Fruit fly, fruit-borer and bark-eating caterpillars are major insect pests, whereas guava wilt, fruit-rot and die-back are important diseases(3).
Pest Management
Fruit fly (Bactocera dorsalis): The fruit fly is the most destructive insect in the
production of guava, particularly during rainy season. When the fly is uncontrolled, the amount of marketable fruit is drastically reduced. Damage occurs as the larvae hatch out from eggs oviposited beneath the skin of ripening fruit and begin to feed on the flesh. Fruit turn progressively soft and mushy as the larvae begin feeding, until the fruits become 'waterlogged and the juice begin to drip on handling.
Approaches and Strategies for Precision Farming in Guava
Management
! The traps are very useful tool in monitoring and control of population of fruit fly. Hanging of bottle traps containing 100 ml of water emulsion of methyl euginol (0.1%) + malathion (0.1%) during fruiting season (April-July) is very effective for control of fruit fly. Ten traps per hectare of orchard give satisfactory control. Traps can be fixed during morning time.
! Collection and destruction of infested and fallen fruits along with maggots useful in reducing the pest population. Ploughing tree basin also helps in checking the pest population as the pupae are destroyed by being exposed to unfavourable temperature and also becomes the prey for predators.
! Adult fruit flies can be controlled by bait spraying of carbaryl (0.2%) + 0.4% protein hydrolysates or molasses at pre-oviposition time.
Bark-eating caterpillar (Inderbela spp.): It is another serious pest of guava found
in all over the India. The old, shady and neglected orchards are more prone to the attack of this pest. The caterpillars bore into trunk, main stem and thick branches of guava trees and remain inside the holes during day. The caterpillars come out in night to feed on the bark and make silken galleries inside.
Management
! After removing the webs of bark-eating caterpillar, all the borer holes except the fresh one, should be plugged with mud plastering.
! Application of monocrotophos (0.05%) or DDVP (0.1%) emulsion in holes and plugging with mud.
Mealy bug (Ferrisia virgata): The problem of mealy bug is more pronounced in
summer months. This occurs on leaves and fruits. Mealy bugs are small, oval, sucking insects which are cottony-white, and waxy covering on their bodies. They are found sticking to the underside of the guava leaves. They secrete honeydew on which sooty mould develops. Fruits covered with the mealy bug and sooty mould lose the market value. All the commonly used insecticides do not provide adequate control because of the waxy coating over their bodies.
Management
! Release of predator Cryptolaemus sp. @ 10-20 beetles/tree gives very effective control within 30-45 days of the release.
Guava fruit-borer (Virachola isocrates): The guava fruit-borer has been found in
northern region of the country. The caterpillars bore the raw fruits of all sizes and eat the pulp of the fruits. The infested fruits usually dry up.
Management
! Collection of infested fruits with borer and their destruction to check the carry over of the pest.
! The adults may be controlled by spraying of carbaryl (0.1%) or fenthoate (0.05%) or phosalone (0.01%) at the beginning of fruiting season and before ripening of fruits.
! Spraying of carbaryl (0.2%) at the early stage of crop has been found effective in reducing the pest population.
Scale insect (Chloropulvianria psidii): These are small scale like, flat, green insect
which are found sticking to leaves, shoots and sometime fruits. This is serious pest of guava in India. The appearance of sooty mould on tree is the first recognisable symptoms to appear. In a badly infested orchard, trees are covered with scales, and sooty mould. In severe infestations, defoliation and flower abortion can occur, reducing yield drastically. Generally, the infestation is more in summer. The trees become black instead of the usual lush green.
Management
! Prune affected parts and burn at the early stage of infestation.
! Two-three sprayings with monocrotophos (0.05%) at 15 days intervals are necessary in summer.
! Water spraying removes sooty mould.
! In heavy infestation, spray starch 2% or mixture of wetable sulphur + methyl parathion + gum acacia (0.2% + 0.1% + 0.3%).
5 Since ants are nearly always associated with scales, they should also be controlled. DISEASE MANAGEMENT
Guava wilt: Among diseases affecting culture of this crop, wilt is most destructive
disease known to occur mostly in northern and eastern India. Disease starts with the withering and yellowing of leaves. The leaves droop down and epinasty is the main symptom. The plant generally wilts within 15 days to two months. There may be either
Approaches and Strategies for Precision Farming in Guava
partial or full wilting of the plant. The disease occur more severely in alkaline soil. Generally, the incidence is evident only during July-November and is however not observed during winter and summer months. It is severe at the time of fruit bearing. Now it is felt besides pathogens, there are other factors, i.e. soil, nutrition and management, which are also responsible for this malady.
Management
! Remove and destroy wilted branches. Uproot and burn severely affected trees. ! Proper sanitation in the orchards is essential.
! Avoid waterlogging.
! Use of organic and green manures helps in reducing the disease.
! As preventive control, soil treatment with neem cake (4.0 kg/plant) and gypsum (2 kg/plant) is useful.
