Squash



   SQUASH

Cucurbita spp.

FAMILY CHARACTERISTICS

The Cucurbitaceae family is made up of warm season annuals that prefer hot, humid weather. Most plants in this family have spreading growth habits that produce tendrils at the leaf axils, monoecious with separate male and female flowers.. The fruit of the Cucurbitaceae family is a pepo. Fruit referred to as a "pepo" means that the ovary wall is fused with receptacle tissue, thus forming a hard rind and hard dormant seed. Wild gourds were used in prehistoric times as containers for storing and holding food items and water as well as musical instruments. Some of the more popular vegetable crops in this family are cucumbers, watermelon, muskmelon, squash, and pumpkin.

Other family members include:

Benincasa hispida L.; Uax Gourd

Citrullus lunatus (Thung.) Mansf .; Watermelon

Citrullus lunatus var. citroides (Bailey) Mansf.; Citron, Preserving Melon

Cucumis anguria L.; West Indian Gherkin

Cucumis melo L. (Chito group); Mango Melon, Garden Lemon

Cucumis melo L. (Conomon group); Melon, Oriental Pickling Melon

Cucumis melo L. (Flexuosus group); Armonian Cucumber, Japanese Cucumber, Uri

Cucumis melo L. (Inodorus group); Melon, Muskmelon, Winter Melon

Cucumis melo L. (Reticulatus group); Melon, Muskmelon, Cantaloupe

Cucurbita maxima Dutch.; Winter Squash, Pumpkin

Cucurbita mixta Pang.; Pumpkin

Cucurbita moschata Poir.; Winter Squash, Pumpkin

Cucurbita pepo L.; Winter Squash, Marrow, Summer Squash, Pumpkin

Cucumis sativus L.; Cucumber

Lagenaria siceraria (Mol.) Standl.; Bottle Gourd

Luffa acutangula Roxb.; Angled Loofah

Luffa cylindrica Roem.; Smooth Loofah

Momordica charantia L.; Bitter Gourd, Balsam Pear

Sechium edile S.W.; Chayote

Telfairia spp.; Oyster Nut

Trichosanthes anquina L.; Snake Gourd

CROP HISTORY AND DEVELOPMENT

Squash is native to North and Central America and was used widely by settlers in New England because the fruit of winter type squash stored well and could be eaten well into the winter. In the 1500's, squash was introduced to the Europeans by traders returning from the America. Native Americans were eating selected wild types of C. pepo that resembled today's squash type fruits which contained more tissue that was not as bitter as the wild types and, contained less fiber in the editable flesh. Selection of C. pepo types for eating, as opposed to the container types used for storage, occurred long before the arrival of the first settlers from Europe as remains of C. pepo dating back to 8,000 B.C. have been found in Mexico. Wild species have bitter flesh and are more gourd like in appearance. The summer squashes that are so popular in today's garden, crooknecks and straight neck types that were eaten in the immature stage, were selected and developed by the native Indians of North America and were the genetic parents of the squash types grown today.

PLANT CHARACTERISTICS

Roots. Roots of squash plants are generally extensively branched in the top six inches of soil (fibrous root system) with a well developed taproot. Some squash types have enlarged roots. The fibrous root system fills the top foot of soil and spreads the same distance as the vines of the plant extend over the soil (thirteen to nineteen foot spread of the fibrous roots are not uncommon). Adventitious roots form at stem nodes and can grow to be four to five feet long. When the plant is first starting to develop and mature, the root system grows as much as two and a half feet each day.

Leaves. Winter Squash. Leaves of winter squash are large and reniform in shape. They either have no lobes or have shallow rounded ones. Winter squash also has a cordate base with a deep sinus. The leaves are serrated and occasionally have white blotches.

Summer Squash. The leaves of summer squash are six to twelve inches and triangular in shape. They are deeply lobed and also have a deep basal sinus. They have three to seven lobes and are irregularly serrated. Summer squash leaves have prickly petioles and can be found with or without white blotches.

Stem. Squash usually develops a running vine, though the selection for bush growth habit is the preferred for today's summer types grown for the fresh market and home gardens. The stem of winter squash is round and soft with small setae and soft hairs. It is not harsh or prickly to the touch. This squash has branched tendrils and roots grow from the nodes. Summer squash originally developed a trailing vine, but toady's most popular types are found in the form of a short compact bush. It is more common to find compact bush type summer squash than winter type squash. The stem of summer squash has branched tendrils and is more or less erect. This stem has grooves and five angles, and it is harsh to the touch. This is because it has speculate bristles, or sharp, stiff hairs. Flower. The flower of winter squash is monoecious. It has a bright yellow corolla. The stigma is small, yellow, and smooth. The androecium is short, thick, and columnar. The mature peduncle is round and soft, somewhat spongy.

