Guava it’s Diseases and their Management
Guava (Psidium guajava L.) is an important fruit of subtropical countries. It is hardy crop and is cultivated successfully even in neglected soils. It is a small or shrub like evergreen tree. It has slander like trunk with smooth red green bark. Oval shape fruit green to yellow in color. Its height is about 33ft and life span is approximately 40years. Pakistan is second largest guava producing country. According to (PCRSC) survey of Pakistan (2015-16) 70026 hectare area under guava cultivation and its production is 414649 tons annually. Some major and impressive guava benefits on human health are; it manage blood pressure, help in digestion, weight loss, improve immunity system, healthy eyes, prevent from cancer. There are number of pathogens, mainly fungi, which affect the guava crop besides few bacterial, algal and some physiological disorder. About 177 pathogens of which 167 are fungal 3 bacterial, 3 Algal, 3 Nematode and 1 apiphyte. These pathogen causes different type of diseases in guava plant at different stages from growing stage to maturity and fruiting time. Postharvest and fruit diseases are also important which cause serious losses. Fruit disease have also two types i.e.; field disease and postharvest, which develop during storage and transit. In the present communication some major diseases are describe with their symptom and disease management practices.
Diseases Symptoms, survival and spread, Favourable condition and their management:
Muhammad Abdul Rehman
Department of Horticulture, College of Agriculture, University of Sargodha
- In this diseases pathogen mostly attack young as well as old fruit bearing trees
- Symptoms mostly start with the on fall of monsoon appearance of light foliage with the loss of epinesty & turgity
- Roots of the plant also show rooting at the basel region
- Bark of the plant can be easily detachable from the cortex
- Light browned blotch can also be observed in vascular tissue
- Highly rainfall during Aug-Sep
- For long duration stagnation of water in guava field
- RH 76% are conducive with min to max temperature range (23-32°c)
Spread & Survival:
- Mostly spread by water in short distance
- Wild disease can also be predisposes through root injury
- We can manage the disease through proper sanitation.
- Through solarization of the soil.
- Burnt wilted plants and uprooted.
- Treat guava plant with 0.1% water soluble 8 quinolinol sulphate .it may provide protection to the plant for at least 1 year against wilt.
- Harsh pruning followed by a drench with 0.2% Bavistine or Benlate 4time in a year.
- In this disease mostly start of calyx disease of fruit during raining season
- The fruit near soil level coverall with dense foliage are mostly effected under high relative humidity
- With cotton like growth covered the inffected area which develops very fast as fruit matures. Pathogen can be able to cover the entire surface during the humid weather within a period of 3-4 days
- Fruit skin below the whitish cottony growth become a little soft, turn light brown to dark.
- Poorly drained soil and injured, high humidity, temperature from (28-32°c) favourable for the iniation of disease
- High soil moisture, cool, wet enviormental condition favourable to disease development
Spread and Survival:
- Greet no of sporangia and spores can be produce on the surface of diseased tissues principally by pathogen when temperature near to 25°c
- Spores can also be spread through infected plant material or soil by rain splashes
- Kothari (1968) recommended weekly spray of Bordeaux mixture and copper oxychloride.
- Management of dry rot through the use of fungicides like Ziride 0.3%.
- Seed treatment with Bavistin 3g/kg seed controls the disease effectly.
- The symptoms of this disease occur generally on green fruit and rarely on leave
- Effected fruit remain under develop, become hard, mummified malformed and drop. Sometime, small rusty brown angular spots appear on the leaves
- Crater like appearance is more observed on fruit then leaves
- Margin of lesion is elevated and a depressed area is observed in inside
- On start minute, circular, unbroken brown necrotic area appear in fruit advance stage of infection, Tears open the epidermis in a criminate manner
- Spores germination will be maximize at 30°c and can’t germinate below 15°c or above 40 with RH above 96%
Spread and survival:
- The pathogen is primary a wound parasite and avoid injury to fruits
- Spread disease can be controlled by 3 or 4 spray of 1%of Bordeaux mixture or lime sulphate at 15days interval.
