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Pumpkin
Scientific name:
Cucurbita spp. (Cucurbita maxima, Cucurbita moschata etc.)
Order/Family:
Cucurbitales: Cucurbitaceae
Local names:
Budho (Luo), Malenge (Kiwahili), Lisiebebe (Luhya), Marenge (Kikuyu), Risoa (Kisii), Ulenge (Kamba)
Common names:
Squash / giant squash / summer squash / giant pumpkin / butternut
Pests and Diseases:
Anthracnose  Aphids  Black rot  Choanephora fruit rot  Downy mildew  Epilachna beetles  Fruit flies  Fusarium wilt  Powdery mildew  Scab  Virus diseases  Whiteflies 

Anthracnose (Colletotrichum lagenarium (= C. orbiculare))

It is a very destructive disease. It causes defoliation and lesions on the fruits.

The fungus can attack all the above-ground plant parts. Cotyledons (seed leaves) of affected seedlings droop and wilt. Lesions (elongated spots) may form on stems of affected seedlings near the ground. Spots on leaves start as small yellowish areas that enlarge and turn brown. The affected tissue dries, breaks and the whole leaf dies. On vines, the spots are elongated and may kill the vines. Symptoms are most noticeable on fruits. Spots on fruits are circular, black, and sunken. When wet, the centres of the spots become salmon coloured due to a mass of fungal spores. Affected fruits can be destroyed by secondary soft-rot organisms, which enter through broken rind. The fungus is seed-borne. It can survive in crop debris and in weeds belonging to the cucurbit family. Fungal development is promoted by wet conditions, high relative humidity and moderate temperatures (20 to 23.9º C). Its host range includes cucumber, gherkin, gourd, muskmelon, and watermelon. Cucurbit weeds can also be attacked.

What to do:
  • Use certified disease-free seeds.
  • Treat own seeds in hot water for 20 minutes at 135° F (43° C).
  • Plant resistant varieties, if available.
  • Practise crop rotation with non-cucurbits.
  • Destroy volunteer cucurbits and weeds in the field.
Anthracnose
© Clemson University - USDA Cooperative Extension Slide Series, www.insectimages.org

Aphids (Aphis gossypii)

Colonies of green to blackish aphids are found on tender shoots, mainly on the lower leaf surface, where they suck sap. Under heavy attack the growth of attacked shoots is stunted and leaves are curled and twisted. Aphids excrete honeydew, which leads to growth of sooty mould, and may also attract fruit flies. Aphids transmit virus diseases such as the watermelon mosaic virus to pumpkins.

What to do:
  • Use reflective mulch (e.g a polyethylene sheet covered with a thin layer of aluminium that is spread out on the growing bed at planting time). Covering the ground with a material like aluminium foil repels winged aphids, delay aphid colonisation and may delay virus infection
  • Place sticky traps to detect arrival of winged aphids into the crop.
  • Conserve natural enemies. Aphids have a wide range of natural enemies which usually keep them under control.
  • If necessary spray with botanicals (e.g. neem extracts). Spray only attacked plants (spot spraying).
Cotton aphid
© Mississippi State University Archive, Mississippi State University, Bugwood.org

Gummy stem blight and black rot (Didymella bryoniae (= Mycosphaerella citrullina); Phoma cucurbitacearum)

Circular to irregular spots on leaves. On centres of the spots pycnidia (fungal fruiting bodies) develop. The spots may tear and drop out giving the leaves a tattered appearance. Crown and runners turn pale-brown and then crack oozing a reddish gum. The affected areas are studded with pycnidia. Runners may be girdled and die. Affected fruits exhibit black, leathery, sunken spots and under moist conditions pycnidia develop at the centres. On butternut squash, large irregular areas of the fruit become bronzed with distinct concentric rings. Fruits are spotted and rot. Infected fruits have no commercial value.

What to do:
  • A long rotation (at least 2 years) with non-cucurbit crops.
  • Good sanitation in the field is the best preventive control. Conditions conducive to the pathogen development should be avoided.
  • An accurate monitoring of leaves is necessary to detect early infection and start sprays on time.
  • Avoid building of high humidity in the field.
Black rot
© A.A. Seif, icipe

Black rot

Pineapple …

Choanephora fruit rot (Choanephora cucurbitarum)

C. cucurbitarum mostly attacks tissues that have been damaged by insects or mechanical means. Host tissues have a hairy appearance resulting from the tall fungal filaments that produce a cluster of brown spores (conidia) at their tips.

What to do:
  • Destroy crop residues after harvest.
  • Control cucumber beetles, which are responsible for fungal spread.
  • Spray copper when the disease is observed.
  • Avoid humid conditions during storage.
Choanephora fruit rot
© Clemson University - USDA Cooperative Extension Slide Series, www.insectimages.org

Downy mildew (Pseudoperonospora cubensis)

Symptoms on leaves appear as small, pale-yellow areas on upper leaf surface. Under humid conditions, a purplish, grey whitish growth may be seen on the underside of the yellowish spots. Affected leaves curl, shrivel and die. Most downy mildew fungi require cool weather for reproduction and development. This is not true of the cucurbit downy mildew fungus. Optimum temperature for infection is at 16 to 22º C. It can survive when temperatures are over 37.8º C. The most critical factor for infection is a film of moisture and / or long dew periods on leaves.

Disease spread is primarily thorough by wind and rain splash. The fungus attacks only members of the cucumber family, mostly those that are cultivated, although it can infect wild cucumber and a few other weed hosts.

What to do:
  • Use resistant varieties, if available.
  • Avoid wetting the leaves during irrigation.
  • Destroy weeds belonging to the cucurbit family
Downy mildew
© A.M. Varela, icipe

The Epilachna beetle (Epilachna chrysomelina)

Adults of the Epilachna beetle, also known as the African melon ladybird are 6 to 8 mm long, reddish in colour with a number of black spots on the wing cases. The larvae are 7 to 9 mm in length, soft and covered with dark coloured spines. They pupate on leaves. Both adults and larvae feed on the leaves leaving a fine net of veins. Damaged leaves shrivel and dry up. They may also gnaw stems and eat holes in fruits.

