Muskmelon & Watermelon

by Henry G. Taber and Vince Lawson

Department of Horticulture, Iowa State University

Updated: September 2001

 

Topics:

Planting

 Irrigation

 Varieties

 Harvest & Storage

 Flower Types, Bees

 Pest Management

 Fertilizing

 Budget

Muskmelon and watermelons are members of the cucurbit or vine crop family. They are each a distinct genus species and will not cross-pollinate. Muskmelon is classified as Cucumis nelo L. and watermelon as Citrullus lanatur (thumb.). Another misconception is the term 'cantaloupe'. Cantaloupe does not exist in the US and generally refers to a muskmelon that is shipped interstate in the wholesale market.

Both muskmelons and watermelons are warm season crops requiring full sun and a well-drained soil. Most of the Iowa acreage is devoted to the local, fresh market although a portion is shipped out of state to regional markets. Muskmelons and icebox watermelons are high value crops when harvested early in the marketing season. For this reason, transplants, plastic mulch and row covers are key components in the production system.

An excellent reference guide for specific recommendations, including pest management options is FG600, titled "Midwest Vegetable Production Guide for Commercial Growers." A copy can be obtained from your local county extension office or write to Ag Publication Distribution, 112 Printing and Publications Building, Ames, IA 50011.

PLANTING

Windreaks -- are an important and often overlooked component of crop production. young cucurbit plants, in particular, are very vulnerable to wind related injury when growing on smooth plastic mulch. Windbreaks alter air currents decreasing wind speeds and modifying the microclimate around crop plants resulting in better growth. They can be permanent (conifers and deciduous trees or shrubs) or annual (small grains) and sometimes physical structures (board fences, row covers). In general, the zone of protection extends out horizontally a distance of 8 to 10 times the height of the windbreak.

Transplant Production -- For early harvest, muskmelons and watermelons are started as transplants. Because these crops transplant poorly with bare roots, the transplants are grown in Jiffy 7's or plastic cell-type containers with a lightweight, artificial mix so the mass of soil can be carried with the roots. Young plants with one to two true leaves are best for field setting. Using a larger cell size as a 72-cell or 50-cell tray will allow flexibility in the spring so the plant has more room to expand before becoming root or pot bound. Thus, they are less likely to become stunted after delayed planting due to bad weather.

Do not add soluble fertilizer to Jiffy 7's because fertilizer is already in the mix. If using cell trays with your own artificial mix, you will have to add soluble fertilizer.

Start the seeds only 2 to 3 weeks before anticipated transplanting date (probably mid-May). Allow two plants per pot to develop. If you do not have a small hotbed or greenhouse available, place the plants on a wagon, make a teepee arrangement with clear plastic, and wheel the wagon into a barn or covered shed in the evening or during inclement weather.

Transplant as soon as you see the second true leaf growing up between the two thicker cotyledon leaves. Add a cup of starter solution to each hill. Use a fertilizer high in phosphate, such as 10-52-17, 9-45-9, etc. These are warm-season vegetables and will not tolerate frost or soil temperatures below 55 degrees F. In some growing seasons, vine crops that have recently been transplanted or that have recently germinated suddenly wilt and die. Most often this occurs during a period of 4 or 5 days of cloudy, rainy weather. Without sunshine, soil temperatures can drop below 55 degrees to 60 degrees F. At these low soil temperatures, plant roots cannot absorb water from the soil. Consequently, when the sun does reappear, water transpires from the leaves much more rapidly than the roots absorb water, resulting in sudden wilting and death.

Earliness Techniques -- Winds can severly damage the young plants, retarding maturity and reducing yields. For this reason, and to obtain a small amount of frost protection, early plantings are often covered with hot tents or plastic row tunnels for 2 to 3 weeks after field setting. Hot tent use has declined because of the high labor and expense. Use of a plant cover allows 7 to 10 days earlier transplanting than the frost free date in your area. This will depend on the early spring temperatures. Clear plastic tunnels supported by wire hoops can be erected by standard plastic laying machines with some simple modifications. Use the 1 1/2-mil clear plastic 5 or 6 feet wide. Ventilization holes should be drilled into the plastic roll at an 8 x 8 inch spacing before laying. Start about 1 foot from the edge. Use a sharp 3/4-inch drill. Or you can buy preslitted clear plastic mulch in 5- or 6-foot widths.

Rye strips between rows can provide good protection for most of the remainder of the season. One strip every one or two rows is best.

Black plastic mulch laid before planting aids in weed control, reduces root pruning, and gives profitable increases in early yields. For muskmelons, clear plastic is more effective than black in northern Iowa, but chemical weed control is necessary and is not available at this time. Hot, drying wind sweeping down the row under plastic mulch can severely damage tender transplants, so irrigation is a must. Because leaching is retarded, less fertilizer is lost, and nitrogen sidedressings are often unnecessary with the plastic mulch. If nitrogen needs to be added, it can be applied later through the irrigation system.

