Guava

Description

Guava, Psidium guajava, is an evergreen shrub or small tree in the family Myrtaceae grown for its edible fruits. Guava has a slender trunk with smooth green to red-brown bark. The trunk may be branched at the base and the branches droop low to the ground. The plant possesses oval or elliptical leaves which are smooth on the upper surface and hairy on the lower surface. Guava produces solitary white flowers and a berry fruit. The fruit is oval in shape and green to yellow in color. The flesh inside can be white, yellow, pink or red in color and contains numerous yellowish seeds. Guava can reach grow to 10 m (33 ft) in height and lives for approximately 40 years. Guava may also be referred to as common guava and its origin is unknown although it grows native in parts of tropical America.


Uses

Guava fruits may be eaten fresh or processed to produce paste, jellies or preserves. Dehydrated fruit is used to make guava powder.


Propagation


Basic requirements
Guava is mainly grown in the tropics and will tolerate temperatures between 15 and 45°C (59–113°F). Guava will grow optimally between 23 and 28°C (73–82°F) but established trees can tolerate short periods at -3 to -2°C (27-28°F) although temperatures below 15°C (60°F) can cause the tree to cease producing fruit. Guava is also amenable to a wide range of soils and will grow in both sandy or rocky soils in addition to loams, preferring a pH of 4.5–7 but tolerating alkaline soil to to pH 8.5. Guava is more resistant to drought than most tropical fruits and can withstand long periods of dry weather by ceasing vegetative growth until conditions improve.

Propagation
Guavas grown for processing can be grown from seed as approximately 70% of the seedlings will retain the genetic characteristics of the parent tree. Guavas that are grown for fresh fruit are usually vegetatively propagated by air layering or budding.

Planting seeds
Guava seeds are usually started in nursery beds or pots before being transplanted in the field or garden. Only seeds from healthy, vigorous trees with the desired characteristics should be planted. Seeds should be planted in flats containing sandy soil and covered to a depth of 6 mm (0.25 in). Seeds usually germinate within 15 to 20 days of planting. When the seedlings reach 3.8 cm (1.5 in) in height they should be transplanted into individual pots. Seedling are ready to be moved to the field after about 6 to 7 months when they have reached approximately 30.5 cm (12 in) in height.

Transplanting seedlings
Guava trees should be planted in full sun and should be spaced 4.5–7.5 m (15–25 ft) away from other trees and buildings to prevent shading. A hole should be dug which is slightly larger than the existing root ball and the addition of a layer of compost or rotted manure at the bottom of the planting hole. The tree should be planted at the same depth as it was in the nursery by placing the seedling upright into the planting hole and backfilling the soil around the plant. The soil should be tamped by hand around the tree to eliminate any air pockets. Water the newly planted seedlings immediately unless the soil is already damp.

General care and maintenance
Newly planted guava trees should be watered every two days after planting for the first week and then once a week for the following few months to allow the root system to develop and become established. A 0.6 to 1.5 m (2.0-5.0 ft) area around the trunk should be maintained to be free from grass and weeds. Guava trees benefit from the application of a layer or organic mulch such as bark or wood chips around the base. This helps to suppress weeds and conserve moisture in the soil. Do not mound the mulch around the trunk, allow a gap of 20 to 30 cm (8-10 in) between the trunk and the mulch layer. Young trees benefit from fertilizer application with the type an amount varying with area and soil type.

Pruning
Young trees should be pruned to encourage the development of laterals. This is achieved by cutting back existing laterals at 30 to 60 cm (1 to 2 ft). During the first year of growth, 3 to 4 of the lateral branches should be allowed to grow 60 to 90 cm (24-36 in) before the tips are cut to encourage further branching. any new shoots formed by this process should also be tipped when they reach 60 to 90 cm (24-36 in). Pruning of established trees should be carried out to retain a manageable height and to open out the canopy.

Harvesting
Trees grown from seed may not come into production for anywhere between 3 to 8 years. Guava does not ripen off the tree and it can be difficult to distinguish when the fruits are ready for harvest. The best indication is a color change from dark to light green and the development of some yellowing on the fruits. Fruit should be harvested every 2-3 days to prevent fruit becoming overripe.



References

CABI Crop Protection Compendium. (2013). Psidium guajava datasheet. Available at: http://www.cabi.org/cpc/datasheet/45141. [Accessed 15 December 14]. Paid subscription required.

Crane, J. H. & Balerdi, C. F. Guava Growing in the Florida Home Landscape. University of Florida IFAS Extension. Available at: http://edis.ifas.ufl.edu/pdffiles/MG/.... [Accessed 15 December 14]. .

Hamilton, R. A. & Seagrave-Smith, H. (1959). Growing Guava for Processing. University of Hawaii Cooperative Extension. Available at: http://www.ctahr.hawaii.edu/oc/freepu.... [Accessed 15 December 14]. Free to access.

Morton, J. F. (1987). Guava. In: Fruits of warm climates pp 356–363.Echo Point Books & Media. Available at: http://www.hort.purdue.edu/newcrop/mo.... [Accessed 15 December 14]. .

Ploetz, R. C., Zentmyer, G. A., Nishijima, W. T., Rohrbach, K. G. & Ohr, H. D. (eds) (1994). Compendium of Tropical Fruit Diseases. American Phytopathological Society Press. Available at: http://www.apsnet.org/apsstore/shopap.... Available for purchase from APS Press.


