INTEGRATED PEST MANAGEMENT
Growers should be scouting for mealybug regularly, by inspect-ing underneath calyces and thereby determining percentage
of fruit infested. Where mealybug is under good biocontrol, infestation should peak during December in the northern production areas and during January in the Cape production areas. If mealybug infestation does not decline during January and February, respectively, suppression with a chemical treatment is advisable on early maturing cultivars. Unfortunately, buprofezin (Applaud), which was the most effective corrective option for mealybug control, may no longer be used at this time. Therefore, the available corrective options are sulfoxaflor (Closer), fenpyroximate (Lesson) and spirotetramat (Tivoli). These products may not have a specific corrective registration, but their withholding periods do permit late season use. Although registered, methomyl is not a preferred option, as it is not effective at the dose generally registered for mealybug. And methomyl is the only registered corrective option for red scale. It would therefore be wise to restrict corrective usage to red scale alone, in order not to expedite the onset of resistance. Ensure that the pre-harvest interval of any product used is complied with.
The species of mealybug present should also be determined, as it appears that the biocontrol complexes of mealybug species other than citrus mealybug, might not be as effective as that of citrus mealybug. Therefore, treatments can be applied more readily when other species are identified as the dominant species. The phytosanitary status of certain species must also be borne in mind.
Finally, a mealybug infestation can also attract a carob moth infestation. Therefore, if the fruit is to be exported to a market that is sensitive to carob moth, mealybug must be effectively controlled well before harvest.
False codling moth
All growers intending to export to Europe should be fully compliant with the False Codling Moth Risk Management System (FMS) for Export of Citrus to the European Union, and consequently the Good Agricultural Practices (GAP) described in CRI’s Production Guidelines for the Control of FCM on Citrus. For phytosanitary reasons, FCM must be controlled throughout the season to as close to a non-detectable level as possible, using a combination of orchard sanitation and various effective registered control measures. Weekly monitoring of fruit infestation, as described in the FMS, will provide an accurate indication of how effective the control programme has been and what level of compliance there is with the export (shipping) options described in the FMS. The following sprayable insecticides are registered and available for use against FCM: the granulovirus products (Cryptogran, Cryptex and Gratham), Methoxyfenozide (Runner, Walker, Sprint-er, Chaser, Marksman), Delegate, Coragen, Warlock, Broadband and Eco-Bb (both entomopathogenic fungi (EPF)), ensuring compliance with market-specific restrictions. The granuloviruses and EPF can be used up until the day of harvesting. However, note that according to label recommendations, the EPF are not suit-able corrective options for FCM and are thus not listed as such by PhytClean. A virus application should be applied shortly after a peak in FCM activity, determined by the use of a pheromone trap. However, this may be difficult to determine late in the sea-son, when FCM levels are low and generations are overlapping. Methoxyfenozide (Runner or Walker), Delegate and Coragen are all registered to be applied once or twice per season and all have withholding periods of 30 days or less for most markets. Warlock is recommended to be reapplied 7-10 days after the first application. Therefore, these products are suitable for a final application against FCM before harvest, which ideally should not be applied later than 3-5 weeks before harvesting begins. Such a practice is strongly recommended. Other chemical options are triflumuron (Alsystin), teflubenzuron (Nomolt), fenpropathrin (Meothrin) and Cypermethrin. However, there are some difficulties associated with these products, such as prohibitive MRLs for certain markets, development of resistance by FCM, or secondary pest repercussions. They are therefore not preferred as options for FCM. In addition to the insecticides, there are now four mating disruption products – Isomate, Checkmate, Splat and X-Mate – and an attract and kill product, namely Last-Call FCM. However, all of these products are most effective when their use is initiated early in the season, while FCM levels are still low. If this has not been done, initiation of their use late in the season is not recommend-ed. Additionally, as the weather cools towards autumn, these pheromone-based products may become less effective due to a reduction in release rate. In such a case it may be necessary to follow up these treatments with a spray for FCM.
The period February to May is the optimal time for bud mite sprays and fenpyroximate (Mitigate or Lesson) can be used during this period at 150 ml per 100 L water. The pre-harvest intervals for most markets are 28 days. The only exception to this is for citrus types other than mandarins going to South Korea, for which the pre-harvest interval currently remains 150 days, or no applications after the end of October. In trials with fenpyroxi-mate, this product was found to have similar efficacy to Acarol against bud mite. Fenpyroximate will also suppress citrus red mite when sprayed during autumn for bud mite and the Lesson product is registered against all other citrus mites as well, and most recently, also mealybug.