These beetles are most likely to be a problem during establishment when plants are small; young plants can be entirely destroyed. Older plants can tolerate considerable leaf damage, but during flowering fruit set maybe affected. This beetle is a vector of squash mosaic virus. The Epilachna beetle attacks all cucurbits. They often fly into a crop from nearby crops.

What to do:
  • Do not grow pumpkins near crops attractive to the Epilachna beetles (e.g. other cucurbits, potatoes, maize)
  • If necessary apply neem products. Simple neem-based pesticides are effective in controlling this pest. For instance, weekly foliar sprays of aqueous neem kernel extracts at concentrations of 25, 50 and 100 g/l and neem oil applied with an ultra-low-volume (ULV) sprayer at 10 and 20 l/ha significantly reduced feeding by Epilachna beetles in squash and cucumber in Togo (Ostermann and Dreyer, 1995)
Epilachna beetle
© A. M. Varela, icipe

Fruit flies (Bactrocera cucurbitae, Dacusspp. and Ceratitis capitata)

Fruit flies are important pests of cucurbits including pumpkins. Fruit flies pierce the fruits and lay eggs in them. The fruit fly maggots feed inside the fruit causing sunken, discoloured patches, distortions and open cracks. These cracks serve as entry points for fungi and bacteria, which cause fruit rot.

What to do:
  • Avoid continuous cultivation of cucurbits at the same place.
  • Destroy all infested fruit.
  • Wrap or bag individual fruits with newspaper or paper bags to prevent fruit flies from laying eggs on the fruit. Wrapping or bagging should be started shortly after fruit set.
  • Spray with a pyrethrum solution in the evenings after the bees are mostly back in their hives (after 6 pm). There is a product commercially available called "Flower-DS", made of natural pyrethrum and acceptable in organic certified systems (see Hygrotech Company, contact-addresses below).
    - Precautions: Be careful to spray late in the evening, follow the spraying instructions. Wear masks and skin protection.
    All insect poisons are also poisonous to humans even if coming from natural sources.
    - Frequency of spraying: start shortly after beginning of flowering, and repeat approx every 5 days or according to counts.
  • Frequent applications of neem can keep fruit fly attack to a minimum.
    For more information on neem click here.
Fruit fly
© R. C. Copeland, icipe

Fusarium wilt (Fusarium oxysporum f.sp. niveum)

It causes root rot and corky decay of the stem near ground level, leading to wilting and death. Inside wilted stems the vascular tissue may be discoloured. White to pinkish fungus mycelium may grow over affected tissue. Leaves of affected plants turn yellow and eventually wilt and die. It also causes loss of young plants through damping-off, or of older plants through successive wilting. If fruit has formed, it remains small and loose commercial value. Cucurbits are attacked at all stages of growth. When seedlings are invaded, they may damp-off and die. Older susceptible plants wilt initially, occasionally recover at night, but usually wilt quickly and die. In wet weather, a white or pinkish fungal growth develops on the surface of dead tissues. In advance stages of the disease, roots may decompose.

What to do:
  • Raising and maintaining the soil pH to 6.0 ? 7.0 by liming helps limit the disease.
  • Practise crop rotation with non-related crops
  • The plant stems need to be kept free of attack from insects whose bites are entry points for fungi and bacteria.
  • The growing of cucurbits on plots where water stagnates, in overly damp or very heavy soil should be avoided, to help keep the plant collar dry.
  • Excessive nitrogen fertilising is to be avoided. Sufficient application of calcium and potassium seems to reduce attacks
  • The destruction of diseased plants and the elimination of plant debris reduce the inoculum in the soil.
  • Deep tillage of the soil is necessary to bury crop residues so that they decompose completely.
  • The nursery soil can be disinfected through solarisation or the application of damp heat (60°C).
  • Caution is needed to keep from contaminating disinfected plots with agricultural material or contaminated soil.
  • The disinfection of tools (bleach) limits the propagation of the disease.
  • Use of long rotation periods (3 to 4 years).
Fusarium wilt
© A.M. Varela, icipe

Fusarium w…

Fusarium w…

Powdery mildew (Erysiphe cichoracearum; Sphaerotheca fuliginea )

Symptoms first develop as a whitish talcum-like powdery growth on upper leaf surface. The powdery growth is composed of fungal spore mass. These areas covered by white powdery growth may enlarge and join up to cover both lower and upper leaf surfaces. Severely affected leaves dry, turn brown and become brittle. Vines can be also attacked. Secondary effects of the disease include sun-burning and premature ripening of fruits.

Powdery mildew affects cucumber, gourd, muskmelon, pumpkin, squash and watermelon. Other hosts include African violets and pawpaws. The powdery mildew fungi are influenced by plant age, humidity and temperature. Foliage is most susceptible 16 to 23 days after unfolding. The fungi reproduce under dry conditions. Infection increases as humidity increases, but does not occur when leaf surface is wet. Optimum temperature for infection is about 27.4º C. However, infection can take place at a temperature as high as 32º C and relative humidity as low as 46%.

What to do:
  • Use resistant varieties, if available.
  • Spray with sulphur based organic fungicides, which provide good control.
  • Destroy weeds belonging to the cucurbit family.
Powdery mildew
© A.M. Varela

Powdery mi…

Powdery mi…

Scab (Cladosporium cucumerinum)

It attacks all aboveground plant parts. Initial symptoms on leaves appear as light water-soaked or pale green spots. The spots are numerous and can appear on and between veins. Elongate spots may develop on petioles and stems. The spots later turn grey to white and become angular. The fine veinlets in the spots may be brown and are distinct against a white background. Dead leaf tissue cracks and breaks away until the whole leaf is ragged. Fruits can be attacked at all stages of growth. However, young fruits are most susceptible. Plant tissue near the spots may produce sap, initially watery but later becomes gummy to hard.

