The guava is subjected to the attacks of numerous insect, animal and fungal enemies.

Insect pests of guava:

About 80 species of insect pests have been recorded on guava in India, but only few of them had been identified as pest of regular occurrence and causing serious damage. These are bark eating-caterpillar (Indarbela spp.), fruit fly (Bactrocera spp.) and scale insect (Chloropulvinaria psidii), but, this and other scale insects are generally kept under control by their natural enemies.

Scale insect (Chloropulvinaria psidii)		Fruit fly (Bactrocera correcta)

The bark eating-caterpillar and fruit flies have wide distribution, while scale insects and mealy bugs are more common everywhere. In India, cockchafer beetles feed on the leaves at the end of the rainy season and their grubs, hatched in the soil, attack the roots. The larvae of the guava shoot borer penetrate the tender twigs, killing the shoots. Sometimes aphids are prevalent, sucking the sap from the underside of the leaves of new shoots and excreting honeydew on which sooty mold develops. Studies conducted in the recent past have revealed some of the important facts on the occurrence and status of insect pests on this crop. Intensive surveys of guava growing regions of Uttar Pradesh revealed of fruit borer, Deudorix isocrates (Fab) the increase in incidence (2.5-22.5%) with crop loss range of 5-35%. Common occurrence of another fruit borer, Dichocrocis punctiferalis (Guenee) in rainy season guava was also noticed. Fruit flies have been a major limiting factor in production of rainy season guava. Infestation of fruit fly ranged from 20-46 % with crop loss of 16-40 %, which is a matter of serious concern. Infestation of scale insects, aphids and mealy bugs, on leaves, shoots and fruit was also common in most of the orchards surveyed but these insects were in check by the presence of their natural enemies. The infestation of mite and shoot borer caused the drying and dying of affected leaves and twigs which adversely affected growth of plants, flowering and fruiting of guava.

Guava fruit borer, Deudorix isocrates Fab

The principal pests on guava in Florida are redbanded thrips, Caribbean fruit fly, guava moth, and guava whitefly. Scale insects may also intermittently infest guava plantings. The green shield scale, Pulvinaria psidii, requires chemical measures in Florida, as does the guava white fly, Trialeurodes floridensis, and a weevil, Anthonomus irroratus, which bores holes in the newly forming fruits. The red-banded thrips feed on leaves and the fruit surface. The list of scale insects injurious to guavas is a particularly long one, including numerous species belonging to the genera Aspidiotus, Ceroplastes, Icerya, Pseudococcus, Pulvinaria, and Saissetia. All of these can be held in check by the usual means, i.e., spraying with kerosene emulsion or some other insecticide, but little attention is given to this matter in most tropical countries.

Green shield scale, Pulvinaria psidii		Guava white fly, Trialeurodes floridensis

The fruit-flies, including species of Anastrepha, Ceratitis, and Dacus, cause serious trouble in many regions. It is said that 80 % of the guavas produced in Hawaii have in some seasons been infested with the larvae of the Mediterranean fruit-fly (Ceratitis capitata Wied.). The guava fruit worm, Argyresthia eugeniella, invisibly infiltrates hard green fruits, and the citron plant bug, Theognis gonagia, the yellow beetle, Costalimaita ferruginea, and the fruit-sucking bug, Helopeltis antonii, feed on ripe fruits. A false spider mite, Brevipalpus phoenicis, causes surface russeting beginning when the fruits are half-grown. Fruit russeting and defoliation result also from infestations of red-banded thrips, Selenothrips rubrocinctus. The coconut mealybug,

Red-banded thrips (Selenothrips rubrocinctus)

Pseudococcus nipae, has been a serious problem in Puerto Rico but has been effectively combatted by the introduction of its parasitic enemy, Pseudaphycus utilis.