Fruit flies are pests of phytosanitary concern. There is a zero tolerance of fruit fly eggs and larvae in fruit consignments for export. The fruit fly pests affecting citrus are: Ceratitis capitata
(Mediterranean fruit fly or Medfly), Ceratitis rosa (Natal fly) and Bactrocera dorsalis (Oriental fruit fly). The latter is present in the provinces of Lim-popo, Mpumalanga, North West, Gauteng and KwaZulu-Natal (excluding magisterial districts of Amajuba, uMgungundlovu, uMzinyathi, uThuke-la and Zululand). Ceratitis rosa was recently split into two species: Ceratitis rosa and Ceratitis quilicii (Cape fly). Both species are present in SA. The status of citrus for C. quilicii must still be confirmed. For export of citrus to EU, growers must imple-ment the Citrus Fruit Fly Management System
(Citrus FFMS), which consists of two Fruit Fly Systems Approaches (FF SA): one for lemons and limes (FF-SAL), and one for other citrus types (FF-SAO). For both FF-SAL and FF-SAO, Phytclean registration is as prescribed by the False Codling Moth Management System (FMS). In FF-SAL, there are two independent measures that mitigate the risk of fruit flies:
(1) non-host status of commercial export grade lemons and limes for fruit fly pests of citrus and
(2) PPECB phytosanitary inspections of fruit packed for export. In FF-SAO, there are three independent measures that mitigate the risk of fruit flies:
(1) Fruit Fly Good Agricultural Practices (FF GAP) with Packhouse Delivery Inspections as the end point,
(2) packhouse grading and PPECB phyto-sanitary inspections of fruit packed for export and
(3) postharvest shipping conditions as deter-mined by FMS.
FF GAP consists of two components: monitoring and pre-harvest control. Monitoring
of Medfly and Natal fly should be carried out using Capilure and Questlure baited Sensus traps. Monitoring of Oriental fruit fly should be conducted using bucket type traps such as Chempac Bucket trap, McPhail type trap and Lynfield trap baited with Methyl Eugenol
(ME). Thresholds exist for the Sensus trapping systems and the ME trapping systems and these should be adhered to, particularly when fruit are susceptible to attack (at and after colour break). For Medfly, the threshold in a Capilure baited trap is four males per week. For Natal fly, the threshold in a Capilure baited trap is two males per week. When using Questlure in a Sensus trap, the threshold is one female fly per trap per week for all fruit fly pests of citrus. For the Oriental fruit fly, the threshold in a methyl eugenol baited trap set by Department of Agriculture Land Reform and Rural Development (DALRRD) is three flies per trap per week. There are other registered monitoring systems for fruit fly pests of citrus: (1) The Biolure fruit fly containing am-monium acetate, trimethylamine hydrochloride and putrescine in Chempac Bucket trap AND (2) The Chempac FF lure (Trimedlure) in Chempac Delta trap. There are, however no thresholds with the Biolure and Chempac FF lure trapping systems. Monitoring of Oriental fruit fly per Production Unit Code (PUC) is a requirement for phytosanitary registration of citrus, deciduous and subtropical fruit for export to the special markets (USA, Japan, South Korea, China and the European Union – EU). Each PUC should have
at least one ME baited trap for monitoring of Oriental fruit fly. Monitoring of Oriental fruit fly should be carried out throughout the year. Trapping guidelines for surveillance of Oriental fruit fly in fruit production areas should be followed. Guidelines are avail-able at http://www.daff.gov.za under Plant Health/Exporting from SA/Phytosanitary registrations for special export markets or at http://www.citrusres.com/downloads/market-access. Trap details and trap servicing should be recorded as per trapping guidelines. All trapping results should be supplied to Early Warn-ing Systems (e-mail: firstname.lastname@example.org) at the end of each export season. The recommended densities for registered fruit fly trapping systems are provided in the fruit fly chapter of the Integrated pest and disease management volume of the citrus production guidelines (http://www.citrusres.com/downloads/production-guidelines). All fruit fly traps must be checked weekly and trapping records should be documented. Lures and insecti-cides inside traps must be replaced every 6-8 weeks. Detection of suspect Oriental fruit fly specimens in areas considered free of this pest should be reported immediately to the relevant surveil-lance co-ordinator (Citrus – Aruna Manrakhan: 013 759 8000) or to DAFF (Jan Hendrik Venter: 012 319 6384). Fruit fly control should be initiated in middle to late summer (either January or February, depending on regions). However, for farms either with mixed fruit crops (such as mangoes or deciduous fruit) or near fruit types prone to high fruit fly infestation, fruit fly control should be implemented by December. Fruit fly baiting and good orchard sanitation form the core of fruit fly control practices. For fruit fly baiting, the use of either one or a combination of the following registered methods is recommended: bait sprays
(either mixture of protein hydrolysate and malathion/trichlorfon or mixture of HymLure and cyantraniliprole or GF-120 or FF 240), M3 fruit fly bait station, Magnet MED and Cera Trap. For the use of malathion in bait sprays, the pre-harvest interval is seven days for citrus to all markets (including EU) except Canada (14 days), Switzerland (28 days) and Korea (grapefruit and lemon – 28 days). The pre-harvest interval when using either GF-120 (spinosad) or FF 240 (spinosad) is one day for all markets. The pre-harvest interval with cyantraniliprole (ExirelTM 100SE) is one day for all markets, except for Taiwan. When using either bait stations such as M3 fruit fly bait station and Magnet MED, or mass trapping such as Cera Trap, there is no pre-harvest interval. Precautions must be taken when using bait sprays on specific citrus cultivars when fruit is at certain maturity stages. Ground-based spray application of GF-120 should be avoided on Nadorcott at the green and colour break stages, due to possible phytotoxicity on fruit. Ground-based spray application of GF-120 is, however safe to use when Nadorcott fruit is at the fully coloured ripe stage. In areas affected by the Oriental fruit fly, the Male Annihilation Technique (MAT) must be used. A number of male annihilation methods such as wooden fibre blocks impregnated with ME and malathion (e.g. ready to use Invader-b-Lok, Chempac ME liquid for combination with malathion 500 EC with the mixture impregnated into wooden blocks), as well as SPLAT technology containing ME and spinosad such as STATIC Spinosad ME have been registered for B. dorsalis control in SA. All fruit fly control products should be applied correctly. Instructions provided in labels of control products must be followed strictly. Fruit fly control must always be combined with proper management of insect pests such as FCM, which also damage mature fruit. All records of fruit fly control practices including MAT application need to be kept. In all B. dorsalis infested areas, a removal permit is required
for movement of fruit outside those areas. For applications of removal permits, either contact the relevant officials at DALRRD: 012 309 8735/8791/8763, or send an e-mail to RemovalPermits@daff.gov.za.
Grond en wortelmonsters behoort elke drie jaar geneem te word om sodoende die sitrusaal-wurm en Phytophthora status in sitrusboorde te bepaal. Resultate sal dien as `n bestuurshulpmid-del wat gebruik kan word om grondpatogene effektief te beheer.
Weens die gevaar van fitotoksisiteit op gevoe-lige sitruskultivars tydens hoë temperature, wat gedurende Februarie/Maart kan voorkom, moet die gebruik van fosfonaatblaarbespuiting streng volgens die etiket geskied (GEEN SAGTESITRUS KULTIVARS behoort weens hul gevoelige skille gedurende hierdie tyd van die jaar met hierdie produkte gespuit te word nie). Hoë dagtempera-ture, tydelike vogstremmings en warm bergwinde kan veroorsaak dat fosfonate swart stippeltjies soortgelyk aan koperskade op vrugte veroorsaak. Bome moet daarom nie gespuit word as toestande nie optimaal is nie. ’n Wortelvrot-beheerprogram (blaarbespuiting) sal bruinvrot ook effektief kan beheer.