The fruit spots are cankerous and with time become darker, sunken until a pronounced cavity is formed. Under moist weather, a dark-green velvety layer of fungal growth appears on the cavities. The fungus survives in crop debris, soil and on seed. It is spread by insects, farm tools and wind. The disease is most severe at 100% relative humidity and at relatively cool temperatures (21-25ºC). Its host range includes cantaloupe, gherkin, muskmelon, pumpkin, squash and watermelon.

What to do:
  • Use resistant varieties, if available.
  • Use disease-free seeds.
  • Practice crop rotation with non-related crops.
Scab
© Courtesy EcoPort (http://www.ecoport.org): McKenzie E., Landcare Ltd., New Zealand

Virus diseases

Many important virus diseases affect cucurbits. These include:

Cucumber mosaic cucumovirus (CMV)
Watermelon mosaic 2 potyvirus (WMV-2)
Watermelon mosaic 1 potyvirus
Zucchini yellow mosaic potyvirus (ZYMV)
Squash leaf curl bigeminivirus (SLCV)

Cucumber mosaic virus
It is not seed transmitted except through seed of perennial wild cucumber (Echinocytis lobata) and chickweed (Stellaria media). It is mechanically transmitted and in nature it is spread by various species of aphids. It has a very extensive host range including such varied species as bananas, carrots, cowpeas, lupine, lilies, onions, passion fruit, potatoes and tomatoes.

Watermelon mosaic virus
This virus is mechanically transmitted and also spread by several species of aphids. It is not seed transmitted. Its host range is primarily restricted to cucurbits although one of its strains infects peas.

Squash mosaic virus
It is mechanically transmitted. It is transmitted through seeds of melons and squash. It is also transmitted by spotted, striped and banded cucumber beetles, which attack cucumbers in the Americas. The Epilachna beetle (Epilachna chrysomelina) a pest of cucumber in Africa, is also vector of squash mosaic virus. Its host range includes cucurbits, peas, coriander, and salad chervil.

What to do:
  • Use tolerant / or resistant varieties if available.
  • Remove infected plants (disinfect hands and tools with 70% alcohol after contact with infected plants).
  • Do proper weeding.
  • Control insect vectors. A sustainable approach of controlling aphids is important to prevent aphids reaching the crops and transmitting virus.
  • In case of squash mosaic virus use disease-free seeds.
Virus diseases
© A.A. Seif, icipe

Virus dise…

Mosaic vir…

Whiteflies (Bemisia tabaci)

Whiteflies suck plant sap and excrete honeydew where moulds growth and may affect plant growth. However, the major damage is caused as vectors of various virus diseases, which cause considerable damage to cucurbits.

What to do:
  • Conserve natural enemies. Parasitic wasps are important in natural control of whiteflies.
  • Use reflective mulches (see aphids). Reflective mulch repels whitefly adults in pumpkin, cucumber and zucchini, resulting in delayed and reduced attack by this pest with consequent reduction in damage as shown in experiments USA. Whitefly density on pumpkins and cucumbers plants growing over reflective mulch was reduced 10- to 14-fold as compared to plants growing on bare soil. This was reflected in significantly higher yields in plants grown over reflective mulch than in those grown over unmulched soil (UCANR, 2003; Summers & Stapleton 2002)
  • If necessary spray crop with neem products. Neem-based pesticides are reported to inhibit growth and development of immature stages, and to reduce egg laying by adult whiteflies.
Whiteflies
© B. Nyambo, A. A. Seif, icipe
General Information and Agronomic Aspects
Geographical Distribution of Pumpkin in Africa
Pumpkin refers to certain varieties of Cucurbita moschata, C. maxima, and C. mixta. They are native to North America. These and other related cucurbits provide pumpkins and butternuts (Cucurbita moschata), squashes (C. maxima), gourds (C. argyrosperma), and zucchini or courgettes and ornamental gourds (C. pepo). Distinguishing them is often difficult. Pumpkins have long-running, bristled stems, large deeply-lobed leaves often containing white blotches and yellow or orange flowers separated into male and female types on the same plant. The fruit is variable in shape and colour but is often white, cream or green, containing about 70% flesh and several large white seeds.

Fruits, leaves and flowers of these cucurbits are used as vegetables, and their seeds are consumed roasted as a snack food. Pumpkin fruit contains 1% protein and 8% carbohydrates, and the dried seeds contain 23% protein, 21% carbohydrates and up to 50% oil, but little information is available about the nutritional characteristics of cooked leaves (Woomer and Imbumi, 2005).

There are numerous types and cultivars, which differ greatly in composition and therefore in their suitability for certain culinary uses. The younger leaves are collected and the outer tough skin of petioles (stalk of leaf) removed (together with the large leaf veins) then washed, chopped and boiled.

Immature and mature fruits of C. moschata are used as a blanched, steamed or fried vegetable and as an ingredient of soups. Various desserts are made from the fruits: steamed flesh with grated coconut and sugar, crisps made from steamed mashed flesh mixed with cassava flour, pumpkin custard, pumpkin pudding, pumpkin in coconut milk and sweet pumpkin paste. Ornamental gourds are cultivars of C. pepo with small, bitter and inedible fruits in many shapes, sizes and colours.
The potential of the seeds as a source of vegetable fat and protein has not been fully exploited. Fresh seeds have been reported to be used as a vermifuge, and seed decoctions as diuretic and to reduce fevers.

The pumpkin has been much used as a medicine in Central and North America. It is a gentle and safe remedy for a number of complaints. The seeds are widely used as an anthelmintic. The complete seed, together with the husk, is used to remove tapeworms. They are especially useful effective as tapeworm treatment for children and pregnant women for whom stronger and toxic remedies are unsuitable. The seeds are ground into fine flour, then made into an emulsion with water and eaten. It is then necessary to take a purgative afterwards in order to expel the tapeworms or other parasites from the body. The fruit and seed decoctions have been reported to be used as diuretic and to reduce fevers, and are used for curing indigestion. The pulp is applied to burns and scalds, inflammation, abscesses and boils. It is also used in the treatment of migraine and neuralgia (Plants for a Future 2003; CAB 2006).