Try to lay the plastic as early in the season as possible, such as late April. It should be laid as soon after a heavy rain as the ground can be worked. It is very important that the plastic be laid over moist soil. If the plastic is laid over dry soil, it will actually delay subsequent transplant growth. Also, it is better that the plastic be laid at midday so that it can be stretched tight enough. Do not overdo stretching because cool nights may actually cause the plastic to tear.

The seedbed should be as fine as possible so you can get a good covering; rototilling is preferred. The plastic is laid by burying about 2 inches of each edge.

For further information on plastic mulch and row cover.

Spacing & Seeding
Muskmelons
Seed -- 1/4 to 1/2 lb./A for transplants; 2 to 3 lb. for field seeding.
Rows -- 5 to 7 ft. apart with hills (2 plants/hill) 2 to 3 ft. apart in row.
Watermelon
Seed -- 1/2 to 3/4 lb./A for transplants;
Rows -- 7 to 10 ft. apart with hills (2 plants/hill) 3 to 6 ft. apart in row.
Icebox types -- 5 to 6 ft. apart with hills (2 plants/hill) 2 ft. apart in rows.

Muskmelon

Varieties

Season

Quality

Remarks

 Superstar  Early  Good  large 6-8 lb fruit with deep ribbing
Athena* Early-Mid Excellent Medium net, oval, very firm flesh
Eclipse* Mid Excellent Heavy net, round, very firm flesh
Legend* Mid Excellent Medium net, oblong, large uniform fruit
Starfire Mid-Late Very Good Very large fruit, good netting
Superstar Early Good Very large fruit, excellent netting
Super Sun Mid Very Good Round, heavy net, uniform fruit
*These varieties are especially promising.

Promising Western cantaloupes for the Midwest: Don Carlos, Explorer, HyMark, Primo, Tastysweet, Veracruz

Promising green flesh muskmelons: Makdimon, Passport, Galor 2, Galor 3.

Honeydew and Crenshaw melons for trial: Daybreak, Magic To Do, Venus, Honeydream, Honey Gold, Moonshine, Sunex 7051

-- Daybreak, magic To Do= shipper types, round fruit, 6 to 8 lbs., crack resistance

-- Honeydream = 3 to 4 lbs., green flesh and smooth rind.

-- Venus = round fruit with attractive yellow color, 3 to 4 lbs., early honeydew

notes: Superstar = the standard early maturing 'homegrown' melon in eastern U.S. The large 6 to 8 lb fruit are generally round withprominent ribs and coarse netting, but sensitive to soil pH and at too low pH some fruit develop a 'slick' appearance or lack of net. Fruit soften quickly once mature and have a short shelf life. Powdery mildew susceptible. Best use is the early season local market. Eclipse = midseason variety with good shelf life. The round smooth fruit have good uniformity and weigh 5 to 6 lbs. Powdery mildew resistance and some tolerance to fusarium wilt. Very uniform size. Starfire = a mid to late season variety that produces 5 to 6 lb firm oval fruit with good shelf life. Fusarium wilt and powdery mildew resistance. Most growers using Starfire in preference to Starship (small size). Athena = an early to midseason 'shipper' type with high sugar content. Elongated oval fruit vary in size from 4 to 7 lbs. Food disease resistance to fusarium and powdery mildew. The best yield and ruit size in trials has come when planting is delayed until late spring when air and soil temperatures are consistently warm.

Watermelon

Varieties

Maturity (days)

Fusarium Wilt* Resistance

Color

Shape

Approx. wt. (lb.)

Seeded Watermelons
Carnival

86

7

lt.green, striped

blocky

22-26

Crimson Sweet

88

--

green striped blocky round

20-30

Fiesta

88

9

dk. green, striped blocky

22-26

Matador

95

--

dk. green long oval

25-30

Regency

82

9

dk. green, striped blocky oblong

18-22

Royal Jubilee

95

8

lt. green, striped long oval

25-30

Royal Sweet

85

7

lt. green, striped blocky oval

20-25

Sangria

85

9

dk. green, striped long blocky oval

20-26

Sultan

88

--

lt. green, striped oblong

25-30

Seedless Watermelons**
Crimson Jewel

85

7

med. green, striped oval

12-16

Genesis

85

--

dk. green, striped round

8-14

Millennium
85
--
dk. green round to oval
12-16
Millionaire, Triple prize

90

7

lt. green, striped oblong

12-16

Nova

85

--

dk. green, striped round

14-16

Revelation

85

--

lt. green, striped round oval

15-18

 Treasure Chest  
85
 
--
 yellow flesh  round  
8-14
Shadow

90

7

dk. green, striped round oval

15-18

SummerSweet 5244

90

6

lt. green, striped round oval

16-20

Tri-X-313

90

6

lt. green, striped round oval

16-20

Yellow-fleshed Watermelons
AU-Golden Producer

88

--

lt. green, striped blocky round

20-30

Yellow Baby

68

--

lt. green, striped round

9-12

*Fusarium Wilt Resistanct Ratings for Muskmelon and Watermelon: a score of "9" indicates excellent resistance, a rataing of "1" indicates little or no resistance. Black Diamond has a rating of 1. Cultivars with a resistance rating less than "6" should not be planted in fields with a history of Fusarium wilt. See Purdue Extension publication BP-19 for a more extensive list of wilt-resistant muskmelon and watermelon varieties.
**Pollinators must be planted with seedless varieties. Use a long watermelon such as Royal Jubilee or Sangria as the pollinating variety. Crimson Sweet works well as a pollinator, but its fruit will be seeded and have a similar appearance to most seedless varieties.

