Potato is the fourth most important crop worldwide. Potato is a staple food for more than a billion people worldwide. Potato is very nutritious tuber vegetable and a rich source of starch, vitamin C and B and minerals.
It contains about 20.6% carbohydrates, 2.1% protein, 0.3% fat, 1.1% crude fiber and 0.9% ash. Because of its nutritional values, the potato is a well-balanced diet for developing countries.
Many of weeds, pests, and diseases attacks on potato crop and leads to major yield loses. There is a brief introduction to potato weeds, pests, diseases, and their management.
Management of potato Pests
Jassid is sap sucking small pest that feeds on leaves. The nymphs are of green color and grow two wings as it turns into an adult with black spots on the wings. Adults are quick to move from leaf to leaf.
The early damage is yellowing of the leaves. As the infestation advances, yellowing is followed by crinkling and upward curling of leaf margins and leaves start to fall. Severe damage leads in growth stunting of the plant. The pest also contributes to disease transmission.
- Weeding (uprooting of weeds).
- Chemical insecticide spray (Confidor ultra 250 ml per acre).
Whitefly is another sap feeder bug just like jassids. Adults are very small flies with white powdery wings. Females lay eggs directly on the undersides of plant leaves. The eggs hatch into tiny nymphs that develop into pupae before emerging as winged adults.
As a sap feeder whitefly reduces overall vigor of potato plants. In severe infestation, plants lose leaves prematurely. They also produce sugary sticky (honeydew) material which attracts and facilitate fungal colonization. Along with all other damages, whiteflies are vectors that transmit many plant viruses.
- Removal of host plants (weeds)
- Chemical insecticide spray (Mospylan 125 g per acre).
Cutworms are the larvae of moths that cause actual damage. The adult moths are of brown colour with stripped winges. Female lay eggs in dry soil. The larvae capable of overwintering in the soil or a woodpile.
Cutworm chew through plant stems at the base. They primarily feed on roots and foliage of young plants, and will even cut off the plant from underneath the soil. They attack young shoots which leads to the death of the plant results in huge yield loss.
- Use of Light Traps for adult cutworms.
- Flood irrigation at proper intervals.
- Hand picking of the cutworm larvae at night.
- Chemical insecticide spray (Bifenthrin 200 ml or Endosulfan 800 ml per acre).
Management of potato Diseases
Early Blight of potato
Fungal pathogen (Alternaria solani) causes early blight disease in potato. It infects the stem and leaves of potatoes. Humid weather conditions favor the pathogen and spread the disease.
Concentric target board like spots developed on the stem and leaves. Initially, infection occurs on older leaves. Infected leaves turn into yellow color and result into premature defoliation of potato plant. On tuber, these lesions are of dark color and presses into the potato surface causing the flesh turning dry and brown.
- Field sanitation (to reduce the inoculum).
- Use of disease-free Seeds for cultivat
- Use of resistant variety.
- Chemical fungicide sprays (Difenconazole 125 ml per acre).
Late Blight of potato
Potato late blight disease caused the great Irish famine that claimed more than one million lives. Potato late blight is caused by Phytophthora infestans. The pathogen is favored by moist, cool environmental conditions.
Blackish water-soaked lesions appear on the surface of leaves and stems. Whitish sporulation can be seen around the margin of the lesions. In case of severe attack, the bad odor can be smelled from the field. Lesions may also be produced on the infected tubers.
- Weeding & field sanitation.
- Resistant varieties.
- Crop rotation and use of healthy seed.
- Chemical fungicide sprays(Ridomil gold, Metalaxyl, Mancozeb at initial stages of symptoms).
Rhizoctonia of potato
Rhizoctonia disease of potato is also known as black canker. This disease is caused by fungus Rhizoctonuia Solani Cool temperature, high soil moisture is favorite for development of Rhizoctonia disease of potato.
This fungus is soil-borne and mostly attacks on new emerging plants. It produces lesions of reddish brown to black color on the stem and roots. These lesions start to grow upward as the stem grows and stops the photosynthesis, ultimately cut off the stems. Sclerotia appear on the surface of potato tubers known as black bodies.
- Use of clean potato seeds reduces the risk of disease.
- Crop rotation practices should be followed to reduce the soil inoculums.
- Seed treatment with chemical fungicides (Difenconazole 125 ml + Ridomil gold 250 g for 5 min per acre seed).
Blackleg and Bacterial soft rot
Erwinia carotovora is a bacterial pathogen for this disease. The bacteria mainly attack the fleshy organs of their host. Higher temperature and high humidity are ideal growing conditions for the bacteria.
The early attack may cause non-emergence or stunted, pale-green to yellow foliage upward leaf rolls. Stems easily pulled out. The late attack may cause the collapse of fully developed haulm. Distinguished from leaf roll and stem canker by the presence of blackened stems at ground level or blackened soft pith in dissected stems. Infected tuber becomes very soft and turns into creamy to tan color.
- Good sanitation practices.
- The temperature of the store should be kept low by using an adequate ventilation system.
- The use of hot water treatment on seed tubers may reduce inoculum level.
Management of Potato weeds
In potato, weeds cause 20 to 30% yield losses. Potato crop cultivated in September and October weeds which is suitable for Itsit, Deela, Wild oat, Laheli, Madhana grass weeds whereas potato cultivated in November and December Philaris minor(Sitti booti) and Wild oat are major weeds.
Weeds can be controlled by adopting good cultural practices as well as by using chemical spray against weeds. In case of deela weed and other seasonal weeds use of S-metolachlor or Dewalgold are the best weedicides. In case of only seasonal weeds and Parthenium weed, Pendimethalin or metribuzin are best weedicides.
A preventive spray of weedicides like S-metolachlor or Dewalgold 200ml per acre or Pendimethalin 33% 1200 ml per acre is mostly recommended as pre-emergence weedicides. But in case of curative spray Paraquat 1 L per acre can be used as post emergence weedicide.
HEFZA AFZAL : Agriculture Officer( PP) pest warning and Quality control of pesticides