Case Study 12
Cotton
Pollination Aware
This case study is the primary source of information on potential pollination services for the industry. It is based on data provided by industry, the ABS and other relevant sources. Therefore, information in this case study on potential hive requirements may differ to the tables in the Pollination Aware report (RIRDC Pub. No. 10/081) which are based on ABS (2008) Agricultural Commodities Small Area Data, Australia 2005-06.
Introduction Cotton (Gossypium hirsutum) is grown worldwide for its soft, staple fibre that develops around the seeds of the plant into a form known as a boll. The shrub is native to tropical and subtropical regions around the world, including the Americas, India and Africa. The fibre is most often spun into yarn or thread and used to make a soft, breathable textile which gives it the status of the most widely used natural-fibre cloth in the world (Rhodes 2002). Additionally, cotton seeds can be crushed for oil or animal feed and the leaves may be used as mulch (CA 2009).
Cotton was first brought to Australia in the late-seventeenth century by the first fleet and since then has grown into a significant industry. Today, not only is cotton an important part of many regional communities, it also contributes $1.7 billion to the national economy each year, despite competition from large subsidised cotton producers such as the USA and China (CA 2009). In Australia, most on-farm cotton activities occur from September/October/November (planting) to March/April/ May (harvest).
Cotton production in Australia All Australian cotton is grown in New South Wales and Queensland (see Table 1 and Figure 1) on about 800 farms, the majority of which are run by families (CA 2009). The major production areas in New South Wales stretch from the Macintyre River on the Queensland boarder and cover the Gwydir, Namoi and Macquarie valleys as well as along the Barwon and Darling Rivers in the west and the Lachlan and Murrumbidgee rivers in the south. In Queensland, cotton is grown mostly in the south, in the Darling Downs, St George, Dirranbandi and Macintyre Valley regions. The remainder is grown near Emerald, Theodore and Biloela in central Queensland. Although a relatively small producer on the world scale, Australia is the world’s third-largest cotton exporter, producing sustaina-
ble, high-quality, low-contaminant cottons that attract a premium on the world market. Up to 98% of cotton grown in Australia is exported, mainly to Asian spinning mill customers (ICAC 2007) and in 2005/06 China, Indonesia, Thailand, South Korea and Japan were the main markets for Australian cotton (ABS 2008). In 2006/07 a total of 487,000 tonnes of raw cotton, valued at around $832 million, was exported; however, output in this year was severely drought affected and was only about 64% of ‘normal’ production (ICAC 2007). The enormous growth in Australia’s cotton production in recent years has coincided with growth in the textiles markets of some of Australia’s nearest trading neighbours in Asia (CA 2009).
Case Study 12
weight) (tonnes)
44,712
0
44,712
Total area (ha)
197,465
129,729
327,194
Total cotton lint production (tonnes)
345,328
0
345,328
Total seed cotton production (tonnes)
916,178
0
916,178
Pollination Aware
Figure 1 Production regions within Australia (ABS 2008)
F igure 1
Table 1
P roduc tion regions within Aus tralia (AB S 2008)
Cotton production in Australia (ABS 2008)
Pollination in cotton
Cotton is commonly regarded as being a partially cross-pollinated crop, and largely self-fertile and self-pollinating (McGregor 1976), although introducing insect pollinators into the crop during QLD NSW flowering has resulted in increased quantity and quality of cotton lint and seed (McGregor 1976; pollination on the one day Irrigated – area (h) Rhodes 2002; Moffett et al. 1975). Each cotton flower is only available for 168,863 100,844 the flower opens, with the corolla and stiminal column falling off on the second day (Rhodes 2002). is secreted(tonnes) by floral nectaries inside the flower and by extra floral329,347 nectaries on the outer or Irrigated – cotton lintNectar production 192,328 sub-bracteal, foliar, and unipapillate (microscopic) areas on the flower peduncles and young leaf petioles (McGregor(total 1976),module with all nectar secreting sites shown to be attractive to foraging honey bees Irrigated – seed cotton production weight) (tonnes) 871,467 490,335 (Rhodes 2002).
