Melon growing

November, 1995

Melons are a popular summer-maturing crop grown in the Mallee. There is a vast range of types of melons, excluding watermelons, such as cantaloupes (rock melons), honeydew melons, hami melons, green-flesh musk melons and galia melons. The two main cultivar types are cantaloupes and honeydew melon.

Cultivars

Cantaloupe

For early crops choose Early Dawn, which is the most popular and earliest maturing variety. However, the fruit does not carry well. Eldorado is another very popular variety but matures later than Early Dawn. It is a very vigorous melon with a tendency to produce very large fruit in mid-season. The fruit is sutured but carries well.

Other varieties include Eastern Star and Malibu. There are a large number of varieties available, and growers need to be aware that new varieties are continually becoming available.

Honeydew

Honeydew melons may be either white or yellow in colour with sweet green flesh. They are a large fruit from round to elongated in shape, with a smooth skin. The major variety grown is the hybrid Dewcrisp.

Other melon types

Hami melon

Hami melons are oval, have a green yellow speckled skin and are partially netted. The flesh is pale salmon in colour and it is crisp and sweet. This melon originated in China: there are a number of hybrids available.

Musk melon (green flesh)

Musk melons are similar to cantaloupes in external appearance, but are green fleshed and very sweet and juicy. They are a very popular and high priced speciality fruit in Japan. The major variety grown in Australia is Emerald Delight.

Galia

Galia melons are round; the colour of their skin ranges from green to yellow and turns golden as they ripen. The fruit is green fleshed and very sweet. Galia melons were bred in Israel. They are a popular fruit in Europe.

Soils

Melons can be grown on a wide range of soil types provided drainage is good. The best soils are deep fertile sands. Melons can be grown on heavier soils if well drained; then raised beds may be beneficial. Light soils warm more quickly and suit early cropping, whereas heavier soils will be more suitable for mid-season crops.

Cover crops are beneficial for they improve both drainage and soil structure. Cover crops should be ploughed in at least four weeks before sowing.

Sowing

Most crops in Victoria are direct seeded but transplants may also be used. A soil temperature of above 15°C is necessary for germination. Melons are sensitive to frost so crops should not be planted until the risk of frosts has passed. Seeds can be sown from September through to January. Fruit will be mature in from 90 to about 120 days after sowing depending on the variety and the time of planting. Crops can be planted in January but late plantings will run an increasing risk of frost. Early crops are sown in August under plastic mulch and in polythene tunnels. Transplants may be of some advantage for the production of early crops but their growth will be checked and any advantage reduced if it is cold.

Spacing

The plants should be spaced about 500 mm apart in the row but early plantings should be spaced closer to compensate for reduced growth. Spacings between rows vary; spacing may range from about 1.5 to 2.5 m between rows.

Windbreaks

Windbreaks are essential, particularly for early crops. Benefits from windbreaks include control of windblown sand, reduced wind damage to plants and fruit, increased temperatures around plants and increased activity of bees. Windbreaks need to be established early enough to be effective at the time of seeding. Cereals in the form of rye corn or wheat make good natural windbreaks. They should be sown at right angles to the prevailing winds, but running down a slope to allow air drainage and thus reduce the risk of frost damage to melons. Windbreaks provide protection for a distance about 10-12 times their height. If windbreaks are established for every row of melons, care should be taken that they do not shade the crop. Once plants are running and starting to cover space in the row, windbreaks can be removed. It is beneficial to leave some windbreaks to form bays.

Fertilisers

The method of applying fertilisers depends on the method of irrigation. Trials have shown that melons grown in mallee soils can respond to nitrogen when it is applied at rates of more than 200 kg/ha. Indications are that a nitrogen (N) to potassium (K) ratio of N1:K0.5 is suitable unless potassium is low; then it may be N1:K1. If furrow or overhead irrigation is used, a complete NPK fertiliser should be applied as a base dressing at a rate of up to 1.5 t/ha of 6:6:6, 2:2:1 or an equivalent NPK fertiliser. This can be worked in several weeks before sowing or better still, banded into the rows on either side of the seeds.

Side-dressings should be applied when plants begin to run and at flowering or fruit set. Only nitrogen and potassium need to be applied then with a total of around 200-300 kg/ha of N20:P0:K16. This can also be applied through the overhead irrigation system as urea (100 kg/ha) and potassium nitrate (100-150 kg/ha).

For trickle-irrigated crops, a small amount of complete NPK fertiliser, 700 kg/ha of 6:6:6 and superphosphate at around 1 t/ha can be applied before planting, the remaining fertiliser should be applied via the irrigation system. From two to four weeks after germination, fertiliser can be applied twice a week through the trickle line. Once the plants start to run, this can be increased to three applications per week. A total of up to 220 kg of urea and 270 kg of KNO3 should be applied per hectare with around 75% of fertiliser to be applied by the time fruit reaches the size of a cricket ball.

These are general recommendations for the application of fertiliser assuming that no cropping has been carried out previously. To determine more accurately the requirements for fertiliser, a soil test should be taken before planting. Fowl manure applied before sowing will benefit melon crops; if it is applied at a rate of 30 m3/ha, the rate of complete fertiliser can be reduced by one sixth.