Recently a new pumpkin relative, butternut has captured the market in Kenya. It was originally imported from South Africa and sold at very high prices in the upper level market, but is now widely grown by small farmers. Butternut has smooth yellow-orange flesh, is very nutritious and is widely used cooked and mashed as baby food. As the price came down this vegetable has gained wide popularity all over the country.


Nutritive Value per 100 g of edible Portion
Raw or Cooked Pumpkin Food
Energy
(Calories / %Daily Value*)		 Carbohydrates
(g / %DV) 		Fat
(g / %DV) 		Protein
(g / %DV) 		Calcium
(g / %DV) 		Phosphorus
(mg / %DV) 		Iron
(mg / %DV) 		Potassium
(mg / %DV) 		Vitamin A
(I.U)		 Vitamin C
(I.U)		 Vitamin B 6
(I.U)		 Vitamin B 12
(I.U)		 Thiamine
(mg / %DV) 		Riboflavin
(mg / %DV) 		Ash
(g / %DV)
Pumpkin cooked 20.0 / 1% 4.9 / 2% 0.1 / 0% 0.7 / 1% 15.0 / 1% 30.0 / 3% 0.6 / 3% 230.0 / 7% 4992 IU / 100% 4.7 / 8% 0.0 / 2% 0.0 / 0% 0.0 / 2% 0.1 / 5% 0.6
Pumpkin raw 26.0 / 1% 6.5 / 2% 0.1 / 0% 1.0 / 2% 21.0 / 2% 44.0 / 4% 0.8 / 4% 340 / 10% 7385 IU / 148% 9.0 / 15% 0.1 / 3% 0.0 / 0% 0.1 / 3% 0.1 / 6% 0.8
*Percent Daily Values (DV) are based on a 2000 calorie diet. Your daily values may be higher or lower, depending on your calorie needs.


Climate conditions, soil and water management
Pumpkins and squashes (various Cucurbita spp.) are grown in the tropics from the lowlands up to 2500 m altitude. They are warm-season crops adapted to monthly mean temperatures of 18-27°C. C. maxima is the most tolerant of low temperatures, C. moschata and C. argyrosperma the least, with C. pepo intermediate. C. maxima and C. pepo have long been cultivated in temperate regions. Butternut appreciates part shade in very hot conditions, such as can be obtained when intercropped with other crops or grown under fruit trees.

Pumpkins and squashes respond very well to medium to heavy applications of compost or well- decomposed manure. They can be cultivated on almost any fertile, well-drained soil with a neutral or slightly acid reaction (pH 5.5 to 7). They are drought-tolerant, requiring relatively little water, and are sensitive to waterlogging. Excessive humidity is harmful because of the development of leaf diseases, so none of the species do well in the humid tropics.

Propagation and planting
Pumpkins and squashes are grown from seed. Seeds may be sown in containers and transplanted to the field when they are 10 cm high. Direct seeding of 2 to 3 seeds per hill is commonly practised. Trailing types are planted at distances of 2-3 m either way; the seed requirement is 2 to 3 kg/ha. The bushy types (mainly C. pepo) are planted closer, for example, plants spaced 60 to 120 cm in rows 1 to 1.5 m apart; the seed requirement is 3 kg/ha for pumpkin and 7 kg/ha for summer squash (C. pepo). Do not use seeds from plants where edible pumpkins and ornamental gourds are grown close together. Offspring will be bitter or even inedible.

Varieties of butternut available in Kenya
  • "Butternut 401". It has resistance to powdery mildew
  • "Bugle". It has resistance to powdery mildew.
  • "Early Butternut F1". It has resistance to powdery mildew.
  • "Ultra F1". It has resistance to Fusarium wilt and powdery mildew.
  • "Waltham". It has resistance to powdery mildew.
Seeds of the above listed varieties are available at the major seed companies in Nairobi (e.g. East African Seed Company Ltd., Amiran Kenya Ltd. and Simlaw Seeds Co. Ltd)


Husbandry
Sole cropping is sometimes used for commercial production. Pumpkins and squashes are also planted in home gardens or mixed with field crops such as maize. Cultural practices to improve growth and development include the removal of growing tips (in trailing varieties) to check growth, and the bagging of fruits in paper to protect against fruit fly and other pests. Fruit setting may be stimulated by manual pollination. The fruit may rot when in contact with moist soil, so often cut grass or leaves are placed beneath the fruit.

Harvesting
Winter squashes and pumpkins are picked when mature in an once-over harvest or in several rounds, about 90 to 120 days after planting depending on variety.

Pumpkins are considered to be among the most efficient of vegetable crops when evaluated on nutritional yield in relation to land area and labour needed. Indicative figures for seed yield of C. pepo are 400 to 1500 kg/ha. A valuable source of oil and protein is thus neglected if the seeds are left unutilised. In seed production, isolation between fields of different Cucurbita species is recommended, not only for reason of purity but also for obtaining maximum yields (pollen of other species may cause reduced fruit set).
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Fresh Quality Specifications for the Market in Kenya
The following specifications constitute raw material purchasing requirements

© S. Kahumbu, Kenya
© S. Kahumbu, Kenya

back to Index
Information on Pests
Pumpkin and butternut are affected by similar pests as other cucurbits; since they belong to the family Cucurbitacea, including melons, squash, zucchini (courgettes) and cucumber.

For more information on pests attacking cucurbits refer also to page on cucumber click here
Examples of Pumpkin Pests and Organic Control Methods

Aphids (Aphis gossypii)

Colonies of green to blackish aphids are found on tender shoots, mainly on the lower leaf surface, where they suck sap. Under heavy attack the growth of attacked shoots is stunted and leaves are curled and twisted. Aphids excrete honeydew, which leads to growth of sooty mould, and may also attract fruit flies. Aphids transmit virus diseases such as the watermelon mosaic virus to pumpkins.

Cotton aphid
Cotton aphid (Aphis gossypii) is a small aphid. Adults range from just under 1-1.5 mm in body length.