FLOWER TYPES & BEES

Flower Types -- Two basic types of flowers are borne on the vines of these crops. They are the male (staminate) and female (pistillate). The flowers are found in the axils of the leaves along the vine and can be easily distinguished from each other by the immature fruit formed on the base of the female flower. For example, the female flower will have a small, immature melon fruit below the bright yellow petals. The male flower will not have the small fruit attachment. This type of flower arrangement is known as monoecious -- separate male and female flowers but both on the same plant. Beginning at the base of the plant, the first few leaves will bear male flowers after which a mixture of male and female flowers will be evident along the vine for several leaves or nodes. Finally, the vine will produce primarily all female flowers at the tip. The actual arrangement is dependent on the genus-species.

Pollination by Bees -- Because the cucurbits have separate flower structures, they require cross-pollination to transfer the pollen from the anthers of the male flower to the stigma of the female. This is accomplished by honeybee activity. Domesticated honeybees, wild honeybees, as well as other wild bees are important for pollination. Recent research has indicated the triploid watermelon varieties need greater number of bee visits for maximum fruit set.

Flowers are open or receptive only one day. The more bee visits per flower, the more seeds, larger size (rapid growth), and fewer misshapened fruit. For instance, there are several hundred ovules in each fruit ovary, most of which have to be pollinated before the fruit will develop properly. Lack of pollination is one of the reasons for poorly-shaped fruit and culls. Cool, wet weather will limit bee activity and is one of the most common causes of lack of pollination. Also, low temperatures affect the flower structure, preventing the release of pollen at the time the pistil is receptive.

Honeybees usually pollinate flowers more thoroughly within 100 to 200 yards of their colonies than they do flowers at greater distances. To obtain the best coverage, you should distribute honeybee colonies in groups throughout the field. A common practice is one hive per acre.

FERTILIZING

Lime -- Important to maintain a minimum pH of 6.0 to 6.8. Muskmelon, particularly some varieties as Superstar, do not grow well and produce poor quality fruit on acid soils.

Fertilizer Rates Before and At Planting -- N: 50 to 75 lb./A. Use the lower rate on sandy loam soils and the higher rate on upland soils. When using plastic mulch, use the lower rate. Fertilizer should be banded and incorporated into the soil that will be under the plastic mulch.

Phosphate: 50 to 150 lb./A adjusted according to soil test.

Potash: 50 to 150 lb./A adjusted according to soil test.

Starter: When setting out transplants, apply a common starter solution, such as 10-52-8, 9-23-7, 10-34-0, etc. at the rate of 1 pint per hill. Starter solution is made by dissolving approximately 3 lb. of dry fertilizer per 50 gal. of water. Follow directions on the label.

Application: Broadcast 50 percent of the fertilizer before plowing or disking. Apply the remainder in bands 2 inches below the seed and 2 inches to the side of the row at planting or after transplanting. See comment above for plastic mulch culture.

Sidedress: For sandy loam soils or coarser, apply 30 to 60 lb. N/A when vines begin to spread about June 1. If heavy rainfall occurs during June, apply an extra sidedressing. If trickle irrigation is used, all of the P and K and up to 50% of the N should be applied preplant just before laying the plastic. The remainder of the N can be applied through the trickle system. Some states recommend that 50% of the K be applied through the trickle irrigation system, but Iowa research has shown that this is not necessary.

IRRIGATION

If you have used transplants, row covers and black plastic on sandy soil with a southern slope, you will find growth to be very rapid, much more rapid than without the use of the plastic. Hot, drying wind sweeping down the row under plastic mulch can severely damage tender transplants, so irrigation is a must. Irrigation is also essential on sandy soils. An overhead sprinkler or trickle irrigation system is satisfactory to supply the roots with enough water to maintain rapid growth. If, for the first year, you do not have irrigation available, you may wish to plant the crop on a more heavy textured soil, such as a loam or silt loam, but you run the risk of poor fruit quality, i.e., low sugar, poor shape, more rots, etc. If so, still use the black plastic since it will definitely enhance your early yield.

Trickle irrigation is recommended for use with plastic mulches. The frequency of irrigation depends on the soil type, soil water-holding capacity, environmental conditions and stage of crop growth. Frequent probing with a soil tube or hand trowel under the mulch around the plant row to keep a good check on soil moisture conditions is necessary. irrometers at the 6 and 12 inch depth in the mulched bed will give a more objective measure of soil moisture.

The goal is scheduling irrigation is to maintain an even and uniform water supply in the rooting zone so as to not to induce crop water stress. Crop visibly wilting during the growing season is a sign of severe stress and indicates scheduling needs to be modified for more frequent or longer running times. Coarse sandy soils provide an additional challenge of having low water holding capacities and running the system too long merely saturates a small volume of soil under the plastic and leaches nutrients below the root zone, thus dandy soils require shorter but more frequent irrigation. Crops at full ground cover can use up to 0.2 to 0.3 acre-inch of water per day.

