A field trial was conducted in 2012-2013 at Pukekohe to determine the efficacy of wettable sulphur, applied as a foliar treatment within a reduced insecticide programme, to control tomato-potato psyllid (TPP). Three of the four treatments included wettable sulphur (Kumulus® DF; at 6 kg/ha), either alone or in combination with other insecticides. The remaining treatment was a standard 7 day insecticide spray programme. Spraying for all treatments began at 60% plant emergence on 29 November 2012, and continued until 14 March 2013. The study demonstrated that although sulphur applications may reduce TPP nymph numbers on potato foliage, especially when used in combination with insecticides, sulphur alone is not an adequate TPP management strategy. The field trial results for sulphur-only treatments support previous work suggesting that although sulphur may slow the build-up of TPP populations by deterring egg-laying, the lack of repellence or anti-feeding properties still results in the transmission of Candidatus Liberibacter solanacearum by TPP. Given the ZC results, it is difficult to draw conclusions from this trial about the efficacy of sulphur/insecticide combinations for TPP management.

Tomato potato psyllid (TPP) (Bactericera cockerelli) vectors Candidatus Liberibacter solanacearum a phloemlimited bacterium that can cause a mottled browning discolouration (zebra chip; ZC) in fried crisps Sulphur is mainly used as a fungicide but is also registered in New Zealand as an insecticide against erineum mite (Colomerus vitis) on grapes A field trial to determine TPP response to foliarapplied sulphur found that weekly applications (no insecticides) significantly reduced psyllid nymph numbers in foliage compared with the control (nosulphur noinsecticide) However the incidence of severe ZC in frycooked tubers was higher in the weekly sulphur treatment than with a commercial insecticide spray programme Tubers from both the nonsprayed control and the weekly sulphur treatment had significantly lower yields and specific gravities than those treated with insecticide Sulphur applied alternately with insecticides gave similar results to the commercial insecticide programme promising for the industrys goal of reducing insecticide applications

Zebra chip (ZC) is mottled browning discolouration of cooked potato crisps caused by the bacterium Candidatus Liberibacter solanacearum (CLso) ZC has caused significant problems in the New Zealand potato industry Tomatopotato psyllid (Bactericera cockerelli) (TPP) is a vector for CLso Surround WP formulated from nontoxic kaolin clay and a spreadersticker is effective in protecting fruit trees from various insect pests Sulphur has been widely used to control arthropod pests especially mites Fosetylaluminium has no bactericide properties as such but can change the host susceptibility to some bacteria such as fire blight (Erwinia amylovora) A field trial conducted at Pukekohe to determine the effects of kaolin clay sulphur and fosetylaluminium applied as foliar sprays on TPP potato yields tuber dry matter content and incidence of ZC found that while not reducing ZC sulphur demonstrated potential for reducing TPP nymph numbers in the crop Kaolin and fosetylaluminium were not effective in controlling either TPP or ZC

The tomato potato psyllid (TPP Bactericera cockerelli) survives on volunteer potatoes growing in frostfree areas in winter in the Auckland region and therefore could transmit Candidatus Liberibacter solanacearum (Lso) to commercial crops The survival and oviposition of laboratoryreared Lsoinfected TPP were tested under four selected environmental conditions 1212 h lightdark at 10C; 1311 h lightdark at 12C; 1410 h lightdark at 14C; and 159 h lightdark at 16C on excised leaves from volunteer potatoes (grown in the field during winter) and tomato (grown in the glasshouse) One hundred pairs of adult TPP (10 pairs/leaf) were tested on either potato or tomato in each environmental condition for 7 days Survival of females on potato or tomato was not significantly different between photoperiod but remained unhatched in all tested temperatures Results revealed that Lsoinfected TPP could feed (as indicated by excretory droplets) oviposit and survive on volunteer potatoes in Auckland winterlike conditions and potentially transmit Lso to crops grown in these cooler months

An IPM programme originally developed for vegetable brassicas is now being adapted and extended into other brassicagrowing systems in the South Island including vegetable fodder and seed brassica crops MAFs Sustainable Farming Fund and various industry partners plus government funding is supporting research into best practices to manage the major foliage insect pests in these brassica crops A pest risk assessment survey was undertaken this year to determine in which seasons areas and growing systems pests are a problem Pheromone trap data showed that diamondback moth (DBM) Plutella xylostella survived overwinter as resident populations in localised brassica crops DBM and leaf miners caused serious problems for many growers DBM is resistant to standard broadspectrum insecticides but growers are still applying these insecticides which disrupt natural enemies of insect pests European leaf miner Scaptomyza flava is the key leaf miner pest and appears not to be attacked by the larval parasitoid Asobara persimilis which could be introduced from the North Island Field surveys also showed that the recently introduced larval parasitoid of white butterfly Cotesia rubecula has spread naturally to North and South Canterbury