© Mississippi State University Archive, Mississippi State University, Bugwood.org
More Information on Aphids
What to do:
  • Use reflective mulch (e.g a polyethylene sheet covered with a thin layer of aluminium that is spread out on the growing bed at planting time). Covering the ground with a material like aluminium foil repels winged aphids, delay aphid colonisation and may delay virus infection
  • Place sticky traps to detect arrival of winged aphids into the crop.
  • Conserve natural enemies. Aphids have a wide range of natural enemies which usually keep them under control.
  • If necessary spray with botanicals (e.g. neem extracts). Spray only attacked plants (spot spraying).

Whiteflies (Bemisia tabaci)

Whiteflies suck plant sap and excrete honeydew where moulds growth and may affect plant growth. However, the major damage is caused as vectors of various virus diseases, which cause considerable damage to cucurbits.

Whiteflies
Whiteflies on chilli leaf. Adults are about 1mm long.

© B. Nyambo, A. A. Seif, icipe
More Information on Whiteflies
What to do:
  • Conserve natural enemies. Parasitic wasps are important in natural control of whiteflies.
  • Use reflective mulches (see aphids). Reflective mulch repels whitefly adults in pumpkin, cucumber and zucchini, resulting in delayed and reduced attack by this pest with consequent reduction in damage as shown in experiments USA. Whitefly density on pumpkins and cucumbers plants growing over reflective mulch was reduced 10- to 14-fold as compared to plants growing on bare soil. This was reflected in significantly higher yields in plants grown over reflective mulch than in those grown over unmulched soil (UCANR, 2003; Summers & Stapleton 2002)
  • If necessary spray crop with neem products. Neem-based pesticides are reported to inhibit growth and development of immature stages, and to reduce egg laying by adult whiteflies.

The Epilachna beetle (Epilachna chrysomelina)

Adults of the Epilachna beetle, also known as the African melon ladybird are 6 to 8 mm long, reddish in colour with a number of black spots on the wing cases. The larvae are 7 to 9 mm in length, soft and covered with dark coloured spines. They pupate on leaves. Both adults and larvae feed on the leaves leaving a fine net of veins. Damaged leaves shrivel and dry up. They may also gnaw stems and eat holes in fruits.

These beetles are most likely to be a problem during establishment when plants are small; young plants can be entirely destroyed. Older plants can tolerate considerable leaf damage, but during flowering fruit set maybe affected. This beetle is a vector of squash mosaic virus. The Epilachna beetle attacks all cucurbits. They often fly into a crop from nearby crops.

Epilachna beetle
Epilachna beetle (Epilachna chrysomelina) and damage caused on water melon

© A. M. Varela, icipe
What to do:
  • Do not grow pumpkins near crops attractive to the Epilachna beetles (e.g. other cucurbits, potatoes, maize)
  • If necessary apply neem products. Simple neem-based pesticides are effective in controlling this pest. For instance, weekly foliar sprays of aqueous neem kernel extracts at concentrations of 25, 50 and 100 g/l and neem oil applied with an ultra-low-volume (ULV) sprayer at 10 and 20 l/ha significantly reduced feeding by Epilachna beetles in squash and cucumber in Togo (Ostermann and Dreyer, 1995)

Fruit flies (Bactrocera cucurbitae, Dacusspp. and Ceratitis capitata)

Fruit flies are important pests of cucurbits including pumpkins. Fruit flies pierce the fruits and lay eggs in them. The fruit fly maggots feed inside the fruit causing sunken, discoloured patches, distortions and open cracks. These cracks serve as entry points for fungi and bacteria, which cause fruit rot.

Fruit fly
Adult Fruit fly Ceratitis fasciventris are 4.5-6 mm long, brightly coloured, usually in brown-yellow patterns. The wings are spotted or banded with yellow and brown margins.

© R. C. Copeland, icipe
More Information on Fruit flies
What to do:
  • Avoid continuous cultivation of cucurbits at the same place.
  • Destroy all infested fruit.
  • Wrap or bag individual fruits with newspaper or paper bags to prevent fruit flies from laying eggs on the fruit. Wrapping or bagging should be started shortly after fruit set.
  • Spray with a pyrethrum solution in the evenings after the bees are mostly back in their hives (after 6 pm). There is a product commercially available called "Flower-DS", made of natural pyrethrum and acceptable in organic certified systems (see Hygrotech Company, contact-addresses below).
    - Precautions: Be careful to spray late in the evening, follow the spraying instructions. Wear masks and skin protection.
    All insect poisons are also poisonous to humans even if coming from natural sources.
    - Frequency of spraying: start shortly after beginning of flowering, and repeat approx every 5 days or according to counts.
  • Frequent applications of neem can keep fruit fly attack to a minimum.
    For more information on neem click here.
back to Index
Information on Diseases
Pumpkin and butternut are affected by similar diseases as other cucurbits; since they belong to the family Cucurbitacea, including melons, squash, zucchini (courgettes) and cucumber.

For more information on diseases attacking cucurbits refer also to page on cucumber click here
Examples of Pumpkin Diseases and Organic Control Methods

Anthracnose (Colletotrichum lagenarium (= C. orbiculare))

It is a very destructive disease. It causes defoliation and lesions on the fruits.

The fungus can attack all the above-ground plant parts. Cotyledons (seed leaves) of affected seedlings droop and wilt. Lesions (elongated spots) may form on stems of affected seedlings near the ground. Spots on leaves start as small yellowish areas that enlarge and turn brown. The affected tissue dries, breaks and the whole leaf dies. On vines, the spots are elongated and may kill the vines. Symptoms are most noticeable on fruits. Spots on fruits are circular, black, and sunken. When wet, the centres of the spots become salmon coloured due to a mass of fungal spores. Affected fruits can be destroyed by secondary soft-rot organisms, which enter through broken rind. The fungus is seed-borne. It can survive in crop debris and in weeds belonging to the cucurbit family. Fungal development is promoted by wet conditions, high relative humidity and moderate temperatures (20 to 23.9º C). Its host range includes cucumber, gherkin, gourd, muskmelon, and watermelon. Cucurbit weeds can also be attacked.