At preharvest, 7 to 10 days before harvest, reduce the irrigation rate by 50%. This will improve fruit flavor and quality by increasing soluble solids content of the melon fruit. Cutting water off completely or inducing severe water stress will hurt late season yield.

HARVEST & STORAGE

Muskmelons should be harvested at full slip when the ground color under the net starts to turn yellowish. Eating maturity follows in 1 to 3 days and best flavor is obtained if melons are held near 70 degrees F. for this final ripening. If muskmelons are to be held longer, 50 degrees to 55 degrees F. is best.

Watermelons must be picked when table ripe. This takes experience. Use the criteria of approximate size for variety, a dull gloss surface, and the yellowing of the ground spot. Hold the harvested fruits at 50 degrees to 60 degrees F.

PEST MANAGEMENT

Resources for this section were obtained from North Central Regional Extension Publication #261, titled: Wilt Disorders of Cucurbits, and from Iowa State University Cooperative Extension Publication Pm-1049, titled: Cucurbit diseases - An aid to identification and control.

An excellent reference guide for specific recommendations, including pest management options is FG600, titled "Midwest Vegetable Production Guide for Commercial Growers." A copy can be obtained from your local county extension office or write to Ag Publication Distribution, 119 Printing and Publications Building, Ames, IA 50011.

Diseases

Insects

Weed Control

 

DISEASES

 

Gummy Stem Blight -- Gummy stem blight on muskmelon, watermelon and cucumber is caused by Didymella bryoniae (Mycosphaerella melon is), the same fungus that causes black rot disease in pumpkin and squash. Early infections result in reduced fruit yields and abnormal fruit maturation. Pumpkins and squash are especially prone to fruit infections, which result in an unmarketable product.

Infected stems first appear water-soaked and then become dry, coarse and tan. Older stem lesions (dead tissue) reveal small black fruiting bodies (pycnidia) within the affected tissues. Large lesions girdle stems and plants wilt in the heat of the day. Stem lesions on melons exude a gummy, red-brown substance which may be mistaken for a symptom of Fusarium wilt.

The fungus overwinters on infested crop residue and in the spring produces spores that infect young stems and leaves. The pathogen also may be carried in or on seed. Pycnidia in stem lesions releases spores when splashed by rain or irrigation water. Splashed spores become airborne and cause additional foliage and fruit infections.

Use of disease-free seed and transplants is essential to prevent serious crop losses. Periodic applications of fungicide can help limit secondary infections, especially on fruits. Fall plowing and extended rotations with other crops can significantly reduce the amount of inoculum in infested fields.

 

Bacterial Wilt -- Bacterial wilt (Erwinia tracheiphila) occurs primarily on cucumbers and melons, though it is seen occasionally on squash and pumpkins. Wilting on squash, pumpkin or watermelon can usually be attributed to squash vine borer damage. Symptoms differ significantly among hosts.

On cucumber and melon, generally a distinct flagging of lateral and individual leaves occurs. Affected leaves turn a dull green. Sometimes wilting occurs on leaves that have been injured by cucumber beetles' feeding, but in many cases obvious feeding is not apparent. Leaves adjacent to the wilting leaves will also wilt, and eventually the entire lateral is affected. The wilt progresses as the bacteria move from the point of entry through the vascular system toward the main stem of the plant. Eventually the entire plant wilts and dies. If you cut through the stem of an affected plant and squeeze both cut ends, a white, sticky exudate will often ooze from the water-conducting tissue of the stem. This exudate is composed of bacterial material that plugs the vascular system of the plant. Affected stems do not appear significantly discolored. One useful identification technique is to cut an affected stem, squeeze the sticky exudate out, push the two cut ends together, then pull them apart. You should get a stringing effect. Another technique, which we find more successful, is to place a cut end of an affected stem in a glass of water. Springs of ooze will flow into the water.

The symptoms are slightly different on squash and pumpkins. The affected leaves initially wilt and turn a dull grayish-green, then darken to bronze and shrivel on the petiole. Internally, little vascular discoloration occurs. Also, it is much more difficult to do a bacterial ooze test by stringing together two cut ends. Placing the cut stem in a glass of water is more successful.

Bacterial wilt is closely associated with either the striped or the spotted cucumber beetle. The bacteria overwinter in the bodies of adult cucumber beetles. The beetles carry the bacteria when they emerge in the spring. The bacteria are spread either through the feces of the beetle or from contaminated mouthparts. When the beetles feed on young leaves or cotyledons, they open entry points for the pathogen. Once inside the plant, the bacteria travel quickly through the vascular system, causing blockages that in turn result in wilting of the leaves. The disease progresses from plant to plant when a carrier beetle moves through the field or when clean beetles pick up the bacteria from a diseased plant and fly to healthy plants. Larvae are not known to carry the wilt organism.

In general, more bacterial wilt is seen on the edges of fields where beetles first encounter plants. Rigorous control of the beetle reduces the opportunity for infection and spread. This disease is of greater importance in Northern and Great Plains growing regions than in the South because the bacterium is quite heat sensitive.

