SUNFLOWER PRODUCTION IN BOTSWANA

SUNFLOWER (Helianthus annus L.)

OVERALL OBJECTIVE

Assessing the production levels of sunflower in Botswana

SPECIFIC OBJECTIVES

• To assess the production level of sunflowers in farming of Botswana.
• To compare the production levels of traditional and commercial farming systems of Botswana.

INTRODUCTION

Sunflower (Helianthus annus L.) is the most important oil seed crop in Southern Africa at present and is being grown virtually in all summer rainfall areas. Marginal soils are being utilised more for production of sunflower which is less risky and require lower production inputs. It is expected that the demand for vegetable oils and proteins will increase in future, and sunflower is the ideal crop for oil production. Since the advent of hybrid sunflower, the traditional problems such as uneven height and maturity have been largely eliminated as a result it sis now easier to handle and has become an excellent crop to maize and sorghum. Sunflower requires low humidity and sunny conditions for optimal plant growth and development making it suitable for production in Botswana.

WHY GROW SUNFLOWER

• Shorter growing season and better cold tolerance makes it suitable for later planting
• Ideal for crop rotation and cultivated under varying climatic conditions
• Have deep taproots and can obtain nutrients from deeper parts of the soil profile 1.5 to 1.8 which are unavailable for most annual crops making sunflower a hood rotational crop
• Performs well under drought conditions since its roots can extract water from deeper parts of the soil profile where other crops’ roots cannot reach
• Sunflower seeds are more tolerant to frost thus making sunflower an attractive crop where frost may occur during seedling stage.
• Sunflower responds to fertilisers but requires less fertilisers than most crops
• Economically viable crop alternative
• It is well adapted agronomic ally to both irrigated production and dry land cropping systems
• Higher yielding cultivars exhibit the highest water use efficiency

CLIMATIC AND SOIL CONDITIONS

Sunflower requires low humidity and sunny conditions for optimal growth and development with optimum temperatures 23˚C - 27˚C. Temperature for germination should not be below 4˚C - 6˚C and seedlings may withstand short periods of frost down to ˗˗5˚C (Van der Vossen and Fagbayide 2007). In Botswana a well distributed annual rainfall of between 500 and 600mm is ideal and deep soils with high water holding capacity allow sunflower to fully utilise its extensive root system for exploitation of moisture and nutrients. Sunflower also grows best on soils with good drainage and pH range of 6.5 to 8.5 (Tsuaneng and Maphanyane 2000).

LAND PREPARATION

The seedbed should be prepared so that it is moist and firm with the surface rough enough to minimise soil drifting (Grady 1999). Deep winter ploughing improves soil moisture infiltration and storage. Secondary cultivation may be required to kill weeds and prepare a fine seedbed (Tsuaneng and Maphanyane 2000). Soil structure breakdown or compaction caused by excessive land preparation should be avoided because it promotes reduced aeration and water movement and increases the probability of Downy mildew in areas where the disease is prevalent (Schneifer and Miller) 1995).  

FERTILISER REQUIREMENTS

In general sunflower does not respond to high N input but a basal application of 40 kg/ha of N is recommended. The recommended Potassium and Phosphorous rates are 50kg/ha and 20 – 30 kg respectively. Boron is important and should be applied on the basis of soil test results (Tsuaneng and Maphanyane 2000) but an application of 1 – 4kg/ha is normally adequate. Recommended applications of fertilizer to sunflower crops with expected seed yields of 1.5 – 2.5 t/ha vary 50 – 120 kg N, 20 – 30 kg P and 40 – 80 kg K. Seed oil content tends to decline and protein content to increase with higher Nitrogenous fertiliser application (Van der Vossen and Fagbayide 2007).