Anthracnose
Anthracnose (Colletotrichum orbiculare) damage to pumpkin leaf (Cucumis sativus).

© Clemson University - USDA Cooperative Extension Slide Series, www.insectimages.org
More Information on Anthracnose
What to do:
  • Use certified disease-free seeds.
  • Treat own seeds in hot water for 20 minutes at 135° F (43° C).
  • Plant resistant varieties, if available.
  • Practise crop rotation with non-cucurbits.
  • Destroy volunteer cucurbits and weeds in the field.

Gummy stem blight and black rot (Didymella bryoniae (= Mycosphaerella citrullina); Phoma cucurbitacearum)

Circular to irregular spots on leaves. On centres of the spots pycnidia (fungal fruiting bodies) develop. The spots may tear and drop out giving the leaves a tattered appearance. Crown and runners turn pale-brown and then crack oozing a reddish gum. The affected areas are studded with pycnidia. Runners may be girdled and die. Affected fruits exhibit black, leathery, sunken spots and under moist conditions pycnidia develop at the centres. On butternut squash, large irregular areas of the fruit become bronzed with distinct concentric rings. Fruits are spotted and rot. Infected fruits have no commercial value.

Black rot
Black rot on cabbage leaf (internal symptom). Note blackening of veins.

© A.A. Seif, icipe


More Information on Black rot
What to do:
  • A long rotation (at least 2 years) with non-cucurbit crops.
  • Good sanitation in the field is the best preventive control. Conditions conducive to the pathogen development should be avoided.
  • An accurate monitoring of leaves is necessary to detect early infection and start sprays on time.
  • Avoid building of high humidity in the field.

Fusarium wilt (Fusarium oxysporum f.sp. niveum)

It causes root rot and corky decay of the stem near ground level, leading to wilting and death. Inside wilted stems the vascular tissue may be discoloured. White to pinkish fungus mycelium may grow over affected tissue. Leaves of affected plants turn yellow and eventually wilt and die. It also causes loss of young plants through damping-off, or of older plants through successive wilting. If fruit has formed, it remains small and loose commercial value. Cucurbits are attacked at all stages of growth. When seedlings are invaded, they may damp-off and die. Older susceptible plants wilt initially, occasionally recover at night, but usually wilt quickly and die. In wet weather, a white or pinkish fungal growth develops on the surface of dead tissues. In advance stages of the disease, roots may decompose.

Fusarium wilt
Fusarium wilt on passion fruit. Note browning of water conducting tissues

© A.M. Varela, icipe


More Information on Fusarium wilt
What to do:
  • Raising and maintaining the soil pH to 6.0 ? 7.0 by liming helps limit the disease.
  • Practise crop rotation with non-related crops
  • The plant stems need to be kept free of attack from insects whose bites are entry points for fungi and bacteria.
  • The growing of cucurbits on plots where water stagnates, in overly damp or very heavy soil should be avoided, to help keep the plant collar dry.
  • Excessive nitrogen fertilising is to be avoided. Sufficient application of calcium and potassium seems to reduce attacks
  • The destruction of diseased plants and the elimination of plant debris reduce the inoculum in the soil.
  • Deep tillage of the soil is necessary to bury crop residues so that they decompose completely.
  • The nursery soil can be disinfected through solarisation or the application of damp heat (60°C).
  • Caution is needed to keep from contaminating disinfected plots with agricultural material or contaminated soil.
  • The disinfection of tools (bleach) limits the propagation of the disease.
  • Use of long rotation periods (3 to 4 years).

Choanephora fruit rot (Choanephora cucurbitarum)

C. cucurbitarum mostly attacks tissues that have been damaged by insects or mechanical means. Host tissues have a hairy appearance resulting from the tall fungal filaments that produce a cluster of brown spores (conidia) at their tips.

Choanephora fruit rot
Choanephora fruit rot (Choanephora cucurbitarum) on Cucurbita maxima.

© Clemson University - USDA Cooperative Extension Slide Series, www.insectimages.org
What to do:
  • Destroy crop residues after harvest.
  • Control cucumber beetles, which are responsible for fungal spread.
  • Spray copper when the disease is observed.
  • Avoid humid conditions during storage.

Powdery mildew (Erysiphe cichoracearum; Sphaerotheca fuliginea )

Symptoms first develop as a whitish talcum-like powdery growth on upper leaf surface. The powdery growth is composed of fungal spore mass. These areas covered by white powdery growth may enlarge and join up to cover both lower and upper leaf surfaces. Severely affected leaves dry, turn brown and become brittle. Vines can be also attacked. Secondary effects of the disease include sun-burning and premature ripening of fruits.

Powdery mildew affects cucumber, gourd, muskmelon, pumpkin, squash and watermelon. Other hosts include African violets and pawpaws. The powdery mildew fungi are influenced by plant age, humidity and temperature. Foliage is most susceptible 16 to 23 days after unfolding. The fungi reproduce under dry conditions. Infection increases as humidity increases, but does not occur when leaf surface is wet. Optimum temperature for infection is about 27.4º C. However, infection can take place at a temperature as high as 32º C and relative humidity as low as 46%.

Powdery mildew
Powdery mildew on peas

© A.M. Varela


More Information on Powdery mildew
What to do:
  • Use resistant varieties, if available.
  • Spray with sulphur based organic fungicides, which provide good control.
  • Destroy weeds belonging to the cucurbit family.

Downy mildew (Pseudoperonospora cubensis)

Symptoms on leaves appear as small, pale-yellow areas on upper leaf surface. Under humid conditions, a purplish, grey whitish growth may be seen on the underside of the yellowish spots. Affected leaves curl, shrivel and die. Most downy mildew fungi require cool weather for reproduction and development. This is not true of the cucurbit downy mildew fungus. Optimum temperature for infection is at 16 to 22º C. It can survive when temperatures are over 37.8º C. The most critical factor for infection is a film of moisture and / or long dew periods on leaves.

Disease spread is primarily thorough by wind and rain splash. The fungus attacks only members of the cucumber family, mostly those that are cultivated, although it can infect wild cucumber and a few other weed hosts.

