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Zucchini/Courgette
Scientific name:
Cucurbita pepo
Order/Family:
Violales: Cucurbitaceae
Common names:
Ornamental gourd, Marrow, gourd, Summer squash
Pests and Diseases:
Anthracnose  Aphids  Downy mildew  Epilachna beetles  Fruit flies  Powdery mildew  Viruses  Scab  

Anthracnose (Colletotrichum orbiculare)

It is the most 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 resistant varieties, if available.
  • Use certified disease-free seeds.
  • Practise crop rotation.
  • Destroy volunteer cucurbits and weeds.
Anthracnose
© 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 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
© 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 beetle (e.g. other cucurbits, potatoes, maize)
  • If necessary apply neem products. Simple neem-based pesticides are effective 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, Dacus spp., Ceratitis capitata)

Fruit flies are the most serious insect pests on zucchini/squash with the ability to totally wipe out any marketable fruit.

Fruit flies are about 4-7 mm long, they pierce the fruits and lay eggs in fruits. 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, causing fruit rot.

What to do:
  • Frequent applications of neem can keep fruit fly attack to a minimum.
    For more information on neem click here.
  • Avoid continuous cultivation of cucurbits at the same place since this may lead to fruit fly outbreaks.
  • Destroy all infested fruit.
  • In small plots, wrap individual fruits or bag them with newspaper or paper bags to prevent fruit flies from laying eggs into the fruits. 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.
Fruit fly
© M. K. Billah, icipe

Fruit fly

Fruit fly

Fruit fly …

Powdery mildew (Sphaerotheca fuliginea and Erysiphe cichoracearum)

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 fungicides, which provide good control.
  • Destroy weeds belonging to the cucurbit family.
Powdery mildew
© A.M. Varela

Powdery mi…

Powdery mi…

Virus diseases

The important virus diseases affecting 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).

What to do:

© Courtesy EcoPort (http://www.ecoport.org): S. Pone
General Information and Agronomic Aspects
Geographical Distribution of Zucchini in Africa
Fruits, leaves and flowers of Zucchini and other Cucurbita species are used as vegetables, and their seeds are consumed roasted as a snack food (CAB 2006). Zucchini has a mild flavour and is very watery. It is often harvested when still very young. At this stage it is also called squash or courgette. Because the fruit has very little flavour of its own it is often used as a base for making savoury dishes. The seeds can be scooped out of and a replaced with a filling - this can then be baked (Plants for a Future 2003). Ornamental gourds are cultivars of C. pepo with small, bitter and inedible fruits in many shapes, sizes and colours (CAB 2006).













Nutritive Value per 100 g of edible Portion
Raw or Cooked Zucchini 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)
Zucchini with skin cooked 16.0 / 1% 3.9 / 1% 0.1 / 0% 0.6 / 1% 13.0 / 1% 40.0 / 4% 0.4 / 2% 253 / 7% 1117 IU / 22% 4.6 / 8% 0.1 / 4% 0.0 / 0% 0.0 / 3% 0.0 / 2% 0.6
Zucchini with skin raw 16.0 / 1% 3.3 / 1% 0.2 / 0% 1.2 / 2% 15.0 / 1% 38.0 / 4% 0.4 / 2% 262 / 7% 200 IU / 4% 17.0 / 28% 0.2 / 11% 0.0 / 0% 0.0 / 3% 0.1 / 8% 0.6
*Percent Daily Values (DV) are based on a 2000 calorie diet. Your daily values may be higher or lower, depending on your calorie needs.


Climatic conditions, soil and water management
Zucchini requires a rich, well-drained soil that is able to retain moisture. It grows best in a sunny and sheltered position. Plants are tolerant to light shade. It prefers a pH of 5.5 to 5.9, but tolerates up to 6.8 (Plants for a Future 2003). It responds very well to fairly heavy applications of good compost or well-decomposed manure in the planting hills or ridges. Drought stress quickly reduces fruit setting, so during dry spells irrigation is a must, preferably watering below the leaves or using drip irrigation.


