Disease of Chilli and their Management

 

Diseases of chilli and their management

1. Anthracnose/Fruit Rot/Die-back of Chilli-

       Causal organism: Colletotrichum capsici. 

Symptoms 

The disease occur in two forms; Die­back and Ripe fruit rot.

Die­back 

1. The disease causes necrosis of tender twigs from the tip to backward. The entire branch or  the entire top of the plant may wither away.

2. Numerous black dots (acervuli of fungus) are found scattered all over the necrotic surface  of the affected twigs.

3. Only the top or few side branches may be killed or in severe attacks the entire plant is  withered. Partially affected plants bear fruit which are few and low quality.

Ripe fruit rot 

1. Although red ripe fruits are frequently affected, anthracnose symptoms appear even on well  developed green fruits.

2.  Small black circular spots are appeared on the skin of the fruit and spread along the long  axis of the fruit and thus becoming more or less elliptical.

3. The spots are usually sunken with black margin. Badly diseased fruit turn straw colour  from normal color. Sunken spots are covered with pinkish mass of fungal spores.

4. The fruits with many spots drop off prematurely, resulting heavy loss in yield. Seeds are  also infected by this fungus.

Favourable condition  

▲ High temperature (28 C). 

▲ High relative humidity (92% or above). 

▲ Heavy and prolong dew deposition after rainy season.

Management/Control Measure 

A. Cultural control  

♦  Seeds should be collected from spotless fruits. 

♦  Disease crop debris should be collected and burnt.

B. Chemical control  

♦ Seed treatment with Vitavax­200, Brassical @ 2g/ kg of seed. 

♦ Spraying with Dithane­M 45 or Bavistin @ 0.2% solution, 3­4 times after 15 days interval   when fruit begin to ripe.

Mosaic of Chilli 

Causal organism: Tobacco mosaic virus.

Vector: Aphid (Aphis gossypii).

Symptoms 

1. The most characteristics symptom appearance of dark green and light green areas on the  leaf surface.

2.  Leaves are greatly in size and filamentous like.

3. The diseased plant produces less flower and fruits. The fruits are usually deformed and  rough in texture.

Transmission 

The virus is sap transmissible. It is also transmitted by aphid.

Management/Control Measure 

♦  Field sanitation.

♦  Roughing and cultural practices.

♦  Use of optimum doses of nitrogenous fertilizer in the field.

♦  Destruction of lateral alternate host.

♦  Spraying  with  Malathion/Metasistox/Diazinon/Sumithion  @  0.1%  solution  at  10  days  interval, starting from early stage of plant growth and stopped at least 20 days before plucking  of fruits.

Leaf Curl disease of Chilli 

Causal organism: Leaf curl virus.

Vector: White fly (Bamici tabaci).

Symptoms 

1. The leaf curl is characterized by severe stunting of the plants with downward rolling and  wrinkling of leaves.

2. Leaves become small in size; internodes are shortened, giving the plant as witches broom  appearance.

3. Leaves are pale yellow coloured.

4. Fruiting is stopped or fruits that formed are small and deformed. Alternate Hosts Tobacco, Tomato, Papaya etc.

ransmission 

The virus is not sap transmissible or not seed borne. It is transmitted by white fly.

Management/Control Measure 

♦  Field sanitation.

♦  Roughing and cultural practices.

♦  Use of optimum doses of nitrogenous fertilizer in the field.

♦  Destruction of lateral alternate host.

♦ Apply Carbofuran 3G @ 4­-5 Kg/acre in the mainfield to control sucking complex and  insect vectors selectively.

♦ If it is not possible spray the crop with systemic insecticides. Dimethoate 2 ml or Acephate  1g per litre of water.

♦  Collect and destroy infected virus plants as soon as they are noticed.

This is all about Diseases of chilli and their management. I think this discussion will help us to know the symptoms of chilli diseases and their management at the right time. Before going to management we should carefully identify the exact disease. Without proper identification, we can’t get the best result of management.

Plant Nematology and Entomology: Reniform nematode

Plant Nematology and Entomology: Reniform nematode:       Renifom Nematode ( Rotylenchulus reniformis, R.parvus ) : Kingdom                 Animalia Phylum                Nematoda Clas...