Fusarium Wilt -- Fusarium wilt is an economically important disease of muskmelon and watermelon. Two species of fungi are involved: Fusarium oxysporum f. sp. melonis attacks muskmelon and Fusarium oxysporom f. sp. niveum attacks watermelon. Both fungi contribute to damping-off of seedlings, but most significant losses occur after young plants are infected in the field. Plants infected early in the season often produce no marketable fruits. Plants that begin to show wilt symptoms at or near maturity produce fewer and lower quality fruits.

The first symptoms of Fusarium wilt are wilting and chlorosis (yellowing) of older leaves. The wilt is most evident during the heat of the day. Plants may appear to recover by morning, only to wilt again in the afternoon. Stem cracks and brown streaks often appear near the crown of the plant and are associated with a red-brown exudate. Fusarium wilt also causes vascular browning that is visible in stem cross-sections.

The Fusarium wilt fungus overwinters in Midwestern soils as thick-walled chlamydospores (fruiting bodies) associated with crop residue. Roots can be infected at any time during the growing season; however, initial symptoms are most noticeable soon after plants begin to vine. The fungus colonizes root tissues and multiplies throughout the vascular tissue. Chlamydospores form within the roots as plants die.

Planting resistant cultivars is the only reliable way to keep infested fields in production. Commercially acceptable resistant cultivars exist, but extremely high pathogen populations in the soil can overcome their resistance. Therefore, methods to reduce Fusarium populations in the soil also should be employed. These methods include extended rotations with crops other than cucurbits and fall plowing of severely infested fields.

 

Anthracnose -- Anthracnose, caused by the fungus Colletotrichum orbiculare (= C. lagenarium), can significantly damage cucumber, muskmelon and watermelon. The general vine blight caused by anthracnose reduces bulk yield, and fruit infections decrease market value.

The diagnostic features of anthracnose vary with the host. Sunken, elongated stem cankers are most prominent on muskmelon, though leaf and fruit leasions also occur. Large lesions girdle the stems and cause the vines to wilt. Stem cankers are less obvious on cucumbers, but leaf lesions are very distinct. Watermelon foliage affected by anthracnose appears scorched; sunken fruit lesions are easy to recognize.

The anthracnose fungus overwinters on diseased crop residue. There also are reports that the pathogen is carried in or on cucurbit seed. In wet conditions each spring, the fungus releases airborne spores that begin new infections on vines and foliage. Anthracnose usually becomes established in mid-season, after the crop canopy has fully developed.

The primary anthracnose control strategy is to prevent foliar infection with protective fungicides. Good coverage and repeated applications are necessary to prevent development of serious epidemics. Reducing the amount of overwintered inoculum through such cultural practices as fall plowing and crop rotation greatly enhances the effectiveness of chemical control programs. Anthracnose resistance exists in several cucumber and watermelon cultivars.

Sudden Wilt -- Unlike bacterial wilt, which can occur any time during the season, sudden wilt generally occurs late in the season and is closely associated with a heavy fruit load on the plant. Cucumbers and melons appear to be most sensitive to sudden wilt.

Initial symptoms are a slight flagging of the plants in midday even when abundant moisture is present. This flagging will continue to worsen so that, by the third or fourth day, many of the plants are completely wilted. Disease progression is rapid, hence the name sudden wilt. After five to six days, all of the vines have melted down and only the immature fruits are left in the fields. Affected plants appear to lack feeder roots; other roots become slightly misshapen and thick.

Currently it is thought that sudden wilt is caused by a root rot complex involving Pythium sp., Rhizoctonia solani and Fusarium sp. that invade the roots and further colonize the root tissue. It is thought that stresses such as excess moisture and drought, prolonged periods of low temperatures (below 50 degrees F) and attack by the several viruses that commonly affect mellons and/or cucumbers individually or in combination weaken plants so that soil-borne pathogens can rapidly colonize the root systems.

Control is best achieved by rotating cucumbers or melons to areas where these crops have not been grown, or by fumigating ground on which these crops are to be grown. These strategies may lower the population of soil-borne organisms that affect these crops. Use of cucumber mosaic virus-resistant varieties of cucumbers and a vigorous aphid spray control program to avoid the transmission of viruses by aphids will help reduce the incidence of viral diseases and associated stress. Alleviation of stress factors will also reduce the occurrence of sudden wilt.

Powdery Mildew -- The powdery mildew fungus, Erysiphe cichoracearum, attacks muskmelons, squash, cucumbers, gourds, and pumpkins. It is evident as a superficial, powdery, grayish-white growth on upper leaf surfaces, petioles, and even main stems of infected plants. Affected areas turn yellow then brown and die. In dry seasons, powdery mildew can cause premature leaf drop and premature fruit ripening.

Some early disease results from spores produced on overwintering cucurbit debris or weeds but the major source of disease inoculum is windblown spores from southern crops. Warm, dry weather conditions favor the development of powdery mildew.

Powdery mildew may be controlled by prompt application of recommended fungicides.