In most cultivars, however, as the peduncle ages, it becomes irregularly thickened with a soft cork. The calyx lobes are short and narrow. The peduncle has been reported to have anywhere from no expansion to great expansion at the fruit attachment.

The flower of summer squash is also monoecious. The corolla is bright yellow to orange yellow, and goes from being narrow at the base to enlarging closer to the outer end. The flower has erect or spreading lobes that are short and narrow. The sepals are short, the androecium is short, thick, and conical. The stigma is small, yellow, and smooth. The

peduncle has little or no expansion at fruit attachment. The mature peduncle is hard and sharply five angled. There is no cork development in the peduncle of summer squash.

Squash flower

Fruit. Winter squash has fruit with either a soft or a hard shell. It also ranges in color from dull to bright. The flesh of winter squash can be various shades of yellow and are finely grained. Summer squash ranges in size from small to large, color from uniform to variegated, and varies in shape. The lower surface of summer squash can be round to flat. The shell can be anywhere from hard to medium to soft and is usually dull in color. The flesh is white to dark yellow and has coarse grains. The fruit is borne on a woody, five sided, deeply grooved peduncle, and is smooth to deeply scalloped. Seed. The seed of winter squash is plump, smooth, and white to pale brown. It is not easy to separate the seed from the pulp in winter squash. The seed has a smooth, obtuse margin and is sixteen to twenty-two millimeters in length. Summer squash has a flat seed that is dingy tan to white. It has a raised, smooth margin and is obtuse. This seed is ten to eighteen millimeters in length.

Spaghetti squash

Cultivars Winter squash cultivars usually take between 80 and 105 days before they are ready to be harvested. Two common cultivars are 'Table Queen' and 'Waltham Butternut'. 'Table Queen' is harvested after 85 days and weights about 0.7 kilograms, or 1 1/2 pounds. It is heart shaped and dark green with ribbed skin. This is a good market type. 'Waltham Butternut' also takes about 85 days until harvest. It weighs 2 kilograms or 4 1/2 pounds. It is creamy tan in color and a straight cylinder in shape. This cultivar provides delicious flavor.

Summer squash cultivars usually take between 40 and 50 days before they are ready for harvest. Two common cultivars of summer squash are 'Seneca Prolific Hybrid' and 'Early Prolific Straightneck'. The 'Seneca Prolific Hybrid' is mature in 44 days and is 15 to 18 centimeters in length. The fruit is tapered and bright yellow. This is a uniform, attractive cultivar. 'Early Prolific Straightneck' matures in 46 days and is 13 to 18 centimeters in length. This fruit is a tapered cylinder that is lemon yellow in color. Many different cultivars make squash a popular vegetable for market and the garden.

Squash Varieties

Butternut and acorn squash

Patty Pan squash

Waltham squash

Butternut squash

Various winter squash varieties

PROPAGATION METHODS

Squash as F1 hybrids are mainly direct seeded for commercial plantings and home use today. Transplants are seldom used unless an early planting for market or home use is the objective.

Direct seeding. Bush squash: 2-4 feet in rows that are 3-5 feet apart, 2-6 pounds of seed per acre. Vining squash: 6-8 feet in rows that are 10-12 feet apart, 2-6 pounds of seed per acre. Seed are planted about 2 cm deep in heavy soils and about 5 cm deep in sandy soils. Many seeds per hill are planted to ensure a vigorous stand, and some thinning is needed to obtain a final stand of 2 plants per hill. Seeds are planted 1 inch deep. 70-95 °F is the best temperature for germination. Germination usually takes 7 days.

Transplants. Seeds are planted 5-7 weeks prior to transplanting, the entire roots must be transplanted to the field. Home gardens will plant 3 to 5 seeds in a four to six inch pot in a peat based potting soil and , after germination and three to six inches of top growth has developed, transplant the entire pot as a squash hill in the garden.

CULTURAL PRACTICES Soil requirements. As other cucurbits, squash require warm soils for successful germination at optimum of 75°F. They prefer a well drained, fertile soil that has a high organic matter content for growth. Organic matter aids in growth by supplying some plant nutrients, increasing soil structure, and increasing soil water holding capacity. Light soil is good for early maturity due to its ease of these type soils to be warmed by the early spring sun. Heavy soil is good for late season squash growth due to higher water holding capacity of these type soils. Soil pH around 5.5-7.5 is best for squash production, but squash plants are sensitive to saline conditions (soils or water with salt or sodium chloride).