Reniform nematode

      Renifom Nematode (Rotylenchulus reniformis, R.parvus)

:Kingdom                 Animalia Phylum                Nematoda Class                 Secernentea Order                Tylenchida Family          Hoplolaimidae Genus             Rotylenchulus Species           R. reniformis

INTRODUCTION-

Reniform nematodes in the genus Rotylenchulus are semiendoparasitic (partially inside roots) species in which the females penetrate the root cortex, establish a permanent-feeding site in the stele region of the root and become sedentary or immobile. The anterior portion (head region) of the body remains embedded in the root whereas the posterior portion (tail region) protrudes from the root surface and swells during maturation. The term reniform refers to the kidney-shaped body of the mature female.There are ten species in the genus Rotylenchulus. Rotylenchulus reniformis is the most economically important species (Robinson 1997 ) and is called the reniform nematode

DISTRIBUTION AND HOST RANGE-

Rotylenchulus reniformis is largely distributed in tropical, subtropical and warm temperate zones in South America, North America, the Caribbean Basin, Africa, southern Europe, the Middle East, Asia, Australia, and the Pacific (Ayala and Ramirez 1964). It was first found on cowpea roots in Hawaii (Linford and Oliveira 1940), and first reported as a parasite of cotton in Georgia and of tomato in Florida. Today, it is found throughout the southern United States.In Florida, reniform nematodes are especially common in the southernmost counties, Miami-Dade and Monroe, where Rockdale soils favor reniform nematode population development. Reniform nematodes are also common in the northwestern counties of Florida (Panhandle region), from Jefferson to Santa Rosa, especially in the cotton production area with heavier soils such as sandy loam, sandy clay and clay loam (Kinloch and Sprenkel 1994).At least 314 plant species can act as hosts to reniform nematodes. Among them, cotton, cowpea, soybean, pineapple, tea and various vegetables are the most common hosts. A list of hosts and nonhosts for reniform nematode was recently published by Robinson et al. (1997). Many weed and ornamental hosts to reniform nematode in Florida have been reported by Inserra et al. (1989, 1994a, b). In southern Florida, sweet potato, papaya, and several edible aroids are excellent hosts to reniform nematodes. The reniform nematode was also associated with several kinds of tropical fruit trees (McSorley 1980; McSorley et al. 1982, 1983).

LIFE CYCLE-

Eggs hatch one to two weeks after being laid. The first-stage juvenile molts within the egg, producing the second-stage juvenile (J2) that emerges from the egg. The infective stage is reached one to two weeks after hatching. Once root penetration occurs, one or two more weeks are required for females to reach maturity. The male, which remains outside of the root, can inseminate the female before female gonad maturation. Sperms are stored in the spermatheca. Soon after female gonad maturation, the eggs are fertilized with sperm, and about 60 to 200 eggs are deposited into a gelatinous matrix. Typically, there is an equal number of females and males in a population. Some populations of reniform nematodes reproduce parthenogenetically (egg production without fertilization).The life cycle of this nematode is usually shorter than three weeks, but depends on soil temperature. However, it can survive at least two years in the absence of a host in dry soil through anhydrobiosis, a survival mechanism that allows the nematode to enter an ametabolic state and live without water for extended periods of time (Radewald and Takeshita 1964).

MANAGEMENT-

No cotton or pineapple cultivars are resistant to reniform nematodes. However, cotton breeding lines tolerant of reniform nematodes have been developed. Soybean cultivars Peking, Dyer, Custer, and Pickett are highly resistant to reniform nematode (Rebois et al. 1970). Certain tomato cultivars are resistant to this nematode (Balsubramanian and Ramakrishnan 1983).rop rotation with resistant or immune plant species is recommended. These include mustard (Brassica nigra), oats, rhodesgrass (Chloris gayana), onion, sugarcane, and sun hemp (Crotalaria juncea) (Robinson et al. 1997, Caswell et al. 1991). Pineapple is rotated with sugarcane or pagolagrass in Puerto Rico (Roman 1964). Sorghum, maize and reniform nematode resistant soybeans are recommended as rotation crops for cotton (Starr and Page 1990).Currently, Hawaiian pineapple plantations manage plant-parasitic nematodes by fallowing after pineapple for six to 12 months, then fumigating before planting, and applying postplant non-fumigant nematicides (Apt and Caswell 1988). However, dry fallow may be ineffective as a means of control since this nematode can enter into anhydrobiosis in slowly drying soils and revives when environmental conditions are favorable (Apt 1976). Apt suggested that moist fallow would be more effective as a means of control. Fallow with weeds is also unfavorable because many weeds could be hosts to reniform nematodes.Areas free of reniform nematode impose regulation against this nematode. Chile and Switzerland are among the countries that have quarantine against reniform nematode. The United States, Arizona, California and New Mexico restrict possible importation of reniform nematode to protect their cotton industries. Due to this regulation, the ornamental industries of southern Florida and Hawaii must undergo extensive sanitation of their plants and facilities to be sure they are not exporting plants contaminated with reniform nematode.