Irrigated – area (h)
Total 269,707 521,675 1,361,802
Non-irrigated – area (ha)
28,602
28,885
57,487
Non-irrigated – cotton lint production (tonnes)
15,981
0
15,981
119 (tonnes) Non-irrigated – seed cotton production (total module weight)
44,712
0
44,712
Total area (ha)
197,465
129,729
327,194
Total cotton lint production (tonnes)
345,328
0
345,328
Total seed cotton production (tonnes)
916,178
0
916,178
Pollination in cotton
Cotton is commonly regarded as being a partially cross-pollinated crop, and largely self-fertile and self-pollinating (McGregor 1976), although introducing insect pollinators into the crop during flowering has resulted in increased quantity and quality of cotton lint and seed (McGregor 1976; Rhodes 2002; Moffett et al. 1975). Each cotton flower is only available for pollination on the one day the flower opens, with the corolla and stiminal column falling off on the second day (Rhodes 2002). Nectar is secreted by floral nectaries inside the flower and by extra floral
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nectaries on the outer or sub-bracteal, foliar, and unipapillate (microscopic) areas on the flower peduncles and young leaf petioles (McGregor 1976), with all nectar secreting sites shown to be attractive to foraging honey bees (Rhodes 2002). About 50 ovules must be fertilised if a full complement of seeds is to be produced; therefore, at least 50 viable pollen grains must contact the stigma (McGregor 1976). Insect pollination, in particular honey bee pollination, can aid in this process and result in higher yields and better quality lint (Rhodes 2002; Kaziev
Cotton 1960). Several authors have shown that honey bees are effective and total number of seeds per sample (16.5%) for plots receivpollinators of cotton (Rhodes 2002; Moffett et al. 1975; Kaziev ing the highest number of bee visits compared to plots receiving 1960). Benefits of honey bee pollination include increases in the lowest number of bee visits (Table 2). the percentage of bolls per 100 flowers, more seeds per boll, more seed cotton Table 2 Values for variable measure for the three per boll and more seed cotton per flower cage treatments (Rhodes 2002) (Rhodes 2002). Improvements in lint Variable Control Cage with Cage withquality characteristics such as fibre strength (open plots) bees out bees and length have also been demonstrated (McGregor 1976). Total boll mass (g) 29.5 19.4 9.8 Rhodes (2002) found significant increases in the total number of bolls harvested (11.1%), total mass of bolls (16.5%), total lint mass (15.8%), total seed mass (19.7%)
Total seed mass (g)
16.3
10.0
4.9
Total lint mass (g)
14.2
7.8
4.1
Total number of seeds per sample
246
117
76
Pollination management for cotton in Australia There are a number of factors within the field which have a direct bearing on the pollination efficiency of honey bees:
Crop layout
• Row spacing and blossom density: Cotton seeds are most
•
commonly planted in spring, in long rows using specialised farm machinery. Seed capsules (bolls) can grow as big as an egg whereby after a further 35–55 days, the bolls burst open and expose the cotton. The point at which most of the bolls are open indicates that the crop is ready to pick (Ward and Ward 2001). Access: From a beekeeper’s point of view, all-weather truck access is highly desirable. Limited access may lead to an increased workload for the beekeeper, uneven placement of hives and thus inefficient pollination.
Density of bees
There is little in the way of recommendations as to honey bee management on cotton crops apart from recommendations of one hive per hectare by Ward and Ward (2001). Rhodes (2002) and Moffet et al. (1975) both recommend the use of honey bees on cotton crops but give no indication as to the density of hives required for adequate pollination. Rhodes (2002) used an apiary of 30 hives on a 47ha plot of irrigated cotton (0.6 hives/ha) which showed significant improvements in quality and quantity of cotton lint and seeds.
Arrangement of hives
Most seed is set within a 100m radius of a colony. Research has suggested colonies should be deposited in groups of 12–18 per location, with about 150m between locations(Somerville 2005).
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Case Study 12
Pollination Aware
The distribution of honey bees within the crop suggest that bees tend to forage around the edges of the crop. Use of a greater number of bee hives may improve the result by increasing honey bee activity in the centre of the crop. Whatever the distribution, pattern hives should be placed in shady areas to avoid extreme temperatures. Honey bees collect significant amounts of water for use in the hive and as temperatures rise, the need for water increases, diverting many field bees into water gathering duties. Ensuring hives are located relatively close to water and in shady areas will significantly reduce stress levels of colonies, aiding in optimal pollination of the target crops (Somerville 2005).
