Ky IPM Home

Apple IPM Home

Apple Scouting Manual

Consumer Information

Grower Information

IPM Final Reports

Animal Science



Plant Pathology

Kentucky Apple Integrated Crop Management Manual


For these measurements, use the trees that have the pheromone traps.

One time - Record the bloom dates, i.e., first bloom (10% blooms open), and full bloom (70% blooms open).

Weekly - If weed control other than mowing is used, record the method, date of treatment and rate, the density, 0-5 (1 = sparse, 5 = full coverage of weed) height (inches) and major weed species in the treated area. Weeds under the tree canopy compete with the tree for water and nutrients and increase disease problems because of higher humidity.

Weekly (From bloom until 5 weeks after bloom) - Measure, mark and tag a 3 foot terminal on 4 separate limbs on each tree. The 3 foot terminal is measured from the bottom of the previous season's terminal growth down the limb. It does not include any side branches. Count the number of buds, blooms and/or fruit on each tree, divide by 12 to determine the number of fruit per foot of terminal growth. Before counting, look at each pedicel to see if it is light brown. A light tap on the blossom or fruit will help determine if the fruit structure is alive since dead and dying fruit structures will abscise. Most commercial cultivars crop annually with adequately sized fruit when fruit spacing averages 6"-8" apart on the fruit bearing terminals.

Weekly (Starting 3 weeks before the anticipated harvest) - Select at random 2 fruit per sample tree, record the cultivar, then determine the following indices of maturity: skin color (striped or solid), seed color, soluble solids and fruit pressure. Taste, dark brown seeds, skin color, pressure test in the 16-19 lb. range, Starch-Iodine Test and days from bloom to picking are used to determine optimum time of harvest. The following table shows the anticipated days from bloom to harvest for a number of cultivars:

Yellow Transparent70-100
Lodi 75- 95
Golden Delicious, Jonathan140-145
Mollies Delicious, Empire140-145
Grimes Golder, Red Delicious140-150
York Imperial155-175
Rome, Winesap160-165
Granny Smith180-210

Leaf Analysis
Leaf analysis (foliar analysis) is a more reliable indicator of a tree's nutritional status than soil analysis. Foliar analysis kits can be obtained from your County Extension Office. County Extension Offices can request the kits from Dr. Bill Thom, Department of Agronomy, Ag. Sci. Bldg. N., University of Kentucky, Lexington, KY 40546.

Follow the procedure for taking leaf samples outlined below. Correct sampling techniques are essential for reliable results.

Take a soil sample from the same general area that each leaf sample is taken. Sample the upper 6 to 8 inches of soil under the tree's drip line. See AGR-16 for information regarding soil sampling. Problem blocks should be sampled annually until corrected. Normal blocks are sampled every 3-5 years.

Plant analysis has 2 main applications: (1) to confirm a suspected nutrient deficiency indicated by visual symptoms, and (2) to monitor the plant nutrient element status to determine whether each tested nutrient is sufficient for optimum yield.

Ideally, monitoring the nutrient status of an orchard with a regular foliar analysis program helps maintain high quality production while minimizing nutrient deficiency problems. Regular sampling lets the grower detect upward or downward trends in a nutrient's concentration that could lead to a deficiency or imbalance.

WHEN TO SAMPLE: The concentration of any nutrient varies during the growing season. As the leaves become more mature, a period of relatively stable nutrient composition occurs. This is the time to collect leaf samples because differences in analytical values reflect differences in the nutrient status of the tree and not differences due to time. The optimum time for collecting leaf samples in Kentucky is the last two weeks in July.

When a suspected nutrient deficiency or excess exists, take samples as soon as visual symptoms appear. Take samples both from trees where the suspected nutrient problem exists and from "normal" trees of the same variety, but keep the samples separate. The closer the "affected" and "normal" trees are to each other in the orchard, the better the comparisons will be. Do Not Include Dead Or Severely Affected Leaves In The Sample.

HOW TO SAMPLE: To increase the reliability of leaf analysis results, take leaves from different trees but from the same areas on the trees. Pull leaves from all sides of the trees in a band 4 to 6 feet above ground.

Collect leaves from the middle of the current season's shoot growth or if there is little or no shoot growth, collect spur leaves. Do not include the oldest or youngest leaves on a shoot. For one sample, collect 4 to 8 leaves per tree from 25 trees of the same cultivar and apparent condition.

Avoid selecting dusty or soil-covered leaves if possible. Under normal conditions rainfall is frequent enough to keep leaves fairly clean. If necessary, brush or wipe with a damp cloth to remove dust. If leaves are covered with spray materials, wash quickly in a mild detergent solution and rinse quickly in water. Don't let samples remain in the wash or rinse water very long.