! The soil may be drenched with Bavistin at the early stage of infection.
! Incidence of the disease can be minimised by application of Aspergillus niger strain AN17. Culture of A. niger is mixed in FYM at the rate of 1%, allow to multiply it and after 10-15 days incubation the enriched FYM is applied at the rate of 5 kg/ plant.
Fruit canker: The fruit canker is widely prevalent in India. It produces numerous
circular to raised dark coloured corky cankerous growths on fruits. Infected fruits are deformed and give a chickenpox appearance. They do not ripe and are not palatable.
Management
! The disease can be effectively controlled by two sprayings of Dithane M-45 (0.2%) during green fruit stage.
Anthracnose : High humidity and frequent rains favour the spread and intensity of
disease attack. It occurs mostly on fruits during rainy season. Most characteristic symptoms include the appearance of small spots of the size of pinhead, which are first observed on unripe fully grown fruits during rainy season. They are dark brown to black in colour, sunken, circular and bear numerous minute black pinhead growth in the centre of the lesions. In favourable weather, several spots coalesce to form bigger lesions. The diseased portions are comparatively harder than the healthy tissues. Ripe fruits become soft. Unopened flowers and buds are also attacked and they are shed.
Management
! Pruning of diseased twigs and destruction of fallen leaves and fruits are also helpful in controlling the disease.
! Dithane M-45 (0.2%) or Topsin M (0.1%) or Bavistin (0.1%) or copper oxychloride (3g/litre of water) on mature fruits reduce the infection.
Stylar-end rot: Severe infestation occurs during rainy season which reduces the quality
of fruits. The symptoms start as a circular, water-soaked lesions at the stylar end and later on they become reddish brown in colour.
Management
! The disease can be controlled effectively by spraying of Bavistin or Topsin M (0.1%) at 15 days interval during fruit maturity stage. However, no spraying is done before 15 days of harvesting.
Fruit rot: The symptoms appear on mature green fruits as a water-soaked lesion that
develops very rapidly to affect entire fruits. This is very serious during rainy weather and spoils nearly 20-25 per cent of the fruits before harvesting.
Management
! Removal of diseases fruits from the orchard and destroying them so that fruit flies and other insects cannot land on the fungal mass to pick up spores for reinfection. ! Pre-harvest spraying of carbendazin or thiophonate methyl (Bavistin or Topsin
M,.5%) 15 - 20 days before harvesting. HARVESTING
Harvesting of guava fruits is determined on the basis of visual fruits colour observations. Fruits attaining maturity show signs of changing colour from pale green to yellowish green. However, experience is the best guide. During the peak period of season, harvest interval cannot be more than 2-3 days otherwise losses of over-ripe fruits become a problem. When only fully ripe fruit are harvested on a 3-day cycle, losses between 35 and 40 per cent can occur, as fruits ripen so rapidly and abscise. It is desirable to harvest the fruits with the stalk along with one or two leaves. It delays ripening and the fruits are attractive in appearance. The fruit is soft and requires considerable care in picking and handling. The fruit is picked selectively by hand. Once picked, the fruit deteriorates rapidly if left standing in the hot sun in the fields. Hence, while in the field, they should be stored in a cool location under trees or in a centralised
Approaches and Strategies for Precision Farming in Guava
shed protected from the scorching sun. Over-ripe fruits and those severely infected with fruit flies and diseases should be destroyed rather than left to fall and rot in the field, as these fruits become the source of continuous field infection. If the fruit is to be shipped to distant market it should be mature, full sized and of firm texture, but without an obvious colour break on the surface. Fruits for local market can be harvested in a more advanced stage of maturity.
Packaging and Storage
Being a fruit of highly perishable nature, it must be sold out soon after its arrival in the market. These fruits have less weight loss, high vitamin 'C', a high organoleptic score and no adverse changes in fruit quality. For larger markets, storage at 5 oC
extends post-harvest life by two weeks in comparison with storage at 20 oC. Fruits
packed in polythene bags can be stored at 8-10 oC for 14 days. Yield
The yield of guava varies greatly depending upon the variety and agroclimatic conditions prevailing in a region. At the end of the second year or at the beginning of third, the grafted guava trees can be put into production cycle. The production begins from third year with about 8 tonnes/ha and increases to 25 tonnes/ha by seventh year. By adopting optimum package of practices for cultivation, guava trees can be made even to bear up to 40 years of age. The most economic period of the plants (plants with heavy bearing) is up to 20 years, and thereafter declines gradually.
Handling
The fruit is delicate and should be handled with great care. To avoid damage, it should be graded and transported in small boxes rather than in large crates immediately after harvesting, when it is still firm, it should reach the consumer before it soften. Utilization
The guava is a sweet, juicy and highly flavoured fruit, eaten mostly as fresh or processed. Guava puree is an important product predominantly used now in the production of guava juice or nectars, cakes, sauce, jams, jellies, pastry, and other products. Guavas are also dehydrated and powdered.