Bruinvrot ontwikkel slegs wanneer die klimaats-toestande gunstig is vir die patogeen (Phytoph-thora) om te infekteer en te ontwikkel. Indien dit dus ŉ droë najaar is en geen of slegs ligte reënbuie voorkom, is voorkomende fosfonaat-blaarbespuitings nie nodig nie. Indien dit egter ŉ nat najaar is kan bome met kontakmiddels soos koper of mancozeb (let op beperkings na markte) asook sistemiese produkte soos fos-fonate (let op etiket-aanbevelings vir weerhou-dingstydperk en waarskuwings), gespuit word om bruinvrot te beheer. Bo en behalwe droogte en hitte kan ŉ oormaat vogtige toestande (baie reën) ook bome onder tydelike verwelkte toe-stande plaas, wat ŉ gevaar inhou vir blaar-bespuitings. Bome moet dus nie tydens of kort na sulke toestande gespuit word nie. Laastens beïnvloed drag ook ŉ boom se gevoeligheid vir droogtespanning. Hoe hoër die drag, hoe gevoeliger is die boom vir uitdroging en hoe groter is die risiko vir fitotoksisiteit.
Wortelmonsters kan enige tyd van die jaar getrek word om die status van die sitrusaalwurmpopulasies in boorde te bepaal. Wyfietellings word gebruik om te bepaal of die toediening van ŉ aalwurmdoder gereg-verdig is. Die drempelwaarde voordat ŉ aalwurmdoder oorweeg word is 1000 wyfies/ 10 g wortels. Daar word aanbeveel dat aalwurmdodertoedienings ’n aanvang neem tydens die begin van die reënseisoen. Dit sou daarom die regte tyd wees vir produsente in die Wes-Kaap om hulle aalwurmmonsters in Maart te trek, sodat hulle weet watter boorde om te behandel wanneer winterreëns begin. Residu-weerhoudingstydperke moet in ag geneem word. Dit is belangrik om ŉ aalwurm-beheerprogram te volg aangesien ŉ enkele aalwurmdodertoediening nie effektief genoeg is nie, en het geen noemenswaardige onder-drukking van die aalwurmpopulasies op die lange duur nie. Meermalige toedienings twee maande uit mekaar verseker dat die larwes wat uitbroei gedood word voordat hulle volwasse wyfies kan raak wat weer eiertjies kan lê. Tydens die toediening van aalwurmdoders is dit uiters belangrik dat ten minste 40 mm besproeiing toegedien word nadat produkte toegedien is, om te verseker dat die middels in die grond-profiel ingewas word. Die meeste aalwurmdoders loog baie stadig. Die effektiwiteit van die doders word dus belemmer, indien hulle nie behoorlik deur die wortelsone versprei word nie. Geen aalwurmdoder behoort deur drupbesproeiing-stelsels toegedien te word nie. Indien toedienings in boorde met druptoediening gedoen moet word, behoort die middels as ŉ bandplasing (half meter aan beide kante van die drupperlyn) oor die drupperlyn gedoen te word. Dit kan wel deur mikro-besproeiingstelsels toegedien word. Indien dit beplan word om ŉ boord te verwyder behoort ŉ aalwurmmonster geneem te word voordat die boord verwyder word, sodat dit bepaal kan word of sitrusaalwurms teenwoordig is. Dit dien as ŉ bestuursriglyn om ’n geskikte onderstam te kies in gevalle waar ŉ herplant-strategie uitgewerk moet word.
Fruit production and quality
If properly timed, regulated deficit irrigation can result in increased total soluble solids (TSS) and an increase, or no response in titratable acidity. Deficit irrigation retards the breakdown of acid and can influence the solids:acid ratio at harvest for better or worse, depending on cultivar characteristics. It is mainly aimed at early cultivars like Satsuma, but other early maturing cultivars with low internal quality could benefit. Less water is applied, and at longer intervals. Therefore, irrigation is continued but at a reduced level. Trees should be irrigated lightly two weeks prior to harvest. No water stress should be imposed during the initial growth phase of the fruit, i.e. during and after flowering, but only during the final maturation phase, i.e. the last two months prior to harvest (January for Satsuma). Any water stress earlier than the end of January could lead to reduced fruit size and loss of rind integrity. In high rainfall areas, regulated deficit irrigation may not be successful. The deficit should be imposed slowly, so that the trees can adjust without symptoms of drought. Severe water stress can have adverse effects on tree health, fruit size and fruit quality. High nitrogen is antagonistic to the effect of deficit irrigation. Management of this technique is much easier when trees are planted on ridges, and when the right scheduling equipment is used. Additionally, regulated deficit irrigation imposed the last two months prior to harvest also enhances the rate of colour development. Selective harvest of outside fruit and delaying harvest of inside fruit will result in a higher proportion of fruit with higher TSS and better colour. Maturity indexing on early cultivars like Satsuma should commence.
