Tim G Grout and Kim C Stoltz Citrus Research International Nelspruit Killing Hitchhikers Without Affecting IPM

Quarantine Pests vs. IPM Pests of little economic significance in the orchard sometimes become market barriers Efforts to control these pests at the levels required by export markets eliminate natural enemies and compromise the sustainability of Integrated Pest Management If we can control these quarantine pests with postharvest fumigants, we can improve IPM in the orchard

The Hitchhiker: Grain Chinch Bug Macchiademus (Blissus) diplopterus (Lygaeidae) is a wheat pest in the W Cape In , in SA fruit exports to the EU it was the 2 nd most important insect, representing 38% of insect interceptions (worse than fruit fly)* Aestivating adults are extremely tolerant to cold *Europhyt, non-EU trade alert list

Seeking Sites for Aestivation When wheat is harvested GCB looks for suitable cracks and cavities in which to aestivate Orchards with fruit having a stylar-end opening such as pears or navel oranges are most susceptible

The Grain Chinch Bug Problem Bottom of a pear box Base of pear Cut pear base Navel opening Cut navel opening

Materials and Methods Only adults infest fruit and were easy to collect from behind bark on Eucalyptus trees While aestivating, adults survive well in the presence of moisture without any food Vapormate is a GRAS fumigant comprising a patented mixture of ethyl formate and carbon dioxide Early trials in plastic ventilated containers without plant material: compared Vapormate with 60% CO 2 Further trials where bugs were sprinkled on pears and navel oranges and given 20 h to hide before fumigation. Also increased Vapormate dosages. Large-scale verification trials were conducted with bugs in ventilated containers surrounded by fruit

Fumigation Apparatus Used Vaporiser Vapormate Compressor Gas + air mix to chambers Gas analyser

Grain Chinch Bug Fumigation GCB fumigated without fruitGCB left for 20 h to move into navels Fumigation of infested pears

GCB Early Results: No Fruit Treatments at 25 °C Mortality (%) Vapormate 112 g/m 3 for 24 h100 Vapormate 112 g/m 3 for 4 h97.8 Vapormate 170 g/m 3 for 4 h98.8 Vapormate 170 g/m 3 for 6 h (3 623 bugs)100 Carbon dioxide 60% for 24 h100 Carbon dioxide 60% for 4 h0 Vapormate was more effective than carbon dioxide

Grain Chinch Bug Results: With Fruit Fruit type Treatments at 25 °C Mortality (%) GCB on/in fruit (%) PearsVapormate 170 g/m 3 for 6 h (1 942 bugs) Navel oranges Vapormate 197 g/m 3 for 6 h (1 588 bugs) Some Vapormate may have been absorbed by the fruit, resulting in lower efficacy

GCB Results: Diff Dosages + Fruit Treatments at 25 °C NumberMortality (%) Vapormate 250 g/m 3 for 4 h Vapormate 315 g/m 3 for 4 h Vapormate 250 g/m 3 for 6 h Vapormate 315 g/m 3 for 6 h Vapormate at 250 g/m 3 for 4 h looked promising

GCB Results: Diff Temps + Fruit Treatments: Rep 1NumberMortality (%) Vapormate 250 g/m 3 for 4 h at 15°C Vapormate 250 g/m 3 for 4 h at 25°C Decided to verify efficacy of Vapormate at 250 g/m 3 for 4 h at 15°C Treatments: Rep 2NumberMortality (%) Vapormate 250 g/m 3 for 4 h at 15°C Vapormate 250 g/m 3 for 4 h at 25°C Treatments: Rep 3NumberMortality (%) Vapormate 250 g/m 3 for 4 h at 15°C Vapormate 250 g/m 3 for 4 h at 25°C504100

GCB Verification Results: With Fruit Treatment: Rep 1NumberMortality (%) Untreated but held for 4 h at 15°C2904 Vapormate 250 g/m 3 for 4 h at 15°C Treatment: Rep 2NumberMortality (%) Untreated but held for 4 h at 15°C5021 Vapormate 250 g/m 3 for 4 h at 15°C Treatment: Rep 3NumberMortality (%) Untreated but held for 4 h at 15°C1784 Vapormate 250 g/m 3 for 4 h at 15°C Vapormate at 250 g/m 3 for 4 h at 15°C killed GCB with no survivors

Effect on Fruit Quality Vapormate Control Packham Triumph pears

Effect on Fruit Quality Nectarines

Effect on Fruit Quality Peaches

Fruit Quality: Waste Accelerated Damaged pears had large necrotic areas around wounds after fumigation with Vapormate This was not seen with sound fruit and no off-tastes were detected with any fruit types after 4 h fumigation

Siculobata sicula Oribatulidae Scavenger mites present in high numbers at harvest under calyx Survive packhouse treatment and emerge after palletisation.

Siculobata sicula Oribatulidae Vapormate 250 g/m 3 for 4 h at 25°C 100% mortality of mites

Other Promising Results: Mealybug Treatments at 25°CLife stageMortality (%) Vapormate 225 g/m 3 for 4 h2 nd and 3 rd instar P. citri & P. ficus 100 Vapormate 112 g/m 3 for 4 hAdults100 Vapormate 112 g/m 3 for 2 hAdults100 Vapormate 56 g/m 3 for 4 hAdults100 Vapormate 112 g/m 3 for 6 hEggs0 Vapormate 112 g/m 3 for 18 hEggs98.3 Vapormate 112 g/m 3 for 24 hEggs99.7 Vapormate 225 g/m 3 for 24 hEggs99.9

Mealybug: Vapormate & CO 2 TreatmentsEgg hatch (%)* Vapormate 225 g/m 3 for 4 h3.0 a Vapormate 170 g/m 3 for 4 h7.6 § Vapormate 112 g/m 3 for 4 h33.2 b Carbon dioxide 60% for 24 h15.6 b *Relative to an untreated control; § From a different trial Vapormate was more effective than carbon dioxide

Mealybug: Results Egg Hatch Treatments at 25°CSpeciesHatch (%)* Vapormate 250 g/m 3 for 4 h at 25°CP. citri2.2 Vapormate 250 g/m 3 for 10 h at 25°CP. citri0.5 Vapormate 250 g/m 3 for 24 h at 25°CP. citri0.1 Vapormate 250 g/m 3 for 24 h at 15°CP. citri4.6 (NS) Vapormate 250 g/m 3 for 24 h at 25°CP. ficus3.4 *Relative to an untreated control Little difference between 4 and 24 h fumigation Fumigation alone will not provide Probit 8.7 control levels

Promising Results for FCM* Eggs Vapormate was more effective than carbon dioxide Vapormate at 250 g/m³ for 4 h will probably cause more than 90% mortality of FCM eggs TreatmentsMortality (%) Vapormate 112 g/m 3 for 24 h100 Vapormate 225 g/m 3 for 6 h94.5 Carbon dioxide 60% for 24 h87.9 *False codling moth, Thaumatotibia leucotreta

Conclusions Vapormate 250 g/m 3 for 4 h is very effective in controlling the Grain Chinch Bug and should be registered to prevent further fruit export rejections Motile life stages of mealybug are very susceptible to Vapormate and registration should be pursued, but complete control of eggs cannot be guaranteed Vapormate at 250 g/m 3 for 4 h will probably control many external, motile insects and mites on fruits and flowers

Acknowledgements Fruit growers for providing some of the fruit Shelley Johnson, Martin Gilbert and Jade North for providing us with grain chinch bug Peter Stephen for some photographs The Post-Harvest Innovation Programme for partial funding Afrox for gas and vaporiser