Downy mildew
Downy mildew on cabbage

© A.M. Varela, icipe
What to do:
  • Use resistant varieties, if available.
  • Avoid wetting the leaves during irrigation.
  • Destroy weeds belonging to the cucurbit family

Scab (Cladosporium cucumerinum)

It attacks all aboveground plant parts. Initial symptoms on leaves appear as light water-soaked or pale green spots. The spots are numerous and can appear on and between veins. Elongate spots may develop on petioles and stems. The spots later turn grey to white and become angular. The fine veinlets in the spots may be brown and are distinct against a white background. Dead leaf tissue cracks and breaks away until the whole leaf is ragged. Fruits can be attacked at all stages of growth. However, young fruits are most susceptible. Plant tissue near the spots may produce sap, initially watery but later becomes gummy to hard.

The fruit spots are cankerous and with time become darker, sunken until a pronounced cavity is formed. Under moist weather, a dark-green velvety layer of fungal growth appears on the cavities. The fungus survives in crop debris, soil and on seed. It is spread by insects, farm tools and wind. The disease is most severe at 100% relative humidity and at relatively cool temperatures (21-25ºC). Its host range includes cantaloupe, gherkin, muskmelon, pumpkin, squash and watermelon.

Scab
Citrus scab on leaf

© Courtesy EcoPort (http://www.ecoport.org): McKenzie E., Landcare Ltd., New Zealand
More Information on Scab
What to do:
  • Use resistant varieties, if available.
  • Use disease-free seeds.
  • Practice crop rotation with non-related crops.

Virus diseases

Many important virus diseases affect cucurbits. These include:

Cucumber mosaic cucumovirus (CMV)
Watermelon mosaic 2 potyvirus (WMV-2)
Watermelon mosaic 1 potyvirus
Zucchini yellow mosaic potyvirus (ZYMV)
Squash leaf curl bigeminivirus (SLCV)

Cucumber mosaic virus
It is not seed transmitted except through seed of perennial wild cucumber (Echinocytis lobata) and chickweed (Stellaria media). It is mechanically transmitted and in nature it is spread by various species of aphids. It has a very extensive host range including such varied species as bananas, carrots, cowpeas, lupine, lilies, onions, passion fruit, potatoes and tomatoes.

Watermelon mosaic virus
This virus is mechanically transmitted and also spread by several species of aphids. It is not seed transmitted. Its host range is primarily restricted to cucurbits although one of its strains infects peas.

Squash mosaic virus
It is mechanically transmitted. It is transmitted through seeds of melons and squash. It is also transmitted by spotted, striped and banded cucumber beetles, which attack cucumbers in the Americas. The Epilachna beetle (Epilachna chrysomelina) a pest of cucumber in Africa, is also vector of squash mosaic virus. Its host range includes cucurbits, peas, coriander, and salad chervil.

