Guava is hardy, aggressive, and a perennial that has only recently become a cultivated crop. The guava (Psidium guajava L., Myrtaceae), is one of 150 species of Psidium most of which are fruit bearing trees native to tropical and subtropical America. The guava plant grows symmetrically dome-shaped with broad, spreading, low-branching canopy and a shallow-rooted small tree of 3 to 10 m in height, branching close to the ground and often heavily suckering from the base of the trunk. The green to reddish-brown and smooth bark on older branches and trunk peels off in thin flakes. The four-angled young twigs of guava are easily distinguished. The simple leaves of guava are opposite, 10 to 15 cm long, oval to oblong-elliptic, smooth, and light green in color.
Pests and Diseases of Guava
Guava trees are seriously damaged by the citrus flat mite, Brevipa1pus californicus. The guava tree is attacked by 80 insect species, including 3 bark-eating caterpillars (Indarbella spp.) and the guava scale in India, but this and other scale insects are generally kept under control by their natural enemies. 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 larvae of the guava shoot borer penetrates 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.
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, Pseudococcus nipae, has been a serious problem in Puerto Rico but has been effectively combatted by the introduction of its parasitic enemy, Pseudaphycus utilis.
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, A. 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 Puerto Rico, up to 50% of the guava crop (mainly from wild trees) may be 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.
Fruits punctured by insects are subject to mucor rot (caused by the fungus, Mucor hiemalis) in Hawaii.
Algal spotting of leaves and fruits (caused by Cephaleuros virescens) occurs in some cultivars in humid southern Florida but can be controlled with copper fungicides. 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.
In Bahia, Brazil, severe deficiency symptoms of guava trees was attributed to nematodes and nematicide treatment of the soil in a circle 3 ft (0.9 in) 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.
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. Anthracnose may attack the fruits in the rainy season. Pestalotia psidii sometimes causes canker on green guavas in India and rots fruits in storage.
Severe losses are occasioned in India by birds and bats and some efforts are made to protect the crop by nets or noisemakers.