PLANTING AND PLANT POPULATIONP

Planting in Botswana should be done in early December except in North Eastern Botswana where planting after mid January is advisable. The seeding rate is 5kg/ha but it may change depending on cultivar and the planting depth is 4 – centimetres. Between row spacing of 0.75m is recommended except for Pandamatenga where row spacing of 1m is usually used. Within row spacing should be adjusted according to interow spacing to achieve a plant population of 30 000 to 35 000 plants per ha (Tsuaneng and Maphanyane 2000). However optimum final densities vary with environmental and cultivar with 15 000 – 30 000 plants/ha for rainfed and 40 000 – 60 000 plants/ha for irrigated sunflowers. Sunflower has some ability compensate for low densities or irregular crop stands by increasing total biomass, seed size and number of seeds per plant provided other growth factors such as moisture and nutrients are not limiting. Intercropped with groundnuts, pulses and millets. Higher plant populations are planted for oil types  than for confection hybrids (Van de vossen and Fagbayide 2007).

TYPES OF SUNFLOWER

There are two types of sunflower. There are oil seed hybrids which are used for oil production and are either linoleic or oleic types. These hybrids are generally black seeded and have a thin hull and adheres to the kernel. They have about 38-50% oil and 20% protein. The non oil seed hybrids are referred to as confectionery and they are striped or large seeded varieties with a thick hull which remains loosely attached to the kernel permitting more complete dehulling. They also have lower oil percentage and test weight (Schneifer and Miller 1995).

CULTIVARS

Recommended cultivar for Botswana is Russian number 4 that matures in 140-150days and grows to a height of 150-165cm. Its seed size is 1-1.5cm long and 0.5-0.8cm wide. Its colour is black, with black grey stripes. The yield potential is 8t/ha (Tsuaneng and Maphanyane 2000).

MANAGEMENT PRACTICES

Sunflowers are very susceptible to seed placed fertiliser injury. To avoid seedling injury, place fertiliser in a band 5cm below or beside the seeds. Sunflowers are usually planted at low densities and grow slowly during the first 2 weeks. Weeds that emerge and establish during this time can be competitive and reduce sunflower yield (Hurt 2008). Weeds should be controlled by hand hoeing, inter-row cultivation or herbicides. Herbicides recommended for use on sunflower  in Botswana are dinitramine (cobex), trifluran (treflan), pendimenthalin (stomp), alachlor (lasso) and metalachlor (dual ) (Tsuaneng and Maphanyane 2000). Good weed control conserves soil moisture and management practices which promote infiltration of water in the soil and limit evaporation from soil generally will benefit sunflower in terms of available moisture. Sunflower yield is most sensitive to moisture stress during the flowering period and least sensitive during the vegetative period and so farmers are edged to irrigate at flowering if there are less rains (Grady 1999).   For bird control avoid planting sunflower within a quarter mile of marshes, dams and rivers as they harbour large quantities of birds and contain water late in summer. Farmers should also leave at least a 100 yard buffer strip of a crop not as attractive to birds adjacent to shelter belts, groves or other wooded areas. Mechanical frightening or chemical agents can also be used to control birds.

YIELD

The yield potential of sunflower is 8t/ha in Botswana (Tsuaneng and Maphanyane 2000) and world average yield is 1,2t/ha and national averages in Africa range between 0,4-1,3t/ha ( Van de Vossen and Fagbayide 2007).

PESTS AND DISEASES

The African bollworm is an occasional problem in sunflowers while doves are a persistent problem (Tsuaneng and Maphanyane 2000).Other pests include cutworms, mole crickets, grasshoppers, leafminers, aphids and diseases include rust, alternaria blight, septoria leaf spot and viral diseases include sunflower mosaic virus (SuMv) and tobacco leaf curl virus (TLCV) and attacked by nematodes meloidogyne and rotylenchus species (Van de Vossen and Fagbayide 2007).   

HARVESTING AND STORAGE

Sunflowers are harvested when heads have turned yellow-brown and seed moisture content is 10-12 %. Harvesting is done by hand or machine and a combine harvester should be used when the crop is completely dry (Tsuaneng and Maphanyane 2000). Chemical desiccants can be used to dry sunflower for machine harvesting. Sunflower should be stored indoors in bags in an elevated platform. A crop produced for oil processing should be sent to the market as soon as possible to avoid deterioration in oil content and quality (Hurt 2008).

