Citrus canker

Host: Citrus fruits including orange, lemon, lime, calamondin, etc.
Pathogens: Xanthomonas axonopodis pv. citri

Distribution

Citrus canker is thought to be originated in the region of South Asia-India. The disease is now of global concern and reported from India, Bangladesh, Japan, Middle-East, South and Central Africa, Pacific Islands, Florida and some parts of South America. Australia is free from citrus canker since 2009[1].

Symptoms

Lemon leaf showing canker
Infected leaf of lemon showing canker (Photograph was provided by Mr. Pradeep Singh)


Citrus canker
Lemon fruit showing canker (samples were provided by Shivani from her kitchen garden)

Citrus canker is recognized by warty, rusty brown spots (cankers) on the leaves, twigs and fruits. The spots at first appear as small, slightly raised, round, light green colored. Later, spots become grayish white, rupture, and appear corky with brown, sunken centers. The margins of the lesions are often surrounded by a yellowish halo. Infection of fruits can cause premature drops. The infected fruits loss it shiny color and marketability is reduced. Citrus canker is favored in the regions of hot and wet climates.


Pathogen

The causal organism of citrus canker, Xanthomonas axonopodis pv. citri is gram negative, rod-shaped, monotrichous bacterium. It overseasons in the leaves, twigs and fruits lesions. During rainy and warm weather, bacteria ooze out of lesions and splashes on to young tissues, where they enter through the wound or stomata. In older tissues, however, bacteria enter only through the wounds.

Control measures

  • In the areas, where the disease in not endemic, quarantine measures should be implemented.
  • The disease should be controlled through the Integrated Pest Management (IPM).
  • Exclusion should be adapted to check the import of diseased materials.
  • Once new infection in an area is reported, it should immediately be eradicated to the check the further spread.
  • As the disease is spread by mechanical means, the personals and equipment used in the citrus orchards should be decontaminated.
  • Infection can be prevented by removing the infected branches and spraying the plants with Bordeaux mixture (5:5:50).
  • In infected plants antibiotic streptocyclin @ 1 g in 45 liters should be sprayed 3-4 times.
  • The disease can be controlled by spraying suspension of neem cake @ 1 kg in 20 liters of water.

References




Leaf eater of lemon

Host: Lemon (Citrus sp.)
Pathogens: Papilio demoleus L. (Citrus butterfly/Lemon butterfly)

Distribution

Citrus butterfly (Papilio demoleus) belongs to the Papilionidae of Lepidoptera. It is one of the serious pests of the lemon. Citrus butterflies are distributed throughout the tropical and subtropical countries of Middle East, Southern and Southeast Asia (Minh et al., 2015). In India, Citrus butterfly is of common occurrence in Citrus orchards, nurseries and in kitchen gardens.

Symptoms

Citrus butterfly
Eaten leaf of lemon

Caterpillars of the butterfly (larva and pupa) feed on the young as well as mature leaves and flowers of citrus. Larva and Pupa eat-up whole the leaf including lamina and midrib (author’s personal observation). Beside the citrus, larvae as well as pupae also feed upon the curry leaf. Single larva can up to 2-4 leaves of lemon in one week.



Control measures

  • As a part of IDM (Integrated Disease and Pest Management), control measures should not be applied until and unless the population of caterpillars goes beyond the threshold level.
  • In mild cases, leaves along with caterpillars should be hand-picked and removed.
  • In severe cases Monocrotophos @ 1.5 ml per liter of water should be sprayed on leaves.

Reference

  • Minh, H.G., Giang, H.T.T. and Trang, H.T.Q., 2015. Studies on some aspects of the biology and ecology of Citrus butterfly Papilio demoleus (Papilionidae: Lepidoptera) on citrus in Vietnam. Journal of Tropical Asian Entomology, 4(1), pp.20-27

Content first created on 15-09-2020
last updated on 24-11-2021