National Tested Seeds

Guide to the Production of Cucurbits 2 | P a g e

INTRODUCTION AND HISTORY OF PUMPKIN AND SQUASH

Pumpkins, squashes and melons belong to the family Cucurbitaceae and are therefore related to calabash marrow, calabashes and cucumbers. Pumpkins and squashes probably originated in North or South America from where they spread to Europe and other parts of the world. Jan van Riebeeck imported pumpkin seed from Brazil and this crop was therefore cultivated as a vegetable in the Cape long before the start of the Great Trek.

In all members of the family Cucurbitaceae are mostly unisexual and the plants monoecious (male and female flowers are separate but are borne on the same plant). Under certain climatic conditions both male and female and sometimes androgynous (male and female parts in one flower) flowers as well, can be found on the same plant.

PLANT DESCRIPTION

Cucurbits are warm-season, herbaceous annuals. The growth habit of individual plants may either be determinate (shoot tip ends in a flower) with a bushy growth habit, or indeterminate (shoot tips grow continuously with flowers in leaf axils) with a prostrate and spreading growth habit. Leaves are borne singly and may be simple or lobed. Tendrils are found in the leaf axils on all species except some species in the genus Cucurbita.

All plants in the Cucurbit family have extensive, shallow root systems. Tap roots of the Cucumis genus (cucumber and melon) can grow up to 100 cm deep. Tap roots of the Cucrbit genus (pumpkins and squash) can grow up to 200 cm deep in search of water. Horizontal roots spread fast to cover the area under the vines. The anchor root that originates from the axils of the vine should not be damaged as this might lead to fruit abortion. The seedling stem develop into the main stem, with several lateral branches originating from the basal axils of the main stem. Compact, dwarf of bushy plants are normally the result of shortened internodes, not the lack of lateral vines.

Cultivated cucurbits bear imperfect flowers with are either pistillate (female) or staminate (male). Sex expression (the combination and ratio of female and male flowers on a plant) is primarily variety specific, but can be affected by either chemical or environmental factors. The first flowers of a plant are normally staminate and the females flowers are formed a few days later. Cucurbit pollen is large and sticky and need to be transferred by insects to the stigma of pistillate flowers. Honeybees are the main pollinators of all cucurbit crops. Poor fruit set may be an indication of poor pollination or stress brought about by wind, rain or cold that reduced bee activity during the time pollination should have occurred. Some cucurbit crops are self-pollinated and others cross-pollinated. Cross-pollination never affects flavour, size, shape or colour of the fruit, but it does affect the genetic characteristics of seed borne in that fruit. If you have seeds from cross-pollinated (hybrid) plants and plant them, the new plants might have any combination of new characteristics.

PUMPKIN AND SQUASH TYPES

The names of the different types of the genus Cucurbita cause considerable confusion. The botanical types that are of economic importance in South Africa and with which we will deal in this document are Cucurbita maxima, C. pepo and C. moschata.

The cultivars Flat White Boer (Plat Wit Boer), Ponderosa, Crown Prince, Maxi Prince, Sampson, Bush Fire and Green Hubbard fall under Cucurbita maxima. In South Africa, Flat White Boer and the grey skin cultivars are classified as pumpkins in popular terminology, while Green Hubbard and Bush Fire are wrongly known as squashes. To prevent confusion, the Cucurbita maxima group will be called pumpkins in this document.

Cucurbita maxima (pumpkins)

This group has coarse, hairy, trailing shoots with round kidney-shaped or lobular leaves of an even green colour. The shoots usually form adventitious roots at the leaf axil. The fruit stalk is cylinder-shaped, soft and spongy but without a thickening at the fruit junction. The seed is large, white or brown to coppery, with a slanting seed mark and an edge of the same colour and texture as those of the seeds.

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Most of the C. maxima group are consumed at full maturity and store well.

Cucurbita pepo (squashes)

Cucurbita pepo includes gem squashes (Gemini, Smarag) baby marrows and Sweet Dumpling

In South Africa the following are generally classified as squashes. Little Gem (gem squashes), Sweet Dumpling (edible gourd), Small Wonder, Caserta, Zucchini and Patty pans including many other cultivars are classified as vegetable marrows.

Plants of C. pepo have pointed prickly leaves with deep incisions between the lobes of the leaf. The fruit stalks are five to eight-sided, grooved and hard, and swollen at the fruit attachment. The seed is fairly small and usually brown, with a horizontal or round mark and edges of the same colour and texture as the seed itself. The growth habit varies from a short stem, which creates a bushy appearance such as Caserta, to the wide trailing gem squash type like Smarag.

In our markets, most of the C. pepo group are harvested and consumed in an immature form. They have a limited shelf life and are often referred to as Summer squash internationally.

Cucurbita moschata (Winter squash)

The best-known cultivars are the butternut (Atlas, Apollo, Barbara, Pluto, Venus and Waltham) and Ceylon "pumpkin". This species has hairy runners with leaves similar to those of C. pepo but which are not incised as deeply. The fruit stalks are hard and cylinder-shaped but not grooved and not noticeably swollen at the fruit attachment. The seed is greyish-white to brown with a slanting horizontal or round mark and a wavy edge with a deeper colour and a texture different from that of the seed itself.

Most of the C. moschata group are consumed at full maturity and store well, but the immature market is growing in South Africa. They are also commonly referred to as “Winter squash” internationally.

Sakata butternut varieties: Atlas, Pluto and Venus.

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Cucumis sativus (Cucumber)

There are two major types of cucumber viz: processing (pickling, gherkin) or slicing (fresh) cucumber. Most slicing cucumbers are grown under protection and are normally parthenocarpic (seedless).

WATER MELON TYPES

Water melons (Citrullis lanatus) have their origin in the Khalahari (Tsamma) and was grown in ancient Egypt about 5 000 years ago. It is though to reach the US with the slave trade in the 13th century where it was known aa “Southern food”. Of all commercial fruit and vegetables, water melons contain the highest content of lycopene. It is also rich in two amino acids that play a role in arterial dilation (“good for the heart”), namely citrulline and arginine. In addition water meon is also a good source of vitamins A and C.

Table 1. Different types of water melon are recognised in the trade:

Type Class Common size (kg) Seed Shape 9 – 20 Large sized Oblong Picnic Jubilee 7 – 16 Medium sized Round to oblong Crimson Sweet 8 – 16 Small sized Oblong All Sweet 2 - 7 Dark seeds Round Ice Box Ice box 4.5 – 15 Black seed Round Yellow Seeded 4.5 – 15 Absent Round Seedless 2 - 10 Absent Round to oblong Seedless Seedless 0.5 – 3 Mostly absent Round Mini Red flesh 0.5 – 3 Mostly absent Round Yellow flesh

The types most popular in South Africa are Crimson Sweet types in the south and All Sweet types in the northern areas of the country. Seedless water melons are becoming popular as fresh processing increases.

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SWEET MELON TYPES

Table 2. Many different types of sweet melon (Cucumis pepo) are distinguished in the trade:

Type Region of Rind texture Rind Shape Size (kg) Flesh Flavour & popularity colour colour texture Medium-fine Very sweet, Ananas Middle East netted Orange Oval 1.5 - 2 Pale green to aromatic Coarsely netted Athena Eastern US and slightly Oval Yellow- Sweet (cantaloupe) sutured orange Very mild, Canary europe Smooth Bright yellow Oblong Pale cream juicy

Casaba Europe Oval & pointy Almost white Very sweet Christmas Very pale (Piel de Sapo) Europe Warted Green Football 2 – 4 orange – light Sweet mottled green Charentais Grey – grey- (French Europoe Sutured and blue Oval 1 - 3 Orange Fruity, sweet melons) netted Galia Paler than Pale green to Spicy sweet (Isreali melons) Israel Netted cantaloupe Oval almost white or banana- like White – Subtle and Honey Dew Smooth greenish Green, white sweet. white. Some or orange Texture same may be as yellow cantaloupe Musk melon (American US Netted Orange cantaloupe) Sweet. Entire Oriental Orient Sutured White, with Elongated 500 g Pale peach - fruit is edible: with sutures white soft rind and small seed Dark brown, Persian Middle East Netted with light Oval Bigger Bright pink- Delicate brown than ornage flavour netting. cantaloupe Turning light green when ripe True cantaloupe Europe Rough warty Winter melon (catchall name for long season, long keeping)

In South Africa, Athena-type cantaloupes are the most popular. Our variety Divine falls into this class. Charentais, Galia and Honey Dew types are becoming more popular.

CLIMATIC REQUIREMENTS OF CUCCURBITS

The important factors regarding climatic requirements for Cucurbits are soil temperature, air temperature and humidity.

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Soil temperatures

Pumpkin and squash are warm-season crops and perform best when soil and air temperatures are above 15 C. Above 15 C, seedlings should emerge within seven days. Seed germinates poorly below 13 C and requires two to three weeks to emerge. No germination takes place at temperatures below 10 C. Seed may decay before germination if planted in cold, wet soils.

The optimum temperature for root development is 20 C. In comparison with other cucurbits, pumpkin and squash seed are more resistant to the injurious effects of low temperatures. Black plastic on raised beds will speed soil warming and can dramatically increase early and total yields. Seed or transplants can be planted through the plastic by hand or with machinery designed for direct seeding through plastic.

Air temperature

Vegetative growth, flowering and fruit-set are greatly affected by temperature. Cucurbits are sensitive to frost and are injured at temperatures below 0C. Almost no growth takes place at temperatures below 15 C, but rapid growth will take place at temperatures of 18 - 27 C. Plants generally grow more luxuriantly at higher temperatures.

Relatively low temperatures and short daylight periods promote the formation of more female flowers in relation to male flowers. However, as the temperature and daylight period increase, there is a reversal in the exhibition of male and female flowers. At extremely high temperatures only male flowers may be formed. Temperatures have an important effect on dehiscence of the pollen sac. This applies especially to the minimum temperature, as pollen will still be released above the optimum temperature but not below the minimum temperature.

The length of the growing season is determined by temperature. This fact must be kept in mind when plantings are planned. Early plantings are subjected to relatively low temperatures at the beginning of the growth period, while late plantings, on the other hand, are subjected to relatively low night temperatures at the end of their growth period. Under these conditions the period of the crop on the land is extended. The length of the growing season from planting to harvesting is more or less as follows:

Squashes 60 - 75 days Butternut 90 - 100 days Pumpkins 110 -150 days Sweet melon 80 – 110 days Water melon 90 – 120 days

Humidity

Pumpkins prefer long periods of warm dry weather. Areas with a high humidity during the growing season can be troubled with fungus diseases especially if the moist period occurs at the end of the growing season.

Pumpkins, cucumbers and squashes are less sensitive to these diseases than watermelons and muskmelons. In these areas production is dependent on a highly efficient spraying program. A long rainy period just before or during harvesting can cause the fruit to rot, especially on heavier soil types.

Plantings must be planned in such a way that blossoming does not occur during periods when cool, cloudy or moist weather is expected. Bee activity is greatly reduced under such conditions with the result that pollination and fruit-set will be poor.

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SOIL REQUIREMENTS

Cucurbits produce best on well-drained, fertile soil. The plants produce large, shallow root systems very rapidly in the top 20 - 25 cm of soil, which should be prepared into a firm, well-fertilized seedbed. Squash and pumpkins do well in soils where 25 - 30 tons of well-rotted manure has been applied per hectare. To help avoid soil borne disease problems, select fields that have not had other vine crops, tomatoes or peppers for at least three years.

