Gourd

Description

Gourds are annual trailing or climbing vines in the family Cucurbitaceae grown for their fruit of the same name. The two most commonly grown types of gourd are Lagenaria species and Cucurbita species. Gourd plants produce long vines with long-stemmed, large, oval or triangular lobed leaves. The Cucurbita gourds produce yellow flowers and unusually shaped fruit which can be smooth or warty, plain or patterned. The Lagenaria gourds produce white flowers and smooth, knobly or ridged fruit which can range in size from 7 cm (3 in) up to 1 m (3 ft). Gourd vines are capable of climbing over 3.5 m (12 ft) and as annual plants, survive only one growing season. Gourds may also be referred to as dudi, cucuzzi, spaghetti squash or calabash and are believed to have originated in Africa.


Uses

Young gourds can be cooked and eaten as a vegetable while the mature gourds are used to make decorative items such as bottles, containers and utensils. In the US, gourds have become a very popular household decoration in the Fall.


Propagation


Basic requirements
Gourds are warm-season crops, requiring lots of sun and good drainage to develop optimally. Plants will grow best at temperatures between 18 and 25°C (65–75°F) in a fertile, well-draining soil, rich in organic matter and with a pH between 6.5 and 7.5. Gourd plants should be planted in full sun and provided with ample soil moisture. Vining varieties can grow to very large sizes and require a good deal of space.

Sowing seeds
Gourds can be direct seeded or sown indoors and transplanted. If direct seeding,seeds should be sown after the last frosts and when the soil has warmed to at least 15.6°C (60°F). Sow 1–2 seeds 1.3–2.5 cm (0.5–1.0 in) deep, at least 90 cm (~3 ft) apart if growing bush varieties and 120–150 cm (4–5 ft) apart if growing vining varieties. Allow a further 1–3 m (6–10 ft) between rows depending on the variety. If transplanting, seeds should be sown 3–4 weeks before the last frost date in your area and transplanted before the plants develop their second set of true leaves. Sowing seeds in 3–4 inch pots help to minimize disturbance to the roots prior to transplanting. Peat pots can be transplanted with the seedlings eliminating the need to disturb the roots entirely. Seeds in sown both indoors and out require lightly moist soil for germination, care should be taken to avoid overwatering. Seeds should germinate in 5–10 days depending on the soil temperature.

General care and maintenance
Gourd plants sprawling and require plenty space to grow. Vines can be trained to grow on a trellis or fence. Plants also require a continuous supply of water and where drip irrigation is not being used, plants should be watered deeply once per week, providing at least an inch of water. Shallow watering or watering less frequently encourages a shallow root system. Mulches can be used to conserve soil moisture and black polyethylene mulch has the advantage of warming the soil. Gourds produce both male and female flowers (monoecious) and are pollinated by insects such as bees. Poor fruit set is often caused by poor pollination.


References

Dana, M. N. & Lerner, B. R. (2000). Gourds. Purdue University Cooperative Extension. Available at: http://www.hort.purdue.edu/ext/HO-135.... [Accessed 12 December 14]. Free to access.

Jones, T. (2009). Gourds. University of Kentucky College of Agriculture. Available at: http://www.uky.edu/Ag/NewCrops/intros.... [Accessed 12 December 14]. Free to access.

Zitter, T. A., Hopkins, D. L. & Thomas, C. E. (1996). Compendium of Cucurbit diseases. American Phytopathological Society Press. Available at: http://www.apsnet.org/apsstore/shopap.... Available for purchase from APS Press.


Common Pests and Diseases

Angular leaf spot
Pseudomonas syringae

Symptoms
Small water-soaked lesions on leaves which expand between leaf veins and become angular in shape; in humid conditions, lesions exude a milky substance which dries to form a white crust on or beside lesions; as the disease progresses, lesions turn tan and may have yellow/green edges; the centers of the lesions dry and may drop out leaving a hole in the leaf
Cause
Bacterium
Comments
Spread through infected seed, splashing rain, insects and movement of people between plants; bacterium overwinters in crop debris and can survive for 2.5 years
Management
Use disease-free seed; do not grow plants in field where cucurbits have been grown in the previous 2 years; protective copper spray may help reduce incidence of disease in warm, humid climates; plant resistant varieties