USES                                  

• Produce oil which is used as cooking and salad oil in the manufacture of margarine, paints, varnishes and soap.
• Sunflower meal is rich in protein and is used as livestock feed. Defatted sunflower meal is also suitable for human consumption as a substitute for wheat flour in baking bread and cakes.
• Stalk and flower heads are processed into cellulose and fibre mats.
• Seeds from non-oil cultivars are consumed directly, roasted and salted and some as hulled kernels in various confectionery and bakery products and the smallest seed as bird seed and pet food.
• Sunflower is also grown as a forage crop, as an ornamental or as a pot plant and is an important bee plant (Van de Vossen and Fagbayide 2007)

Sunflower yield in kg/ha per region

Region	Year
	1989	1990	1993	1995	1996	1997	1998	1999	2001	2002
Southern	200	200	69	192	32	146	40	38	183	86
Gaborone	100	200	-	-	-	176	48	130	69	-
Central	-	-	9	217	429	125	-	100	184	92
Francistown	-	-	8	-	623	-	-	194	-	-
Maun	-	-	-	-	-	-	-	-	-	-
Western	-	-	-	-	-	-	-	-	-	-
Traditional	64	100	50	185	65	147	32	69	156	85
Commercial	400	500	453	354	310	831	504	454	-	690
Total	200	300	120	204	88	346	466	431	156	663

DISCUSSION

The average sunflower yield (kg/ha) was almost constant from 1989 to 1995 mostly in the Southern region but was very low with less than 200kg/ha.This maybe of poor rainfall conditions which prevail in Botswana. There was however a sharp increase in yield in 1996 in the Francistown and Central regions with a maximum of above 600kg/ha in Francistown. From 1997 onwards the yield for all regions was very low with averages being below 200kg/ha.

The average total yield from 1989 to 1996 was fluctuating between 88 and 300kg/ha. It rose steadily to above 400kg/ha in 1998 and99 and declined in 2001, only to rise again to reach a maximum of above 600kg in 2002. There was however a steady increase in yield in the commercial system from 1989 to 90 followed by a steady decline in the subsequent 3 years. The yield then increased sharply to reach a maximum of above 800kg/ha in 1997 then declining to below 500kg/ha, and then increasing again in 2002 to above 600kg/ha. The traditional yields were fluctuating over  the period from1989 to 2001 between 50 and 200kg/ha and the reasons for the fluctuations may be due to different seasonal rainfall patterns.

Description of trends is difficult particularly because its hampered by unavailability of data from some regions.

CONCLUSION

Yields of oil crops are consistently low in all farming regions as they are below the expected Botswana yields and this is probably due to poor rains and substandard management. The subsistence farmers are  getting lesser yields as compared to the commercial farmers and most of these small scale farmers who are growing oil seed crops have limited access to resources and markets. Most of them cannot at present afford expensive capital developments or purchased inputs. The physical, financial, technical, commercial and administrative support which farmers in the industrialised countries are getting is not mostly available to them. However significant improvements are already technically possible as new cultivars with durable and stable resistances, tolerances and adaptations to biological and environmental constraints have been and are being developed. Establishment of local industries that use oil crops as raw materials can also help to provide market for the oil crops produce and thus gives farmers an incentive for spending more on inputs and thus produce more.

