Success with Growing Melons, Part 2

 

I recently posted Success with Growing Melons, Part 1, which took us from the gleam in the eye to transplanting or sowing. Here I cover the rest of the season, and finish with more resources.

Care of Melon Plants

Avoid working the crop (including harvesting) when the foliage is wet, as fungal diseases spread this way. In bare soil, hoe soon after the seedlings emerge, and thin the plants if you sowed thickly. Larger spacing can be used later in the year when vines grow faster.

If the weather is less warm than you hoped, use hoops and thick rowcover until you are more confidant in the temperatures, then switch to insect netting, such as ProtekNet. We hoop and net our melons immediately after transplanting or sowing, to keep the bugs off. We keep the netting on until we see female flowers (they have miniature melons between the flower and the plant). Melons require pollination, so it is important to remove the netting.

Drip irrigation and plastic mulch can do a lot to improve the quality, yield and earliness of melons. Plastic mulches work well with rowcover, as there will not be weeds growing out of sight, concealed by the rowcover during the critical weed-free period as the vines grow. Plastic mulches can also reduce cucumber beetle numbers, as they deter egg laying and larval migration. Reflective mulches especially reduce beetle populations.

If weeds emerge through the mulch, pull them slowly, while stepping next to the melon stem. Melon roots near the surface can easily be injured. As melons ripen, put a piece of cardboard under the fruit to help prevent rot. With the late summer planting, you can pinch off new flowers to steer the plant’s energy into fruit that has already set. Keep the soil around melons watered with 1-2” (2-5cm) per week, up until the last week or two before harvest. Holding back on water during this time leads to sweeter melons.

Crop Rotations for Melons

Because of the many cucurbit pests and diseases, good crop rotation is important. We have only two big cucurbit plantings, winter squash and watermelon. These are three years and seven years apart in our ten-year rotation. Our other melons are grown in smaller amounts and fitted into spaces that also fit in with the rotation concept. Cucumber beetles are quite mobile, so rotation to a plot next to last year’s crop will not reduce their numbers.

Succession Crops of Melons

In our climate we can sow melons four times, a month apart. The first row is from transplants, set outside May 3-6. We direct sow the second bed on May 25, then June 25 and July 6-15 for a “Last Chance” crop. The recommended last date for sowing melons is 100 days before your average first frost date.

Pests of Melons

Like most cucurbits, melons are vulnerable to striped and spotted cucumber beetles. These pests chew on plants and spread diseases, such as bacterial wilt and mosaic virus. Protect against cucumber beetles with rowcover or insect netting on hoops, installed at sowing or transplanting, or hunt them with tweezers every morning on leaves and inside flowers, when beetles are more slow-moving.

Watch for aphids, as they can also spread viruses. You can usually hose off leaves or apply an insecticidal soap to kill aphids before they inflict too much damage.

As always, encouraging beneficial insects and predators will reduce pest numbers. Soldier beetles (Pennsylvania Leatherwings) and Wolf Spiders are good predators. Predatory stink bugs, assassin bugs, spined soldier bugs and two native egg parasitoids will reduce Brown Marmorated Stink Bug (BMSB) numbers, but do not give adequate control. Soapy water will kill BMSB nymphs – be cautious: cucurbit seedlings are sometimes damaged by soap sprays. In one study, one spraying killed about two thirds of the adult bugs. Other studies found soaps ineffective. Heterohabditis nematodes, available commercially, can control cucumber beetles, and may carry over into the next year.

Rowcover or insect netting will keep beetles from vines, but will need to be removed (except for parthenocarpic varieties) when the female flowers open. Some people report good control using the yellow plastic sticky traps along with the cucumber beetle lure sachets sold by Johnny’s Seeds. These can last a whole season and be moved from one crop to the next, suspended on wire hoops. To make your own sticky traps, use yellow plastic cups stapled to sticks so the cups are just above foliage height. Coat the cups with 1 part petroleum jelly to 1 part household detergent (if you are not prevented by USDA Organic certification) or the insect glues available commercially. Cucumber beetles are attracted by clove and cinnamon oils, which can be used to lure them. Use one trap per 1000 ft² (92 m²). Another approach is to grow a trap crop of a crop particularly attractive to the beetles, such as Cocozelle summer squash, Seneca or Dark Green zucchini, along the edge of the field. The trap crop is then flamed or tilled in when pest numbers build up. If all else fails, and action is imperative, Spinosad will kill them. Neem doesn’t kill them, but does deter them.

Diseases of Melons

To minimize diseases, choose disease-resistant melon varieties, provide favorable growing conditions, plow in or remove and compost any plant refuse, and control insect pests. Diseased foliage reduces the ability of the fruit to develop sugars.

In warm, humid climates like ours, melons are subject to powdery mildew, which can wipe out a melon crop if not caught in time. Mildewed leaves cannot photosynthesize well, so the yield and flavor of the melons will not be as good.