Timing
Australia’s cotton growing season lasts approximately six months, starting in September/October/November (planting) and ending in March/April/May (picking) – depending on the region. Each cotton flower is only available for pollination on the one day the flower opens, with the corolla and stiminal column falling off on the second day (Rhodes 2002). Thus to ensure sufficient pollination, bee hives must be available after around 5% of the cotton crop has begun flowering and stay until flowering has ceased (Robertson and Rhodes 1992).
Bee husbandry in the paddock
Moving hives into a crop during the night is less stressful on the bees, because they are not flying and the representatives are generally cooler.
Attractiveness, nutritional value of pollen and nectar
In cotton, honey bees collect nectar from extra-floral nectaries as well as floral nectaries and may be foraging in a cotton crop before, during and for a short time after the crop has flowers present. Honey bees require nectar and pollen to satisfy their nutritional requirements. The quality of pollen collected by honey bees directly affects the welfare of a colony. Poor quality or low volumes of pollen can equate to shorter lived bees and a colony that has a greater susceptibility to disease. The sugar
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content of one sample of nectar collected from the sub-bracteal nectar produced a reading of 17% sugar content, which is an acceptable level for foraging bees (Robertson and Rhodes 1992). Cotton honey is light in colour and flavour and like all flower honeys, has a tendency to crystallise fairly rapidly. This is because tree honeys generally granulate more slowly and some of the sugars are stable as a crystal, not as a liquid (Rhodes 2002; Robertson and Rhodes 1992).
Availability of honey bees for pollination While cotton may be a significant crop for the grower, it is not seen as a primary resource by apiarists. The nutritional value of cotton has been said to be acceptable for honey bee foraging, having a sugar content of 17% (Robertson and Rhodes 1992), although research describing pollen and nectar characteristics is lacking. Use of honey bees in cotton is not common in Australia thus little information exists on pollination contracts and associated costs.
Feral bees
The majority of recent research in Australia identifies significant production benefits when introducing honey bees into cotton crops. Cotton growers relying on feral bees for part or all of their pollination services should be similarly aware first, that feral colonies are unlikely to be at full strength at the time that cotton flowers bloom and, second, that even if they were, foraging by these bees is unlikely to be sufficiently intense to achieve the level of pollination required for optimal seed production.
Risks
Pesticides: Placing hives well back from the crop also may help the grower. If a crop needs spraying with pesticide the location of the hives is crucial. The further the beehives are placed away from the crop the better. If spraying is necessary, then this should be conducted in late afternoon or evening when foraging bees have ceased their foraging activities. One of the biggest dangers of placing bees near any agricultural crop is the possibility of colonies or field bees being sprayed by pesticides.
Cotton It is strongly recommended that growers take the following steps to prevent or reduce bee losses:
• Apiarists should always inform cotton growers where hives •
•
•
are located Cotton growers should always inform beekeepers when they are likely to spray and with what insecticides, so that the beekeepers may take precautionary measures. Due to the logistics involved in moving an apiary, beekeepers require as much warning time as possible and, where practical, 24 hours warning is required. Apiarists should position their hives deep within tree stands where practicable to minimise possible spray drift impacts. Apiarists should avoid locating hives on the prevailing downwind side of cotton fields. Where possible and practical, cotton growers should restrict spray activities (within flight range of apiaries) until after 4.00pm by which time the numbers of honey bees present in a cotton crop would be at low levels. Growers and applicators need to be aware, though, that it is in the early mornings and late afternoons that inversion layers are either present or forming and this can increase the likelihood of spray drift.
activity tends to remain at a relatively high level. Decreases in both numbers of bees visiting blossoms and the distance from the hive at which bees forage occur with a decrease in temperature. Under rainy conditions bees fly between showers but only usually for very short distances. Wind, particularly strong wind, tends to reduce the ground speed of bees and hence reduces the number of flights per day. Colony strength will also have a direct bearing on the temperature at which honey bees will leave the hive. Only strong colonies will fly at lower temperatures. Bees need to keep their brood nests within their hives at a constant temperature of 37oC. The cooler the external temperature, the more the bees are required within the hive to maintain that temperature. Hence if the colony is strong in numbers the surplus bees not required for maintaining hive temperature are available for foraging duties. Environmental factors have a direct bearing on the amount of nectar secreted. It has also been found that nectar is the most concentrated in old flowers about to wither, but nectar concentration fluctuates widely in accordance with the relative humidity throughout the day. The number of honey bees that visit the blossom has been directly correlated with the amount and concentration of nectar produced.
