Carnation flower harvesting and post harvest handling

Harvesting of Carnation flowers depend on the size of bud and growth of petals. Standard Carnations are harvested when they are half open and the first petal lays horizontally or at paint brush stage. Spray types are harvested when at least two flowers have opened and remaining buds are showing colour.

Flowers are best harvested during the morning hours when they are turgid. Keep the flowers in fresh, clean water or preservative solution for about 4-6 hours and then place in cold store at 4-6 o c. Do not cut the flowers too deeply as this may adversely affect production during the next season.

Grading of flowers is based on stem length, flower diameter and physical conditions like stem sturdiness, freedom from pest, diseases and physiological abnormality. They are grouped in bundles of 20 and kept at 0-2oc for 12-14 hours and then packed in corrugated cardboard boxes.

Vase life and storability of flowers can be increased by placing flowers in 10 % sucrose + 1 mm STS for 8-10 hours. Carnation flowers are very sensitive to ethylene gas. Now day’s anti-ethylene compound 1-MCP (1- methyl cyclopropene) is being used as floral preservative.

Carnations - Insect, pest, Disease and Physiological disorders:

Insect Control: The most common insects attacking the Carnation are aphids, thrips and red spider mite.

Aphids (Myzus persicae) suck the sap from new shoots and leaves. They leave sticky substances on leaves and flower buds. Foliar spray of Rogor (2ml/ litre) or 0.25% demeton-methyl found to be effective.

Thrips (Thrips tabaci) also suck the sap of leaves and turn them yellow and patchy. Under severe attack they also cause streaks and spots on flowers and stems. Pink and red cultivars are more susceptible. Malathion or Rogor (dimethoate) or dichlorovos, all at 0.1-0.2 % gave the best control of Carnation thrips.

Red spider mite (Tetranychus urticae) is the most serious pest of Carnation. They are very small red coloured insects mostly feeding on the lower sides of leaf and suck the sap. Leaves become yellow with dusty coating and fine webs on their surface.

The most effective chemical against mite is propargite, which is effective against adults, eggs and larvae.

Disease: Carnations are attacked by a number of diseases like Fusarium, Alternaria, Bacterial wilt, Rust, Rhizoctonia, and stem rot.

Fusarium wilt caused by Fusarium oxysporum f. Sp.dianthi, also known as vascular wilt, is one of the most serious diseases of Carnation. It is soil born, invades the plant through roots and damages stem tissues resulting in wilting and death of plant. Soil fumigation and treating the beds with Bavistin (0.1%) and Dithan M-45 (0.1%) at regular interval is effective.

Leaf spot caused by Alternaria dianthi is another serious air-born disease. It is characterized by grayish- brown spots on leaf and stem. High temperature and humidity favours the disease spread. Removal of infected leaves and foliar spray of Mancozeb (Dithan M-45) @0.2% or Bavistin 0.1% controls this disease.

Bacterial wilt (Pseudomonas caryophylli) is prevalent at high temperatures. It is soil born disease attacking older plants. Production of grayish green foliage, rotting of roots and deep longitudinal cracks on internodes are the major symptoms. Soil sterilization, treating the plant material with 0.01 % streptocycline and using disease free plants helps in reducing the incidence.

Physiological disorder: Splitting of calyx is a serious disorder affecting the quality of Carnations. In this disorder sepals beneath the flower are unable to form a cylindrical calyx tube which supports the base of the petals. As the bud opens and size of petals increases, calyx may split down either half or completely because it is unable to contain the load of extra petals. The primary cause of calyx splitting is unknown but may be due to genetical, environmental like low temperature & fluctuation in day night temperature and nutritional like low level of nitrogen and boron. The problem of calyx splitting can be reduced by placing of rubber band around the calyx of the flower bud, when they have just started opening. Increased level of potassium & boron, choosing the cultivars which are less prone to splitting and uniformity in day night temperature can reduce the problem.