Bitter Pit in Apple: Calcium Deficiency and Foliar Calcium Feeding

Apple is the most widespread fruit crop grown in Ukraine (almost 70% of orchard area). Its fruits can keep commercial and consumer quality indicators for a long time. Fresh apples contain minerals, vitamins, easily digestible sugars, organic acids, and pectin and aromatic compounds valuable for the human body. The biochemical composition of fruits depends largely on the biological features of the variety, climatic and weather conditions, soils and the system of their management. The physiological disease of apples, bitter pit, substantially worsens fruit quality and storability, which leads to losses.

Bitter pit (subcutaneous spotting) shows on fruits still on the trees and occurs, first of all, because of calcium shortage. It shows on fruits as greenish «sunken» spots. During storage the spots turn brown, and the flesh in the pits becomes brown and bitter to taste. Development of the disease is promoted by excessive pruning of trees and premature or very late harvesting. The disease is pronounced in years with high humidity in spring and summer. High temperatures and low relative humidity in storage also provoke the disease.

The literature shows that bitter pit practically does not appear if the calcium content in fruits, calculated as oxide, is above 1.9% for the period late July to early August.

To control the disease, acidic soils are limed and calcium foliar feeding is carried out during the growing season.

As research shows, calcium deficiency in fruits sets in at the start of fruit formation. It has been established that the maximum calcium intake into apple fruits occurs during the six weeks after the end of flowering. Calcium ions move very slowly in apple trees, so the first feeding should be done as early as possible, right after flowering. To achieve a positive effect, 2–4 feedings at intervals of 10–14 days are desirable.

Which fertilizers are best suited for foliar calcium feeding? Chelated ones. Much has been written on this subject, so in our opinion there is no need to carry out additional research with fertilizers in the form of simple salts or organo-mineral complexes. Experience shows that using calcium salts, especially chlorides, can have negative consequences, particularly in hot weather. This fertilizer can cause burns on leaves and fruits and in the worst case leads to heavy leaf drop, which adversely affects the yield of both the current and the next year.

Since 2015 « ECOORGANIC» has offered the special fertilizer ECOLINE Calcium-Boron (Chelate) (N – 2.1%, CaO – 4.2%, B – 0.7%). This combined concentrated microfertilizer was developed to eliminate calcium and boron deficiency and for foliar feeding of crops especially demanding in calcium and boron supply (sugar beet, sunflower, rapeseed, vegetable and fruit crops). It contains calcium in chelate form and boron as an organo-mineral complex with monoethanolamine. The microfertilizer is suitable for use together with crop protection products and ensures plant stress and cold resistance.

ECOLINE Calcium-Boron(Chelate) is intended for foliar feeding of cereals, industrial, vegetable and fruit crops. This fertilizer provides:

• regulation of boron nutrition in the critical phases of plant development;
• improved functioning of the root system;
• regulation of the flowering process;
• resistance to stress factors;
• increased plant productivity;
• improved harvest quality.

Dose and frequency of application:

The fertilizer combines well in tank mixes with the vast majority of crop protection products without lowering their effectiveness.