Bacterial leaf spot

Xanthomonas campestris

Symptoms
Dark, angular lesions on leaves; leaf lesions may coalesce and cause severely blighted foliage; water-soaked lesions which enlarge and develop into tan scabs, or blisters, on the fruit; blisters eventually flatten as they reach their full size
Cause
Bacterium
Comments
Disease can spread rapidly in a field; disease can be introduced through contaminated seed
Management
Avoid overhead irrigation; rotate crops away from cucurbit species to prevent disease building up; use new seed each planting as saved seed is more likely to carry bacteria; apply appropriate protective fungicides; copper containing fungicides generally provide good control

Alternaria leaf blight
Alternaria cucumerina

Symptoms
Small, yellow-brown spots with a yellow or green halo which first appear on the oldest leaves; as the disease progresses, lesions expand and becone large necrotic patches, often with concentric patternation; lesions coalesce, leaves begin to curl and eventually die
Cause
Fungus
Comments
Disease is prevalent in growing areas where temperatures are high and rainfall is frequent
Management
Cucurbits should be rotated with another crop every 2 years to reduce levels of inoculum; crop debris should be removed from the field as quickly as possible after harvest or plowed deeply into the soil; applications of appropriate protective fungicides can help to slow the development of the disease; water plants from the base rather than from above to reduce periods of leaf wetness which are conducive to the development and spread of disease

Anthracnose
Colletotrichum orbiculare

Symptoms
Tan to brown lesions with dark spots inside on leaves and petioles, main stem and fruit
Cause
Fungus
Comments
Disease favors warm weather
Management
Plant resistant varieties; use only certified seed; apply appropriate protective fungicides; rotate crops every year

Downy mildew
Pseudoperonospora cubensis

Symptoms
Angular brown lesions on upper side of leaves; purple to gray spores and gray mold on underside of leaves; brown leaves; dead leaves that remain attached
Cause
Fungus
Comments
Disease favors cool, humid weather
Management
Do not overcrowd plants; avoid overhead irrigation, water plants from base; apply appropriate fungicide

Gummy stem blight
Plectosporium tabacinum

Symptoms
V-shaped yellow to brown areas on stem; cracked dry areas on stem; lesions leaking a sappy material
Cause
Fungus
Comments
Disease may be seed-borne
Management
Use disease free seed; treat seeds prior to planting; rotate crops every 2 years

Phytophthora fruit and crown rot
Phytophthora capsici

Symptoms
Sudden wilting of plants; brown lesions on stems and roots; rotting fruit; stunted plant growth; downy growth may be present on lesions during periods of high humidity
Cause
Oomycete
Comments
Disease emergence favored by heavy rainfall and poorly draining, waterlogged soils
Management
Do not plant in poorly draining soils; avoid over-watering plants; rotate cucurbits with non-susceptible plants for a period of at least 3 years

Powdery mildew
Sphaerotheca fuligniea

Symptoms
Powdery, white spots on the undersides of leaves; yellowing leaves
Cause
Fungus
Comments
Disease emergence favored by dry weather and high relative humidity
Management
Plant in sites with good air circulation and sun exposure; do not overcrowd plants; sanitize equipment regularly

Scab
Cladosporium cucumerinum

Symptoms
Angular brown lesions on leaves confined by small veins; pale green and water soaked lesions; holes in leaves from dried out lesions; lesions may also be present on petioles, stems and fruit
Cause
Fungus
Comments
Fungus survives in soil on crop debris; may be seedborne; disease emergence favored by wet weather and temperatures below 21°C (69.8°F)
Management
Rotate cucurbits with non-susceptible crops for a period of at least 2 years; plant only in well-draining soils; spray plants with appropriate protective fungicides

Western striped cucumber beetle (Western spotted cucumber beetle, Banded cucumber beetle)
Acalymma vittata
Diabrotica undecimpunctata
Diabrotica balteata

Symptoms
Feeding damage to leaves, blossoms and stems
Cause
Insect
Comments
Beetles overwinter in soil and leaf litter and can transmit bacterial wilt
Management
Monitor new planting regularly for signs of beetle; apply appropriate insecticides