Mediterranean fruit-fly (Ceratitis capitata Wied.)		Fruit-sucking bug, Helopeltis antonii

In Malaysia, the adult red-banded thrip or cacao thrip feeds the surface and caused death to the young shoots of guava trees. Young guava fruits will be scarred after attack by this pest, thus reducing the aesthetic value of the harvested fruit. The severity of attack will be very high during dry period which requires immediate control. The damage to the guava crop caused by of Helopeltis theobrome Miller during certain times of the cropping season also can be devastating. The adults and nymphs suck cell sap from the shoot, young leaves, flower buds and fruitlets leaving tiny watery spots that will merge into bigger spots and finally turn black. The shoots wilted and die whilst the flower buds and fruitlets dropped. The attacked surface of the fruit will be infected by a secondary fungus Pestaliolipsis psidii that causes the formation of scabs on the fruit surface thus lowers the quality of the fruit. However, the attack from Helopelthis psidii can be controlled by spraying one of these insecticides namely, Mipcrin 75 WP, Mospilan 5 EC Aerogor, Sevin 885, Pestec and Lebacyd 550 EC.

Mealy bugs (Dysmicoccus breviceps Ckll., Planococcus citri Risso., Pseudococcus lilanus Morq. & Ckll. And Ferrisiana (Pseudococcus) virgata Ckll.), both the adult and nymph feed on the cell sap from the surface of the guava fruit and caused severe damage to the feeding site. The damage resulted in the formation of black spots on the fruit surface thus lowers the fruit quality. At the same time, these pests excrete sweet exudate suitable as medium for the growth of black mold causing the fruit to become black in color and dirty. Not only that, the sweet exudate causes the built up of ant population in the orchard which can be a great nuisance to the workers harvesting the fruits. Harvested fruits do not keep long since they are susceptible to secondary attack by the fungus. However, attack from mealy can be controlled effectively by insectidal spraying of one of these chemicals, namely Albarol, Shell Miscible White Oil, Nurelle-D505 EC, Aeorogor and CH Malaxion 84 EC.

Other insect pests of guava found in Malaysian orchards are spiralling whitefly (Aleurodicus dispersus Russell), carambola fruitfly or Asian papaya fruitfly (Bactrocera carambolae Drew & Hancock, B. papayae Drew & Hancock, B. cucurbitae Drew & Hancock and B. latifrons Hendel), leaf roller (Spilonota semicanella Walker & Spilonota rhotia Meyr), atlas moth (Attacus atlas L.) and bagworm (Crematopsyche pendula Joanis & Mahasena cobetti Tams), which are quite serious and very damaging to guava crops affecting its production and crop economy per se. Meanwhile, the carambola fruitfly and Asian fruit fly are usually controlled by repeated insectidal sprays at intervals of 7-10 days with malathion (e.g Hextar Malathion 840, 8ml/4.5 liter H2O), cypermethrin (e.g Chiptrin 5.5, 10 ml/10liter H2O), deltamethrin (e.g Decis, 10-22 ml/10 liter H2O), acephate (e.g Orthene 75 SP, 11 g/10 liter H2O) or dimethoate (e.g Dimet 40, 5 ml/4.5 literH2O) directed at almost matured fruits and the spraying must be stopped 7-10 days before harvesting of fruits.

Fruit bagging with paper bags		Yeast autolysate bait (PROMAR)

Baited sticky fly trap		Homemade fly trap

Insect traps are sometimes used to monitor the insect population in the orchards and their continued usage can help in reducing the insect population. Fruit wrapping is also practised to control insect pests from damaging the fruits. The fruits are wrapped when they are about the size of a pingpong ball with wrapping paper/ bags. Spraying of fruits with one of the approved insecticides before wrapping is strongly recommended. At the same time, good field sanitation such as collection of damaged, dropped and diseased fruits is practiced to remove potential hosts or harbors for the insects. Nymphs and pupas are also collected from the affected trees to be destroyed.