Maturity indexing is done to predict the rate of change in fruit maturity in order to harvest fruit at optimal maturity, to maintain acceptable commercial shelf life. The aim is to define changes or rate of change in acids and sugars and to build up a data base over a number of years for comparison. Random sampling of fruit every week from each of 10 representative trees should start 4-6 weeks before the expected harvest date. Titratable acidity is determined by titration with sodium hydroxide. Sugar content(Brix) is determined using a refractometer, and the sugar:acid ratio calculated and fruit colour should be read from a colour chart. All the parameters mentioned above should be plotted on a graph over time. Once plotted, trends will become apparent, harvest dates can be estimated, and problem areas in internal and external quality parameters can be identified and manipulated.
Fruit growth and size: Fruit growth during this time is important to achieve optimum size at harvest. Fruit growth is in the peak of phase II, in which the majority of fruit size increase takes place for most cultivars (Figs. 1 and 2). Ensure optimal irrigation and try to avoid stress conditions, as this might have an adverse effect on fruit size. Fruit thinning plays a critical role in fruit size (see Cutting Edge no. 32: Fruit size improvement). Correct pruning practices are the most effective way to manipulate the number of fruit per canopy volume and the eventual fruit size. For more information, refer to SA Fruit Journal Oct/Nov 2015: The reproductive phenol-ogy of Citrus III: Morphogenesis from flower to fruit.
Regrowth control should be done, especially after heavy pruning earlier in the season. A lot of regrowth adversely affects fruit size and is antagonistic to fruit colour development, especially for early maturing cultivars.
Oleocellosis: Late summer vegetative growth of bearing trees should be kept to a minimum as excessive vegetative vigour during this period is associated with high incidence of oleo at harvest.
Rind colour development: Late nitrogen application and the use of heavy summer oil sprays should be avoided, as these treatments are antagonistic to rind colour development.
Figure 1. Historical fruit growth rates (mm per day) of different citrus cultivars in the Western Cape region
Figure 2. Historical fruit growth rates (mm per day) of different citrus cultivars in Limpopo
Figuur 3. Voorstelling van die posisie van die blare wat vir blaarontleding geneem moet word | Figure 3. Illustration of the position of the leaves that must be sampled for analysis
GEÏNTEGREERDE BEMESTING/INTEGRATED FERTILISATION
Neem van blaar- en grondmonsters
Die periode van Februarie tot Junie moet ge-bruik word vir jaarlikse blaar- en grondontle-dings. Blaarmonsters behoort jaarliks geneem te word, terwyl grond elke drie jaar gemonster kan word. Omdat die waarde van die ontleding ge-heel en al afhang van die mate wat die monster die blok se voedingstatus verteenwoordig, moet baie moeite gedoen word met die monster- nemingsproses. Standaardiseer die monster-nemingsprosedure.
Monsterblare elke jaar:
1) Rondom dieselfde datum – pluk blaarmonsters elke jaar vir elke spesifieke blok gedurende ’n bepaalde week vanaf Februarie tot einde April.
2) Vanaf dieselfde groep bome (sogenaamde“indeksbome”) – verdeel boorde in monster-nemingseenhede wat nie groter as 5 ha is nie -kies dan drie tot vier indeksrye wat verteenwoor-digend van die hele eenheid is – merk die rye en gebruik elke jaar dieselfde rye vir monsterne-ming. Swak of geil kolle moet egter afsonderlik gemonster en gemerk word.
3) Op dieselfde posisie in die bome – slegs blare agter ’n vrug, wat in die lente op dieselfde takkie as die vrug ontwikkel het, word gemon-ster – d.w.s. blare wat tussen vyf en agt maande oud is (Figuur 3) – monsterblare tussen heup- en skouerhoogte.
Pluk tussen 50 en 70 blare, plaas dit in ’n skoon plastieksakkie, druk die lug uit en knoop die sakkie toe. Merk die monster deeglik – moet nie direk op die sakkie skryf nie, aangesien selfs permanente ink geneig is om af te kom.