The ideal soil depth for cucurbits, particularly pumpkins, is 900 mm and deeper. These crops should not be cultivated on soils less than 450 mm deep. The highest concentration of roots is found in the top 300 mm of soil. Tillage banks and impenetrable layers occurring at less than 450 mm should therefore be broken with a sub-soiler.

As far as soil acidity is concerned, Cucurbits are moderately sensitive to acid soils. Good results can he expected over a wide range of pH values extending from 5.5 - 7.5 (H20). If the soil pH is lower than 5.5, agricultural lime should be applied in accordance with the analytic findings. The agricultural lime should be ploughed in four weeks or more before the planting season.

Examination of the soil

The producer should first determine whether the field is suitable for the production of cucurbits. The most important factors determining this are drainage and soil depth. A soil that is 900 mm deep and well drained to that depth is considered ideal. The minimum requirements are set at 450 mm.

The fertiliser and lime requirements are determined by a laboratory analysis of a representative soil sample. In view of the fact that lime should be applied at least 4 to 8 weeks before planting the soil sample should be submitted for analysis by a soil scientist as early as possible. Disregarding the lime requirement could cause a significant reduction in yield.

Clean cultivation

The field should be clean cultivated for 6 - 8 weeks before planting. This practice controls cutworms by the removal of host plants from the field and also facilitates weed control. Organic material usually decomposes during this period, therefore preventing a nitrogen negative period after planting.

Fumigation to control nematodes

Precautionary measures are essential, as cucurbits are particularly susceptible to nematodes. The field should be fumigated at least 14 days before planting. Residual gases are allowed to escape by cultivating the soil with a disc harrow or rotavator 3 days before planting.

During cool conditions, such as those occurring in spring in the Western Cape, the fumigation period should be extended from 2 to at least 4 weeks. This makes allowance for the slower breakdown of the gases at a low temperature.

Crop rotation

The main purpose of a rotational system is to combat soil-borne diseases and pests associated with specific crops. Systems are often designed to include a green-manure crop in order to increase the organic content of a soil. Cucurbits may follow any unrelated vegetable in a rotational system. The potato is an exception as there is some evidence that certain Fusarium species attack both cucurbits and potatoes. Grasses or grain crops, such as oats in the Western Cape and Babala in the hot areas of the Limpopo, are the most suitable green-manure crops. Nematodes or any of the diseases associated with vegetable crops does not generally attack them. These crops should be ploughed in while they are still green and at least 8 weeks before planting.

National Tested Seeds Kencor House, 750 Lorraine Drive, Bluff Hill, Harare Zimbabwe. Tel.No:04-310284-7 Cell: 0772 235 000 E-Mail: [email protected]

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National Tested Seeds Kencor House, 750 Lorraine Drive, Bluff Hill, Harare Zimbabwe. Tel.No:04-310284-7 Cell: 0772 235 000 E-Mail: [email protected]

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SEEDLING PRODUCTION

Majority of pumpkin and squashes are direct seeded, however with the more expensive F1 hybrid seed, trends are towards a portion of the crop being established by seedlings.

Age of seedlings

In summer, 2 - 3 week old seedlings are ideal, whilst in winter this may have to stretch to 5 - 6 weeks. A good norm to use is to transplant after the development of the first true leaf. Very quick varieties are especially prejudiced by seedlings being too old. The result of old seedlings is a reduction in yield, as plants mature quickly after transplanting. The faster a variety matures, the more it is set back if the seedlings are too old when transplanted. It is further critical that seedlings do not become root bound as this seriously influences yield potential, general disease tolerance, maturity, etc.

Hardening off

Hardening off is especially necessary when the plants are to be planted out during warm conditions. The seedlings should be kept fairly dry but not allowed to wilt and should be moved to an area with about 15 % shade, or in the open for 2 - 5 days. Seedlings must be drenched immediately before planting.

Seedling inspection prior to planting

Check that the terminal bud is not damaged. Terminal bud damage results in a blind unproductive plant that should be thrown away. Check for pests and diseases like Pythium, Fusarium and Rhizoctonia.

Transplanting

Seedlings should be watered prior to planting and should be transplanted into a pre-wetted soil, preferably deep wetted. Transplanting should occur once one can get into the lands without puddling. Roots should be straight and seedlings should be planted up to their cotyledons. A planting stick should be used.

Watering should occur directly after transplanting into the compressing hole on the side of the seedling (about 1 litre per seedling). This should eliminate air pockets around the roots and facilitate contact with the pre- moistened subsoil. Capillary action will keep the seedling moist and encourage downward root growth. Cutworm bait is essential.

Seedling production in seedless watermelon

The price of seed of seedless varieties is higher than diploid hybrids and seedless varieties require special conditions for seed germination, emergence and early plant development. It is therefore common practice to use seedlings in stead of direct sowing.  The time required is approximately 27 – 30 days in summer and 45 – 50 days in winter.  Germination is optimal at a constant temperature of 24 – 25 C and RH of 80 – 90 % (not higher). These conditions can best be maintained in a dark growth chamber. Remove the trays from the chamber when radicles are approximately 1.5 cm. Check for germination after 48 h. If radicles are not visible, leave for another 24 h and repeat every 24 h. Trays are not irrigated during this period.  For seedling emergence and development, the temperature must be kept > 16 C and the night temperature must be 5 - 6 C lower than the day temperature.  Sow seed in trays with large holes (90) and use a medium with good drainage and aeration properties, especially in winter. A good medium may consist of peat, vermiculite and perlite with added ‘slow release’ fertiliser to ensure sufficient nutrition for 50 days. The medium must be moist, but not wet.  To ensure uniform emergence and development, seed should all be sown at the same depth (1 – 1.5 cm).

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 It is critically important to maintain a constant moisture level during all stages of seedling production. A good method to use is to weigh seedling trays after sowing and to monitor the weight during germination (the first 10 – 12 days). Only irrigate when the trays show a loss in weight and only enough to replace the moisture (weight) loss. If medium is too wet, the roots will not ‘search’ for water and will grow in the upper part of the compartment.

PLANTING TIME

Cucurbits may be planted from early spring to midsummer, or as soon as the danger of frost is over. The decision of planting date depends on the market and environmental conditions. The size of insect populations and humidity are of particular importance. Insect population increases as the season progresses and accordingly the occurrence of mosaic virus diseases.

In the summer rainfall areas, the increase in humidity during summer gives rise to serious problems with leaf diseases. These can be avoided to a large extent by planting early. On the other hand, in the winter rainfall areas, early plantings are more susceptible to leaf diseases due to high humidity and low temperatures.

The earliest planting date is at the time when the soil temperature has risen above 15 C and when there is no danger of frost. Even at 15 C the seed germinates slowly and poor stands may be obtained if unfavourable weather sets in..

The length of the growing season and the time when winter weather sets in determines the latest planting date. See section 5.2 for time of growth required for the different cucurbits.

FERTILISER

General recommendation

Because of the diversity of soil types, it is not possible to give a standard fertilisation program. Such a program should be based on the results of a soil analysis. The following recommendations therefore merely serve as a general guide, 25 kg N, 50 kg P and 50 kg K per ha, applied at planting, followed by a topdressing of 30 kg N at the 4 leaf stage, and an additional topdressing of 30 kg N and 50 kg K per ha when the first flowers appears.

For Zucchinis, Patty pans and gem squashes, the norm is 35 kg N, 55 kg P, and 75 kg K as base dressing. Additional topdressing of 30 kg N at the 4-leaf stage, and another 50 kg N when the first flowers appear is recommended (however, it is recommended that the soil should be analyzed for a more accurate fertilisation recommendation). Pumpkins respond very well to manure applications and should be taken into account when determining the amount of fertiliser needed.

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Table 3. Fertiliser guidelines for pumpkin and squash according to soil analysis results

Soil Test Results Amount Needed (ppm) (Kg/ha)

Phosphorus Phosphate (P) Low 32 or less 60 – 90 Medium 34 - 67 30 – 60 High 67 - 90 1 – 60 Very High above 90 0

Potassium Potash (K) Low 225 or less 190 – 250 Medium 225 - 336 90 – 190 High 337 - 505 50 – 90 Very High above 505 0 - 50

It is very important to note that this is only a guideline and should be adapted for each soil type.

Applying the fertiliser

Cucurbits are planted in rows. The question arises as to whether the fertiliser should be broadcasted over the whole planting area or applied in the planting holes or furrows. In the case of gem-squashes and baby marrows that are more closely planted, broadcasting is recommended. For pumpkins that are spaced further apart, band application is preferred.

If large quantities of fertilisers have to be given, broadcasting is recommended. Smaller quantities are preferably incorporated in or near the planting holes or furrows. However, in the case of very large quantities, a combination of broadcasting and band application may be more suitable. Half the amount is broadcast and the remainder applied in the rows.

If it is known that a high percentage of the phosphates will be "fixed" in the soil, band placing is recommend as more effective. A third of the fertiliser may be applied with or without kraal manure by band application: the remainder should then be worked into the soil to a depth of 100 - 150 mm in strips 200 mm from the plants on both sides of the row. This should be done not later than two weeks after germination.

Time of application

Except in the case of agricultural lime, all fertilisers should be incorporated into the soil as near to planting time as possible.

Soils with a low pH factor (acidic) will tend to convert the phosphorous into a form that makes it unavailable to the plants. The extent of 'binding' of the phosphate will vary from soil to soil. Phosphate fertilisers should therefore only be applied to acid soils shortly before planting time. Nitrogen fertilisers are soluble in water and after heavy rainfalls the nitrates are liable to leach below the root- zone. Because nitrogen is easily washed out of the soil by rain or frequent irrigation’s, it should be applied at intervals during the growing season. Sometimes, fertilisers are applied after the first fruit have set.

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Micro-elements

Plants require extremely small quantities of micro-elements, which are essential for healthy growth and production. Often only single plants or groups of plants show symptoms of micro-element deficiencies. Soil analyses will assist in determining the micronutrient content of the soil; however, leaf analyses will identify the actual content within the plant.

Molybdenum deficiencies occur frequently in the Lowveld and the Western Cape where the pH of the soil is below 6.0. Plants showing these deficiency symptoms are usually small, light green in colour and the edges of the leaves tend to curl upwards. Later these leaves turn white and eventually die off. The very young fruit are liable to abort. Should this deficiency be prevalent in an area, it is recommended that producers should soak the seed in a solution of 15 g sodium or ammonium-molybdate, diluted in 4.5 ℓ water for a period of 4 - 6 hours the day before planting.

The following are recommendations to rectify the more common deficiencies that may occur. Applications should be applied once or twice while the plants are still young.

Molybdenum (Mo) 130 g sodium- or ammonium-molybdate in 500 ℓ water Boron (B) 1.4 kg borax in 500 ℓ water Zinc (Zn) 1 kg zinc oxide or 1.4 kg zinc sulphate in 500 ℓ water Manganese (Mn) 1.4 kg manganese sulphate in 500 ℓ water Copper (Cu) 1 kg copper sulphate in 500 ℓ water

METHODS OF ESTABLISHMENT

The crop can be established using various techniques. The method used will depend on the humidity and rainfall of the production area, and the types of soil, implements and irrigation systems available.

The land must first be examined for ploughing soles and impervious soil layers shallower than 450 mm. If these layers occur they should be broken using a rip plough. Following this, the soil must be ploughed to a depth of 200 - 300 mm and the planting should then be established using one of the following methods.

Level ground

The fertiliser can be broadcast or banded, and incorporated using a disc plough. The seed is planted on a level surface with no further cultivation. This technique is not suitable for heavy soil types or for areas where rain occurs frequently during the growing season. Sprinkler irrigation should be used under these circumstances.

