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Winter melon is a robust plant and most of what appears on it during a season is cosmetic. The mistake is treating everything with equal urgency, which spreads your attention thinly across problems that do not matter and away from the two or three that end the crop. With only one or two fruit riding on each plant, losing a plant in midsummer means losing a fifth of a year's work.
The rule of thumb is simple. Anything that attacks the crown or the fruit needs same-day action. Anything that attacks the leaves in the second half of summer usually does not, because by then the fruit are largely made and the plant only has to hold on.
| Problem | How fast it does damage | Response |
|---|---|---|
| Vine borer in the crown | Kills a plant in days | Act the same day you see frass |
| Bacterial wilt | One to two weeks | Pull the plant, control the beetles |
| Fruit fly stinging young fruit | Ruins individual fruit | Bag or cover fruit at set |
| Squash bugs | Weakens over weeks | Crush eggs weekly from first flowering |
| Powdery and downy mildew | Weeks, often survivable | Space, airflow, remove worst leaves |
| Underside fruit rot | Weeks, discovered too late | Board under every fruit at set |
Borers and wilts: the ones that end plants
A vine that is standing fine one evening and lying flat the next morning, with moist soil underneath it, is almost never short of water. It is either a borer inside the stem or a bacterial wilt in the vascular system, and the two need completely different responses.
The borer signature is unmistakable once you have seen it: wet, orange-brown, sawdust-like frass pushed out of a small hole in the bottom foot (30 cm) of the main stem. Bacterial wilt leaves no hole and no frass, and the leaves stay green as they collapse.
- Check the stem base weekly From the time the vines start to run, look at the bottom twelve inches (30 cm) of stem once a week. You are looking for frass, not for the insect itself.
- Cut the larva out the same day Slit the stem lengthways above the hole with a sharp knife, find the fat white grub and take it out. Mound moist soil over the cut and the stem often heals and carries on.
- Root the runners as insurance Bury a node every four or five feet (1.2 to 1.5 m) as the runners go. Each rooted node feeds the vine independently, so a borer in the crown no longer kills the whole plant.
- Test for bacterial wilt Cut a wilted stem, press the two cut faces together and draw them slowly apart. A fine sticky thread between them is the bacterium. There is no cure, so pull the plant and remove it from the plot.
Because you may only have one or two plants, a rooted runner network is worth far more here than on a crop where you have a dozen. Ten minutes burying nodes in early summer has saved many a winter melon crop.
Fruit fly, squash bugs and beetles
In warm regions the pest that ruins the most winter melon is fruit fly, which stings young fruit and lays eggs under the skin. The fruit looks fine for a week, then develops a soft weeping patch and is lost from the inside. Since you are only carrying one or two fruit per plant, losing one to a sting is expensive, and protection at set is far more effective than anything you can do afterwards.
| Pest | What you see | What to do |
|---|---|---|
| Fruit fly | Small puncture, then a weeping soft patch | Bag or sleeve each fruit as soon as it sets |
| Squash bug adults | Flat gray-brown bugs scattering under a lifted leaf | Lay a board by the crown and collect them at dawn |
| Squash bug eggs | Bronze clusters in the vee of leaf veins | Rub them off weekly with a gloved thumb |
| Cucumber beetles | Striped or spotted beetles inside open flowers | Cover young plants, uncover at first flowering |
| Aphids | Colonies on shoot tips, sticky leaves | Hose off, encourage predators, avoid excess nitrogen |
| Melon worm or leaf roller | Webbed shoot tips, chewed young fruit | Pinch out affected tips and remove them |
Any fruit bag or sleeve must be breathable and loose. Sealed plastic around a developing fruit traps condensation against the skin and destroys the bloom, which costs you the storage life you were growing the crop for.
Mildews and leaf disease
White floury patches on the upper leaf surface from midsummer onwards are powdery mildew, and on this crop they are close to inevitable. Downy mildew is different: angular yellow patches bounded by the leaf veins, with gray fuzz underneath in damp weather, and it moves considerably faster. Both are managed the same way, by airflow and by not wetting the foliage.
What mildew costs you is the last few weeks of skin finishing. Keep the leaves that shade the fruit, because a fruit suddenly exposed to full sun after its canopy collapses will scald on the shoulder, and that scald is where it will fail in store.
- Space generously Give each plant its full spread of five to six feet (1.5 to 1.8 m). A crowded patch holds humidity under the canopy and mildew arrives a fortnight earlier for the same management.
- Water the soil early in the day Water at the crown in the morning. Overhead watering in the evening leaves foliage wet all night, which suits every leaf disease there is.
- Remove only the worst leaves Take off leaves more than half covered and carry them off the plot. Stripping healthy foliage to open the plant up costs more yield than the mildew does.
- Rotate the ground Leave two or three years before any cucurbit follows this crop. Ground that grew cucumber, squash or melon counts as the same slot for soil-borne disease.
Problems on the fruit itself
Because the fruit lies on the ground for two months, most of what goes wrong with it is a matter of contact and moisture rather than of pests. A fruit resting on damp soil rots where it touches, and since nobody lifts a twenty pound (9 kg) fruit to check, the damage is usually found at harvest when it is far too late.
| Symptom | Cause | Prevention |
|---|---|---|
| Soft brown patch on the underside | Prolonged contact with damp soil | Board, tile or straw pad under every fruit |
| Gray mold at the flower end | Dried flower held moisture | Flick off the dried flower once it is brown |
| Patchy or missing white bloom | The fruit has been handled or wiped | Do not turn, wipe or wash the fruit |
| Split running down the fruit | Heavy water after a dry spell | Water evenly, do not let the plant dry out hard |
| Pale scalded patch on the shoulder | Canopy collapsed and exposed it to sun | Keep shading leaves, shade cloth if needed |
What to record so next year is easier
Pest pressure repeats in roughly the same place at roughly the same time each year, which makes a written record more useful on this crop than almost any other. Dates and positions, nothing elaborate.
- The date you first found frass Note the day you see the first borer damage. Your stem collars and node burying want to happen two weeks before that date next season.
- The date of the first white patch Record when mildew first appears. If it arrives before the fruit have reached full size, your spacing is too tight.
- Which plant or fruit failed first, and where it sat Note the position. The sheltered end of the plot and the ground nearest last year's cucurbits are the usual answers.
- Whether a stored fruit failed at the stalk or the underside This one note distinguishes a harvest problem from a field problem, and usually ends the loss for good after a single season.