Sample soil at least every three years:
1) When fertilisation has stopped or application rates are low – e.g. late summer to autumn (Feb-ruary to June).
2) From the same position (e.g. the index trees): use the same three to four index rows that are used for leaf sampling – they must be represent-ative of the whole unit. Take samples according to the fertiliser application pattern/wetted zone– micro-irrigated blocks must be sampled under the tree canopy, while drip-irrigated blocks are sampled either between the dripper and the perimeter of the wetted zone. Or if the wetted zones of adjacent drippers overlap, take it halfway between two drippers. Ten to 15 sub-samples must be taken and mixed in a bucket, from which a 500 g representative sample is then sent to the laboratory. Poor or vigorous areas must be sampled separately.
3) At the same depth: remove organic debris from the soil’s surface and take the sample from the top to 30 cm depth. If occurrence of soil acidity or salinity is suspected, an additional sample must also be taken from the 30-60 cm layer.
Use either an auger or spade to take the samples over the full
top 30 cm. Put the sample in a plastic bag that can be thoroughly sealed and mark it properly (do not write directly on the plastic bag).
Interpretation of leaf analyses
Leaf analyses are an indicator of the nutritional status of the trees. There is an established relationship between the concentration of the nutrient elements in the leaves and tree performance. The goal should be to achieve a plant nutrient status that falls within the optimal range for each nutrient.
Interpretasie van grondmonsters
Grondontledings verskaf inligting wat help om te besluit watter stappe geneem kan word om tekorte, wanbalanse en oormate in die voedingstatus van die bome reg te stel. Ongelukkig word interpretasie van die chemiese resultate dikwels gekompliseer deur die verskeidenheid ekstraksie-metodes en maniere waarop resultate uitgedruk word. Interpretasie van grondontledings moet dus met inbegrip van die ekstraksie-metodes gedoen word.
POST HARVEST PATHOLOGY – PRE-PACKING POINTERS
Orchard sanitation: Just before the picking season starts, sanitation is of crucial importance. For reducing fungal spore load, as well as keeping FCM and fruit fly under control, remove all fallen and decayed fruit (including in the trees) from the orchard. Bury or macerate fruit and allow to dry in the sun away from the orchards and packhouses.
Skirt trees for sour rot and brown rot control: Ensure that trees are adequately skirted, preventing low hanging fruit, especially in heavily laden trees, thereby reducing the risk of Phytophthora brown rot infection during the rainfall season. Remove dead wood from all citrus trees to reduce the spore load of the latent citrus pathogens.
Prevent injuries: Ensure that picking teams are trained to focus on the prevention of injuries. Avoid snap picking, unless pickers have mastered the technique. Injuries are the number one cause of postharvest decay.
Packhouse sanitation: Before any fruit is brought to the pack-house in the 2020 season, the entire building and line need to be thoroughly cleaned. Use an appropriate sanitiser to clean everywhere from the roof to the floor. Include walls and hard to reach nooks and crannies.
• Never allow any fruit, and more importantly, any fungicide-treated fruit, to lie around in the packhouse.
• Spray the packhouse with sanitisers regularly and immediately after finding a single rotten fruit.
• Constantly monitor concentrations of sanitisers in dump tanks, sprays, rinses, etc. Ensure that these sanitisers are being used according to the correct specifications (e.g. pH).
• Wash trailers/harvesting bins with a suitable sanitiser before they leave for the orchard.
• Ensure that packed cartons are cooled as soon as possible to prevent decay development.
• Store retention samples for each consignment and check them regularly for waste and other developing factors.
Selection of fungicides: In many packhouses the chemicals that will be used during the 2020 season are being sourced and negotiated. Decide on a chemical program for the coming season that is in line with decay control and export market regulations. Make use of the CRI Postharvest Factsheets that are provided at the Postharvest Workshops during January and February every year. If using a new product, ensure that it is safe to do so (possible phytotoxixity; MRL restrictions) and that it is applied correctly.
In light of the increased cold-temperature shipping and FMS protocols, it is important that packhouses use thiabendazole (TBZ) for all fruit being exported. TBZ applied in the wax pro-vides protection against chilling injury and is also very important to help control latent pathogen infections.