Weed control

The only residual herbicides registered for use in honeydew and cantaloupe melon crops for control of some grasses and broadleaves is Prefar/Alanap. Prefar/Alanap can be applied before or immediately after sowing. If fumigants have been applied, use of these herbicides may not be necessary. Fusilade and Sertin are the only post-emergence selective herbicides registered for grass control in cucurbits.Regular cultivation while vines are small is another form of weed control but this must cease when runners cover the beds.

Irrigation

Cucurbit plants require regular moisture during the growing period and may need watering every 3-4 days or more often if trickle irrigated. Furrow irrigation can be used successfully. Spray irrigation is easier to manage and waters the plants more evenly. Drip or trickle irrigation is the preferred method which provides even regular water, improved quality of fruit and the opportunity to manage the crop better. Tensiometers can be used to monitor the requirements for irrigation.

Pollination

Insects are essential for pollination of cucurbit flowers because pollen grains are too large and sticky to be transferred by wind. Bees are the most effective pollinators and may need to be introduced to a crop. A lack of native bees caused by clearing of native bush or application of pesticides may result in lower yield and quality because of poor fruit set. Around 5-6 hives per hectare are required and in large crops they will need to be clustered throughout the crop. Hives should only be introduced once flowering has commenced otherwise the bees will not work effectively when flowers do appear. Bees are susceptible to many pesticides and great care needs to be taken when applying these.

Harvesting

Rockmelons are fully mature when the fruit reaches "full slip" which occurs when the fruit can be clearly separated from the stem by applying slight pressure. Honeydew melons will be over-mature at full slip and must be cut from the stem. Honeydews should be harvested when the skin is white (or yellow depending on variety). The fruit may have a slight green tinge or feel slightly waxy and be with or without a fine fuzz. The blossom end should be firm to slightly springy and may have a slight aroma at room temperature.

Hami melon, Musk melon and Galia should all be clipped at harvest. The external colour of the hami melons should be light green with some yellowing and a partial net. The background colour of musk melons (green flesh) changes to a lighter green at maturity; the blossom end should be firm to slightly springy with a slight aroma at room temperature. Galia melons are mature when the skin colour has turned partially yellow to orange; the blossom end may be slightly springy with a slight aroma.

Yield

A good crop of melons in the Sunraysia area yields around 1400 cases per hectare. This may vary depending on the type of soil, cultivar and management, from 600 up to 2000 cases per hectare.

Post-harvest handling

Melons have a very short shelf life. It is only two weeks for rockmelons and up to four weeks for honeydew melons. Crops should be harvested in the cool of the morning and once picked they should be washed, packed and cooled to the holding temperature as quickly as possible. All rockmelons to be exported must be treated with fungicide to maximise storage life. Rockmelons can be stored at 5°C (lower if stored for a short term). Honeydew, musk and hami melons should be stored at 7-8°C.

Melons should be graded according to size; they are usually packed into cartons of around 20-22 kg. Large melons or melons for export are packed into a 14-15 kg tray.

Diseases

Fusarium, a soil-borne fungus is a limiting factor in growing successful cucurbit crops in the north-west. It causes damping-off of seedlings, wilting, loss of vigour and death of mature corps. The first symptom is wilting of the older leaves during the day followed by partial recovery at night. The infected foliage becomes pale (chlorosis); wilting extends throughout the plant which loses vigour. Infected plants can be recognised by a brown discolouration in the centre of the stem and root. Control of fusarium can be achieved through rotation. Cucurbit crops should not be grown in the same soil for more than two consecutive years to avoid a build up of fusarium. Do not grow melons in soil infected with fusarium for at least four years. If soil is continually cropped, it should be fumigated because fumigation is the only means of controlling the fungus.

Powdery mildew can be a major problem in curcubits. The development of this disease is favoured by heavy dews or rain. Conditions become ideal in the later part of the season when nights are cool and dewy and dry conditions prevail during the day. The disease is characterised by white powdery spots on the stems and leaves usually starting on the underside but spreading rapidly until the entire leaf is covered and ash grey in appearance. Once powdery mildew is established in a crop it is difficult to control. It is therefore important to establish a preventative spray program, Chemically resistant strains of powdery mildew have been isolated; it is important to treat plants alternately with a suitable protectant and a systemic spray.

Gummy stem blight infection is favoured by mild weather. It causes some wilt and loss of vigour, reduces yield and damages the fruit. Infected stems first appear to be water soaked then they develop dry black or tan spots on stems and leaves. Leaves may show large wide-shaped necrotic areas and stem lesions may exude a gummy red-brown substance. Control is difficult once plants are infected, therefore it is better to have a preventative spray program. Resistant varieties of melons should also be grown. Anthracnose and angular leaf spot are the other diseases that commonly occur and can cause problems.

Fact sheets

Melon Necrotic Spot Virus fact sheet (PDF - 219.0 KB)
Melon Necrotic Spot Virus fact sheet  (WORD - 2.0 MB)

Insect pests

Pumpkin beetles or aphids are sometimes a problem but they can be controlled by spraying.

Molybdenum deficiency

This a physical disorder caused by the deficiency of the trace element molybdenum. Typical symptoms are stunting of plants, paling of the interveinal area of the leaf and browning of the leaf margin. This can be corrected with a foliar spray of sodium molybdate at 250 g/100 L of water before flowering.

Rob Dimsey, Bairnsdale