RECOMMENDATIONS

The market demand should be sustained so that an efficient and reliable seed industry can deliver improved seeds to  farmers. Farmers should  also purchase seed from reputable seed companies or dealers with a good technical service record if production problems do occur and assistance or consultation is required. The cultivars which the seed companies must offer should provide a measure of insurance against pests, diseases and drought and this would encourage both small scale farmers and large scale farmers who are entering agriculture to use more productive methods including timely sowing and control of weeds to ensure higher productivity. Farmers should also use several criteria in sunflower hybrid selection and so they should also  look at seed potential yield, stalk quality or reaction to damage from pests, high winds, uniform stalk height at maturity, oil percentage (genetic potential), physiological maturity ratings, test weight and self compatibility (ability of sunflower to pollinate itself in the absence of insects) and  also select varietal plant types with head types that face down after flowering to minimise bird damage. The farmers should always seek for assistance from the nearest offices of the Department of Agriculture

REFERENCES

Grady K. 1999. Sunflower production. South Dakota State University.

Hurt E.F. 2008. Sunflower for food, fodder and fertility.

Schneifer A.A and Miller J.F. 1995. Sunflower production. Northern Dakota State University.

Summerfield R.J and Roberts E.H. 1985. Grain legume crops. Cpllins Professional and Technical Press.

Tsuaneng M.M and Maphanyane G.S. 2000. Field crops reference Handbook in Botswana Department of Agriculture Research.

Van de Vossen H.A.M and Fagbayide J.A. 2007. Helianthussannus L. Plant Resources of Tropical Africa. http://database.protabase.org. Accessed 17^th April 2009.

10. Wynne J.C and Rowe R.C. 1998. Advances in Agronomy.

DIAMOND BLACK MOTH (plutella xylostella) IN CABBAGE AND MUSTARD IN BOTSWANA

INTRODUCTION

The Diamond black moth (plutella xylostella) is a pest of brassicas and thrives mostly in hot and dry conditions and several generations may be completed on one crop in a field. The larvae cause the most damage as compared to the adult and so needs to be controlled inorder to get a better yield. Pheromone traps are used to catch adult the moth and the information obtained is used to assess the incidence of pests. Sampling for stages of the moth also provides information on pest incidence and effect of control measures. The monitoring of Diamond black moth and its natural enemies is a critical activity in its management especially when implementing integrated pest management and this can be done at different levels and this guides farmers to make timely pest control decisions. An effective monitoring programme for Diamond black moth at different developmental stages provides information about its status and so enables the farmer to define treatment thresholds and therefore effectively apply different levels of integrated pest management.

LITERATURE REVIEW

PEST STATUS

Diamond black moth (plutella xylostella) shortened as DBM attacks all species of brassicas including cabbage and mustard (Wikepedia 2009). Severe attacks occur especially in hot and dry weather. In deserts such as Namib, hot conditions enable the pest to develop rapidly almost throughout the year. Under these deserts conditions a generation can be completed in 2 weeks in summer and 3-4 weeks in winter. Several generations may be completed on one crop in the field and with pest population numbers increasing significantly (Keizer 1999).

DESCRIPTION
                                                                                                             DBM Larvae           

   





                  


                                                                                                                                                               

The adult moth is about 7-8mm long, grey in colour with pale triangular markings on the inner edge of each forewing forming a triple diamond pattern when the wings are folded over each other ( Wikepedia 2009). Eggs are white and cigar shaped and are laid singly or in small groups near the midrib or a strong vein of the leaf. Incubation period is 3-8 days depending on environment. Pupation takes place inside a gauze-like silken cocoon about 9mm long which is stuck to the underside of a leaf. The pupa is greenish at first and changes to brown as the moth develops and the pupal stage lasts from 5-10 days (Keizer 1999). The larvae are pale green with a black head capsule and sporadic black hairs. A single female moth may live for 114 days and lay more than 400 eggs. In the tropics, breeding is continuous with as many as 15 generations a year (Bellows 2002).

DAMAGE

Caterpillars of DBM feed on leaves usually on the undersides, eating into tissue, leaving only the veins and the upper epidermis giving the leaves a windowed appearance which grows in size and eventually forming holes as the leaves grow and the dead tissue tear. On seedlings the growing point is usually damaged often resulting in death of plants. In older plants, new shoots are produced and the attacked plants produce several heads of little value (Thacker 2002). The adult DBM feed on small amounts and damage is so light that it will go unnoticed. It is the larvae that causes significant economic damage and economic damage is most severe after heading begins where the larvae burrows into head destroying its marketability (Keizer 1999).