Squash field

Temperature and Photoperiod. Squashes are warm season annuals that do not tolerate frost. Best growth is obtained at a soil temperature of 70-95 °F. Growth stops at a soil temperature of 100 °F. Hot caps, black plastic, and plastic row covers have been used to warm the soil when cool temperatures exist in the early spring. This practice accelerate the germination process and improved the number of plants that survive and produce fruit. Photoperiod has a profound effect on flowering and sex expression. The male flowers are present usually when there are long hot days. Long days and warm temperatures seem to keep squash in the staminant flowering phase and delays the pistillate phase and fruit development.

Fertility requirement. Squash require a fertile soil for best development. Fertilizer applications are usually split. Half of the recommended fertilizer is applied as band or broadcast at seeding while the other half is applied in one or two side dressings. Exact levels of fertilizer used should be based on a soil test, soil type, climate, spacing, management, etc. Addition of organic matter through use of manure or green manuring will be beneficial. Macronutrients are usually applied in a 1: 1:1 to 1:2:2 ratio. Typical California and Florida recommendations for N: P: K are 121:60:24 lb/acre and 150:120:80 lb/acre respectively.

Although no one micronutrient is limiting in squash production, attention to their availability is necessary, especially on sandy and muck soils. Muck or organic soils can restrict availability of copper or manganese. Sandy soils may be low in boron, sulfur, or zinc. Boron (1 lb/acre) in the fertilizer or as a foliar spray is often used as a maintenance treatment. Sulfur (10 lb/acre) may be used in fertilizer. If soil test zinc is low, apply 5 lb/acre of zinc. An overabundance of nitrogen may promote vegetative growth and reduce yield, but a continuous supply at the proper rate will help in fruit development.

Tissue norms for essential nutrients are as follows:

N% P% K% Ca% Mg%

3.5-6.0 0.25-0.60 2.75-5.0 1.0-2.5 0.3-0.6

Mn ppm Fe ppm B ppm Cu ppm Zn ppm

50-300 50-300 25-75 5-60 20-50

When taking tissue for analysis, select recently matured leaves near the growing tip. Take analysis prior to or at initial fruit set. Irrigation. Although squashes are adapted to dry areas and prefer well drained soils, a continuous supply of water is needed for high quality and yield. Water should be applied when soil water tension exceeds 300 millibars in the root zone for the best yield. This will mean frequent irrigation. Trickle irrigation of squash is best. especially in conjunction with plastic mulch, to reduce weed growth and disease. Flooding is not suitable for Cucurbits because of the increased amount of fruit rots due to surface moisture.

Weed control. Squashes have extensive root system and, if well established, can compete well for water and nutrients in the soil with weeds. However, heavy weed growth causes competition for sun, harvest problems, and may harbor pathogens and insects. Cultivation after root establishment should be shallow and away from the plant due to the concentration of shallow roots near the surface. Herbicides to reduce weed competition is a common cultural practice before vine spreading.

Irrigation of squash field

INSECTS

The insects found on other cucurbits are also found on squash. These insects include aphids, cucumber beetle, pickleworn, leafhoppers, and spider mites. Two insects that cause substantial losses to squash are stem borers and squash bugs.

Cucumber beetle. Three distinct types-banded (Diabrotica baltrata ), striped (Acalymma vittatum), and spotted (D. Undecimpanctata) cucumber beetles attack squash. Leaf feeding by adults and root feeding by immature may stunt small plants, but cucumber beetles are not as serious as on cucumber. In addition to feeding damage, cucumber beetles spread virus and bacterial wilt.

Pickleworm. Pickleworm is the larvae of Diapheni nitidalis, a moth. The moth lays eggs on the plant and the hatching larvae feed on stem, flowers, leaves, or fruit. The latter damage renders fruit unsellable.

Squash bug. Squash bug (Anasa tristis) is found wherever squash are. Squash bugs are brownish-black, flat backed, and hard shelled. They lay their eggs in rows on the undersides of leaves. These bugs cause wilting and usually smell foul when crushed. The control recommendations are the same as for borer.

Squash vine borer. Squash vine borer (Melittia cucurbitae) is wasp-like with copper-green fore wings and reddish-orange, black abdomens. The damage sign of this insect is a hollowed out stem, with a green slimy exudate. This causes wilt on the leaves. It can also kill entire stems or plants. the insect over winters in the soil as a larva or pupa. When the vines begin to run, the pupa surfaces and splits to release the small black wasp-like moth. The moth lays eggs on the basal potion of the stem, and in 1 to 2 weeks, borers emerge and penetrate the stem. Control is difficult, but sprays applied during egg laying and hatching are recommended.

Other insects. There are minor insects such as thrips, flea beetles, melon leaf hopper, leafminer, and cutworm. The melon leafhopper transmits curly top virus.