Beds and mulching

The fertiliser should be applied in bands and beds are made above these bands. The beds are covered with black plastic mulch. The width of the beds is determined by the size of the plastic. If the plastic is 1.5 m wide, a one meter wide bed would be covered effectively. With this practice drip irrigation is used and the dripper lines are placed underneath the plastic.

An advantage of this method is that the undersides of fruit are protected from continuous contact with the soil which may result in fruit damage and rot. The plastic also restricts weed development. Producers must observe the amount of water applied by the drippers, and be careful of water logging due to over-irrigation. Be sure also to use quality plastic mulch with UV protection.

Furrows

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This method is used where fertiliser is applied by hand in the rows, or where flood irrigation is used. Furrows are drawn at the required spacing by means of a suitable implement. Fertiliser is applied in the furrows, and is lightly mixed with the soil in the middle of the furrow, using a toothed implement. Broadcasting the fertiliser could also be used in this situation. The furrows can now be irrigated using flood irrigation. After a suitable drainage period, the seeds or plants are planted just above the level at which the irrigation water flows.

Spacing, planting depth and planting of seed

The spacing listed below may be used as a general guide, and may be adapted to some extent to climatic conditions and/or available implements.

Table 4. Spacing suggestions for cucurbits.

Type Spacing between Spacing within Final stand rows (m) rows (Plants/ha) Pumpkins (Vining) Pumpkin (Bush) 2.0 - 3.5 500 – 1 000 6 000 – 8 000

Squash (bush) 1.2 - 1.5 500 15 000

Squash (butternut) 1.2 - 2.0 500 15 000

Squash (gem) 1.2 - 2.0 500 12 000 – 13 000

Water melon 3.0 60 – 100 5 000 – 6 000

Sweet melon 1.2 – 1.5 500 15 000

When directly seeded, two or preferably three seeds (1 - 2 on F1 hybrids) are planted near each other at the suggested distances within the rows. Seedlings that have been established in seedling trays are transplanted at the suggested spacing to ensure the correct plant population. After 2 - 3 weeks when the plants are established, the seedlings are thinned to single plants. The excess plants should be cut off and not pulled out. If the plants are pulled out the roots of the remaining plants will be disturbed and injured.

Pumpkin and squash seed is planted 30 - 40 mm deep. Under ideal conditions the field should be thoroughly irrigated before planting. The seed should make good contact with the seedbed and be covered with dry soil or soil that is not so wet that it forms an impervious layer on drying. No irrigation should be applied before emergence as this may cause the formation of a crust. Should it rain before emergence and a crust be formed, it should be kept damp with light overhead irrigation for the seedlings to be able to emerge.

During hot weather it is advisable to protect the soil surface from drying out by means of mulch. After emergence, the mulch should be removed to prevent the development of spindly plants.

The seed should not be planted too shallow, as the top layer of the soil will dry quickly, resulting in poor field germination. It should also not be planted too deep as the seedlings are more prone to disease, due to the extended pre-emergence period.

CULTIVATION PRACTICES AND MANAGEMENT AFTER ESTABLISHMENT

Weed control

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No chemical herbicides are registered at present for use in cucurbits.

The roots of cucurbits are shallow and spread widely. They develop at more or less the same rate and in the same direction as the vines. Weeds must therefore be controlled by shallow cultivation in order to prevent root damage. Within row cultivation it is done manually with a light hoe. This process will also assist in breaking up any hard layer that might have developed. Tine implements are used for cultivating between rows during the first five to six weeks of growth. Mechanical cultivation at a later stage may damage the plants, and is in any event not necessary, as the dense foliage tends to smother the weeds.

Cultivation should preferably not take place when the plants are wet, as diseases are easily transmitted under such conditions. The vines are often trained along the rows to permit the passage of implements. This must be done before any roots develop at the leaf axils on the vine. Damage to the root gives pathogens easy access to the vine, and may lead to fruit abortion.

Weeds act as host plants for insect pests and may be a source of mosaic virus.

Irrigation

Irrigation requirements for cucurbits are influenced by many factors. As a general guide, observe the following for a sandy loam soil type.

Table 5. Suggested amounts of water needed by cucurbits.

Days from planting: Root depth Total amount of water required (mm) (cm) per week 0 - 30 15 30 31 - 70 30 35 71 - 110 45 55 111 - Maturity 61 75

FLOWERING, POLLINATION AND FRUIT SET

Squash, pumpkins, sweet melons and water melons have separate male and female flowers on the same plant. Pollen must be transferred from the male flowers to the female flowers by bees or other insects in order to get high yields of good quality fruit. Bees are the most important pollinators of cucurbits. If bees are not abundant in the field at flowering time, hives should be placed next to the field, with at least 2 - 3 hives per hectare placed within 150 m of the field. Poor yields often result when too few bees are available. There should be no other flowers in the vicinity that are more attractive to bees like Lucerne, etc. Special precautions should be taken with insecticide treatments during flowering. Only systemic pesticides should be sprayed and should be done in the afternoon or on cool, cloudy days. Bees only visit flowers in the morning. Systemic pesticides sprayed the previous afternoon should be absorbed by the following morning and minimum number of bees will therefore be killed.

Each seed in a fruit results form fertilisation of one ovule with one pollen grain. Pollination and the developing seed result in the formation of hormones which stimulate fruit growth. Fruit size is generally determined by the number of seeds in the fruit and thousands of pollen grains must normally land on the stigma of a female flower and successfully fertilise a large number of ovules.

Pollination is affected by temperature: . < 8 ºC : No pollen dehiscence . 8.9 – 10 ºC: Minimum temperature for pollen sack splitting. Bee activity severely reduced. . 10 – 12.8 ºC: Optimal temperature for pollen sack dehiscence

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Some varieties of pumpkins grown under high temperatures (22 C night/32 C day) produce female flowers that wither and die before they open. The same thing may happen if pumpkin plants are heavily shaded. In both situations, male flowers develop normally and open on schedule, but few if any female flowers are seen in the field. In some cases female flowers may appear but fail to bear fruit because of pollen sterility at high temperatures.

Problems

The effect of environmental factors is illustrated by the difference in the response of pumpkins to high temperatures and long days versus low temperatures and short days. Plants tend to favour the production of male flowers when high temperatures and long days are experienced. Under extremes of heat and long day length, plants can also produce under-developed male flowers, which shrivel up and die before pollen development (anthesis) occurs. The female phase is dominant at lower temperatures and during shorter days. Female flowers can produce parthenocarpic fruit due to lack of pollination, which later abort under these conditions.

Humidity also has an effect on the type of flowers set, where in conditions of relatively high humidity female flowers will be favoured whilst male flowers at lower humidity.

The yield is dependent on the early production of a large number of flowers and the early fertilisation of a large percentage of female flowers. The dehiscence or splitting of pollen sacks to release pollen is dependent on temperature as already discussed. The minimum temperature for the dehiscence is 8.9 - 10 0C with optimal temperatures 10 - 12.8 0C. These temperatures should be reached during the diurnal swing and are very important for successful pollination. In other words, if you were planning to establish your crop and you expect temperatures not to reach the critical 10 - 12.8 0C, you should expect lower than normal yields.

Successful pollination is essential for fruit set. Bees should visit a flower many times (8 - 30 times) to ensure sufficient pollination for normal fruit development. Inadequate pollination may lead to the production of lopsided, poorly shaped fruit or fruit abortion. It is necessary to see that you have an adequate amount of bees for pollination.

The activity of bees is also affected by environmental factors that should be taken into consideration. It is important to take into account that pumpkin flowers generally open at daybreak and chances of pollination after noon are poor. Bees are sensitive to temperature and humidity. Flying is severely reduced when temperatures are below 9 0C or when the humidity is very low. Pollen will dehydrate if the humidity is low and temperatures high, bees will also not visit the flowers under these conditions. With pumpkins, pollination is most effective prior to 9 am. Poor yields can often be attributed to a poor supply of effective pollinators, such as bees, especially in larger plantings. Bees cannot pollinate pumpkin flowers effectively if the vines are too dense.

Pollination of seedless water melons

Fruit set and development in water melon is stimulated by growth regulators released during pollination, seed set and fruit development. Flowers of seedless varieties (triploid) are highly sterile and do not produce enough viable pollen to release the growth regulators required to induce fruit develop-ment. Fertile diploid plants are therefore inter-planted with seedless plants to provide viable pollen. Polliniser varieties are available. However, diploid varieties with fruit easily distinguishable from the triploid fruit can be used successfully.

We suggest 5 000 – 5 500 seedless plants per hectare. An additional 20 – 25 % of the polliniser needs to be inter- planted to provide viable pollen. To ensure enough bee visits to each female flower of the seedless variety we suggest the following planting spacing methods:

P – S - S – S – S – P – S – S – S – S – P (A seedless plant every meter, with every 5th plant a polliniser). or

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S – S - S – S – S – S – S – S – S – S – S P P P (A seedless plant every meter and next to every 5th plant, a polliniser). Do not plant one complete row of seedless plants in every 5th row as bees tend to forage from one plant to the next in a row. Planting density affects fruit size, the higher the density, the smaller the fruit. Plants of seedless varieties initially develop slower than diploid plants. Pollinisers can therefore be planted one week after the seedless variety. This delay normally ensures that the two varieties reach the flowering stage at the same time.

Stimulation of female flowers

Stimulation of female flowers may be done as follows, but experimentation and strict management is essential:  Seed treatment: Soaking seed fro 24 h in a solution of 0.05 % Boron (B) and Manganese (Mn), agitated with air blown into the water will react on a faster emergence, increase the female flowers and subsequently the total yield.  Use seed that was stored for 1 - 2 years, fresh seed will produce more male flowers.  One spray of Ethephon at 200 ppm at the second to third leave stage may increase the number of female flowers.  When night temperatures are between 12 and 14 C and the day temperatures are 23 C, spray Chlorflurenol on the flowers at 10 ppm in order to encourage parthenocarpic fruits.  The ideal temperature for female flower development is 25 C during the day and 18 C during the night. Temperatures above 40 C will suppress the total number of flowers. The use of evaporative cooling by using light sprays regularly during the day will help to reduce the surrounding temperature and alleviate the stress on the plant. Mulching the soil with plastic will also prevent heat accumulation. The mulch will also control the amount of water in the soil and assist with weed control on the bed and/or ridges.  The reduction of radiation by 30 % will decrease the proportion of female flowers.  Increasing the plant population may tend to decrease the female flower proportion.  A well balanced fertigation programme will increase the female flower proportion. The N:P:K:Ca:Mg ratio should be 1:0.01:0.88:0.4:0.04 respectively. A constant supply of micro-elements must also be supplied, especially Mo and B.

Thinning and normal abscission of blossoms and fruit

Producers should be able to distinguish between normal and excessive blossom abscission. According to research on the common pumpkin done at Pretoria, it appears that only about 20 % of all pistillate flowers formed, eventually bear mature fruit. It is therefore normal for as much as 80 % of the pistillate flowers to abscise. This percentage is much lower for cucumbers and squashes. In pumpkins, watermelons and muskmelons the development of a fruit on a vine has an inhibitory effect on the development of additional fruit on the same vine. The producer can take advantage of this phenomenon by removing all poorly developed and damaged fruit at an early stage. Normal fruit can then set in its place.

Occasionally two pistillate flowers may develop next to each other on a vine resulting in one or both developing poorly or asymmetrically. A shortage of nutrients to each fruit might probably be the cause. If labour is available, thinning can be applied advantageously.

One of the regular complaints farmers have is the abortion of perfectly normal flowers at bud stage. The presence of growing fruit on vines has a profound effect on the setting of additional fruit. Growing fruit may inhibit the set of any additional fruit on the same vine with resultant flower drop. Fruit setting will be resumed as soon as the inhibiting fruit are removed. This is nature's way of controlling fruit set. It is evident that the first fruit set has a definite effect on subsequent settings.