There are good photos in Identifying Diseases of Vegetables from Penn State. The University of Tennessee has a concise list of melon diseases and pests in its publication Producing Cantaloupes in Tennessee. The Cornell University Resource Guide for Organic Insect and Disease Management has information on dealing organically with most common diseases:

• Angular Leaf Spot (bacterial) occurs during cool, wet weather. Symptoms include interveinal browning of the leaf and small round spots on the fruit. The leaf damage is tan, not dark.
• Anthracnose, a fungus disease, is most common during warm rainy weather. It causes angular haloed dark-brown spots on the leaves and dark, round, sunken spots on the fruit.
• Bacterial Wilt (Erwinia) causes sudden dramatic wilting and death of the vines.
• Black Rot/Gummy Stem Blight (Didymella bryoniae) is a fungus occurring with cool or warm wet weather.
• Downy Mildew occurs in wet, cool spells and plants may recover if the weather heats up.
• Mosaic Virus causes a yellow and green mottling of the leaves and reduces plant vigor.
• Phytophthora Blight occurs in some regions but not others.
• Powdery Mildew occurs during hot, dry spells.
• Scab is not usually a problem to those growing resistant varieties. The fungus, Cladosponum cucumerinum, is worse in cold wet weather. Try compost teas or baking soda spray.

Harvesting Melons

See my post on harvesting melons

“Days to maturity” in catalogs are usually from direct seeding; subtract about 10 days to calculate from transplanting to harvest date. At the beginning of July our Asian melons start coming in, following those, our Kansas muskmelons.

I recommend harvesting daily, in the mornings, once the dew has dried, to avoid spreading fungal diseases.

With muskmelons, when the background-color of the skin beneath the “netting” changes from gray-green to buff or a yellowish color, the melon is almost ripe. A honeydew melon will turn a light yellow-white color when it’s ripe.

“Full slip” is the term for melons that separate cleanly from the stem with only the very lightest pressure. Waiting too long leads to rotten fruit, especially in hot weather. Look carefully at the point where the stem joins the melon, and as it ripens you will see a circular crack start to open around the stem. This small disk of melon stays with the stem when it slips off the vine. More usually, growers give the stems a “little nudge” to see if the melon will fall off the vine. Depending on the delay between harvest and sale, you may need to pick at half-slip or three-quarter slip (when half or a quarter of the stem disk sticks and breaks rather than slipping free). Harvest your melons at half-slip if you are going away for the weekend, or you worry the groundhogs will get it if you don’t. But if you are harvesting to eat right away, harvest at full slip for best flavor and aroma.

Crenshaw and Canary melons require a good tug (“forced slip”). Honeydew, Charentais, and Piel de Sapo must be cut from the vine – don’t wait for them to slip!

If you are growing melons on a large scale, it will be worth buying a refractometer to test sugar levels. Melons at full slip should register 12-14%, while those at half-slip should show at least 10%. Half of the final sugars accumulate in the last week of ripening. Full flavor develops a day or two after picking, but the sugar content does not increase. I like nothing better than eating fruit fresh from the field, still warm from the sun.

Melons do not need to be rushed to the cooler as greens and sweet corn do, so they can be picked and set in the shade until a full load of produce is ready to be moved. Melons are subject to sun-scald if left unprotected in the sun after harvest.

Melon Storage

Storage time for melon depends on the type. Relative humidity should be 85-95% for best results. Refrigeration is a tad too cold. Honeydew can be stored up to three weeks at 50°F (10°C). Store other melons at 45-50°F (7-10°C) for 7-14 days.

Muskmelons can be stored at 36-41°F (2-5°C) and 95% relative humidity, for up to 2 weeks.

Muskmelon bruising and splitting can happen if melons are dropped more than 8” (20 cm) onto hard surfaces. When they are stacked more than six layers deep or are transported over rough roads, pressure bruising can result, leading to discolored flesh.

Season Extension for Melons

Early crops can be grown in a hoophouse, using transplants, with rowcover while the nights are chilly. Research at Virginia State University has shown success with Asian melons transplanted into hoophouses at the end of March at Randolph Farm, in Petersburg, Virginia.

Late crops can be covered with rowcover to fend off a few light frosts. Pollinators won’t be able to get at the flowers, but that doesn’t matter if you already have enough fruits on the plants. You can pinch off immature fruits to concentrate the plants’ energy into ripening the bigger fruits. It isn’t worth it to coddle every last little nubbin of a fruit, as the smallest ones won’t ripen in cool temperatures and will get killed by heavier frosts.

Melon Seed Saving

Melon varieties need to be isolated by 660’ (200 m) for home use, and a minimum of 0.5-1 mile (0.8-1.6 km) for seed for sale. Note that all 8 melon groups cross with each other.

Resources for Growing Melons

Melons for the Passionate Grower, Amy Goldman

ATTRA, Cucumber Beetles: Organic and Biorational Integrated Pest Management

Oklahoma Cooperative Extension Service Guide for Identification and Management of Diseases of Cucurbit Vegetable Crops (Cantaloupe, Cucumber, Pumpkin, Squash and Watermelon)