Weather
Temperature and rainfall have a marked effect on honey bee activity. Bee activity is very limited below temperatures of 13oC with activity increasing up to around 19oC, above which
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Case Study 12
Pollination Aware
Potential pollination service requirement for cotton in Australia
Optimal use of managed pollination services in all cotton plantations in Australia would require a service capacity as indicated in Table 3 below. Table 3
Potential pollination service requirement for cotton in Australia
State
Month (flowering)
NSW
September
197,465
0.6
118,479
QLD
October
129,729
0.6
77,837
Total
Area (ha)
Average hive density (h/ha)*
327,194
Estimated Number of hives required
196,316
Notes: * Area sourced from ABS (2008) Agricultural Commodities Small Area Data, Australia 2005-06, flowering times and average hive density estimated from McGregor (1976)
References
AUSTRALIAN BUREAU OF STATISTICS (ABS) 2008. Agricultural Commodities: Small Area Data, Australia, 2005–06 (Reissue), ABS No 7125.0. COTTON AUSTRALIA (CA) 2009. 2008/2009 Annual Report – Advancing Australian Cotton. Cotton Australia. INTERNATIONAL COTTON ADVISORY COMMITTEE (ICAC) 2007. The International Cotton Advisory Committee. The International Cotton Advisory Committee. KAZIEV, T. 1960. ‘The influence of bee pollination on cotton quality’. Pchelovodstvo, 37: 33–35. MCGREGOR, S.E. 1976. Insect pollination of cultivated crop plants. USDA, Tucson, Arizona. MOFFETT, J.O., STITH, L.S., BURKHART, C.C. & SHIPMAN, C.W. 1975. ‘Honey bee visits to cotton flowers’. Environmental Entomology, 4: 203–206.
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RHODES, J. 2002. ‘Cotton pollination by honey bees’. Australian Journal of Experimental Agriculture, 42: 513–518. ROBERTSON, L.N. & RHODES, J.W. 1992. ‘Honey bee (Apis mellifera L.) deaths near sprayed cotton and observations on bee foraging behaviour in flowering cotton (Hymenoptera: Apidae)’. Australian Journal of Entomology, 31: 243–246. SOMERVILLE, D. 2005. ‘Best practise in a honeybee pollination service’. Agnote. NSW Department of Primary Industry, Goulburn. WARD, R.N. & WARD, K.E. 2001. ‘Impact of honeybee pollination activities on Bt cotton production in northern Alabama’. In: Annual meeting of the Entomological Society of America, South Eastern Branch, 2001, Augusta, GA.
Cotton Notes
This case study was prepared as part of Pollination Aware – The RealValue of Pollination in Australia, by RC Keogh, APW Robinson and IJ Mullins, which consolidates the available information on pollination in Australia at a number of different levels: commodity/industry; regional/state; and national. Pollination Aware and the accompanying case studies provide a base for more detailed decision making on the management of pollination across a broad range of commodities. The full report and 35 individual case studies are available at www.rirdc.gov.au.
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This project is part of the Pollination Program – a jointly funded partnership with the Rural Industries Research and Development Corporation (RIRDC), Horticulture Australia Limited (HAL) and the Australian Government Department of Agriculture, Fisheries and Forestry. The Pollination Program is managed by RIRDC and aims to secure the pollination of Australia’s horticultural and agricultural crops into the future on a sustainable and profitable basis. Research and development in this program is conducted to raise awareness that will help protect pollination in Australia.
RIRDC funds for the program are provided by the Honeybee Research and Development Program, with industry levies matched by funds provided by the Australian Government. Funding from HAL for the program is from the apple and pear, almond, avocado, cherry, vegetable and summerfruit levies and voluntary contributions from the dried prune and melon industries, with matched funds from the Australian Government. RIRDC Publication No 10/119 ISBN 978-1-74254-089-4