Propagation and planting
Zucchini and squashes are grown from seed. Seeds may be sown in containers and transplanted to the field when they are 10 cm high or have 2 real leaves. Direct seeding of two to three per hill is also commonly practised. Trailing types are planted at distances of 2 to 3 m either way; the seed requirement is 2 to 3 kg/ha. The bushy types are planted closer, for example, plants spaced 60 to 120 cm in rows 1 to 1.5 m apart. The seed requirement for Zucchini is 7 kg/ha. Plant densities vary from 5,000 plants per ha for the long-running trailing forms to 20,000 plants per ha for the bushy types (CAB 2006).

Husbandry
Sole cropping is normally used for commercial production. Zucchini and squashes are also planted in home gardens as fresh vegetables. Cultural practices to improve growth and development include the removal of growing tips to check growth in case of trailing varieties.


Harvesting
Zucchini and other summer squashes, from which the immature fruit is used as a fresh vegetable, develop very rapidly. The first marketable fruits can be harvested 50 to 60 days after planting, or 3 to 6 days after appearance of the female flower. During the harvest season the fruits are harvested two to three times per week. (CAB 2006)

Crop yields for summer squash (immature fruits) are 7 to 12 t/ha. Unless grown for seed, mature fruits are not marketable, so plants are removed when yields become too low. Indicative figures for seed yield of zucchini and other squashes are 400 to 1500 kg/ha. 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).

Summer squash of good quality can be kept for up to 14 days when stored at 7 to 10°C and 85 to 95% RH (CAB 2006).

Information on Pests
General Information
Courgettes are affected by similar pests as other cucurbits as they belong to the same family of Cucurbitacea. Other members of this family include melons, squash, pumpkin, and cucumber.

The leaf-feeding Epilachna beetles are a serious problem for Cucurbita growers. Aphids and various leaf beetles can also cause problems on courgetes.

For more information on courgette pests refer to datasheet on cucumber (click here).

Information on Diseases
General Information
Courgettes are affected by similar diseases as other cucurbits as they belong to the same family of Cucurbitacea. Other members of this family include melons, squash, pumpkin, and cucumber.

Anthracnose (Colletotrichum orbiculare) is the most destructive disease. It causes defoliation and lesions on the fruits.

Other fungal diseases, mainly affecting the leaves and stems are:
  • Powdery mildew (Erysiphe cichoracearum)
  • Downy mildew (Peronospora cubensis)
  • Scab (Cladosporium cucumerinum)

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).

For more information on these diseases refer to datasheet on cucumber (click here).

Information Source Links
  • AIC, Nairobi (2003). Fruits and Vegetables Technical Handbook
  • AVRDC International Cooperators' Factsheet on Cucurbits www.avrdc.org
  • Beije, C.M., Kanyangia,S.T., Muriuki, S.J.N., Otieno, E.A., Seif, A.A., Whittle, A.M. (1984). Horticultural Crops Protection Handbook. National Horticultural Research Station, Thika. KEN/75/028 and KEN/80/017/
  • 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). Veralgh Paul Parey. ISBN 3-489-64826-9.
  • CAB (2005). Crop ProtectionCompendium, 2005 Edition. © CAB International Publishing. www.cabi.org
  • CAB (2006). Crop ProtectionCompendium, 2006 Edition. © CAB International Publishing. www.cabi.org
  • 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. 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.
  • Nutrition Data www.nutritiondata.com.
  • Ostermann, H. and 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? 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
  • Park SoDeuk, Kwon TaeYong, Lim Yang Sook, Jung KiChae, Choi BooSull (1996). Disease survey in melon, watermelon, and cucumber with different successive cropping periods under vinylhouse conditions. Korean Journal of Plant Pathology, 12(4):428-431.
  • Plants for a Future (2003). Edible, medicinal and useful plants for a healthier world. www.pfaf.org
  • Sherf, A.F., Macnab, A.A. (1986). Vegetable Diseases and Their Control. 2nd. Edition. John Wiley & Sons Inc. USA. ISBN: 0-471-05860-2
  • University of Georgia: College of Agricultural and Environmental Sciences, Department of Horticulture Vegetable Crops: Pumpkin.
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: andrew@hygrotech.co.ke
Zucchini plant
Crop rotation
Crop rotation is the practice of growing different crops in succession on the same land.
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'.
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.
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.
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.
Necrosis
Necrosis is the death of some or all of the cells in an organ or tissue, caused by disease, physical or chemical injury.
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.
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.