http://entnemdept.ufl.edu/creatures/nematode/r_reniformis.htm

Plant Nematology and Entomology: Life cycle of potato cyst nematode

Plant Nematology and Entomology: Life cycle of potato cyst nematode: Species of Globodera have several pathogenic types and occur over much of the world. They have been identified in at least 58 countr...

Life cycle of potato cyst nematode

Species of Globodera have several pathogenic types and occur over much of the world. They have been identified in at least 58 countries. The potato cyst nematode of major concern in North America is G. rostochiensis or the golden cyst nematode which is characterized by gold-colored females. It is under strict quarantine regulations in North America. A related species, identified in 2006 in a field in Idaho, is G. pallida or the pale cyst nematode. Females of this species are characterized as being white or creamy colored.

LIFE CYCLE-

Eggs of G. rostochiensis hatch due to a stimulant released by potato roots into the soil. At first, juveniles develop within the female. The female gradually turns from white to creamy yellow to gold, and upon death a dark brown cyst forms. From the cyst, juveniles emerge and enter the root system in which they feed. After cycling through three to four juvenile stages, the male leaves the root with a wormlike appearance. Females are spherical; they grow and rupture through the root, protruding their bodies outwardly. Males mate with the protruding female. The time from eggs to adults is between 38 and 48 days depending on temperature and there is one generation per season. Population increase between generations is 12 to 35 fold.

SYMPTOMS AND DAMAGE-

Vine symptoms due to infection are similar to that of plant under water stress. There is chlorosis, then wilt and finally early death. Potato roots have small cysts that are dark brown and encapsulate 200 to 500 eggs. Cysts are the bodies of dead females that retain viable eggs. The cysts can persist in the soil for 20 years. Heavy infestations can result in total crop loss of potato. G. rostochiensis has been reported to cause synergistic losses with Rhizoctonia solani and Verticillium dahliae.

MANAGEMENT-

The primary method of managing the golden cyst nematode is through strict quarantine regulations. This nematode has been under these regulations on Long Island, NY, and recently the nematode has been identified in Quebec and Alberta, Canada. G. rostochiensis spreads readily through the transport of infected soil on seed tubers, equipment and containers. Planting infected seed tubers will spread the nematode into the soil. Once the nematode is established in the soil, it is nearly impossible to eradicate. Some varietal resistance is known due to a gene bred into a few commercial varieties but is effective only against some pathogenic types of G. rostochiensis and G. pallida. The host range of the golden nematode is limited to tomato, eggplant and a few Solanaceous weeds. Crop rotation is effective and the rotation interval depends on the degree of infestation. Fumigation has been used for quick and drastic reduction in populations. Currently in the U.S.A. there is no non-fumigant nematicide available. Biological controls have not shown much success. Management practices for controlling an infected field requires an integrated approach using various methods over many years. The best approach is not to plant any seed tubers from an infected field or move any equipment off infected fields or storage onto a clean field or into clean storage. Observe quarantine procedures.

https://cropwatch.unl.edu/potato/potato_cyst

Dagger Nematode

                    Dagger Nematode (Xiphinema spp.)

