Production calendar arrives in citrus mailboxes

production calendar was sent out to West Australian citrus growers in August. The poster was produced as part of an R&D project using State government funding, providing timely reminders for good management practices, such as irrigation, nutrition, pest management and canopy management.

As growers review packouts for 2019 and plan for the 2020 season, some reminders for the next three to four months are in the next few pages.

Pruning after harvest encourages new growth that will bear bigger fruit, more efficient application of foliar nutrient and gibberellic acid (GA) sprays and assists in reducing crop load in an ‘on’ year.

Pre-bloom to flowering stage

Keep an eye out for bud break and record when it happens for each variety and block.

Pre-bloom to flowering is a critical period for spring flush and flower development and is a high demand period for nutrients. The key management goal for this stage is to ensure the trees are well supplied with all required nutrients leading into flowering and fruit set.

☑ Tag the spring flush to ensure you collect the correct leaves for nutrient analysis in February/March. The buds that have burst (as shown in the photo) will form your spring flush.

☑ After harvest consider foliar applications of low biuret urea and micro nutrients to promote flowering for the coming season, particularly if you suspect a light flowering year.

Further foliar micronutrient sprays applied to the new spring flush when it emerges will also boost tree nutrition and help improve fruit set and fruit size. Apply the spring micronutrient spray when leaves of the new spring flush are at least 1.5cm long — large enough to adsorb a good proportion of the applied nutrients.

☑ Aim to apply 40 to 50% of annual nitrogen requirements in the prebloom to flowering period (August to October). Nitrate forms of nitrogen such as calcium nitrate and potassium nitrate are the best forms to use during this stage as they are quickly and easily taken up by the roots. Ammonium and urea forms of nitrogen can be too slow to convert to nitrate in the soil and can therefore be lost before they are taken up by the roots.

Apply nitrogen in split applications to avoid loss to leaching.

☑ Phosphorus is also important at this time and should be applied just before and during the bloom period. Apply the bulk of phosphorus now and the remainder at monthly intervals. Apply 30 to 40% of annual potassium during the prebloom period.

Petal fall

The key management goal for this stage is to ensure the trees are well supplied with all required nutrients leading into fruit set.

☑ Record the timing of petal fall as it is an important stage for wind and thrips blemish.

☑ Review packout data for the incidence of wind blemish. Monitor wind speed and direction from petal fall for six weeks to assess the potential need or effectiveness of windbreaks.

A high percentage of rind blemish is a direct result of wind events in the first six to twelve weeks after petal fall, that is until late December. As soon as the petals fall and the small immature fruit is exposed, wind blemish to the rind can occur with any movement of leaves, branches, twigs, dead wood, thorns and even other fruit.

☑ Adequate water in their root zone is important to take up nutrients, monitor irrigation requirements very closely.
Although your soil may appear moist, if you have a dig around, you may be surprised that the soil is not as wet as you think. Small amounts of rain (5mm or less) should not be factored into your irrigation schedule.

Fruit set & fruitlet shedding

Cell division starts at the end of petal fall and goes until fruit reach approximately 30mm in diameter in late December.

It occurs in fruitlets that remain after fruit set and shedding.

Over 60% of potential fruit size at harvest is determined in the Cell Division stage.

Adverse climatic conditions, water stress and nutrient deficiencies will negatively impact on fruit development and size at harvest. Water stress at this time can also cause excessive fruit drop.

Mild climatic conditions will favour fruit set and above average minimum temperatures will enhance fruit growth.

☑ In addition to pruning, chemical thinning in mid November can be used to thin a heavy crop in an “on” year. This will assist in maintaining good fruit size.

☑ Apply 25% of annual nitrogen at the end of the vegetative growth flush in November. Preliminary studies suggest that nitrogen applications during early fruit growth can assist in the management of internal dryness in imperial mandarins. Be careful not to over stimulate trees with nitrogen during this period as any growth flush will compete with the fruitlets and result in poor fruit set.

☑ Apply 30% of annual Potassium after fruit set (10mm size). Supplement potassium with foliar applications of KNO3 at 15–20mm size to promote cell division.

☑ Calcium is important during this period to reduce albedo
breakdown. A series of calcium foliar sprays are recommended throughout the cell division stage for the management of albedo breakdown. Magnesium, nitrogen, phosphorous and potassium compete with the uptake of calcium. Application of these nutrients should be closely related to leaf analysis and should not be over supplied. Stress to the plant can also affect the uptake of calcium so conditions should be monitored.

☑ Good water availability is critical during the cell division stage — now is not the time to skimp on water applications. Any water stress during this stage will have negative impacts on fruit development that cannot be made up for in later stages. Monitor irrigation requirements closely, ensuring an adequate supply of water at all times. Continuous water flow through the plant is also critical for the transportation of nutrients through the plant (particularly calcium). There are opportunities to cut back on water applications in later stages of fruit growth.

As the temperature warms up it’s important to identify insects in your orchard, whether they are pests or beneficials. Monitor, include and add biosecurity pests to your sheet to record their absence.

• Weeds: maintain a good weed control program to reduce the incidence of Fullers Rose Weevil (problem in export markets) and to help control snail populations.

• Citrus gall wasp: monitor for galls in last year’s spring flush and for wasp emergence from any existing galls. Act quickly by pruning off any galls and destroying the material. https://agric.wa.gov.au/n/3398

• Thrips, including Kelly’s citrus thrips: monitor for thrips weekly from petal fall to calyx closure. https://agric.wa.gov.au/n/1122


• Fruit fly: continue monitoring and bait spray programs for fruit fly until after harvest, clean up any fruit left in the orchard. https://agric.wa.gov.au/n/1608.

• Red scale: monitor scale crawlers, applying targeted oil sprays when crawler activity is evident. If red scale is a problem consider the release of Aphytis melinus as a biological control in October/November.

• Ants: will require monitoring and control throughout summer.

• Aphids: if controlling aphids, only spray the growth flushes.

• Snails: baby snails are on the move in Spring. When snails are present in trees copper foliar sprays may be necessary as copper acts as a repellent to snails. Spraying the whole tree can help move snails down to where bait is at the base of the tree. Copper should not be used alone as it does not kill the snails.

Band spraying trunks can provide a barrier to going up tree.

Young snails, less than 7mm in diameter for round snails and 7mm in height for conical snails, are not likely to be controlled by baits. So monitoring for size and repeat baiting may be necessary. In the summer, if snails are a problem bait while conditions are still moist before the summer dormancy period.

MORE INFORMATION
More information about pests and their management is available on the Department of Agriculture and Food website at www.agric.wwwa.gov.au and in the NSWDPI crop protection manual.