The use of bait sprays comprising an attractant (protein hydrolysate from maize, acid hydrolysate, yeast autolysate) and a toxicant is often practiced to reduce the fruitfly population in the orchard. In Malaysia, the protein source used in bait sprays is a yeast autolysate produced as a by-product of the brewing process in the production of stout. It is marketed under the name of 'Promar'. It has proven to be an excellent attractant for local species of fruit flies. It is ideal for medium to large orchards or where adjacent properties use the technique

The protein bait acts as a food attractant and its effectiveness relies on the fact that immature females need a protein meal for developing mature eggs. The bait spray residue on the foliage is ingested by the flies and kills them. Because the bait spray relies on its attractant properties for its mode of action, overall coverage of the tree canopy is unnecessary and a 'spot spraying technique' is adequate.

Mealy bugs ( Planococcus citri Risso)		Bagworm (Mahasena corbetti Tams & Crematopsyche pendula Joanis)

Spider mite, Brevipalpus phoenicis		Melon fly (Anastrepha ludens)

Leaf roller (Spilonota semicanella Walker & Spilonota rhotia Meyr) damaging the leaves and the surface of matured guava fruit

Dacus cucurbitae		Dacus dorsalis

Spiralling whitefly (Aleurodicus dispersus Russell) infesting the guava leaves

Guava mealybugs (Planococcus minor Maskell)		Thrips (Rhipiphorthrips cruentatus Hood)

Soil-inhabiting white grubs require plowing-in of an approved and effective pesticide during field preparation in Puerto Rico. There are other minor pests, but the great problems wherever the guava is grown are fruit flies. In Egypt, guava trees are seriously damaged by the citrus flat mite, Brevipa1pus californicu.

Control: The guava is a prime host of the Mediterranean, Oriental, Mexican, and Caribbean fruit flies, and the melon fly-Ceratitis capitata, Dacus dorsalis, Anastrepha ludens, Anastrepha suspensa, and Dacus cucurbitae. Ripe fruits will be found infested with the larvae and totally unusable except as feed for cattle and swine. To avoid fruit fly damage, fruits must be picked before full maturity and this requires harvesting at least 3 times a week. In Brazil, choice, undamaged guavas are produced by covering the fruits with paper sacks when young (the size of an olive). Infested fruits should be burned or otherwise destroyed. In recent years, the Cooperative Extension Service in Dade County, Florida, has distributed wasps that attack the larvae and pupae of the Caribbean fruit fly and have somewhat reduced the menace.

More recently in Torres Strait Islands and Cairns area of northern Queensland, using the method of Male Annihilation Technique (MAT) involves the use of a high density of bait stations consisting of a male lure combined with an insecticide (usually technical malathion and more recently fipronil), to reduce the male population of fruit flies to such a low level that mating does not occur. Using lengths of string or cord soaked in methyl eugenol and malathion was successful in eradicating Asian papaya fruit fly (Bactrocera papayae) from several places. A similar method, using caneite blocks nailed to trees instead of using string, was used to successfully eradicate Asian papaya fruit fly.

Caneite blocks and coconut husk blocks for male annihilation (Photos: Allan Allwood)

Fungal diseases of guava

Fruits punctured by insects are subject to mucor rot (caused by the fungus, Mucor hiemalis) in Hawaii. On some trees, 80% of the mature green fruits may be ruined.

Algal spotting of leaves and fruits (caused by Cephaleuros virescens) occurs in some cultivars in Malaysia and in humid southern Florida but can be controlled with copper fungicides.or can be reduced by maintaining tree vigor with cultural techniques such as proper fertilization and irrigation, proper pruning to enhance air circulation within the canopy and sunlight penetration, managing weeds and wider tree spacing. Managing insect, mite and other foliar diseases increases tree vigor and lessens susceptibility to this disease.

During the rainy season in India, and the Province of Sancti Spiritus, Cuba, the fungus, Phytophthora parasitica, is responsible for much infectious fruit rot. Botryodiplodia sp. and Dothiorella sp. cause stem-end rot in fruits damaged during harvesting. Macrophomina sp. has been linked to fruit rot in Venezuela and Gliocladium roseum has been identified on rotting fruits on the market in India.