Squash vine borer
Melittia cucurbitae

Symptoms
Plant or runner wilting suddenly; entry holes in vines; sawdust like material at the base of the plant; may be yellow to brown feces coming out of holes
Cause
Insect
Comments
Insect overwinters in soil as larvae or pupae and adults emerge in spring; adults lay eggs on leaves and larvae burrow intro stems to feed
Management
Apply appropriate insecticide if eggs are found on leaves; plow plants into soil after harvest

Verticillium wilt
Verticillium dahliae

Symptoms
Symptoms generally appear after fruit set; chlorotic leaves which develop necrotic areas; leaves collapsing; symptoms only on one side of vine; discoloration of vascular tissue in roots
Cause
Fungus
Comments
Fungus can survive in soil for many years; disease emergence favored by cool or mild weather in Spring
Management
Do not plant in areas where other susceptible crops have been grown previously; delay planting until temperatures are warmer

Cercospora leaf spot
Cercospora citrullina

Symptoms
Initial symptoms of disease occur on older leaves as small spots with light to tan brown centers; as the disease progresses, the lesions enlarge to cover large areas of the leaf surface; lesions may have a dark border and be surrounded by a chlorotic area; the centers of the lesions may become brittle and crack
Cause
Fungus
Comments
Fungus survives on plant debris; spread by wind and water splash; occurs mainly in tropical and subtropical growing regions
Management
Any diseased plants should be removed and destroyed to prevent further spread; crop debris should be removed after harvest or plowed deeply into the soil to reduce inoculum

Septoria leaf spot
Septoria cucurbitacearum

Symptoms
Initial symptoms of disease are small dark water-soaked spots on the leaves which turn beige to white in dry conditions; lesions develop thin brown borders and the centers may become brittle and crack; small white spots may erupt on the surface of infected butternut and acorn squash and pumpkin fruit
Cause
Fungus
Comments
Pathogen can survive on crop debris for periods in excess of 1 year
Management
Scout plants during cool wet conditions for any sign of spots; early application of an appropriate protective fungicide can help limit the development of the disease if spots are found' cucurbits should be rotated with other crops every 2 years to prevent the build-up of inoculum; crop debris should be removed and destroyed after harvest

Aster yellows
Aster yellows phytoplasma

Symptoms
Foliage turning yellow; secondary shoots begin growing prolifically; stems take on a rigid, upright growth habit; leaves are often small in size and distorted, may appear thickened; flowers are often disfigured and possess conspicuous leafy bracts; fruits are small and pale in color
Cause
Phytoplasma
Comments
Disease is transmitted by leafhoppers and can cause huge losses in cucurbit crops
Management
Remove any infected plants from the field to reduce spread; control weeds in and around the field that may act as a reservoir for the phytoplasma; protect plants from leaf hopper vectors with row covers

Cucumber mosaic
Cucumber mosaic virus (CMV)

Symptoms
Plants are severely stunted; foliage is covered in distinctive yellow mosaic; leaves of plant curl downwards and leaf size is smaller than normal; flowers on infected plants may be deformed with green petals; fruits become distorted and are small in size; fruit is often discolored
Cause
Virus
Comments
Transmitted by aphids; virus has an extensive host range; can be mechanically transmitted via tools etc.
Management
Control of the virus is largely dependant on the control of the aphid vectors; reflective mulches can deter aphid feeding; aphid outbreaks can be treated with mineral oils or insecticidal soap applications; some resistant varieties are available

Squash mosaic
Squash mosaic virus (SqMV)

Symptoms
Symptoms vary with variety being grown but plants can show symptoms which include include green veinbanding, mottled leaves, blisters, ring spots or potruding veins at leaf margins; some squash varieties may develop leaf enations; infected plants are often stunted and fruits may be malformed with mottled skin
Cause
Virus
Comments
Virus can be transmitted through infected seed and spread by striped cucumber beetles
Management
Use only certified disease-free seed

Watermelon mosaic
Watermelon mosaic virus (WMV)

Symptoms
Symptoms vary widely depending on species, cultivar, virus strain and environmental conditions; symptoms on leaves may include green mosaic patternation, green vein-banding, chlorotic rings and disfigured leaves
Cause
Virus
Comments
Virus is found in almost all Cucurbit growing regions in the world; virus is spread by over 20 aphid species
Management
Treatments that control populations of aphid vectors can also reduce the incidence of the virus; spraying plants with mineral oils or insecticidal soaps can help to reduce aphid numbers