Common Disease Problems
Alternaria Leaf Spot: Small, round reddish brown spots with white to gray centers form on the upper surface of the leaves and along the midrib. The lesions may encircle the stems and cause wilt. This disease is worse in warm, wet or very humid weather. Burpee Recommends: Avoid getting water on the foliage. Remove infected plant parts and do not work around wet plants. Provide plenty of air circulation. Contact your Cooperative Extension Service for fungicide recommendations.
Anthracnose: This is a fungus disease that attacks the fruit as it is ripening. The first visible sign is a circular spot on the skin that is slightly sunken. The spots enlarge and turn black; the fruit rots. Extended periods of heat and humidity facilitate anthracnose growth. The fungus overwinters in diseased plant debris. Burpee Recommends: Plant resistant varieties, provide sufficient space between plants for good air circulation, avoid overhead watering which can spread the fungus spores, keep a clean garden, remove and discard all diseased plant material and rotate crops. Use a mulch to prevent spores from splashing from the soil onto plants.
Bacterial Leaf Spot: First signs are small translucent spots with a broad yellowish edge that slowly enlarge and become angular or irregularly circular with a reddish center. It thrives in cooler temperatures.Burpee Recommends: Remove infected plants. Rotate crops with plants in a different family. Avoid overhead watering. Do not work around plants when they are wet.
Downy Mildew: This fungus causes whitish gray patches on the undersides and eventually both sides of the leaves. Burpee Recommends: Rotate crops with plants in a different family. Avoid overhead watering. Provide adequate air circulation, do not overcrowd plants. Do not work around plants when they are wet.
Powdery Mildew: This fungus disease occurs on the top of the leaves in humid weather conditions. The leaves appear to have a whitish or greyish surface and may curl. Burpee Recommends: Avoid powdery mildew by providing good air circulation for the plants by good spacing and pruning. Contact your Cooperative Extension Service for fungicide recommendations.
Common Pest and Cultural Problems
Aphids: Greenish, red, black or peach colored sucking insects can spread disease as they feed on the undersides of leaves. They leave a sticky residue on foliage that attracts ants. Burpee Recommends: Introduce or attract natural predators into your garden such as lady beetles and wasps who feed on aphids. You can also wash them off with a strong spray, or use an insecticidal soap.
Blossom End Rot (BER): Blossom End Rot causes large brown or black dry or sunken spot(s) to appear, usually starting at the blossom end (opposite the stem) of the fruit. Fruits often ripen prematurely. BER occurs when a plant cannot metabolize the calcium it needs to develop properly. This can occur when there is not enough calcium in the soil or when root damage and water stress reduce the uptake and movement of calcium through a plant. Occasionally, BER is the result of excessive nitrogen fertilization. It only takes a day for a lack of calcium to affect fruit, and that day can occur any time after blossom set.
- Once a fruit has BER it will not recover. The plant is still healthy, just remove the affected fruit from the plant. The fruit is still good to eat if you remove the affected part.
- BER most frequently occurs on fruit produced earlier and later in the season as this is when natural fluctuations in precipitation and cold weather occur.
- To avoid BER, properly site and prepare your garden bed before planting. Most crops need full sun and loose, well-drained organic soil. Make sure soil pH is slightly acidic, between 6.2 to 6.8, for optimum nutrient uptake. Test your soil to see if calcium is recommended. If it is, apply lime in the recommended quantity according to manufacturer's instructions.
- Avoid planting too early in cool soils as this can inhibit early root development, making the plant more susceptible to BER. Start with a quality transplant: a healthy seedling with strong roots will make a healthy plant.
- Avoid wide fluctuations in soil moisture by applying 2-3 inches of mulch. This will moderate the release of water to plant roots, and also keep the soil from drying out when it is directly exposed to the sun.
- Avoid drought stress by making sure your plants get at least 2 inches of rain or water per week. Apply enough water to moisten more than the top inch of soil. Container grown plants will need more than 2 inches of applied-water per week in hot weather, check them daily if possible. Consider using drip irrigation or soaker hoses. One or two soakings are better than many light waterings.
- Avoid over-fertilizing during the early fruiting stage, especially if the fertilizer contains high percentages of nitrogen.
- Avoid close cultivation around the base of plants when weeding. A layer of mulch should help prevent the possible disturbance or damage of fragile roots accidentally.
Cucumber Beetles: Beetles may be spotted, striped or banded and can be very harmful. Beetles are usually ¼ to ½ inch in size. Beetles start feeding as soon as they hatch and can kill or slow the growth of the plants. Beetle larva can bore through the roots of the plants. Beetles can also transmit diseases from plant to plant. Burpee Recommends: Knock off adults into a jar of soapy water and destroy them. Spade the soil to destroy dormant beetles before you plant. Use a row cover to prevent adults from feeding on young plants. Consult your Cooperative Extension Service for other insecticide recommendations.
Spider Mites: These tiny spider-like pests are about the size of a grain of pepper. They may be red, black, brown or yellow. They suck on the plant juices removing chlorophyll and injecting toxins which cause white dots on the foliage. There is often webbing visible on the plant. They cause the foliage to turn yellow and become dry and stippled. They multiply quickly and thrive in dry conditions. Burpee Recommends: Spider mites may be controlled with a forceful spray every other day. Try hot pepper wax or insecticidal soap. Check with your Cooperative Extension Service for miticide recommendations.
Squash Vine Borer: The brown headed larva will bore into stems, feed through the center of the stems, block the flow of water and the plants will collapse and die. The first sign of this pest is that the plant will wilt during the day and perk up at night. Check the base of the plant for holes and you will see what looks like sawdust.Burpee Recommends: Pull and destroy any plants killed by squash vine borers. Row covers will prevent the female from laying her eggs. Although you can’t always save the plant, as soon as you see the wilting plant, cut a slit in the stem above the hole using a sharp knife. Kill the borer with the tip of the knife, or pull it out. Mound soil over the cut area and keep the soil moist. New roots may grow and the plant may live. Rotate crops. Consult your Cooperative Extension Service for insecticide recommendations.
Do I have to cure the fruit to make it last? Yes, curing it will help the skin to harden which will help preserve the fruit for several months. Cure them in a warm, dry, well ventilated location in the shade, such as a garage or shed, for at least a week.
Do I need to support my gourds? Yes, gourds grow on long vines that should be supported to keep the fruit off the ground which could otherwise cause the fruit to rot.
How do I make a luffa sponge? When growing luffa gourds to use as sponges, pinch off all but one or two fruits per plant. Allow these to mature until the stem turns yellow and the skin begins to dry and fade. The fruit should be 16-24 inches long. Cut the gourds off the vine with scissors or a sharp knife and allow them to dry in the sun for about two weeks. They are ready when the skin hardens and turns brown. Cut open the larger end of the fruit and shake out the seeds. Soak for a day or two in water. Peel off the outer skin. The sponges may be dingy yellow in color. If you wish to lighten the color, bleach the sponges in a 10% solution for an hour or so. The softness of the sponge will be determined by the color of the skin of the fruit when it is harvested. Greener fruit produce softer sponges, yellower fruit produces tougher sponges. Harvest on the green side for bathing sponges.
Are gourds edible? They are not poisonous, but they have been developed for the ornamental quality of the fruit. There is not much flesh to eat, and the flesh that there is may be bitter or tasteless.
Will mixed gourds cross pollinate and produce strange fruit? Cross pollination will not be a problem unless you are saving the seed.