CONTROL

The recommended treatment threshold from seedling to cupping is when 20% of the plants are infested. After heading begins, the recommended threshold decreases to 5% infestation (Varela 1999).DBM can be controlled by natural enemies like diadgmasp, apanteles, cotesia, and tetrastichus species.Neem (azadirachta indica) based products give good control of DBM and are harmless to natural enemies and they kill the larvae and cause adults to be deformed and have reduced egg laying capacity. Keeping down weeds reduce egg laying sites and uprooting and burning cabbage and mustard remains avoids carry over of the pests to the next brassica crop (Wikepedia 2009).Use of pheromone catch traps which have pheromone substances on a sticky surface which attract insects like DBM can also reduce the DBM population but should be used with other control methods for it to be effective (Persley 1996).

USE OF PHEROMONE TRAPS

• Pest monitoring where information from trap catch is used for detection (early warning) of pest incidence and allows enough time for organisation of control measures and application before larvae have done too much damage.
• Used for surveying (define infested areas).
• Timing of treatments as a threshold catch should be established for any trapping system for before any method of control is justified.
• Timing of other sampling methods as trap catch information is often not sufficient by itself to take pest management decisions. A threshold catch in a pheromone trap triggers the taking of a sample for inspection for eggs or young larvae.
• Risk assessment where information from trap catches provides population trends and population density correlations (Howse et al 1998).
• Mating disruption
• Attract and kill
• Indicate effect of control measures where an increase in numbers shows that control measures are not being effective (Persley 1996).

OBJECTIVES

• To determine the seasonal abundance of diamond black moth.
• To assess the incidence of diamond black moth in cabbage and mustard.

METHODOLOGY

Sampling for developmental stages (adult, larvae, and pupae) of DBM incidence on cabbage was carried out at Mike’s farm and the Horticultural council’s farm on 13/02/09, 13/03/09 and 27/03/09 in the afternoons. Visual inspections for presence or absence of the moth were carried out along 2 diagonals of each farm at 5 different rates (1 plant, 2 plants, 3 plants, 4 plants and 5 plants per diagonal) and the numbers were recorded. The amount of time taken to complete the assessment was also recorded.

Sampling for DBM incidence on Mustard was also carried out on the Horticultural council farm but only on the 13^th of February since it was removed thereafter. The same method of sampling was used and the data was recorded.

Pheromone traps were set up at Mike’s farm (3a on cabbage and 3b on maize) and Horticultural council farm (5, 5a on cabbage and 5b on mustard). The number of adult DBM caught were counted and recorded on 13/02/09, 27/02/09, 13/03/09 and 27/03/09. The information obtained from the sampling and traps was then analysed and a report was prepared.

RESULTS

Number of adult DBM caught

Date	Mike ‘s farms			Horticultural council farm
				Cabbage			Mustard
	3b Maize	3a Cabbage		5		5a	5b
13/02/09	2		26	8	38		5
27/02/09	2		18	47	27		8
13/03/09	3		35	78	69		0
27/03/09	32		119	83	22		5
Total	39		198	216	156		18
Grand total	39		198	390

Average number of developmental stages of DBM from sampling

Date	Adult			Larvae			Pupae
	Mike farm	Council cabbage	Council mustard	Mike farm	Council cabbage	Council mustard	Mike farm	Council cabbage	Council mustard
13/02/09	0	40	0	0	8	12	0	112	0
13/03/09	0	34	-	2	0	-	0	0	-
27/03/09	10	-	-	0	-	-	0	-	-
Total	10	74	0	2	8	12	0	112	0
Grand total	10	74		2	20		0	112

Minor pests found in both Cabbage and Mustard were mostly aphids.