Control. Sanitation and good cultural practices will aid in insect control. Crop rotation away from cucurbits for 3 years, destroying plant residue, and deep turning of land will prevent some problems. Reflective mulches tend to repel aphids.

DISEASES

Major diseases that affect squash include scab, mosaic, powdery mildew, nematodes, black rot, Choanephora. Squash scab. Squash scab caused by the fungus Cladosporium cucumerinum, can destroy up to 50% of squash crop in Georgia each year. The disease requires high moisture and cool temperatures. Fruits are the most severely infected by scab. They have gray sunken lesions appearing with an ooze coming from them. These areas grow and may produce a lesion about 1/2 inch in diameter. The foliage has a green water soaked area that grows and becomes angular shaped. The tissue dies and falls out. This disease is common after harvest. To control scab, use disease free seed, rotate crops, and use sanitation practices in harvesting.

Scab

Mosaic. It is caused by a virus. It usually causes yellow-green mottling on leaves and fruits. This disease is more severe in late summer and early fall. Using western grown seed is the best method of control. There are no fungicides for mosaic.

Powdery mildew. Powdery mildew, caused by the fungus, Erysiphe cichoracearum, is especially prevalent in hot dry conditions. White or brown mealy growth will be found on upper and lower surfaces and stems. Under severe infestations, the plant will be weakened and stunted.

Mosaic virus

Powdery mildew

Powdery mildew

(photos provided by www.acesag.auburn.edu)

Nematode. Root-knot nematode attacks squash roots in Georgia. They enter young roots during feeding and cause a swelling. These nematodes restrict water and nutrient uptake giving the plant a stunted, wilted appearance. Control depends on soil fumigants. Nematode can be controlled with rotation of a grass crop with the squash.

Root-knot nematode damage

Black Rot. Black rot is caused by the gummy stem blight fungus (Didymella bryoniae) and affect mostly winter squash and pumpkins. It first appears as an irregular green or yellow spot that gradually turns brown, then black as the fungus penetrates the rind. A dry rot results, but the affected area often becomes infected with secondary organisms that eventually spread through the entire fruit. The organisms over winter in seed and in plant residue. Crop rotation and use of clean seed are important control measures.

Black rot (field)

Black rot (storage)

(photos provided by www.acesag.auburn.edu)

Choanephora Wet Rot. The organism (Choanephora cucurbitarum) attacks summer squash as the blossoms wilt and quickly spreads down the fruit. A black mold, resembling tiny pinheads, appears on the necrotic area. Spores are spread by insects and splashing water. This disease is common under high moisture conditions.

Other minor diseases. Minor diseases include bacterial wilt and angular leaf spot.

Fruit rot

Anthracnose (gourd)

HARVESTING Squash, both winter and summer, are harvested by hand. Winter squash is ready for harvest after the rind hardens and surface color dulls. This must be done before freezing weather occurs and damages the fruit. Mild freezes are beneficial in harvest by not damaging mature fruits, but killing back the vines and making the fruits more accessible. The fruit should be harvested before prolonged exposure to 50°F occurs. If it is left on the vine at this point, chilling injury will occur. Two to three centimeters of the peduncle should remain attached to the fruit when it is cut.

Harvesting squash

Summer squash should be harvested 2 to 6 days after the blossom falls off, when the fruit are 15 to 20 centimeters long. At this point in development, the summer squash is more tender as well as sweeter than at later stages. They should be harvested every other day to prevent fruit from getting too large on the vine and keeping other fruit from developing. When the squash is cut from the plant, 1 to 2 inches of the peduncle should be left on the fruit.

POST HARVEST

In general, squash stored in temperatures above 60°F do not have as good of quality as those stored at lower temperatures. High temperatures result in high respiration rates, loss in weight results, and loss of moisture. All of this leads to reduced quality in the fruit.

Some cultivars of winter squash can be cured for storage by remaining in temperatures between 20 and 30 °C (80 to 85 °F) at 85% relative humidity for 3 to 20 days. Warm temperatures cause the fruit to heal any wounds it might have before it is put into long term storage or shipped. This is not advised for 'Table Queen'. All winter squashes should be stored in cool, relatively dry conditions. The best temperatures are between 10 and 20 °C (50 to 59° F), and they should also be stored at 50 to 70% relative humidity. Winter squashes can be stored for up to six months. 'Table Queen' only stores well for two months. Summer squash can only be stored for a few weeks after harvest. They should be stored between 7 and 10 °C (about 50 °F), and 85 to 95% relative humidity. These should not be stored at lower temperatures because they will suffer from chill injury.  

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