Scab -- This disease, caused by the fungus Cladosporium cucumerinum, is more severe on cucumbers and muskmelons than on other cucurbits. Scab first appears as water-soaked areas on the foliage. These spots may be quite numerous. As the disease progresses, affected tissues turn brown, then white, and finally die. Dead tissue may tear away giving the leaf a ragged appearance. Most of the damage from this disease is on the fruit which may be infected at any stage of growth. Initially, infected fruits develop small, sunken, circular spots from which a sticky substance is exuded. Spots enlarge and blacken with age.

The fungus survives in infected plant debris and on the seed. Fungal spores are spread by wind, insects, people, etc. Cool, wet weather favors disease development.

Scab may be controlled by planting resistant cultivars, using disease-free seed, rotating with unrelated crops, and applying recommended fungicides.

Alternaria Blight -- This disease, caused by the fungus Alternaria cucumerina, usually occurs on foliage during the middle of the growing season. The disease starts as small, yellow spots which enlarge to form concentric rings on the upper leaf surfaces. Muskmelons are more susceptible than other cucurbits to Alternaria blight. Often muskmelon vines will be almost completely defoliated by this disease. The pathoegen also may cause fruit injury.

Alternaria cucumerina may be carried in and on seed and can also overwinter in diseased plant debris or cucurbit weeds. Spores produced on infected foliage are spread by wind, rain, people, tools, etc. Plants weakened by lack of proper fertilizer or poor soils are more likely to be attacked than young, vigorously growing plants. Warm, wet weather favors development of Alternaria blight.

To control Alternaria blight, plant disease-free seed in fertile, well-drained soil, practice crop rotation with unrelated crops, destroy cucurbit weeds, and use recommended fungicides.

Downy Mildew -- Downy mildew is caused by the fungus Pseudoperonospora cubensis and occurs on cucumbers, squash, muskmelons, and pumpkins and less frequently on watermelons. On cucurbits other than watermelons, small, yellowish areas occur on the upper leaf surface. Later a more brilliant yellow color develops with the center of the lesion turning brown. Usually spots are angular because they are restricted by leaf veins. When leaves are wet, a downy, white-gray-light blue fungus growth can be seen on the underside of individual lesions. On watermelons, yellow leaf spots may be angular to non-angular and turn brown to black.

Spores produced on the lower leaf surface are readily spread by the wind. Rainy, humid weather favors the development of downy mildew.

Downy mildew may be controlled through the use of resistant cultivars and recommended fungicides.

Angular Leaf Spot -- Angular leaf spot caused by the bacterium Pseudomonas lachrymans is most serious on cucumbers, zucchini squash, and honeydew melons but can infect most other cucurbits. Symptoms of the disease firts appear as small, angular, water-soaked lesions on the leaves. When moisture is present, bacteria ooze from the spot in tearlike droplets that dry and form a white residue on the leaf surface. Water-soaked areas turn gray or tan, die, and may tear away leaving irregular holes. Water-soaked spots may also appear on the fruit and are frequently followed by soft rot bacteria.

The bacteria survive in infected plant debries and on seed. Bacteria are spread by rain, overhead irrigation, tools, or workers picking fruit. Warm, wet weather favors disease development.

Angular leaf spot may be controlled by planting disease-free seed, rotating with unrelated crops, keeping workers out of fields when foliage is wet and applying recommended fungicides.

INSECTS

An excellent reference guide for specific recommendations, including pest management options is FG600, titled "Midwest Vegetable Production Guide for Commercial Growers." A copy can be obtained from your local county extension office or write to Ag Publication Distribution, 119 Printing and Publications Building, Ames, IA 50011.

Cucumber Beetles -- The striped cucumber beetle and the spotted cucumber beetle (or southern corn rootworm) are the most common and serious insect pests of cucurbits. Both species overwinter as adults, carry the bacterial wilt organism over the winter and transmit it to plants in the spring. Migration from the South may be another source of new wilt-carrying beetles in the spring. Adults of both species can also damage young seedlings or transplants. Both species lay eggs on the soil and larvae feed on plant roots, reducing plant growth and yields. Larvae of the spotted cucumber beetle feed on a wide variety of hosts, including corn. Larvae of the striped cucumber beetle attach only cucurbits. Two generations of the striped cucumber beetle occur each year. Injury to very young seedlings caused by striped cucumber beetle larvae resembles symptoms of damping-off. Seedlings wilt first, then collapse at the soil line. Close inspection of the damaged area often reveals that the shoot has been severed from the roots. Small (1 cm long), white larvae may be found just below the soil surface near freshly cut seedlings. Large populations of feeding larvae can severely damage roots of mature plants. Feeding by adult beetles results in leaf and stem lesions.

Adults of the western corn rootworm look very much like the striped cucumber beetle. Both may be seen feeding on pollen from cucurbit flowers, but the western corn rootworm does not attack cucurbits to any extent. Although the western corn rootworm can carry the wilt organism, it has not been shown to transmit it. Striped cucumber beetle adults are often a much brighter yellow than the western corn rootworm. Also, the striped cucumber beetle's legs are black and yellow or tan instead of all black. Treatment necessary for control of western corn rootworm is rarely necessary unless severe foliage and flower injury is occurring.