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FRUIT QUALITY

Protection against sunburn

Cultivars with dark skinned fruit are highly susceptible to sunburn. The most effective protection is obtained when the fruit is totally covered by foliage, which is brought about by the application of sound production practices. Branches, straw, chaff, etc. can also be used but are labour intensive and not very effective in windy areas.

Prevention of insect damage

Fields should be inspected regularly and scouted for the presence of the pumpkin fly.

Prevention against wind damage

Developing pumpkin and squash fruit have thin sensitive skins that damage and mark easily. These permanent marks negatively affect the price of the final product, e.g. Crown Prince for export, Gemini for baby gems, etc. Many producers do use wind breaks to reduce this damage.

PEST CONTROL FOR PUMPKIN AND SQUASH

Cucurbits are fairly free of insect pests and damage is mostly caused by pumpkin fly. However, the grower should also be acquainted with the other pests of this crop so that the correct control measures can be applied when necessary.

The safe period of each pesticide must be kept in mind. This is the period that must be allowed to elapse between the last application of the pesticide and harvesting of the crop. Table 6 gives the registered names, the safe period and dosages of various pesticides while trade names appear in Table 7.

Mice damage prior to emergence

Mice tend to dig seeds up as they germinate and have been known to remove seeds across a large area of the field. This is more prevalent when fields are situated near the habitat of mice, e.g. bushes, grass and reeds near a river or pool. Extensive damage can be expected just after winter or when food is scarce. Trials are being conducted with coated seed in order to identify whether mice have difficulty or are put off by unpalatable chemical additions coated around the seed. Results thus far are proving positive.

Control Mice can be controlled with poison baits and fumigants (Table 1). The bait is placed in small heaps (about 50 g), 10 m apart, in one or preferably two rows around the edge or in the land. To protect birds the poison should be placed in firm paper cylinders used for the packing of liquor bottles or old tins. Fumigants must be placed in the entrance to mouse burrows that must then be sealed.

Root damage by root knot nematodes

Symptoms Infested roots have typical knots that limit the normal uptake of water and nutrients. Plant growth rate is retarded and wilting may take place despite regular irrigation.

Control

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Where enough land is available, cucurbits and Eragrostis curvula (Ermelo type) may be planted on a crop-rotation program. A land planted with E. curvula for a period of 3 years will usually be relatively free of nematodes.

The most common control measure is soil fumigation that should be applied at least 14 days prior to planting. The soil must be moist and free of clods and un-decomposed organic material. After application with a hand injector, the holes should be closed immediately. After application with a mechanical apparatus, the soil should be sealed by rolling or sprinkler irrigated to prevent fumes from escaping too quickly.

Work at the ARC has shown that good results are obtained when only the planting holes or rows are treated, although roots can extend beyond the treated zones and become infested.

Damage to the stem

Cutworm (Agrotis spp.)

Cutworms are usually grey to black in colour and can be found coiled up when disturbed. It is active at night when it severs the stems of young plants at or just below the soil surface. During the day larvae can be found underground at a depth of 20 - 50 mm.

The adult moth lays her eggs on a many different plants. A fallow land will usually be free of cutworm.

Control Clean cultivation of the land about 6 weeks before planting will prevent female moths from laying eggs and any cutworms present in the soil will die from lack of food.

Poisonous bait consisting of bran or mealy meal mixed with an insecticide (Table 1) and water may be distributed over the land one or two days before sowing. Ready-mixed baits are also available (Table 6).

Pumpkin stem borer (Apomecyna binubila)

The symptoms of an infestation appear as the main stem or lateral runners near the base showing cracks, which later become dry and cork-like. Heavily infested plants grow poorly and bear little or no fruit. The cream-coloured larvae feed in the stems where they pupate. Recently only cucumbers have been attacked, but pumpkins and squashes are also possible host plants. Until now this pest has occurred only sporadically.

Control No registered insecticide is available at present.

Damage to the leaves and fruit

Pumpkin fly (Dacus ciliatus)

Yellow stripes or spots on its body characterize this brownish fly, which closely resembles a small wasp. When laying her eggs, the female stings the young fruit and this gives rise to the characteristic lesions on the fruit. White maggots will be found inside the fruit at a later stage. Pumpkin flies are normally a problem during wet conditions.

Control Pumpkin flies attack young fruits and therefore the control program must be initiated as soon as the first flowers open. This pest can be controlled in two ways, namely by spraying the fruit or applying bait on the leaves (Table 1). All the fruit should be sprayed thoroughly at intervals of 2 -

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3 weeks. Insecticides used as bait, should be applied as large droplets on the upper and lower surface of the leaves. In the case of small plantings, the treatment should be given twice a week, whilst with large plantings a weekly treatment is sufficient. Always repeat control measures after rain.

Bollworm (Heliothis armigera)

The young larvae are hairy and almost black. With each moult they become lighter until brown to green in colour. A clear yellowish/dirty white stripe runs along either side of the body. The larvae feed on flowers and young fruit. Boll worm is a serious pest in South Africa and attacks almost all vegetable field crops. They occur most frequently in spring, early summer and autumn.

Control For successful control an insecticide (Table 1) should be applied before the larvae are 5 mm long.

Aphids (Aphis gossypii and others)

These tiny (1.5 - 2.5 mm long), pear-shaped insects are soft-bodied with long legs and antennae. They are black or green, with or without transparent wings. Aphids are found in colonies sucking the sap from young growth. Damage by feeding of aphids is, however, less important than the transmission by this insect of many viruses, including Cucumber mosaic virus (CMV).

Control . Plant early in the season. In the Highveld, cucurbits should be planted before the end of November, and in the Lowveld from August to mid-September. . Cucurbits should not be planted near old, infested lands. . Spray with one of the insecticides listed in Table 1 as soon as the insects are noticed and treatment must be repeated when necessary. Pesticides will not control virus diseases transmitted by aphids. . Spraying with light mineral oils to control aphid-borne virus diseases must be done so often, that it is considered impractical and therefore not to be recommended. However, interested farmers should contact the suppliers for further information. . It was found that the light reflected by strips of aluminium foil placed between the rows on the ground, prevents aphids from settling on plants. The occurrence of virus diseases is consequently reduced to such an extent that little damage is done.

Ladybirds (Epilachna spp)

These beetles are light brown with black spots on their elytra, whereas the larvae are orange-coloured and have thick, black, hairy spines. Both the larvae and adult ladybirds feed on the leaves. There are herbivorous and carnivorous ladybirds. The carnivorous (good) ladybirds are shiny whilst the ladybirds that cause damage to plants have a less attractive appearance.

Control The plants should be thoroughly sprayed with a registered pesticide (Table 1). This insecticide should not be sprayed on wet plants as this may cause burning.

Thrips (Thripidae)

These insects are about 1 mm long and have four long, narrow, fringed wings. They are orange-yellow to black and very active. Damage to seedlings can cause malformation of plants. Thrips damage the leaves by piercing and rasping young tissue and feeding on the cell content.

Control Spray the plants as soon as infestation occurs (Table 1).

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Spider mite (Tetranychus spp.)

These minute “spiders” normally occur on the lower surface of leaves, where they feed on the plant sap. As populations increase they spread over the leaves and eventually the whole plant. Symptoms are tiny yellow spots when populations are low. When they occur in high numbers, they weave fine webs (similar to spiders), and leaves become bronzed and dry out.

Control Spray the plants (Table 1) as soon as the pest makes its appearance and repeat the treatment when necessary. A full cover spray is essential and the lower surface of leaves should be sprayed thoroughly.

The use of pesticides

THE PESTICIDES LISTED BELOW, TAKEN FROM PEST CONTROL HANDBOOKS, ARE FOR INFORMATION ONLY, AND ARE REVISED ONLY WHEN SPECIFIC CROPICS ARE HELD. BECAUSE OF CONSTANTLY CHANGING LABELS, LAWS, AND REGULATIONS, SAKATA SAF SEEDS (PTY) LTD., CAN ASSUME NO LIABILITY FOR THE CONSEQUENCES OF USE OF CHEMICALS SUGGESTED HERE. IN ALL CASES, READ AND FOLLOW THE DIRECTIONS AND PRECAUTIONARY STATEMENTS ON THE SPECIFIC PESTICIDE PRODUCT LABEL.

TABLE 6: Registered pesticides for cucurbits

Pesticide and Dosage per 100 ℓ water Safe Pest Remarks formulation or as indicated period One tablet per hole. Aluminium phosphide Seal hole after application. Coumachlor Place in area frequent by pest. Seal passages after application Only for use by pest Mice Calcium cyanide Dust in burrows and passages control operators Place small quantities out at 10 metre intervals in old tins 1 kg + 1 l sunflower oil + 40 kg Zinc phosphide lying on their sides. Pre-baiting is recommended. Not for roasted mealy meal home garden use. May be applied undiluted – see fum-liqd; or diluted – see fum- soln for dosages 20-50 l/ha Field treatment: Apply only with special applicator. Field

EDB (60-150 ml/100m planting row) treatment: Apply by means of mechanical applicator. Root-knot 100 l/ha (1 l/100 m planting nematode row) Field treatment: Inject cold or as hot gas under gas-proof cover kept in place for 48 hours. Aerate soil 3-21 days Methyl bromide 0,5 kg/10 m before sowing depending on soil type, soil temperature and crop. Bait treatment: Not for home garden use. For agricultural crops only. For total surface treatment scatter around at Endosulfan 100 g or 150 ml + 20 kg bran planting time at the rate of 10 kg/ha. For row treatment

or mealy meal 5 – 10 kg/ha apply at the time of planting on the row at the rate of 50 g/100 m for 1 metre rows and 100 g/100 m for 2 metre rows i.e. 5 kg/ha irrespective of row width. Cutworms Bait treatment: Not for home garden use. Not fur use in HHDN 60 g + 20 kg mealy meal lands where edible root crops will be planted within two years after application. Use the lower dosage rate irrespective of row width if Sodium fluosilicate 5 – 10 kg/ha application is made to the rows only. 60 g + 20 kg mealy meal or 15 Bait treatment Trichlorfon kg bran Commercial control measures when first flowers appear

and continue until fruit mature. Full cover spray. Wet fruit thoroughly. Repeat at 2-3 Fenthion 120 ml 10 week intervals. Pumpkin fly Bait treatment – Apply at 35-40 l/ha as a coarse droplet Mercaptothion 300 g or 175 ml + 8 kg sugar 10 spray on underside of foliage For small plots, repeat application twice a week. For Trichlorfon 50 g + 8 kg sugar 10 large plots repeat application weekly and after rain. Bollworm 250 ml 14 Apply preferably before larvae are 5 mm long. Not for Endosulfan 100 g 14 home garden use. Apply when pest is noticed and repeat when necessary. Aphids Dimethoate 75 ml 14 Cover spray

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Fenthion 100 ml 10 Full cover spray. 250 g Full cover spray. Do not apply to plants that are wet. Mercaptothion 1 15 – 30 kg/ha Dosage depends on plant size and density. Mevinphos 75 ml (690 ml/ha) 4 Full cover spray. Oxydemetonmethyl 10 ml/10 l water 21 Cover spray. Small pack only. Full cover spray. Direct spray on underside of foliage. Do 250 g 7 Ladybird Mercaptothion not apply when plant is wet. 100 g 14 Apply at first signs of infestation. Not for home garden Endosulfan 250 ml 14 use. Thrips 10 – 15 kg/ha Mercaptothion 7 Do not apply to plants that are wet. 250 g 200 g 7 Full cover application. Ensure good coverage of the Spider mite 100 ml 7 underside of leaves Dicofol 15 – 20 kg/ha. 7

