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1.8Pre-harvest

1.8.1Cultivars

Grapes have been cultivated in California for over two centuries (California table grape Commission 2012a). Grape production began to boom in California after 1839 when the first commercial table grape vineyard was planted in Los Angeles (California table grape Commission 2012b). There are now over 70 varieties of table grapes grown in California (California table grape Commission 2012b).

The major varieties of table grape by area planted are Flame Seedless, Crimson Seedless, Red Globe and Sugraone (Table 3 .6).

Table 3.6 – Growing area for major table grape varieties in California in 2011 (CDFA 2012a).

Major varieties	Growing area (ha) in 2011
Autumn King	1,021
Autumn Royal	1,813
Crimson Seedless	5,388
Flame Seedless	7,645
Perlette	611
Princess	1,360
Red Globe	4,638
Ruby Seedless	1,217
Scarlet Royal	1,279
Sugraone	2,036
Summer Royal	380
Other varieties	7,899
All varieties	35,287

Autumn Royal	Crimson Seedless	Red Globe	Ruby Seedless
Flame Seedless	Autumn King	Princess	Sugraone

Figure 6 – Popular table grape varieties grown in California (California table grape Commission 2012c)

1.8.2Cultivation practices

Planting

Appropriate site preparation is conducted prior to planting in spring (Peacock et al. 1994). Many popular varieties including Autumn Royal and Crimson Seedless adapt to a wide range of soil types and conditions, although moderate vigour sites may be preferred to limit excessive vegetative growth (Dokoozlian et al. 2000a; Dokoozlian et al. 2000b). Irrigation and nitrogen fertilisation are also controlled to limit extreme canopy growth (Dokoozlian et al. 2000b). Cultivars may be grafted onto rootstocks, with Harmony and Freedom being the most commonly used rootstock for table grape production in the San Joaquin Valley (Dokoozlian et al. 2000a). Some cultivars are frequently spaced 2.1 to 2.4 metres between vines and 3.7 metres between rows, with in-row spacing being reduced to 1.8 metres if vine vigour is expected to be moderate (Dokoozlian et al. 2000a; Dokoozlian et al. 2000b).

Trellis systems

The ‘T’ trellis system has been the standard set-up used over the past 60 years with only minor modifications made through time (Peacock et al. 1994). Due to its simplicity and effectiveness, ‘T’ trellis systems with a single crossarm and two or three foliage support wires have become the industry norm for table grape producers throughout California (Peacock et al. 1994). The set-up for the ‘T’ trellis system normally involves a 0.9 to 1.2 metre crossarm (2 to 5 wires) arranged at the top of a 2.1 metre stake, driven into the ground to a depth of approximately 60 cm (Peacock et al. 1994). Other systems including the ‘Y’ and the Gable trellis set-ups have also been used in Californian vineyards (Peacock et al. 1994).

Pruning

Throughout the first year, vineyards in the San Joaquin Valley are allowed to grow unhindered for maximum leaf area and root system development (Christensen 1999). Vines are pruned back to two buds at the end of the growing season (Christensen 1999). In California, vines are either cane pruned or spur pruned (University of California 2008a). Cane pruning involves cutting back shoots from the previous season’s growth to one or two buds to produce the following season’s canes (Olmstead 2007). Spur pruning involves cutting back spurs along a permanently trained cordon (Olmstead 2007).

In California, some table grape cultivars, such as Autumn Royal, are most productive under a quadrilateral cordon system with spur pruning (Dokoozlian et al. 2000a). Other cultivars, such as Crimson Seedless, may produce adequate yields under either a cane pruning system or a quadrilateral cordon/spur pruning system (Dokoozlian et al. 2000b).

Irrigation

Irrigation is applied to Californian grapevines to ensure berries grow to a satisfactory size, to provide enough leaf area for healthy vine growth, and for the development of a canopy that provides sufficient shade to minimise sunburn to berries (Williams 2012). Irrigation requirements for table grapes in the San Joaquin Valley typically range from 450 to 500 mm between bud break and harvest (Williams 2012). Slightly higher volumes of water use are required in the Coachella region as a result of higher evaporation rates (Williams 2012).

1.8.3Pest management

A year round checklist is used to ensure pest management covers all stages of table grape growth. Table 3 .7 details the chemicals used, the timing of application and the pests targeted throughout California.

Table 3.7 – Integrated pest and disease management for Californian table grapes

Lifecycle stage	IPM activity	Example treatment options
Delayed dormant	Monitor vines for mealybugs, European lecanium scale, spider mites, cutworm and manage if necessary Place pheromone traps for omnivorous leafroller and sticky traps for glassy-winged sharpshooter	Imidacloprid 7–14 fl oz/acre; insecticidal soaps; spinosad 1.25–2.5 oz/acre
Budbreak	Continue monitoring vines for mealybugs, European lecanium scale, spider mites, cutworm and manage if necessary Monitor vines for powdery mildew and treat if necessary Consider treating for phomopsis if rain is forecast Check traps for omnivorous leafroller and glassy-winged sharpshooter Survey weeds and form management plan	Imidacloprid 7–14 fl oz/acre; insecticidal soaps; narrow range oil; spinosad 1.25–2.5 oz/acre Tebuconazole 4 oz/acre; Bacillus pumilis 2–4 qt/acre Kresoxim-methyl 3.2–4.8 oz/acre; mancozeb; ziram; 3–4 lb/acre
Rapid-shoot growth	Monitor leafhoppers Place pheromone traps for mealybugs Continue checking traps for omnivorous leafroller and glassy-winged sharpshooter Continue monitoring vines for powdery mildew and manage if necessary Monitor for diseases including bot canker, eutypa dieback, measles and Pierce’s disease Check for wilting caused by Botrytis shoot blight and branch and twig borer Monitor vines for spider mites, western grape, skeletonizer, leafrollers and other pests	Remove basal leaves or lateral shoots; imidacloprid 7–14 fl oz/acre Tebuconazole 4 oz/acre; azoxystrobin 11–15.4 fl oz/acre; Bacillus pumilis 2–4 qt/acre Canker removal, vine removal, cultural practices to maintain vine vigour, and some fungicide applications may be used
Bloom to veraison	Monitor for western flower thrips and manage if necessary Monitor leafhoppers, spider mites, mealybugs, European fruit lecanium scale, Botrytis bunch rot, powdery mildew and for other pest and disease damage Continue monitoring traps for vine mealybug, omnivorous leafroller and glassy-winged sharpshooters Check for summer rot, Botrytis bunch rot and leafhopper populations	Spinosad 1.25–2.5 oz/acre; narrow range oil 1–2 gal/acre Imidacloprid 7–14 fl oz/acre; narrow range oil; and other appropriate pesticides Remove basal leaves and lateral shoots in the fruit zone at berry set
Veraison	Monitor for pests and check traps, as above Check for bird damage	Manage with netting or scare devices
Harvest	Check traps for glassy-winged sharpshooter and continue managing birds
Postharvest	Continue monitoring mealybugs, scale and western grapeleaf skeletonizer, and continue checking traps
Dormant	Prune vines, remove dried grape clusters and survey weeds

Source: University of California (2012b)