Wilt, associated with the fungi Fusarium solani and Macrophomina phaseoli, brings about gradual decline and death of undernourished 1-to 5-year-old guava trees in West Bengal. A wilt disease brought about by the wound parasite, Myxosporium psidii, causes the death of many guava trees, especially in summer, throughout Taiwan. Wilt is also caused by Fusarium oxysporum f. psidii which invades the trunk and roots through tunnels bored by the larvae of Coelosterna beetles.

Anthracnose (Colletotrichum gloeosporioides) may attack the fruits in the rainy season. Pestalotia psidii sometimes causes canker on green guavas in India and rots fruits in storage.

Phytophthora fruit rot by (Phytophthora nicotianae var. parasitica)		Fruit rot by (Pestalotia psidii)

The guava fruit-rot, a species of Glomerella, is a common fungal disease in some places. In Puerto Rico, up to 50% of the guava crop (mainly from wild trees) is ruined by the uncontrollable fungus, Glomerella cingulata, which mummifies and blackens immature fruits and rots mature fruits. Diplodia natalensis may similarly affect 40% of the crop on some trees in South India.

Mucor rot (Mucor hiemalis)		Algal leaf spots (Cephaleuros virescens)

Other pests

There are other pests, some of them serious, which the guava-grower may have to combat. Severe losses in crop can be caused by nematodes ( Meloidogyne sp.) already present in the soil. Aslo, there are occasions in India the guava fruits are badly damaged birds and bats and some efforts are made to protect the crop by nets or noisemakers.

Root damage by Meloidogyne sp.		Fruit eating bat		Fruit eating bird

Mineral deficiencies in guava

In Bahia, Brazil, severe deficiency symptoms of guava trees was attributed to nematodes and nematicide treatment of the soil in a circle 0.9m out from the base restored the trees to normal in 5 months. Zinc deficiency may be conspicuous when the guava is grown on light soils. It is corrected by two summer sprayings 60 days apart with zinc sulphate.

Physical, physiological and pathological disorders:

Chilling injury: Symptoms include failure of mature-green or partially-ripe guavas to ripen, browning of the flesh and, in severe cases, the skin, and increased decay incidence and severity upon transfer to higher temperatures.

The skin colour of guava changed from light green to greenish yellow on storage at 20°C, whilst bronzing occurred when stored at 5°C with no obvious sign of pulp injury. Wills et al.(1983) found that storing guava fruits at 0°C reduced rotting considerably but that darkening of the flesh of the guava during storage at 0°C and 5°C became evident after 3 weeks and 4 weeks respectively. Broughton and Leong (1979) found that when guava (var. GU3 and GU4) was stored at 4°C and transferred to 20°C, the fruits developed brown blemishes and had a flat taste. Brown and Paxton (1983) reported that common guava showed pulp injury symptoms on cool storage. Fully-ripe guavas are less sensitive to chilling injury than mature-green guavas and may be kept for up to a week at 5°C without exhibiting chilling injury symptoms. Differences in the responses of the various varieties of guava stored under similar temperature conditions may be expected. Commodities grown in different areas as well as varieties of the same crop can differ in their susceptibility to chilling injury and development of chilling injury symptoms.

External (skin) and Internal (flesh) browning: Guavas are sensitive to physical damage during harvesting and handling all the way to the consumer. Symptoms include skin abrasions and browning of bruised areas.

Sun scald: Guavas exposed to direct sun light may be scalded. In some countries, paper bags are used to cover guava fruits and protect them from solar radiation and insect infestation while on the tree.

Most of the postharvest disease problems begin in the orchard as latent infection in developing fruits. Diseases include anthracnose (caused by Colletrotrichum gloeosporioides and associated species), aspergillus rot (caused by Aspergillus niger), mucor rot (caused by Mucor hiemalis), phomopsis rot (caused by Phomopsis destructum), and rhizopus rot (caused by Rhizopus stolonifer).

Disease control strategies include good orchard sanitation, effective preharvest management to reduce infection, careful handling to reduce physical damage, prompt cooling to 10°C and subsequent maintenance of that temperature throughout the handling system.

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