TABLE 7: Some commercial names for pesticides registered for cucurbits

Active ingredients Commercial name Phostoxin Aluminium phosphide Cyanogas Calcium cyanide dust Ratilan Coumar bait block Kelthane, Acarin mitigan, Mitigan acarin, Dicofol Dicofol wp Kelthane, Acarin, Acarin mitigan, Dicofol Dicofol EC Kelthane, Dicofol. Dicofol dust Fetron, Rogor, Aphicide, Roxion, Cygon, Perfekthion, Rogue, Dimeto, Daphene Fort, Dimethoate EC Dimethoate Aquamix, Namatox, EDB EDB fum-ec Agrifume, EDB-4,5 EDB EDB Fum-solution Minifume, EDB EDB Conc-solution Thiojack, Thiodan, Agrisulfan, Indathio, Thiones, Avi-sulfan, Endosulfan Endosulfan EC Thiodan, Thiojack, Agrisulfan, Thionex, Indathio, Endosulfan Endosulfan wp Thiodan Cutworm bait, Snykor, Kits, Cutlok, Avicut-bait Endosulfan Bait Lebycid Fenthion EC Aldrin HHDB Malathion, Datathion, Extermathion, Mercaptothion Mercaptothion wp Malathion, Datathion, Malasol, Extermathion, Avigard, Emmatos, Mercaptothion, Mercaptothion EC Agrothion. Mlrhion, Srrhion, Kopthion, Extermathion, Mercaptothion Mercaptothion dust Brom-O-Gas, Dow-fume, Curafume, Metabrom, Cropfume, Methyl bromide Methyl bromide fumigant-gas Phosdrin, Mefos, Mevinphos Mevinphose EC

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Metasystox R Oxydemeton-mentyl EC Snylok, Cutworm bait, Snykor Super, Superkits Sodium fluosilicate bait Dipterex SP, Danex, Vetrex, Trichlorfon Trichlorfon ws Zinc phosphide Zinc phosphide powder

Formulations: EC: emulsifiable concentrate. wp: wetable powder. ws: water soluble

USE PESTICIDES SAFELY!

Wear protective clothing and safety devices as recommended on the label. Bath or shower after each use.

Read the pesticide label even if you've used the pesticide before. Follow closely the instructions on the label (and any other directions you have).

Be cautious when you apply pesticides. Know your legal responsibility as a pesticide applicator. You may be liable for injury or damage resulting from pesticide use.

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DISORDERS

Fruit disorders and other physiological problems can cause severe losses during some years. A few of the most common disorders are discussed briefly.

Fruit cracking

All pumpkin and squash fruit have the potential to crack. Some varieties are more susceptible to cracking than others and superficial cracks are often regarded as perfectly normal and acceptable for many pumpkin types.

Thin rind and high sugar content both predispose pumpkins and squash to cracking. Cold air temperatures and warm soil temperatures increase the tendency of cracking. Cracking under these conditions is as a result of the equilibrium of water in the plant being governed by root uptake of water and leaf transpiration of excess water. Warm soil enhances water uptake and cool air retards transpiration. Under these conditions water builds up in the plant. Pumpkin and squash fruit with a high sugar level have a higher osmotic potential than fruit with lower sugar levels. Since water travels through the plant from a low to a high osmotic potential and fruit usually has a relatively high osmotic potential, the water is forced into the fruit. If the fruit has an even higher osmotic potential than usual, the water will move with an even greater force than usual. The amount of water that gathers in the fruit cells causes them to swell to such an extent that the fruit may crack; this pressure may be as high as 50 bars.

Cracking, especially when deep cracks are formed is not commercially acceptable, in particular for butternut where the neck is the most sought after part of the fruit.

Cracking is often observed in fields where flood irrigation is practiced, or where drip- or overhead irrigation is applied in the afternoon. To reduce cracking, irrigation in the afternoon should be limited.

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Malformed fruit

Fruit are usually described as malformed if it is round or flat, and at the stalk end if the fruit is long or cylindrical. This is usually as a result of fruit development occurring on one side of the fruit only, resulting in asymmetrically formed fruit. This can be a common occurrence in fields, but it is rarely severe. Malformation can be aggravated by lack of moisture and/or a nutrient deficiency, especially nitrogen, or by diseases attacking the fruit. Two types of malformation are common in butternut.

Thin, poorly developed necks.

Normal seed are found in the fruit, poor pollination is therefore not likely to be the cause of this disorder. Fruit with thin necks and normal blossom ends (bulbs) are more commonly observed in field were nutrition was sub-optimal, which may result as a result of too high a plant population, poor soil, or poor nutrition management. The plant’s priority is to produce viable seed, available nutrients are probably used for seed development.

Fruit without the typical bulb at the blossom end.

Fruit are often cylindrical, very few or no seeds were found in the small seed cavity and he flesh in the neck is often of poor quality. This condition is thought to result when pollination takes place but is not followed by successful fertilisation of the ovules to form seed. Pollination stimulate fruit development, but the initial stimulus is not enough to sustain fruit development. In fruit where many seeds develop, the stimulus is strong enough to sustain normal fruit development.

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Bitter fruit

Many cases of bitter fruit in cucurbits such as watermelons, cucumbers, marankas and calabashes, have occurred in South Africa during recent times. In the pumpkin and squash group, bitterness occurs only in gem- squashes. The flesh of such fruit is very bitter; the bitter substances are glucosides known as cucurbitacins and are poisonous. It has been determined at the A.R.C. that the bitterness is hereditary. Bitter gem-squashes probably originated as a result of crossing with ornamental gourds.

OFF-TYPES AND SIBS

Fruit not resembling those typical for a specific variety, are occasionally seen in the field. One has to distinguish between natural variation (for example the two Atlas fruits on the left of the figure below) and off types (the 3 fruit on the right of the typical Atlas fruits and the giant Gemini at the bottom). Off types are seen occasionally, and in very low percentages. Sibs occur when the female parent was self pollinated during seed production.

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DISEASES

Prevention of disease

Diseases can be prevented to a large extent by the following:

 Rotational cropping  Use of disease-free seed  Good drainage  Regular inspections and an effective spray program  Planting time  Planting against wind direction

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Bacterial diseases

Bacterial blight (Angular leaf spot)

Bacterial blight is found only on cucumbers and vegetable marrows (fruit of Zucchini).

Symptoms Angular leaf spots, initially bordered by the leaf veins, appear on the leaves. At first these spots are water- soaked and later turn grey to light brown after which the tissue dies. With severe infections the spots coalesce, the leaves become torn and the dead tissue falls out. Small, round water-soaked spots appear on the fruit. The fruits excrete gum at the infected parts and sometimes crack. The keeping quality of the fruit is severely affected by this infection. The disease frequently occurs after heavy rains accompanied by high temperatures. It can be transmittable by seed.

Causal agent

(Pseudomonas syringae pv lachrymans)

Spread The pathogen is seed-borne and bacteria spread from plant to plant through splashing irrigation water, insects and human activity. Warm (24 – 28 C), humid conditions favour disease development.The pathogen ca survive in the soil and infected plant rests for long periods – up to two years.

Control These diseases are seed-borne, so use clean seed lots and do not save seed. Preventing the build-up of bacteria is important. To control fruit phases of the disease, scout fields at least weekly and start weekly sprays of copper-containing bactericides/fungicides when foliar symptoms first appear but no later than when fruits are forming (early bloom). If transplants are used, copper sprays should be used.

Bacterial Fruit Blotch (BFB)

The first incidence of BFB was reported in the late eighties and today it is the most economically important cucurbit disease in the world. Watermelon appears to be the primary host plant but sweet melon, cucumber, pumpkin and squash are susceptible to the disease. The disease is not common in South Africa at this stage, but importation of infected seed may lead to introduction of the disease in the country.

Symptoms Symptoms on leaves are not particularly striking and may be confused with symptoms of other diseases. Fruit symptoms, and particularly on water melon have the most impact. The upper surface of he fruit develop irregular, water- soaked or dull-green blotches. The older lesions can turn red to

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brown and necrotic, and the surface of the fruit crack. In seedlings, cotyledons develop irregular, water- soaked lesions.

Causal agent Acidovorax avenae (formerly named Pseudomonas pseudocaligenes)

Spread The disease is spread through: . Infected seed. The seed of many cucurbit seed can be infected. . Crop residues. . Weed and volunteer plants. Disease development is favoured by high temperature and high humidity – conditions which are common in seedling nurseries.

Control The use of disease-free seed is the best way to prevent introduction of the disease. Sakata Southern Africa only source cucurbit seed that have been tested for BFB or that are produced in countries where the disease has never been reported.

Early symptoms of BFB on melon

Symptom progression of BFB on water melon

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Fungal diseases

Powdery mildew

Symptoms Powdery mildew develops as a white, powdery fungal growth on leaves that in time blights the foliage. Its control is critical to successful production in most years.

Causal agent Two fungal pathogens infect cucurbits, namely Sphaerotheca fuligenea and Erypsiphe cichoracearum.

Spread The pathogens are obligate patogens and suvive on volunteer or weed host plants This disease favours temperatures of 20 - 27 ºC. For infection high humidity is necessary whereas for spread of the disease, a low humidity is required. Spore.s are wind blown and can form germ tubes in as little as two hours. Spores can be form within 4 days after infection, thus diseases pread is very rapid when conditions are favourable.

Control Unfortunately, the powdery mildew fungi have developed resistance to many of the systemic fungicides. Chlorothalonil applied in a weekly spray program for other diseases will slow powdery mildew development but is ineffective if poorly applied. Poor spray coverage and poor timing of fungicidal applications contribute to the importance of this disease. Plantings should be scouted for the first symptoms of powdery mildew at least weekly. With the first evidence of powdery mildew, initiate a more aggressive and effective fungicide program by alternating with either a strobiluron or by tank mixing a systemic fungicide with the fungicides used for black rot control, and apply at seven-day intervals. Sulfur is also labelled for powdery mildew and it will do an excellent job when applied correctly; however, cucurbits can be very sensitive to sulfur, especially during hot (32°C or higher), humid weather. The amounts needed for full-season control can lower soil pH. Sulfur will not significantly reduce other diseases that need to be controlled at this time, however. Significant advances are being made in powdery mildew resistant or tolerant summer squash and pumpkin varieties. However, be very careful in selecting a variety based only on its reaction to powdery mildew; horticultural characteristics are of primary importance, and fungicides will still be needed for control of other diseases.

None of the pumpkin and squash cultivars normally recommended are resistant to mildew. The plants should therefore be dusted weekly with vineyard sulfur, dinocap (Karathane, Krotaan, Crotothane) or chinomethionat (Morestan). Dusting must be done in the mornings when the plants are dry. The plants must not be smothered with the fungicide; it should be barely visible on the leaves. The amount used should be about 20 - 40 kg/ha. In very hot weather sulfur can burn the plant.

Farmers usually prefer to dust their crops, but the fungicides are also available in a spray formulation. Wetable sulfur is then used instead of vineyard sulfur National Tested Seeds Kencor House, 750 Lorraine Drive, Bluff Hill, Harare Zimbabwe. Tel.No:04-310284-7 Cell: 0772 235 000 E-Mail: [email protected]

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(Spersul, Thiovit, Kumulus, Gofrisul). The other fungicides are also available in a wetable powder formulation.

During the past years preference has been given to systemic fungicides such as chloraniformethan, pyrazophos and triforine. These fungicides are also recommended for the control of powdery mildew on pumpkins, squash, cucumbers and muskmelons.