             

INTODUCTION

Nematodes of the genus Xiphinema, commonly called dagger nematodes, parasitize plants. Many of these nematodes, the majority of them belonging to the Xiphinema americanum-group, can transfer viruses to plants during feeding (Taylor and Brown 1997, Gozel et al. 2006). Dagger nematodes can cause economic damage and death of host crops through feeding on the roots and also by spreading viral mosaic and wilting diseases (van Zyl et al. 2012, Jones et al. 2013). From a practical standpoint, it is a major challenge to control viral diseases in susceptible crops, partly because of a lack of resistant cultivars that should reduce populations of the virus vectors, Xiphinema spp. However, field studies have shown that some control measures, such as biofumigation and rotation of crops, targeting reduction in population of virus vectors, dagger nematodes, can be effective to some extent (Evans et al. 2007). Field surveys are required in order to implement appropriate and timely nematode management decisions that will minimize crop losses.

DISTRIBUTION AND HOSTS

Species of the genus Xiphinema are widely distributed in both temperate and tropical areas. They occur in South America, North America, Europe, Asia, Australia, New Zealand and Africa. In the U.S., Xiphinema spp. are classified as moderate pests on turfgrasses in landscapes in Massachusetts, Arkansas, California, the Carolinas (Robbins 1993, Ye et al. 2012) and Florida. Five species belonging to the Xiphinema americanum-group have been detected on tomato, grape, oak, sea grape, pines, hackberry, Brazilian pepper and citrus in Florida and Morocco (Gozel et al. 2006, Mokrini et al. 2014). Other hosts include Sudangrass (sorghum), cotton, pearl millet, turfgrasses (Wick 2012, Ye et al. 2012), legumes, sugarcane, chili pepper, banana, sugar beet, corn (Shurtleff 1980), weeds, cassava (Rosa et al. 2014) and many more.

LIFE CYCLE 

Dagger nematodes have six life cycle stages. Parthenogenesis, a form of reproduction that does not require males, is common in many, but not all species. Females lay eggs in soil. The life cycle of a dagger nematode is similar to other ectoparasitic, vermiform nematodes. Juveniles hatch from eggs and molt four times, increasing in size with each molt until they become adults. As vector-capable juveniles feed on virus-infected plants and mature into adults, they can acquire plant pathogenic viruses, commonly known as nepoviruses (nematode polyhedral viruses). The viruses form a lining in the pharynx-stylet tube and are injected into root tissues during feeding (Lamberti and Roca 1987).Dagger nematodes are ectoparasitic, which means that all stages, except eggs, attack and feed on the roots of the host plants. The nematode inserts its long stylet deep into the root while the body remains outside the root, in the soil. The stylet punctures cell walls as it penetrates plant tissues. During feeding, enzymes are secreted to digest plant cell contents. Plant parasitic nematodes produce enzymes such as cellulases, pectinases, hemi-cellulases, and chitinases, which are similar to those produced by bacteria and fungi (Jones et al. 2005, 2013), that digest and destroy root cells resulting in malformed root tissues . Root cells eventually collapse due to feeding.Species of Xiphinema are sensitive to changes in soil temperature and moisture (Malek 1969) and will migrate vertically away from desiccating conditions in topsoil; most dagger nematodes can live and survive deep in soil (Feil et al. 1997)

SYMPTOMS

The damage dagger nematodes cause to root systems is similar to that of other plant ectoparasitic nematodes. The feeding at the meristematic root-tips destroys root cells (Figure 3) and reduces root volume. Terminal galling of roots of woody plants is common (Figure 4). The above-ground effects of damaged roots are stunted growth of crops and patchy fields.Dagger nematodes transmit numerous viruses to plants. Cherry rasp leaf virus, Tomato ringspot virus, and Tobacco ringspot virus are some of the viruses transmitted by dagger nematodes during feeding. According to van Zyl et al. 2012, bermudagrass is a potential reservoir for GFLV (Grapevine fanleaf virus), which is transmitted by dagger nematodes.

MANAGEMENT

Some of the major management strategies include the following:

1. Deep plouging and solarization
2. Crop rotation: Rotation with legumes, soybean, sunflower and paddy is effective rotation with trap/antagonistic crop like sunhemp (Crololaria juncea), marigold (Tague app.), mustard (Brassica rapa), gingelly etc. can minimize the nematode population in soil.
3. Chemical: Aldicarb, carbofuron, ethoprop have been reported to be effective agains: sugarcane nematode at varied sosages. However, 1.5 kg a.i/ha seems to be moderate dose.

Morphology and Anatomy of Nematodes