The soursop, unfortunately, is a shy-bearer, the usual crop being 12 to 20 or 24 fruits per tree. In Puerto Rico, production of 5,000 to 8,000 lbs per acre (roughly equal kg/ha), is considered a good yield from well-cared-for trees.
A study of the first crop of 35 5 year-old trees in Hawaii showed an average of 93.6 lbs (42.5 kg) of fruits per tree.
Yield was slightly lower the 2nd year. The 3rd year, the average yield was 172 lbs (78 kg) per tree. At this rate, the annual crop would be 16,000 lbs per acre (roughly equal kg/ha).
Pests & Diseases:
Queensland’s principal soursop pest is the mealybug which may occur in masses on the fruits. The mealy bug is a common pest also in Florida, where the tree is often infested with scale insects. Sometimes it may be infected by a lace-wing bug.
The fruit is subject to attack by fruit flies—Anastrepha suspensa, A. striata and Ceratitis capitata. Red spiders are a problem in dry climates. Dominguez Gil (1978 and 1983), presents an extensive list of pests of the soursop in the State of Zulia, Venezuela. The 5 most damaging are:
- the wasp, Bephratelloides (Bephrata) maculicollis, the larvae of which live in the seeds and emerge from the fully-grown ripe fruit, leaving it perforated and highly perishable;
- the moth, Cerconota (Stenoma) anonella, which lays its eggs in the very young fruit causing stunting and malformation;
- Corythucha gossipii; which attacks the leaves;
- Cratosomus inaequalis, which bores into the fruit, branches and trunk;
- Laspeyresia sp., which perforates the flowers.
The first 3 are among the 7 major pests of the soursop in Colombia, the other 4 being: Toxoptera aurantii; which affects shoots, young leaves, flowers and fruits; present but not important in Venezuela; Aphis spiraecola; Empoasca sp., attacking the leaves; and Aconophora concolour, damaging the flowers and fruits.
Important beneficial agents preying on aphids are A phidius testataceipes, Chrysopa sp., and Curinus sp. Lesser enemies of the soursop in South America include: Talponia backeri and T. batesi which damage flowers and fruits; Horiola picta and H. lineolata, feeding on flowers and young branches; Membracis foliata, attacking young branches, flower stalks and fruits; Saissetia nigra; Escama ovalada, on branches, flowers and fruits; Cratosomus bombina, a fruit borer; and Cyclocephala signata, affecting the flowers.
In Trinidad, the damage done to soursop flowers by Thecla ortygnus seriously limits the cultivation of this fruit. The sphinx caterpillar, Cocytius antueus antueus may be found feeding on soursop leaves in Puerto Rico.
Bagging of soursops is necessary to protect them from Cerconota anonella. However, one grower in the Magdalena Valley of Colombia claims that bagged fruits are more acid than others and the flowers have to be hand pollinated.
It has been observed in Venezuela and El Salvador that soursop trees in very humid areas often grow well but bear only a few fruits, usually of poor quality, which are apt to rot at the tip. Most of their flowers and young fruits fall because of anthracnose caused by Collectotrichum gloeosporioides.
It has been said that soursop trees for cultivation near San Juan, Puerto Rico, should be seedlings of trees from similarly humid areas which have greater resistance to anthracnose than seedlings from dry zones. The same fungus causes damping-off of seedlings and die-back of twigs and branches.
Occasionally the fungus, Scolecotrichum sp. ruins the leaves in Venezuela. In the East Indies, soursop trees are sometimes subject to the root-fungi, Fomes lamaoensis and Diplodia sp. and by pink disease due to Corticum salmonicolour.