Downy mildew

Symptoms Downy mildew usually appears in late summer causing tiny pale yellow spots on the upper surface of leaves; these spots quickly expand to blight the entire leaf. If the condition is serious, the leaves die from the edges inwards. This symptom is similar to frost damage.

Causal agent (Pseudoperonospora cubensis)

Spread The disease is especially severe under moist weather conditions (humidity of 90 - 100% and temperatures of 15 - 20 ºC), not only when the rainfall is high, but also where heavy dew or mist occurs frequently. If the humidity remains high, infection can take place even if the temperature is high. Pumpkins rarely contract this disease; squashes and watermelons sometimes do, but it is most common in cucumbers and muskmelons. The latter crops can be completely destroyed if conditions for development of this disease are favourable. Overhead irrigation adds to the danger of infection by this disease.

Control Downy mildew rapidly spreads on an infected crop once it has established itself, especially under overhead irrigation and preventive control measures should be taken. If this cannot be done, the crop should be watched closely so that it can be sprayed as soon as the disease breaks out. Weekly spraying with chlorothalonil (Bravo) or mancozeb (Dithane M 45) is recommended. Mancozeb (Dithane M 45) can also be applied as a dusting powder. The treatments should be repeated weekly, but if the disease takes on epidemic proportions, it may be necessary to treat the crop twice a week.

It is further recommended that cucurbits, such as cucumbers and muskmelons that are very susceptible to the disease, be cultivated only in dry areas.

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Leaf blight

Pumpkins, squashes, watermelons, cucumber and muskmelons are all susceptible to this disease.

Symptoms Brown spots, often with a yellowish-green halo are scattered over the leaf. Many of the spots have a dark-brown margin and are light brown to almost white in the centre. The fruit of pumpkins, squashes and muskmelons can also be infected.

Causal agent Alternaria cucumerina

Spread During long, wet periods and when the temperature is between 15 to 26 ºC.

Control The available fungicides tend to be rather ineffective against leaf blight and therefore difficult to control with spraying.

Anthracnose

Symptoms Light brown, more or less circular spots appear on the leaves and later turn dark-brown or black. Under conditions favourable for the development of the disease, the spots coalesce and look as if the leaf has been scorched. Elongated brown spots develop on the stems. The disease is encouraged by wet weather. Lesions with brown concentric rings within which black specks develop, occur on the fruit of pumpkins. Leaves of pumpkins and squashes are seldom attacked.

The greatest problem is with post-harvest phases of the disease. Sunken lesions appear on the fruit and under moist weather conditions masses of pink spores appear at the margins of the lesions.

Anthracnose is usually a minor disease of squash and pumpkins. Watermelons, cucumbers and muskmelons are particularly susceptible to Anthracnose. Muskmelon fruit can be severely infected without showing symptoms on the leaves to any great extent.

Causal agent Colletotrichum orbiculare

Spread Warm, humid conditions (22 - 27 ºC) and very high humidity aid the spread of anthracnose. The pathogen over-winters on infected crop residues. Spores from these residues are spread to plants by means of splashing water, human activity and perhaps also insects. The infect a plant, 24 hours of 100% humidity is required and symptoms first appear 4 days after infection.

Control . This disease can be controlled with weekly sprayings of mancozeb, provided that this is done immediately after the first symptoms are observed. It is recommended that cucurbits, especially watermelons, cucumbers and muskmelons that are

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highly susceptible to the disease, be cultivated in the dry parts of the country only. . Anthracnose can be controlled with a black rot/gummy stem blight control program described below, starting no later than the first appearance of anthracnose. . Use only disease free seed. Rotate with crops other than cucurbits for two or more years.

Foot rot

Symptoms The fungi causing this disease may attack plants as early as the seedling stage (see damping-off). If mature plants are infected, the disease causes total wilting of the plant. The stems of pumpkins and squashes are usually a watery brown near the soil surface. In the case of watermelons, cucumbers and muskmelons the roots turn brown and die. However, the plants can already start wilting before any outward signs are seen on the roots.

Causal agent Fusarium spp.

If the stems and roots are cut open lengthwise, the brown discoloration of the wooden tissue can be clearly seen. The disease usually occurs in patches on the land and is aggravated by high temperatures.

Fusarium spp. can also infect the fruit of cucurbits, especially those of pumpkins and butternuts.

Control No direct control

measures are known. It is recommended that crop rotation be applied and that only certified seed. The fruit must be handled carefully after harvesting.

Pythium wilt

Symptoms The plants wilt as a result of rotting of the root system. Infected fruits become soft and in many cases are covered with a white fungal growth. The disease is encouraged by heavy rains and occurs severely on poorly drained soils. Soft rot of the fruit may occur especially in the Lowveld regions of the country.

Causal agent Pythium spp.

Control No direct control measures are known. It is recommended that the crop must be planted on well-drained soils in a crop rotation. Special precautions must be taken against injuries during harvesting and marketing. Infected fruit must not be packed together with healthy fruit.

Remarks

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Wilting is not necessarily always the result of root rot or Pythium wilt. For example, it can also be caused by drowning after heavy rains. The roots will appear completely healthy even after wilting. Plants struck by lightning would also wilt. The damage in this case is limited to a more or less circular area and the fruit shows jagged lesions.

Black Rot or Gummy Stem Blight

Gummy stem blight and Black rot is of the most important diseases of cucurbits. It afftes the fruit, stems and leaves and huge damage can occur if environmental conditions are conducive to disease development.

Symptoms This disease on fruit is characterised by a ring-like pattern, which becomes bleached white, giving a petrified appearance. The causal organism is Phoma cucurbitacearum, pictured below on butternut squash. Infection on fruit is known as black rot, and on stem, as gummy stem blight.

There are important differences between squash and pumpkins in susceptibility to this disease. The fruit rot phase (black rot) can be very serious during wet seasons on squash (especially butternut and Hubbard types) and pumpkins. Major losses in pumpkins occur in seasons when other foliar diseases are also serious. Wet weather favours gummy stem blight development, and failure to control foliar diseases leads to the fruits being more susceptible to black rot. Black rot does significantly affect the shelf life of pumpkins and squash even though infections occur in the field and should be controlled in the field. Observations suggest significant field tolerance exists in some squash and pumpkin cultivars.

Left: Squash fruit showing symptoms of black rot. Right: Ring-like patterns, bleached white and petrified appearance.

Causal agent (Phoma cucurbitacearum).

Spread

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The disease is seed-borne, it is therefore important to use certified seed. In the field, spores can be spread from an infected crop to other crops by means of wind and water. The pathogen can survive in soil, without any host plant for up to two years. Optimum conditions for infection is 20 – 24 C, especially during humid conditions.

Control Avoid fields with a history of gummy stem blight on any cucurbit crop and practice crop rotation (three to four years) to crops other than cucurbits to reduce build-up of the pathogen. Plant certified seed from reputable suppliers. In squash and pumpkins, fungicide sprays should be applied well and regularly and should begin at vining and continue until harvest.

Waiting until symptoms appear to start a spray program is too late. Regular, preventive fungicide sprays should include chlorothalonil at 2.3 to 3.5 ℓ/ha for flowables or 1.7 to 2.8 kg/ha for dry formulations (WP, DF, DG), maneb 80 WP (also mancozeb on zucchini) at 2.2 to 4 kg/ha for dry formulations (WP, DF, DG) or at 2.3 to 3.5 ℓ/ha for flowables, and Gavel 75 W at 1.7 to 2.4 kg/ha. The strobilurons also perform well in black rot control, but resistant strains are developing. If any strobilurons are used, it should be alternated with chlorothalonil; maneb (also mancozeb on squash) can be used as an alternative product early in the season before powdery mildew is present. Nova is not effective on black rot but is an excellent powdery mildew control product.

Handling during and after harvest greatly impacts the susceptibility of squash and pumpkins to black rot. Wounding or damage to the fruit can negate a good fungicide program. Allowing fruits to be exposed to cool temperatures (below 10°C) in the field or during storage greatly increases susceptibility in some cultivars, especially squash. Allowing fruits to be exposed to frost greatly increases susceptibility in some cultivars.

Damping-off, Seed Rots

(Fusarium, Pythium, Rhizoctonia spp.)

Purchase fungicide-treated seed, or treat small amounts of seed with Thiram at 5.43 ml/kg of seed. Planting into warm, well-drained soils greatly reduce the risk of seedling death. Pythium can be controlled with pre-plant applications (broadcast or band) of fungicides containing mefenoxam at 0.56 to 1.12 kg/treated ha. Greenhouse produced transplants should be seeded into pathogen-free media with the trays on well-drained benches rather than on the soil. Carefully manage watering to minimize prolonged periods of wetness.

Mosaic (watermelon mosaic virus and possibly other viruses)

Symptoms The symptoms are first observed on the youngest leaves. A dark to light-green mosaic pattern appears on the leaves and the leaf surface becomes knobby or uneven. When severely infected, the leaves curl and the plants remain small. Where the leaf tissue within the veins does not develop normally, the main veins protrude like the fingers of a hand.

The fruit of the infected plants has a knobbly appearance, usually remains small and is unmarketable. All cucurbits and various other plants are susceptible to mosaic virus. The virus can be transmitted by handling the plants, e.g. during harvesting, but in practice the disease is spread mainly by aphids. The damage caused by this disease is extremely severe in areas where cucurbits are cultivated throughout the year and the infection is transmitted from older to younger plantings

Causal agent This virus complex (Watermelon Mosaic, Squash Mosaic, Cucumber Mosaic, Papaya Ring Spot, and Zucchini Yellow Mosaic) can be a limiting factor to autumn production of zucchini, especially on farms where spring or summer crops of cucurbits are also present. Breeders have made great strides in

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recent years to improve the tolerance/ resistance of several summer squashes to one or more viruses in the complex. Although squash mosaic is seed-borne, most other viruses over winter in perennial weeds and are spread into squash and pumpkins by aphids. Controlling these insects in autumn plantings is not a practical control solution for this disease complex. Watermelon mosaic has been the most common virus detected in recent years. Control

. Some countries recommend using stylet oils and planting into aluminium foil mulches to delay or reduce virus transmission, but these have not proven to be economically successful. Avoid a series of subsequent plantings adjacent to each other to reduce movement from plants with high concentrations of virus to newly planted crops. Prevent aphid build-up on tobacco; observations suggest that aphids moving from tobacco can acquire and transmit many of these viruses. Also, CMV building up in cucurbits and being vectored to other host crops can create additional problems in our diverse cropping systems, especially tobacco, peppers, and tomatoes planted within 50 meters of cucurbits. Remain alert to new and changing variety options.

Atlas, Sampson & Barnacle Bill, all in the same field, different virus symptoms

. Varieties resistant to virus. Varieties resistant to virus can offer a very effective way to minimise damage of virus infections. Sakata’s new generation butternuts, Pluto, Venus and Apollo, are examples of this. In the figure below, Pluto was planted with Waltham under conditions with a high virus pressure. The difference was evident for an early stage already.

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Waltham (left) is suceptable to virus. Pluto (right) clearly shows resistance to infection. .