Virus diseases
Virus on cucumber

© A.A. Seif, icipe


More Information on Virus diseases
What to do:
  • Use tolerant / or resistant varieties if available.
  • Remove infected plants (disinfect hands and tools with 70% alcohol after contact with infected plants).
  • Do proper weeding.
  • Control insect vectors. A sustainable approach of controlling aphids is important to prevent aphids reaching the crops and transmitting virus.
  • In case of squash mosaic virus use disease-free seeds.
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Information Source Links
  • AIC (2003). Fruits and Vegetables Technical Handbook. Nairobi, Kenya.
  • AVRDC International Cooperators' Factsheet on Cucurbits www.avrdc.org
  • Aggie horticulture, Cucurbit Disorders. A Guide to the Identification of Common Problems. www.aggie-horticulture.tamu.edu
  • Blay, E., Cudjoe, A. R., Braun, M. (Eds) (2000). Handbook of crop protection recommendations in Ghana: An IPM approach. Vol 2; vegetables. Plant Protection & Regulatory Services Directorate (PPRSD) and the Integrated Crop Protection Project, German Development Cooperation (GTZ).
  • Bohlen, E. (1973). Crop pest in Tanzania and their control. Federal Agency for Economic Cooperation (BFE). Verlag Paul Parey. ISBN 3-489-64826-9.
  • CABI. (2006). Crop ProtectionCompendium, 2006 Edition. © CAB International Publishing. www.cabi.org
  • East African Seed Co. Ltd. Africa's Best Grower's Guide www.easeed.com
  • Ecoport. The Consilience Engine. www.ecoport.org
  • Ekesi, S., Billah, M.K. (Eds)(2006). A field guide to the management of economically important tephritid fruit flies in Africa. ICIPE, Nairobi, Kenya. ISBN: 92-9064-179-7.
  • Ministry of Agriculture and Rural Development (Kenya) (MoARD) & Japan International Cooperation Agency (JICA) (2000). Local and Export Vegetables Growing Manual. Reprinted by Agricultural Information Resource Centre, Nairobi, Kenya. 274 pp.
  • National Horticultural Research Station, Thika (1984). Horticultural Crops Protection Handbook. By C.M. Beije, S.T. Kanyangia, S.J.N. Muriuki, E.A. Otieno, A.A. Seif and A.M. Whittle. KEN/75/028 and KEN/80/017/
  • Nutrition Data www.nutritiondata.com.
  • Ostermann, H., Dreyer, M. (1995). Vegetables and grain legumes. In: The Neem tree Azadirachta indica A. Juss. and other meliaceous plants sources of unique natural products for integrated pest management, industry and other purposes. (1995). Edited by H. Schmutterer in collaboration with K. R. S. Ascher, M. B. Isman, M. Jacobson, C. M. Ketkar, W. Kraus, H. Rembolt, and R.C. Saxena. VCH. pp. 392-403. ISBN: 3-527-30054-6
  • Sherf, A.F., Macnab, A.A. (1986). Vegetable Diseases and Their Control. 2nd. Edition. John Wiley & Sons Inc. USA. ISBN: 0-471-05860-2
  • Summers, C.G. and Stapleton, J. J. (2002). Use of UV reflective mulch to delay the colonization and reduce the severity of Bemisia argentifolii (Homoptera: Aleyrodidae) infestations in cucurbits. Crop Protection. Volume 21. Pages 921-928. www.sciencedirect.com
  • The Ohio State University Extension Vegetable Crops. VegNet, Online Library. vegnet.osu.edu
  • UCANR. UC helps pumpkin farmers produce pumpkins without pesticides. October 2003 www.ucanr.org
  • University of Georgia: College of Agricultural and Environmental Sciences, Department of Horticulture Vegetable Crops: Pumpkin.
  • Woomer P. L. and Imbumi, M. (2005).Traditional Green Vegetables in Kenya. In Organic Resource Management in Kenya. Perspectives and Guidelines. Forum for Organic Resource Management and Agricultural Technologies (FORMAT). www.formatkenya.org
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Contact Links
  • For information on small scale farming techniques, seeds, equipment and insecticides(e.g. pyrethrum solution).
    HYGROTECH EAST AFRICA, LTD
    Region :KENYA / TANZANIA - Location: NAIROBI
    Address :P.O.Box 41446, Nairobi, Tigoni Centre, Limuru Road, KENYA
    Phone :+254 (0) 20 205 3916-8
    Fax :+254 (0) 20 205 3921
    E-Mail: [email protected]
  • Corner Shop, Nairobi [email protected]
  • Food Network East Africa Ltd info@organic.co.ke Tel. +254 0721 100 001
  • Green Dreams admin@organic.co.ke Tel. +254 0721 100 001
  • Kalimoni Greens kalimonigreens@gmail,com Tel. +2540 722 509 829
  • Karen Provision Stores [email protected] Tel. +254020885552
  • Muthaiga Green Grocers
  • Nakumatt Supermarket [email protected] Tel. +254020551809
  • Uchumi Supermarket
  • Zuchinni Green Grocers Tel. +2540204448240
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Pumpkin (Cucurbita maxima)
© Courtesy EcoPort (http://www.ecoport.org): Arnoldo Mondadori Editore SpA
Crop rotation
Crop rotation is the practice of growing different crops in succession on the same land.
Cucurbits
Cucurbitaceae is a plant family commonly known as melons, gourds or cucurbits and includes crops like cucumbers, squashes (including pumpkins), luffas, melons and watermelons. The family is predominantly distributed around the tropics, where those with edible fruits were amongst the earliest cultivated plants in both the Old and New Worlds.
Mulch
Plant material such as straw, leaves, crop residues, green manure crops, saw-dust etc. that is spread upon the surface of the soil. A mulch cover helps protect the soil from erosion and evaporation, nourishes soil life, increases soil organic matter content and provides nutrients to the crop.
Conidium
An asexually produced fungal spore.
Disinfect
To reduce, by physical or chemical means, the number of potentially harmful microorganisms in the environment, to a level that does not compromise food safety and suitability.
Fungi
Occurring worldwide, most fungi are largely invisible to the naked eye, living for the most part in soil, dead matter, and as symbionts of plants, animals, or other fungi. They perform an essential role in all ecosystems in decomposing organic matter and are indispensable in nutrient cycling and exchange. Some fungi become noticeable when fruiting, either as mushrooms or molds.

Fungi are responsible for a range of serious plant diseases such as blight, grey mould, bunts, powdery mildew, and downy mildew. Crops of all kinds often suffer heavy losses.

Fungal plant diseases are usually managed with applications of chemical fungicides or heavy metals. In some cases, conventional breeding has provided fungus resistantcultivars.

Besides combatting yield losses, preventing fungal infection keeps crops free of toxic compounds produced by some pathogenic fungi. These compounds, often referred to as mycotoxins, can affect affect the immune system and disrupt hormone balances. Some mycotoxins are carcinogenic.
IPM
A combination of chemical and biological control methods, based on the concept of economic tresholds. Pest management in organic farming uses many biological control methods developed as par of IPM.
Cotyledon
The first leaf of a germinating seed, also called seed-leaf.
organic
Refers to the farming system and products described in the IFOAM standard and not to 'organic chemistry'.
Fungi
Occurring worldwide, most fungi are largely invisible to the naked eye, living for the most part in soil, dead matter, and as symbionts of plants, animals, or other fungi. They perform an essential role in all ecosystems in decomposing organic matter and are indispensable in nutrient cycling and exchange. Some fungi become noticeable when fruiting, either as mushrooms or molds.

Fungi are responsible for a range of serious plant diseases such as blight, grey mould, bunts, powdery mildew, and downy mildew. Crops of all kinds often suffer heavy losses.

Fungal plant diseases are usually managed with applications of chemical fungicides or heavy metals. In some cases, conventional breeding has provided fungus resistantcultivars.

Besides combatting yield losses, preventing fungal infection keeps crops free of toxic compounds produced by some pathogenic fungi. These compounds, often referred to as mycotoxins, can affect affect the immune system and disrupt hormone balances. Some mycotoxins are carcinogenic.
Predator
Animal that attacks and feeds on other animals, such as an insect (e.g. ladybird beetle), bird or spider feeding on pest insects.
Cultivar
Cultivar is a plant variety. It is a group of similar plants which through their structural features and performance can be identified from other varieties within the same species.
Resistance
Ability of a living organism not to get affected by a disease or pest; or of a pest not to be affected by a pesticide.

Pesticide Resistance is the ability of a life form to develop a tolerance to a pesticide. Pests (weeds, insects, mites, diseases, etc.) that become resistant to a pesticide will not be affected by the pesticide. When pests are resistant, it is more difficult to control the pest. Therefore, it is important to try to prevent pesticide resistance.
Ingredient
is a substance, including a food additive, used in the manufacture or preparation of a food or present in the final although possibly in a modified form.
IPM
A combination of chemical and biological control methods, based on the concept of economic tresholds. Pest management in organic farming uses many biological control methods developed as par of IPM.
Symptom
Symptom - the plant's response to the disease causing organism, examples are; changes in plant color, death of infected tissues, and wilting. It is the external or internal physical characteristic of a disease as expressed by the host plant.