­tion with in­sec­ti­cides for ef­fi­cacy against TPP, ef­fect on ZC in­ci­dence and sever­ity, and crop yields and phy­to­tox­i­c­ity to potato plants.

The tri­als were planted in Novem­ber in a ran­domised Latin square de­sign in six rows which were 10 me­tres long and three me­tres wide. There were five treat­ments of five repli­ca­tions each. The five treat­ments were: 1. Seven-day in­sec­ti­cides and reg­u­lar

wet­ting ad­ju­vants.

2. Seven-day in­sec­ti­cides and JMS

Stylet Oil.

3. 14-day in­sec­ti­cides and JMS Stylet Oil al­ter­nat­ing with just JMS Stylet Oil.

4. 14-day in­sec­ti­cides ti­cides plus JMS Stylet

Oil and Du-wett u-wett al­ter­natin­gal­tern with the same treat­ment so there was re­duced wa­ter vol­ume. 5. Seven-day JMS Stylet Oil. In the first sea­son re­sults on Fe­bru­ary 2, 2014: Treat­ment 1 had the higher num­bers of TPP eggs and aphids than treat­ments 2 and 3. Treat­ment 4 had the low­est num­bers of TPP nymphs, eggs but slightly higher num­bers of aphids. Treat­ment 5 had the high­est num­bers of TPP nymphs and eggs, and the high­est aphid num­bers.

_____________________________________________________________ A three-year trial by Plant and Food Re­search sci­en­tists has shown that us­ing in­sec­ti­cides ev­ery 14 days al­ter­nat­ing with JMS Stylet Oil and Du-wett (which re­duced wa­ter vol­ume) low­ered lev­els of ze­bra chip (ZC).

The trial also looked at the ef­fect on TPP preda­tors, in­clud­ing brown lacewing and hov­er­fly adults, lar­vae and eggs: Treat­ment 1 had low num­bers of both in­sects’ eggs, while treat­ment 2 showed no ev­i­dence of ei­ther. Treat­ment 3 had low lev­els of brown lacewing eggs. Brown lacewing adults, lar­vae and eggs were all found in treat­ment 4. Treat­ment 5 had the high­est num­bers of brown lacewing lar­vae and eggs as well as hov­er­fly eggs.

Mar­ketable tu­ber yield was high­est from treat­ment 1. Dry mat­ter con­tent of mar­ketable tu­bers was slightly higher for those grown un­der treat­ment2. Mar­ketable tu­ber yield and dry mat­ter con­tent of mar­ketable tu­bers were low­est in treat­ment 5.

“Min­eral oils have a re­pel­lent ef­fect to in­sect pests that dis­cour­age egg-lay­ing and feed­ing, and can kill in­sect eggs through con­tact tox­i­c­ity and suf­fo­ca­tion”

But Wright said “where the rubber hit the road was the ZC score of pota­toes in the dif­fer­ent treat­ments and the per­cent­ages with se­vere ZC”. Treat­ment 5 had the high­est per­cent­age of se­vere ZC at 18%, while

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