. Planting times. In areas with cold winters, where the cultivation of cucurbits is impossible, and where no host plants will grow in winter, the amount of infection is going to be much less. . In the former Transvaal Highveld regions of the country, viral symptoms are usually not observed before mid- December whilst in the lowveld, with its relatively warm winters, early plantings are often completely infected by October. . It is recommended that cucurbits be planted early in spring. This is also true for the Lowveld, although, this measure is not as effective as in areas with cold winters. . Isolation. From the above it is clear that cucurbits should not be cultivated near old, infected plantings. . Control of aphids. Once a plant is infected with aphids carrying viruses, it acts as a source for subsequent infection to other plants via aphids. It is very important to control the spreading of aphids to other healthy plants. It is important to ensure that all life stages of the aphid are controlled and they are prevented from multiplying. . Spraying with mineral oils. When the plants are covered with a layer of oil, aphids cannot transmit viruses as they are inactivated by the oil. Plants on experimental plots, which were regularly sprayed with a light mineral oil from an early stage, remained healthy until after the flowering stage, in contrast to those on unsprayed plots. As the runners grow rapidly the plants should be sprayed twice a week from the beginning and the sprayings should also be repeated after heavy rains. This method can be considered as impractical and undesirable to growers. . Aluminium foil. Strips of aluminium foil are laid on the soil between the rows. The aphids are discouraged by the bright reflection, with the result that the outbreak of the disease is retarded and little damage is done. . Maize between rows of cucurbits. It has often been observed that maize planted between rows of pumpkins does hamper the movement of aphids, reducing the incidence of mosaic to some extent. This phenomenon has again been observed in recent experimental work in cases where the infection pressure was low. When the infection pressure was high, however, as during the middle and late summer, the planting of maize had no advantageous effect.

HARVESTING, HANDLING AND STORAGE

Pumpkin and Squash

All pumpkins that are stored for times of scarcity must remain on the runner until they are completely ripe and the skin is hard. The Hubbard cultivars are mainly used green. Pumpkins and squashes marketed when still young and green are harvested according to the size of the fruit, condition of the skin and stage of development of the seed. For instance, baby marrows, vegetable marrow and gem-squashes produced as immature squash should have a very soft skin that is at risk of being easily scratched with one’s fingernail. The skin of crops like Crown Prince, Ponderosa, Bounty, Butternuts and Barnacle Bill can already be tough when the fruit are full-grown.

The fruit should be cut from the runner in such a way that a part of the peduncle remains on the fruit. This is done easily with pruning shears. Do not carry a pumpkin by its stem or “handle” since these often break off, reducing the pumpkin’s marketability and its storage life by encouraging decay. It is extremely important that the fruit be carefully handled from harvesting until marketing, as any injury to the skin will promote rotting.

Pumpkin

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Crown Prince, Ponderosa, Maxi Prince, Bushfire, Bounty and Flat White Boer are mainly marketed when ripe. When very scarce or during periods with a high price, they may be marketed in an unripe but mature stage. However, it must be emphasized that in the latter case they should be handled with great care and marketed within a week or two.

In the Middleveld or Highveld pumpkins are mainly cultivated for use during autumn or winter. Under favourable conditions the fruit may be stored for a few months.

Fruit intended for storage should remain on the plants until completely ripe (40 - 50% corking on the stem is a good rule of thumb) and those for curing should remain in the field for a week or two. Ripe mature fruit can tolerate light frost for a short period, but the tissue must under no circumstances be allowed to freeze. Care should be taken that the fruit is not injured during harvesting and that a part of the peduncle remains attached to the fruit. The skin can be hardened during a curing period of 10 to 14 days at 29 - 32C or a month at room temperature before the pumpkins are stored.

Any storing facility with good ventilation and fair temperature and humidity control can be used. Most facilities that are currently being used for the storage of Crown Prince have open doors on both sides for good ventilation. Stacking fruit upon fruit up to 1.5 m (6 - 8 pumpkins high) is common practice. In stores with only moderate ventilation and temperature control, stacking not higher than 6 to 8 pumpkins is suggested and then pumpkins are packed in heaps / bundles with a thin layer of straw protecting fruit from the concrete floors. For the best results with storing, relative humidity should be 55 - 75 % and the temperature 10 – 13 C. It is suggested that pumpkins are not stored with layers of straw between the fruit, as this obstructs ventilation and reduces the shelf life of the pumpkins. Walkways must be worked into the storage area so that the pumpkins with blemishes or rots can be removed.

Some of the large producers in the Western Cape use wooden onion or fruit crates (± 1m x1m). They pack the pumpkins into the crates and stack the crates upon each other in the rooms. Producers who store Crown Prince for the high price season, dip them in Jik or Bravo (use what the label indicates) and then stack them to reduce culls.

Pumpkins are not graded according to fixed specifications, but a certain degree of grading is applied when they are packed. The fruit are selected according to trueness to type, maturity and uniformity of size, shape and colour. Injured and green fruit are not marketed.

The fruits are marketed in sacks with a content of 14, 34 or 54 kg. The most commonly used bags are sugar pockets or green net bags with a mass of 34 kg. Approximately 10 fruits with an average mass of 34 kg fill these bags. To promote sales appeal, which will affect the price favourably, the bag is filled to capacity to leave the top of the last fruit exposed. The bags are then firmly closed by sewing cross-wise with string.

Hubbard squash

Barnacle Bill, Green Hubbard Chicago Warted, and Pacific are harvested when the fruit is fully developed and the skin no longer soft when scratched. At this stage the runners are usually still viable and the fruit soft when cut through. The bright-green colour of the skin has by then also turned a pale or dull green.

As the skin of the Hubbard is more easily damaged than that of the Boer pumpkin, the fruit should be handled with extreme care during harvesting and marketing. They are packed and marketed in the same way as Boer pumpkins. The fruits of the Hubbard cultivars are not suitable for storage over a long period and are usually marketed from the land. The best prices are obtained during the winter months from May to October.

Vegetable marrow (C. moschata)

A few aspects can be regarded as of importance regarding the marketing of marrows. In the first place there is an increasing

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interest in the marketing of baby marrows (very young, immature fruit) on the local as well as European markets. In the second place a fair number of mature vegetable marrows, as they were previously known, are marketed locally.

Baby marrow (also commonly referred to as Courgette or Zucchini) and Patty Pans

For immature fruit there are two main types of packaging for the domestic markets, first and most important; harvested between 80 - 100 mm in length and up to 25 mm in diameter and secondly harvested fruit of approximately 120 - 180 mm long and with a diameter of 25 - 30 mm is harvested. The desired weight per fruit is approximately 60 - l00 g. Grading according to size is essential as the fruit may then have an unattractive appearance. The first fruit may be harvested 45 - 50 days after planting and harvesting can last for up to 50 days. The fruit should be harvested every second day to ensure that the correct size is maintained. The fruit is cut off with a sharp-pointed knife. Varieties that are inclined to abscise their flowers at an earlier stage are very important as this improves yield potential of the smaller export grade or for high value domestic markets. Varieties that fail to lose their flowers, particularly during cooler weather, are not desirable.

The skin of the young fruit is very soft and it must be handled carefully to limit marks caused by grazing and scratching. Harvested fruit should be kept in the shade and transported to the pack house as soon as possible. It must be selected with the least possible handling and the remains of the flowers carefully removed at the same time. Afterwards the fruit is packed into the containers.

In countries specializing in this product, the marrows are treated with soluble plant wax to prevent excessive transpiration, seal the wounds at the stem and blossom end and represses fungus infection. This practice should be examined more closely in South Africa. The containers currently used for domestic marketing by countries with a lot of experience are white cartons containing 3 - 6 kg. In Britain the smaller container is preferred. For local marketing 5 kg boxes are used, whilst chain stores tend to prefer pre-packed containers of up to 500 g. For this purpose the fruit is delivered to the distributor in plastic lug-boxes, where they are packed and delivered to the stores. Baby marrows are produced continuously throughout the year and there is little variation in price.

Butternuts (C. moschata)

Due to the diversification of the market and the demand for higher yields, earliness, quality, uniformity and general disease resistance, the use of hybrids (Atlas, Barbara, Pluto, Venus, Apollo) are increasing rapidly. Waltham Imported is an excellent open pollinated variety.

The popularity of butternut is increasing significantly over that of traditional pumpkin varieties due to improved eating quality, size, convenience and consistency. Butternut in retail outlets is now found in several different forms; whole fruit, halves, stuffed prepared fruit, pre-packed cubes and juliennes for micro-waving, soups packs etc.

Immature fruit are now being used as a substitute or complimentary summer squash (zucchini or patty pan) for both the local and export market. Fruit are usually harvested when 5-10 cm in length and pre-packed onto punnets. Varieties like Waltham and now especially Barbara is commonly in retail stores in this form. There are also yellow varieties and these three colours provide an attractive option to retailers looking for summer squash types with a butternut shape.

Mature fruits whose skins have already hardened are harvested directly from the lands. The fruits are marketed in 10-13 kg orange bags. A common practice with butternuts is to allow the fruits to ripen on the plant. As with Boer pumpkins the fruit can then be stored for later use or marketing in the winter months when the highest prices are obtained.

Squash (C. pepo)

Gemini, Smarag, Sweet Dumpling, and Small Wonder are mainly marketed as mature fruit. The fruit stalks should be cut short to

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prevent fruit from damaging one another. Harvesting should be carried out twice a week to ensure that fruits are not too ripe when marketed. Fruit should be marketed as soon after harvest as possible and is commonly sold in green bags with a mass of 13 kg. The prices are also like other Cucurbits, being much higher in winter.

Immature fruit, like the butternuts, are now being used as a substitute or complimentary summer squash (zucchini or patty pan) for both the local and export markets. There are two main types of packaging, baby gems fruit are harvested between 3-4 cm in diameter, whilst young gems are harvested when 5 - 7 cm in diameter and are pre- packed in punnets. Varieties like Gemini and Smarag are most common. It is important not to have the market confused by the use of round zucchini types like Eight Ball (dark green) and One Ball (yellow), as their flavour, shelf life, taste and texture are far different from immature gem squash.

Control of Post Harvest Pumpkin and Squash Rots

Rots can originate from fruit infections occurring in the field, from a dusting of fungal conidia during harvest, or from direct fruit-to fruit contact in storage.

The following practices should be employed throughout the season: crop rotation, use of disease-free seed, good field drainage, and good insect and weed control, as well as appropriate timing of fungicide sprays, care during harvest, sanitation of storage facilities and containers, and post harvest control of storage temperature and relative humidity. Only mature and disease-free fruit should be harvested and placed under shelter before frost or freezing occurs. Winter squash and pumpkin are chilling-sensitive and may sustain injury at temperatures below 10 °C. Cold damage is cumulative, and the extent of injury is dependent on both time and temperature. Butternut squash are particularly sensitive to chilling injury. Although chilling injury may not be visible during storage at lower temperatures, the symptoms appear later after warming (usually during transit) as sunken pits in the surface where tissue has been weakened or killed by cold temperatures. Secondary pathogens can invade damaged tissue, resulting in rapid decay.

Special care should be exercised to avoid rind injuries, which provide entry for pathogens. Under proper curing conditions, wounded areas heal themselves by producing corky tissue. Curing at 20 - 25 °C for a week will harden the rind but is detrimental to the taste of some varieties. Butternut, Hubbard squash and pumpkins respond well to this treatment. Storage can then proceed at 11-16 °C with 55 - 75 % (optimum 60 %) relative humidity. Control of the oxygen and carbon dioxide content of the air in the storage container does improve storage of the fruit.

Higher humidity favours the development of decay, and lower humidity promotes dehydration and undesirable changes in flesh texture. Good air movement is important in both curing and storage. Squash is ethylene- sensitive, and dark-green-skinned varieties are most susceptible to visible yellowing. Ethylene from natural sources such as apples stored in nearby rooms or from poorly vented kerosene or gas heaters in the storage area will cause undesirable yellowing of the skin.

