Even though the calendar says a couple of weeks until November (already??), fall gardens can still be productive this time of year. Since we are in the swing of the fall garden season, we’re focusing this week on all things cucurbits!
But what does that mean?
The cucurbits are all members of the Cucurbitaceae family, which include squash, pumpkins, zucchini, watermelons, cucumbers, and some gourds. What’s interesting about cucurbits is that they are one of the largest plant families in terms of most plant species used as food for human consumption. The fruits of cucurbits are actually, botanically speaking, a modified berry. Many cucurbits are also vines, sometimes referred to as climbing or trailing vines.
- Cucurbits love heat! If the soil temperature is too cool, the germination of the seed may become stunted. Warm the soil with heavy mulch or black plastic before planting. If not transplanting, don’t be in a hurry to plant; cucurbits are sensitive to frost.
- Cucurbits also love to eat! (Sounds a bit odd/funny, but it’s true) You’ve probably heard of the phrase “heavy feeders” when it comes to growing crops in the garden. Cucurbits are considered heavy feeders because of their vegetative vines, which, naturally, require a lot of energy to produce. They prefer an organic-matter rich soil, high in nitrogen, so topdress appropriately, preferably with compost or an organic fertilizer such as blood meal. It’s also best to practice good soil-building habits early on because that helps to maintain a steady supply of needed nutrients to replace what may become lost or leached in a growing season.
- Rotate your cucurbits; this discourages pest activity. Replace the soil left from the cucurbits with a cover crop.
- Cucurbits have very shallow roots. Irrigate regularly, focusing heavily on the root zone. Plants can become overly stressed if they’re allowed to become too dry.
- Cucurbits prefer a soil pH of 6.0-6.5.
- Inadequate pollination will result in the underdevelopment of flowers (or sometimes no growth at all). Plant pollinator-friendly crops and flowers nearby to encourage pollinators. If you keep your plants covered with row cover, be sure to remove the cover once the plants have flowered. Fun fact: Squash flowers are edible!
As with both pest and disease management, look for resistant varieties (more on that a little later), but in the meantime, you can look for the following pests and help control the populations before a major infestation occurs:
- Cucumber beetles: In addition to the beetles feeding on all parts of the plant, which can cause significant damage, cucumber beetles also transmit bacterial wilt, a disease that overwinters in the digestive system of the beetles and is then transmitted from plant to plant as the beetle continues to feed. Larvae burrow into the roots and stems of plants. Although their name suggests they target cucumbers, cucumber beetles also target pumpkins and melons. For control, handpicking is best, but also the use of a woven row cover deters them, especially when the plants are young.
- Squash bugs: Large, brown to browish-black and flat-backed, squash bugs overwinter and reappear in the spring, laying their eggs on the undersides of leaves, right about the time the vines are beginning to form in squash plants. Affected leaves may appear wilted and feel brittle. Once hatched, they emerge as nymphs and remain for about 10 days, and then develop into adults 4-6 weeks after. Control is best applied at the nymph stage, as adults are much more difficult to control.
- Squash vine borers: The most troublesome of pests among cucurbits, vine borers inflict their damage from within; the larva burrow into the stems of plants and feed on the tissue. Vines will appear wilted, sometimes seemingly overnight. Either cut off the vine completely and bury the cut vine in soil and water to encourage root development and re-growth, or slit the vine lengthwise and remove the larva that way. Bury the slit stem in the same way.
- Squash beetle: Be careful to not confuse them with Mexican bean beetles– they look almost alike! Feeding on primarily the leaves of plants, squash beetles overwinter in crop debris, so be sure to keep your garden clean.
- Thrips: Early in the growing season thrips (slender, small insects that range from orange to dark brown or black) feed on plants that are under stress from drought, so again, it’s important to keep cucurbits well watered. Otherwise, early season thrips are not much of a bother. They also overwinter on plant debris, or in neighboring annual crops during the winter months. Thrips also like to feed on leaves that may have pollen on them, from trees or pine.
For more pests and control options, you can refer to the blog post, “Not So Fantastic Bugs and How to Find Them” in the Resources section below.
- Bacterial wilt: Signs of damage include wilted vines which quickly leads to plant death. It only affects a few vines, but spreads rapidly and then affects the entire vine. It tends to affect cucumbers more than squash, pumpkins, or watermelon. Since cucumber beetles are a transmitter of the disease, keep an eye on those plants first and foremost. Unfortunately no chemical controls exist for remedying bacterial wilt; the best method is to control beetle populations to lessen the spread of potential disease.
- Powdery mildew is usually prominent when temperatures fluctuate during periods of dry weather with high relative humidity. The disease affects the stems and leaves on the plants, during which the affected areas may become stunted in growth or distorted in appearance. Fruit is not directly affected but their size and growth may become stunted as well. Fortunately, many cucurbit varieties offer some resistance to powdery mildew.
- Downy mildew: First signs of damage appear as small yellow spots on the leaves, and as they expand, the leaf begins to wilt and die. On the lower leaf surface of the plant, a grayish mold may appear. Moist conditions accelerate the spread of the disease. As with powdery mildew, there are also resistant varieties. Use fungicide only if the spread of disease becomes severe.
- Fusarium wilt: A fungus that can survive in the soil for many years under favorable conditions, fusarium wilt targets the roots of plants and moves into the stems. Dead or diseased vines may have a white mold appear on them. Young plants will rot at the soil line and eventually wilt and die. Roots will become discolored. There are no chemical treatments available for control, so planting resistant varieties and proper irrigation management is crucial.
Select disease resistant varieties whenever possible. Grow Appalachia HQ has had success with the following varieties: Dasher II cucumbers, Costata Romanesco zucchini, and Sugar Baby watermelon. Other highly rated varieties include Pattypan squash (notice its distinctive shape), Crookneck summer squash, Fordhook acorn squash (recently grown at one of our partner sites), Sarah’s Choice cantaloupe (currently on sale from Johnny’s!), and New England pie pumpkin. (We devoted an entire newsletter last fall to pumpkins).
What varieties of cucurbits can you just not live without in your garden? Found a fool-proof way to tackle the beetles and thrips of it all? Mulling over mulch or confused over compost? Reach out to us on our Facebook, Twitter, or Instagram profiles, or send us an email!
Until next time, happy growing!