Common Pests and Diseases

Algal leaf spot
Cephaleuros virescens

Symptoms
Orange, rust-colored, dense, silky tufts on both upper and lower surfaces of leaves which turn reddish-purple in color as they mature; if tufts are scraped away, a thin gray-white or dark-colored necrotic spot remains on the leaf; bark on twigs and branches may be cracked; young stems and fruit may also be attacked.
Cause
Alga
Comments
Wet, humid conditions promote spread of the disease; zoospores can be spread by splashing water.
Management
Ensure trees receive adequate fertilization, irrigation and and are properly pruned to avoid stress on the plants and promote air circulation through the canopy; periodic applications of a copper based fungicide is usually enough to control the disease.

Rust
Puccinia psidii

Symptoms
Orange to red pustules appearing on leaves, young shoots, flowers and/or fruit; leaves distorted; defoliation of tree; reduced growth; circular lesions on fully expanded leaves with dark borders and yellow halos.
Cause
Fungus
Comments
Disease emergence favored by warm temperatures and high humidity.
Management
Primary method of controlling disease is usually the application of appropriate fungicides; cultural practices that may reduce the incidence of the disease include good sanitation practices and adequate fertilization, irrigation and pruning of trees.

Anthracnose
Colletotrichum gloeosporoides

Symptoms
Sunken, dark colored lesions on mature fruit which may become covered in pink spores; lesions coalesce to form large necrotic patches on surface of fruit
Cause
Fungus
Comments
Disease emergence favors warm, wet weather; spread easily during wet weather by water splash
Management
The primary method of controlling the disease is to plant resistant guava cultivars; both systemic and non-systemic fungicides are effective at controlling the disease and are usually applied shortly before flowering and during fruit develpment

Pseudocercospora leaf spot
Pseudocercospora psidii

Symptoms
Small irregularly shaped or roughly circular dark brown lesions with darker brown border on upper surface of leaves; lesions may also be present on stems and fruit; under humid conditions, fungus may sporulate and gray tufts of mycelium may be visible in the center of lesions; lesions may coalesce to form large necrotic patches.
Cause
Fungus
Comments
Infection of leaves occurs during wet conditions when temperatures are between 13 and 25°C (55-77°F); disease can be spread by splashing water.
Management
In areas where environmental conditions are conducive to the development of the disease, chemical control using appropriate fungicides is necessary to control the disease; copper-containing fungicides are most effective.

Thrips (Redbanded thrips)
Selenothrips rubrocinctus

Symptoms
If population is high leaves may be distorted; leaves are covered in coarse stippling and may appear silvery; leaves speckled with black feces; insect is small (1.5 mm) and slender and best viewed using a hand lens; adult are dark brown to black in color and female has red pigmentation on abdominal segments.
Cause
Insect
Comments
Insect is tropical to subtropical insect; lifecycle is approximately 3 weeks allowing for several generations per year.
Management
Avoid planting next to onions, garlic or cereals where very large numbers of thrips can build up; use reflective mulches early in growing season to deter thrips; apply appropriate insecticide if thrips become problematic.

Fruit flies (Guava fruit fly, Caribbean fruit fly)
Bactrocera spp.
Anastrepha suspensa

Symptoms
Depressions in fruit with dark colored puncture wounds; soft, mushy areas on fruit caused by larvae feedign on fruit; development of secondary rots often cause fruit to drop from tree; insects are small flies - the guava fruit fly is approximately 5 mm in length and is black and yellow in color; the Caribbean fruit fly may reach 12-14 mm in length and is yellow-brown with long patterned wings.
Cause
Insect
Comments
Guava fruit flies are widespread in Southern Asia while Caribbean fruit flies are damaging pests in Cuba, Jamaica, Hispaniola, Puerto Rico and Florida.
Management
Infested fruit should be removed and destroyed; plowing around bases of trees infested with guava fruit flies exposes pupae to damaging heat from the sun and to natural enemies; pheromone traps are used successfully in some regions to control guava fruit flies; millions of sterile Caribbean fruit flies are introduced yearly in Florida to control populations on citrus.

Scale insect (green scale, green shield sale)
Coccus viridis
Pulvinaria psidii

Symptoms
Leaves covered in sticky substance and may have growth of sooty mold; reduced tree vigor; leaves and/or fruit dropping from plants; presence of green or gray flattened scales on leaves, twigs and/or branches.
Cause
Insect
Comments
Insects can produce several overlapping generations per year. Also they have wide host range.
Management
Collect and burn the fallen plant materials. Organically acceptable methods of control include the application of horticultural oils and preservation of natural enemies.

Guava Weevil
Conotrachelus psidii
Conotrachelus dimidiatus

Symptoms
The adult females lay eggs in small unripe fruits. After hatching, the larva enters the fruit. Once inside, the larva feeds on pulp and seeds, causing petrification and premature maturity of fruit. Larva excrement deposited inside fruit causes fermentation. Mature larvae abandon the ripe fruits and pupate underground.
Cause
Insect
Comments
The insect can cause up to 70 to 100 % yield loss.
Management
Collect and burn the damaged fruits. Soil application of entomopathogenic nematodes (EPN) like genus Heterorhabditis and Steinernema as biological control agents against 4th larval instar, pre-pupa and pupa weevil stages.

Root knot nematode
Meloidogyne spp.

Symptoms
Galls on roots which can be up to 3.3 cm (1 in) in diameter but are usually smaller; reduction in plant vigor; yellowing plants which wilt in hot weather.
Cause
Nematode
Comments
Galls can appear as quickly as a month prior to planting; nematodes prefer sandy soils and damage in areas of field or garden with this type of soil is most likely.
Management
Plant resistant varieties if nematodes are known to be present in the soil; check roots of plants mid-season or sooner if symptoms indicate nematodes; solarizing soil can reduce nematode populations in the soil and levels of inoculum of many other pathogens.