Average time taken to complete the assessment in both cabbage and mustard for

Adults                =  30 seconds per plant

Larvae                = 1 minute per plant

Pupae                 = 55 seconds per plant

Natural enemies = 1 minute per plant.

DISCUSSION

The number of DBM in Mike’s farm increased with time and there was a sharp increase in March especially in the cabbage field. This may be because the cabbages had now reached physiological maturity and so there was enough time for DBM to reproduce and increase in numbers. The other reason may be that the farmer had planted another plot of cabbage and so there was more food and breeding places for the pest. The number of DBM in the maize field was lower than those from the cabbage field but the number also increased sharply in March as in Mike’s farm. This lower numbers may be  because DBM is a pest of brassicas especially cabbages and so thrives more in a cabbage field as compared to a maize field. The increase in numbers in March was in conjunction with that of the cabbage field and this may be because the DBM from the cabbage field would flew to the maize field in search for  alternative breeding places since they are in close proximity.

The number of DBM in the Council farm was increasing with time with only 5a decreasing in March. This may be because the crop was removed in March and since plot 5a is in the middle, it had less DBM as compared to plot 5 which is at the field’s end and may be getting DBM which is breeding in weeds and other plants bordering the field. 5b however had the lowest number of DBM in the council field and this may be because mustard is less favoured by DBM as compared to cabbage. The other reason may be because the mustard was removed before the 13^th of February and so there was less food and breeding places. The number of DBM in 5b was increasing at the end of March and this may be because a new mustard crop was planted by then and so the DBM now had a supply of food to support their multiplication.

 There were more adults in cabbage at Council farm as compared to Mike’s farm. The reason may be because Mike was controlling the pest better than at Council’s farm. There were also more larvae and pupae at Council farm as compared to Mike’s farm. The difference may be a result of poor management in Council farm since decision making involves a lot of people and so it takes time to pass a decision and so DBM will have reproduced and increased in numbers by the time a decision to effect a control is passed. Aphids were the predominant minor pests at both farms and although they were not the main pest being monitored, the farmer should control them since they can also result in yield losses if not controlled.

The average time taken to assess the plant for presence of adult DBM in both cabbages and mustard was less or almost half that taken to assess the presence for larvae, pupae and natural enemies. This maybe because it is faster to see if the adults are present since u just have to disturb the plant and they will fly around. It however takes more time to search for larvae, pupae and natural enemies since a person have to look under every leaf and correctly identify them. The amount of time taken to assess the plant for presence or absence of DBM is generally low.

CONCLUSION

Pheromone traps are very useful in detection of pest incidence and so trap catch information can be used to time treatments and other sampling methods. It can also be used to indicate if control measures are being effective and trapping the DBM is a control measure in itself as it attracts and kill and so disrupts mating. The information provided by the pheromone traps and sampling indicates that there is poor DBM control at Council farm as compared Mike’s farm farms. Both methods however showed the same trends and so shows that they are both effective in determining DBM incidence in Brassicas. Since the time taken for assessing the plants for absence or presence of DBM is very low it will therefore not cost the farmers much of their  time to monitor  crops and use the information to decide when to effect a control method. DBM can therefore be controlled by integrated pest management programmes.

REFERENCES

Bellows, T.S.2002.Entomology notes. Department of Entomology.Pennysylvannia State University.

Howse, P.E, Stevens, I.D.R and Jones, O.T.1998.Insect pheromones and their use in pest management. Chapman and Hill.

Keizer, M.J.1999.Manual of integrated pest management course for extension staff.Mashire Agricultural Development Institute, Rundu.Namibia.

Persely, G.J.1996.Biotechnology and IPM.CAB International.

Thacker, J.R.M.2002.An introduction to arthropod pest control. Cambridge University Press.

Varela, A.M and Seif, A.A. 1999. Crop protection manual for brassicas, ICIPE, Nairobi.Kenya.

Wikepedia, The free encyclopaedia. Whiteflies. www.wikepedia.com.Adapted on 7 March 2009.