- Naisk and cultives Sind show good resistance against this disease.
- Safeda and apple color verities are highly resistant against this disease.
- The homoeopathic drugs, potassium iodide and arsenic oxide completely inhibited spore germination.it can also inhibit the growth of pathogen.
Algal Leaf & fruits spots:
- In this disease immature guava leaves infect during early spring fall
- On the leaves minute, shallow brown lesion appear especially on the tip of leaf, areas or margins adjacent the mid vein and as the disease advance, lesion in large in diameter from 2-3mm
- The spot on the leave may vary from specks to big patches which may be scattered or crowded
- The lesion on immature fruit are nearly black, lesion get sunken & cracked frequently as fruit enlarge
- Lesion are smaller than leaf spot. They convert their color from darkish green to black
- By splashing water zoospore spread
- Disease can also spread through humid wet condition
Spread and survival:
- Air borne diseases mostly spread through air or rain splashes
- On the infected plant debris pathogen survive
- High sanitation required because algae can survive on fallen leaves during winter.
- Discard of infected debris carefully to prevent spread of disease.
- Prune plants to improve air circulation and excess of sunlight.
- Avoid wetting of leaves as much give water at the base of the plant.
- Apply Bordeaux mixture or copper based fungicides if plant seriously infected.
Stem canker & Dry fruit rot:
- In this disease pathogen mostly attack on main branches & stem on which it causes cracking of lesions
- In perfect stage diplodia netalensis dry fruit rot, Physalopara psidii causes stem canker
- On the infected stem through fungal perithesia small brown to black structure may develop
- Symptoms appear on the fruits as light brown spots generally at the stalk or calyx end
- The entire fruit becomes dark brown to black & mummified with 4 days
- Twing bearing infected fruits show dieback
- For disease development rainy season is favourable
- Humidity & wet condition required
Spread & Survival:
- Pathogen spread through air from plant to plant
- Patgogen survives beneath the bark of the plant & become active when condition are Favourable
- High sanitation required.
- Management of dry rot through the use of fungicides like Ziride
- Mostly recommended spray of Bordeaux mixture and copper oxychloride
Dieback and Anthracnose (Fruit rot)
- Fruit and leaf infection phase: During rainy season infection can be seen on unripe fruits pinhead spot are first seen which gradually enlarge.
- In dark brown color spots sunken, circular and have minute black stromata in the center of lesion, in moist weather produce creamy sporemasses.
- To form bigger lesion several spots coalesie.
- Infected area of unripe fruits become corky and in case of severe infection often develops cracks.
- Bud and flowers which are unopened are also effected and cause their shedding.
- The fungus cause necrotic lesion usually ashy gray and bear fruiting bodies at the tip or on the margin of the leaves.
- Die back phase: From the top of a branch; plant being to die backwards touxy shoots, leaves and fruits are readily attached. The greenish color of young growing tip change into dark brown and later to black necrotic areas extending backwards.
- Rain splashes, wind encourage the spore production and its dispersal around the canopy.
- Without canopy management closer planting
- Temperature between (10-35°c) with best of (24-28°c).
Spread and survival:
- Through infected foliage moment of plant material.
- By wind borne spores develop on dead leaves, twigs and mummified in the orchard infection spreads.
- Transportation of fruits through high disease prone area.
- Apply streptosporangium pseudovulgare before appearing symptoms.
- Spray copper oxychloride 50%WP @ 4gm/lit.
To conclude the above mentioned are some major diseases of guava. Guava is an important fruit crop of Pakistan and grown on large scale. It is an economic fruit that provides good income to the growers. It is a nutrient-dense super food and provides much health benefits to humans. But due to attack of diseases on this nutritious fruit crop as well as due to lack of knowledge among farmers about disease management annual losses are quiet high. So, we should have to give proper care to guava crop regarding disease management if we want to take benefits from this in future.