Treatment with a systemic insecticide in the soil at planting is recommended for fields where problems are expected. Soil systemic treatment is much less hazardous to bees and other beneficial insects than weekly foliar sprays. Spraying has not been totally effective since beetles feed and transmit the bacteria before the insecticide kills them. At planting treatment may not be economical, however.

Squash Bug -- Anasa tristis can be a problem in some squash, pumpkin and watermelon fields. Squash bugs have several generations per year and overwinter as adults. Adults are dark brown to black and 3/4 inch long. Immature squash bugs (nymphs) are similar to adults in appearance and habits, but are smaller and lighter in color and lack fully developed wings. Infestations occur most commonly in fields planted continuously to host crops. Adults and nymphs feed by sucking plant juices. All parts of the plant, including the fruits, may be attacked. If squash bug numbers are high, feeding injury can result in plant wilting. Young plants are especially vulnerable. Feeding on fruit may result in local tissue necrosis, often on the underside of the fruit.

The squash bug often hides under fruit or foliage, so control is easiest early in the season when the plant canopy is less developed and spray coverage is more complete. Also, young nymphs are easier to control than mature nymphs or adults. Fields should be checked regularly so that treatment, if necessary, can be applied before fruit are injured and before control becomes difficult because of the denseness of the plant canopy.

Seedcorn Maggot -- The seedcorn maggot attacks a wide range of seeds, including curcurbits, beans, corn and others. It overwinters in the pupal stage in the soil. Adults -- brown to black flies of 3/8 inch long -- emerge in late April to May and begin laying eggs in 10 days to two weeks. The flies are attracted to rotting organic material in soil, as well as to germinating or rotting seeds. Larvae feed on organic material in the soil or on seeds or germinating seedlings. Damage can range from destruction of the seed to feeding injury on stems, cotyledons or first leaves that occurs before the seedling emerges from the soil. Injury is usually most severe in cool weather, when seed germination is delayed, or in soils with high organic content, such as a plowed-down cover crop or manure. Three generations of seedcorn maggot occur each year. The first generation causes most of the damage.

Cutworms -- A number of species overwinter as partially grown larvae, 1/2 to 1 inch long, in the soil. Other species overwinter as eggs but may be present as large larvae by mid-May or June. Cutworm larvae feed on a wide variety of weed and crop plants, cutting them off at the soil line. Because the larvae are already present in the soil at planting, injury to cucurbits most often occurs within a few days of transplanting or emergence of seedlings.

Check fields frequently for several days after transplanting or seedling emergence and apply cutworm controls as needed. Treatments should generally be applied at the highest labeled rate. To save cost, nozzles can be centered over the rows and sprays applied in a band rather than broadcast. Systemic insecticides applied to control cucumber beetles will generally not be effective in controlling cutworms.

Rye cover crops or windbreaks, other grasses and small grains are attractive hosts for cutworms. Check them for larvae before cultivating out or spraying off the windbreaks, or check the crop immediately afterward for cutworm injury.

 

WEED CONTROL

Careful planning and use of a variety of strategies will allow you to effectively control weeds. The first step in obtaining acceptable weed control is field selection and/or preparation. Melons should not be planted in fields infested with high populations of difficult to control or perennial weeds. Efforts to control these weeds (hemp dogbane, quackgrass, yellow nutsedge, velvetleaf, etc.) should be made either while producing crops such as corn and soybeans, where more control options are available, or by leaving the land fallow and concentrating control efforts while the land is idle.

The type of control program you select depends on the size of operation, equipment available, and severity of weed problems. Cultural strategies, such as cultivation, hand weeding, and mulches, may provide adequate control when weed pressures are low or the operation is small enough to allow several timely cultivations. Where weed populations are high or labor is limited, you may need herbicides to supplement cultural control measures. You should not abandon appropriate cultural strategies when using herbicides.

Table 1. Herbicides for commercial Melon production

Weeds Chemical Rate/Acre Comments
Germinating broadleaves Alanap L (naptalam) 4-8 qt. Apply immediately after seeding or transplanting. May also be applied postemergence just before plants begin to vine. Postemergence treatments will not control emerged weeds.
Germinating grasses Prefar 4E (bensulide) 5-6 qt. Prefar must be incorporated mechanically or with overhead irrigation to a depth of 1-2 inches immediately following application. Prefar may be applied in combination with Alanap to broaden the spectrum of weeds controlled

Herbicide Selection -- Modern herbicides have been developed to provide consistent weed control with minimal risk of injury to the crop or the environment. However, unfavorable weather conditions before or after application, or misapplication of a herbicide may result in poor weed control or severe crop injury. You should be aware of the inherent risks before using any herbicide. Use a new chemical on a limited basis until you gain experience with it.

An excellent reference guide for specific recommendations, including pest management options is FG600, titled "Midwest Vegetable Production Guide for Commercial Growers." A copy can be obtained from your local county extension office or write to Ag Publication Distribution, 119 Printing and Publications Building, Ames, IA 50011.

Several types of herbicides are available for vegetable producers. You should select a specific chemical based on your cultural practices, weed species present, soil type, and equipment available.

