Mehwish Raza1, Hafiz Muhammad Bilal1*, Asma Khalid 1, Hafiza Tayyba Manzoor2
1. Department of Horticulture, College of Agriculture, University of Sargodha.
2. Department of Zoology, The University of Lahore.
Guava (Psidium guajava L.) is an important fruit crop of tropical and subtropical areas of the world. Major guava producing countries are South Africa, India, Brazil, Egypt, Mexico, Venezuela, Columbia and Pakistan. The guava of the myrtle family (Myrtaceae) is a popular fruit of Bangladesh which is rich in vitamin C. Guava is one of the most nutritious fruit crops of the Indo-Pak subcontinent. Depending on the species, it contains vitamin C (over 200 mg 100-1 g) four times more than oranges, vitamin A, vitamin B, magnesium, potassium and considered as low-caloric food. The presence or absence of fruit on guava trees has a major effect on their photosynthetic performance and growth. It also contains the group of major antioxidants such as polyphenols and carotenoids, which are responsible for its high nutritional value. It claims to be the most important fruit in respect of area and production after mango, banana, jackfruit, pineapple, and melon in Bangladesh. The leaves of the plant have medicinal values, which aid in curing diarrhea, swelling and bleeding of gums. Fruit length, diameter and weight of guava fruit increased gradually from fruit set to harvest.
In Pakistan, it is grown in all the provinces over an area of 58.5 thousand hectares with production of 468.3 thousand tones. The major guava growing areas include Shariqpur, Kasur, Lahore, Sheikhupora, Sangla Hills, Gujranwala in the Punjab; Kohat, Haripur and Bannu in the North West Frontier Province and Larkana and Hyderabad in Sindh. Presently guavas are grown almost entirely for fresh consumption. However, international market for fresh guavas is small. Nevertheless, more trade is carried on processed guava products like Juices and nectars, Jam and Jellies, fruit paste, canned whole and halves in syrup. Some traders believe that there is a good international market potential for fresh guavas and that demand will grow as more consumers become acquainted with this fruit.
The increasing importance of guava as a commercial tropical fruit crop, both for table purposes and processing, demands its wide spread cultivation ensuring regular cropping and higher production. Generally, guava is cultivated using traditional planting system (6.0 x 6.0 m), under which it is difficult to achieve desired levels of production, because large trees provide low production per unit area and need high labor inputs. Moreover, large trees take several years before they come into bearing and overall cost of production per unit area is further increased. Hence, there is overriding need to improve the existing planting system
Among the serious problems associated by the guava is attack of fruit fly that causing readily decrease in yield and quality of guava. (Bactrocera correcta) often referred as guava fruit fly. Almost all species of fruit fly feeds on guava. Fruit flies lays their eggs inside the fruit and maggots feed on flesh, as a result fruit rot and infestation spread quickly. It is widely distributed in Pakistan, India, Nepal and Sri Lanka.
Pre-harvest bagging also reduces agrochemical residues in the fruit and improves insect, disease and bird damage control. Lower percentage of blush on the skin and a paler flesh for mangoes bagged during fruit growth with non-perforated white opaque plastic bags than for no bagged fruit or fruit bagged with paper bags of several such alternatives, pre-harvest fruit bagging has emerged as one of the best approaches in different parts of the world. In this technique, individual fruit or fruit bunch is bagged on the tree for a specific period to get desired results. It is a physical protection technique commonly applied to many fruits, which not only improves fruit visual quality by promoting fruit coloration but also enhances internal fruit quality. Pre-harvest bagging of fruits has been conventionally practiced for fruit growing in Japan, Australia and China as well as in peach, apple, pear, grape and loquat cultivation in order to optimize fruit quality through reduced physiological and pathological disorders and for improving fruit col- oration to increase their market value.
We know that, guava always bears fruit on new growth from mature wood. To maintain regular fruit bearing, it must be ensured a balance between mature wood and vegetative growth. It also ensured production in the next growing season. Huge number of fruits bears on healthy guava trees which resulted in heavy loads of fruits and a chance for breakage of branches. Regular bearing increased fruit size and reduced chance of trunk breakage due to the early stages of fruit thinning. Flower thinning from guava plants during summer, improved fruit quality and increase yield during next winter. Effects of time and severity of flower or fruit thinning or crop load adjustment, and concomitant alteration of fruit: leaf ratios, tree and fruit physiology have been extensively studied to determine their effects on fruit size, yield and quality at harvest. The rate of fruit growth depends primary on crop load. The yield and quality of guava fruit is poor as it has not received the deserved attention in its cultivation. A package of practice is imperative to enhance the growth and quality of guava fruits by crop load and fruit thinning. Excessive crop loading reduces fruit coloration through direct shading of neighboring fruit, or through competition for assimilates needed for coloration. A high fruit to leaf ratio may mean that the leaves cannot produce enough carbohydrates to color or size all of the fruit to their full potential.
It was reported that fruit thinning was found effective in guava to increase individual fruit weight. Hand thinning of fruits in apple with different intensities affected greatly fruit size and the fruit size was largest with severe thinning. It was noticed that the fruit thinning increased fruit quality in guava. Fruit thinning at later stages after fruit setting had decreasing effect on yield.