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Table 8. The recommended storage conditions for different culinary types and their storage life expectancy are as follows:

Culinary type Temperature (°C) Percent relative Storage life expectancy humidity

Pumpkins, general 10 - 13 50 - 70 8 - 12 weeks

Squash, general 10 50 - 70 Varies with variety

Buttercup / Kabocha 10 50 - 70 13 weeks

Butternut 10 - 16 60 - 70 7 weeks

Butternut 10 60 - 70 8 - 11 weeks*

Hubbard 10-16 60-70 27 weeks

Sweet melon 5 - 6 60 - 70 10 – 15 days

Water melon 5 – 10 60 – 70 10 – 20 days *Storage for 4 months or more is possible if all production, curing, and storage recommendations

MARKETING

Pumpkin The following graph indicates the monthly pumpkin prices over the past 13 years at the national fresh produce markets. This graph also emphasizes the advantages that could be gained by producing this type of pumpkin and placing it under storage to obtain better market prices.

TABLE 9 - Average monthly prices of pumpkins on the national fresh produce markets for 13 MONTHLY PRICES OF PUMPKINS 400

350

300

250

200

RAND/TON 150

100

50

0

JUL

JAN

FEB

JUN

SEP

APR

OKT

MAY

DEC

AUG

NOV MAR MONTHS y

TABLE 10 - Average monthly prices of butternuts on the national fresh produce markets over 13 years

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MONTHLY BUTTERNUT PRICES

600

500

400

300

RAND/TON 200

100

0

JUL

JAN

FEB

JUN

SEP

APR

OKT

MAY

DEC

AUG

NOV

MAR MONTHS

TABLE 11 - Average monthly prices of Gem squash on the national fresh produce markets

MONTHLY PRICES OF GEM SQUASH

1000 800 600 400

RAND/TON 200 0

JUL

FEB

JUN

SEP

JAN

DEC

APR

OKT

MAR

AUG

NOV

MAY MONTHS

National Tested Seeds Kencor House, 750 Lorraine Drive, Bluff Hill, Harare Zimbabwe. Tel.No:04-310284-7 Cell: 0772 235 000 E-Mail: [email protected]

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Frequently asked questions

Q - How many fruit (pumpkins) can be expected from a plant?

Although pumpkin plants produce a profusion of flowers throughout the life of the plant, and starting very early in the plants development, only 1 or 2 pumpkins per plant develop to any size. This varies depending on the type and variety of pumpkin grown.

The bush or semi-bush pumpkins yield more than the traditional vine types, and as a general guide to predicting yields, expect only about 1 - 1.5 pumpkins per vine. Therefore, if pumpkins were seeded and thinned to a population of 7000 plants per hectare, then yields should range up to about 9650 pumpkins per ha.

Miniature pumpkins can easily yield 12 - 15 fruit per plant.

Never predict yields by the numbers of blossoms present, but only by the fruit visible!

Q - If there are so many blossoms on any one vine throughout the season, why are there not more fruit per plant?

All pumpkins, squash and melons produce both male and female flowers separately on the same plant (monoecious sex expression). These flowers originate from the axils of the nodes. First, the male flowers form and bloom, allowing pollen to be available as soon as the first female blossom appears.

The order and numbers in which these flowers appear vary somewhat as to the time of year, the stage of plant development and the number of fruit already pollinated and beginning to size. Developing fruit temporarily reduces the occurrence of female blossoms further down the vine.

Pumpkins and squash are relatively insensitive to photoperiod (length of day) during the summer season.

Female blossoms are short-lived and in pumpkins and squash, open first thing in the morning and close a few hours later (24 h at the most), never to re-open again. If these blossoms are not pollinated they abort and fall off the plant. Generally, the female blossom is open from about 10:00 am to about 3:00 pm.

Male flowers typically occur on the vine first. There are typically 10 male blossoms for every female flower. Bees do not prefer one type (male or female) to another, so make sure there are sufficient pollinators to do the job. The proportion of male blossoms usually increases when plants are under stress.

The likelihood of a flower being pollinated depends upon the number of bees present and the number of visits to that flower. During poor weather conditions (cool or wet), bee activity is reduced and poor pollination can be expected.

Q - How do these vines grow and where do the flowers occur on the plant?

Pumpkin plant growth is characterised as either: a) vining (trailing) or b) semi-erect (bush-like). Bush varieties have shorter internodes (distance between leaves), and lack tendrils. The trailing varieties may have between 3 - 8 lateral branches each arising from a separate node (point of leaf attachment). Vine growth on the trailing types can be very vigorous with stem lengths totalling over 42 m in some instances, and with up to about 450 leaves in a 4 month growing season!

The yellow flowers occur singly in the axils of the leaves. In trailing varieties, the staminate (male) flowers occur near the centre of the vine on long, slender stems; the pistillate (female) flowers occur on short, ridged stems, further 'down' the vine than the male

National Tested Seeds Kencor House, 750 Lorraine Drive, Bluff Hill, Harare Zimbabwe. Tel.No:04-310284-7 Cell: 0772 235 000 E-Mail: [email protected]

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Q - How can the size of pumpkins be improved?

Water, temperature, insects and disease, pollination, fertility, soil type, plant population, variety (genetics), weeds all influence the size of crop. By maintaining optimal conditions for growth, one can improve the size of fruit.

Q - How important is it to keep the vine growing late into the season?

For fruit to grow it must continue to receive nourishment from the mother plant. If the vine dies prematurely, from powdery mildew or an early frost, for example, then any further growth of that fruit will be halted.

However, if the fruit is already physiologically mature it will continue to ripen by colouring but without increasing in size. 'Mature' green fruit (showing no colour change), that are not physiologically mature, will not turn colour.

Q - Will earlier seeding or using transplants increase yield?

Generally this will not be the case. Usually there are only 1- 2 pumpkins per plant. As fruit begin to develop, there is a tendency for less female flowers to be produced by the plant. If you seed during the last week of November and up to the 2nd week in December, fruit usually grows to its full size,

Pumpkins are a sub-tropical crop and respond to a longer growing season. However, since the market for this crop is so late, there is little need to hasten its planting.

Q - What can be done to increase the length of the handle (stem or peduncle)

Nothing, other than choosing a variety that exhibits those characteristics. These factors are predetermined genetically and nothing in the line of fertilisers or cultural practices will change this. This is also the case when it comes to the degree of ribbing - some cultivars are mostly smooth while others are deeply ribbed. Chose your varieties based on general market demand and individual customer preferences.

Q - What happens to the appearance of a variety if it is cross-pollinated with another variety grown nearby in the same field?

Varieties grown in close proximity to one another of the same species (Cucurbita pepo in this case) are not influenced in any way by the pollen it receives during that growing season. However, if seed is collected from fruit for the purposes of growing out the following year, then there is a possibility that the plants will not be true to type -particularly if it was a hybrid to begin with.

C. pepo and C. moschata cross readily without having any immediate effect on the quality of fruit. The progeny produce viable seeds, but likely result in an off-type. Therefore, isolate these 2 species for seed production purposes.

National Tested Seeds Kencor House, 750 Lorraine Drive, Bluff Hill, Harare Zimbabwe. Tel.No:04-310284-7 Cell: 0772 235 000 E-Mail: [email protected]

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SEED

Seed Count

Pumpkin: approximately 3,200 – 4,100 seeds per kg. Squash: 10,000 - 12,000 seeds per kg. Butternut: 10,000 - 11,500 seeds per kg Sweet melon: 30 000 – 32 000 seeds per kg Water melon: 10 000 – 25 000 seeds per kg (seeds of open pollinated varieties are much larger than that of F1 hybrids)

Seed supply

It is vital that seed from a reliable source be obtained, because such seed is viable, has the required potential for high quality, uniformity and yield and is free of seed-borne diseases such as gummy stem blight.

Seed Treatment Certain soil-borne fungi, particularly Pythium and Rhizoctonia, attack germinating seeds and therefore all Sakata seeds are pre-treated. These organisms can result in a poor stand if growing conditions are not favourable for the germinating plants and seedlings. The following treatment is necessary, particularly for early plantings as the soil temperature tends to be relatively low. The seed is moistened with a sticker solution and dusted with a powder containing 50% thiram. The sticker solution is prepared according to the instructions on the label. If the sticker is not added the treatment will be less effective as the thiram is easily washed off by irrigation or rain.

National Tested Seeds Kencor House, 750 Lorraine Drive, Bluff Hill, Harare Zimbabwe. Tel.No:04-310284-7 Cell: 0772 235 000 E-Mail: [email protected]

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Cucurbit Seed Quality With Respect To Genetic Purity

What Is Genetic Purity?

There are a number of factors that contribute to genetic purity. Stability of the parent (inbred) lines. This is where “off-types” come from. (Primarily the breeder’s responsibility, but careful rogueing by the production department during stock seed and commercial lot production contributes to minimising this risk ) Isolation distances in the seed production field. If these are not carefully observed, “out-crosses” can occur. Isolation distances are prescribed by the local seed certification scheme, as well as by company protocol. In the case of hybrids, successful pollination of the female parent line by the male line is essential If the female pollinates itself, the result is “sibs” Careless handling This can occur at almost any stage from the sowing of stock seed, to final labeling and dispatch of seed lots can result in mix ups. In the production field, complete removal of the male before harvesting the female is essential, otherwise we run the risk of mixing male seed in with the hybrid. We never contract more than one variety of the same specie to any grower to avoid on-farm mix ups. In addition, mix ups can occur during cleaning, drying packing……even at labeling stage. This is undoubtedly the area of greatest risk in the seed trade, since it is virtually impossible to distinguish between different varieties by just looking at the seed. We should not forget the seedling grower’s role in this and should actively support lot number traceability in the seedling system.

Some natural variation is acceptable - so the grow out reader must be sensitive to this as well as to the influence of environmental conditions.

How Do We Test Genetic Purity?

We test genetic purity either in the lab by means of Electrophoresis (EP) or Polymerase Chain Reaction (PCR), or in the field by means of a Grow Out. – Although lab tests are quick and relatively cheap to conduct, they are not suitable for all crops / varieties, and cannot distinguish between off-types and out-crosses. Before relying solely on the results of an EP test, grow outs are conducted to verify the accuracy of the test protocol for the particular variety involved. – Grow outs are conducted according to detailed protocols in terms of sample size, and reference material. In most cases the lot being checked is grown alongside the female, male and previously tested lot. The Grow out evaluator must also have a “Variety Profile” to refer to, which includes details of the parent lines, and possible problems to look out for.

National Tested Seeds Kencor House, 750 Lorraine Drive, Bluff Hill, Harare Zimbabwe. Tel.No:04-310284-7 Cell: 0772 235 000 E-Mail: [email protected]

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ABOVE Left, Off-type from male line, Right, normal fruit (round to slightly oblong)

ABOVE: Strong vine associated with over sized fruit (OT)

National Tested Seeds Kencor House, 750 Lorraine Drive, Bluff Hill, Harare Zimbabwe. Tel.No:04-310284-7 Cell: 0772 235 000 E-Mail: [email protected]

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Our minimum standard for the genetic purity of cucurbits is 98%. While 100% is the goal, we cannot expect to produce seed at a realistic cost if we accept no less than 100%.

When investigating a complaint relating to genetic purity it is essential to walk along an entire row, and count a minimum of 100 plants, before estimating the extent of the problem. In most cases the Off-Type appears to be present at a higher percentage than it actually is simply because the eye is drawn to the “odd man out”. This situation is exacerbated when the sibs/off-types/outcrosses are markedly different from the hybrid.

National Tested Seeds Kencor House, 750 Lorraine Drive, Bluff Hill, Harare Zimbabwe. Tel.No:04-310284-7 Cell: 0772 235 000 E-Mail: [email protected]