Selective herbicides normally control a fairly specific group of weeds. Because of this, choose a herbicide that is effective against the predominant weeds in a field. A combination of herbicides may be required in certain fields to provide adequate control of all the weeds present.

Important aspects of herbicide use are sprayer calibration and maintenance. Consistent results can only be obtained when a herbicide is uniformly applied at the recommended rate. A sprayer capable of applying spray volumes ranging from 20 to 50 gal. per acre at pressures between 20 and 50 psi will be adequate. Flat fan nozzles are well adapted for most herbicide applications. Herbicides should not be applied at the high pressures (80 to 120 psi) used to apply many fungicides and insecticides. Do not use a sprayer for applying fungicides or insecticides if it has been used to spray 2,4-D or related compounds.

The herbicides currently registered for use in cucurbits are listed in table 1. These herbicides are for preemergence control of germinating weed seedlings. They have little or no effect on weeds already established at the time of planting. There are no herbicides cleared for use for control of established weeds in cucurbits. Dacthal and Alanap may be applied after the crop is established; however, they have little effect on weeds that have already emerged.

BUDGET

This section prepared in cooperation with Dr. William Edwards, extension economist, Iowa State University. Data below is from 1996.

Muskmelon

 Receipts

Quantity

Unit

$/Unit

Total

Early Sales 266 cwt 40.00 $10,640.00
Late Sales 134 cwt 35.00 4,824.00

Preharvest

       
 Machinery Oper        
  Rotovator 1 times over 7.08 7.08
Transplanter 1 times over 6.32 6.32
Sprayer 7 times over 2.02 14.14
Sprayer w/Disk 2 times over 3.20 6.40
Plastic layer 1 times over 7.46 7.46
Supplies        
Nitrogen 50 lbs 0.25 12.50
Phosphate 50 lbs 0.26 13.00
Potash 150 lbs 0.13 19.50
Urea sidedress 80 lbs 0.23 18.40
Alanap 2L 6.00 qts 6.86 41.16
Prefar 4E 5.00 qts 10.30 51.50
Poast 1.5E 1.00 pt 14.10 14.10
Pounce 3.2E 24.00 oz 1.49 35.76
Thiodan 50W   2.00 lbs 6.03 12.06
Bravo 720 8.00 pts 7.15 57.20
Bayleton 6.00 oz 3.67 22.02
Labor        
land preparation 1.00 hrs 7.00 7.00
transplanting 0.68 hrs 7.00 4.76
pesticide appl. 2.48 hrs 7.00 17.36
hand hoeing 4.00 hrs 7.00 28.00
irrigation 3.84 hrs 7.00 26.88
laying plastic 1.00 hrs 7.00 7.00
row tunnel appl. 36.00 hrs 7.00 252.00
Miscellaneous        
Irrigation system
electricity 5.00 acre-inch 2.07 10.35
tubes/plastic 1 year 250 250.00
Plastic Layer        
  clear plastic 6300 ft 0.02 126.00
Row Tunnels        
row tunnel 6300 ft 0.06 378.00
wire hoopes 1260 hoopes 0.09 113.40
Interest on Pre 2,189.35 dollars 0.06 131.36
TOTAL PREHARVEST COSTS       $2,320.71

Harvest

       
  Wagon/hauling 4 trips 10.01 40.04
Crates (50 lb) 800 crates 1.10 880.00
harvest labor 168.00 hrs 7.00 1,176.00
grading/washing 10.00 hrs 7.00 70.00
room cooling 800 crates 0.03 24.00
TOTAL HARVESTCOST       $2,190.04

PlasticDisposal

       
  remove hoopes 4.00 hrs 7.00 28.00
remove tunnels and plastic mulch 18.00 hrs 7.00 126.00
TOTAL DISPOSAL COSTS     $164.00

Cover Crop

       
  disk w/drag 1 times over 1.83 1.83
grain drill 1 times over 2.16 2.16
seed - rye 1.50 bu 4.00 6.00
  labor 0.61 hrs 7.00 4.27
TOTAL COVER CROP COSTS       $14.26

Total Variable

       
  per acre       $ 4,689.01
per bushel       11.72

Ownership Costs

       
irrigation system       76.00
machinery       42.15
land       105.00
room cooling       246.35
TOTAL OWNERSHIP COSTS       $ 246.35

TOTALCOSTS

       
  per acre       $ 4.935.36
per bushel     12.34

RETURNS OVER VARIABLE

      $ 10,744.99

RETURNS OVER TOTAL

      $ 10,528.64

............Justice for All

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, gender, religion, age, disability, political beliefs, sexual orientation, and maritial or family status. (Not all prohibitied bases apply to all programs). Many materials can be made available in alternative formats for ADA clients. To file a complaint of discrimination, write USDA, Office of Civil Rights, room 326-W, Whitten Bldg., 14th and Independence Avenue, SW, Washington DC 202590-9410 or call 202-720-5964, issued in furtherance of Coop[erative Extension Work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Stanley R. Johnson, director, Cooperative Extension Service, Iowa State University of Science and Technology, Ames, Iowa.