Air-dry the samples in a paper bag before mailing. Once the sample has dried, it should be mailed directly to the University of Georgia in the self-addressed kit obtained from your County Extension Office. Samples will be analyzed only if an appropriate check for the analysis costs are included. Your check should be made payable to the University of Georgia. The charge for this service is $17 per sample and includes spectrographic analysis for several elements plus total nitrogen. Analysis results will be returned to the University of Kentucky Horticulture Department for interpretation and recommendation.

Fruit Maturity Analysis

Pressure testing is one means to determine fruit maturity. A suitable sample will consist of 10 fruit selected at random from a number of trees within a block and from various locations within the trees. Two measurements should be taken on each fruit, one on the blush side and the other on the opposite side, at the midpoint of each side, after removing a -3/4" diameter disc of peel. (See Appendix 5.)

Use a 7/16 (large) plunger. Hold the fruit firmly in the left hand while holding the fruit pressure-tester between the thumb and forefinger in the palm of the right hand. Set the indicator hand to zero and then place the plunger against the fruit and press with increasing strength until the plunger tip penetrates into the pulp up to the notch.

Slow penetration of the plunger is essential. Sharp movements and sudden pressure application may impair your measurements. In order to avoid mistakes and to assure slow penetration of the plunger. Hold the apple firmly and keep your arm rigid. You may want to hold the apple on a table for this.

The starch-iodine test is used to determine apple maturity and harvest dates. As an apple matures and ripens it converts its stored reserves of starch to sugars. If a freshly cut fruit is stained with an iodine solution, the distribution and amount of starch become readily apparent. Sugars do not show up in the starch-iodine test. By monitoring the reduction in the distribution and amount of starch a determination of when apples are at the correct stage of maturity for harvesting can be made.

The pattern of starch accumulation and loss varies between seasons and apple cultivars. Consequently starch-iodine staining patterns for a number of the most common apple cultivars have been included. Note that the pattern of starch loss begins in the core area and proceeds toward the peel. It is normally necessary to monitor starch loss using this test on a weekly basis beginning three weeks prior to normal harvest. Fruit for testing should be freshly harvested as described under the section on pressure testing fruit and be at room temperature. You can use the same fruits that were used for pressure testing if they have not been refrigerated.

Make the 1.0% potassium iodide, 0.1% iodine solution by dissolving 1 level teaspoon of potassium iodide crystals (10 grams) in 1/8 cup of clean water in a 1-quart container. Swirl the liquid in the container to dissolve the crystals. Next add 1/4 teaspoon of iodine(2.5 grams), and swirl the liquid until the iodine dissolves. Then dilute the solution with clean water to make one quart.

Since this solution is sensitive to light, it should be stored in a dark brown bottle or the jar should be kept covered with aluminum foil. Make a fresh solution up at the beginning of each season. These chemicals may be available at your local drug store. However, you may need a prescription to purchase them. Contact your County Extension agent if you have problems obtaining these chemicals. Use 10 to 20 freshly harvested apples that are at room temperature for the test. Pour iodine solution at room temperature into the bottom of a shallow glass pan to a depth of 1/4 inch. Cut each apple in half across its equator. Soak the cut surface of the stem end of the apple in the iodine solution for about one minute. The stem makes a good handle. Next, remove the apple halves and place them cut surface up to drain. Within five minutes the starch on the cut surfaces will have turned a dark blue-black color.

Score each fruit by comparing it with the appropriate starch- iodine staining pattern chart and calculate the average score for each lot of apples.

Apples will exhibit starch-iodine staining scores ranging from 1 to 9 over the several week long harvest season. The appropriate score for harvesting depends on when the apples will be marketed and the use for which they are intended. Fruit intended for the fresh market or for processing are usually harvested when more starch has disappeared than fruit for long term storage.

In general, an average test score of 1, 2, or 3 indicates that the fruit are too immature for harvesting. These fruit will not develop good eating quality and are more prone to scald and other disorders in storage. Fruit with an average rating of 4 are suitable for long term storage of up to three months. An average rating of 5 or 6 indicates that fruit are ready for fresh market. While ratings of 7, 8, or 9 indicate that fruit are over mature and may have poor eating quality or may not store well.

When these tests are used with other maturity tests a reasonably good indication of fruit maturity can be obtained.

WARNING: Iodine is very poisonous. The iodine solution should be properly labeled and kept away from children and pets. Apples used in the test should not be eaten or used in composting. In case of ingestion of either iodine, or iodine treated apples, induce vomiting and quickly consult a physician.

The Starch-Iodine staining technique was adapted for use in Kentucky from publications originally produced by the North Carolina Agricultural Extension Service, The University of Massachusetts Cooperative Extension Service and The Ontario Ministry of Agriculture and Food.

North Carolina Authors:
Mikal E. Saltveit, Jr., Assistant Professor
Susan A. Hale, Research Technician

Massachusetts Authors:
Duane W. Greene, Professor
Wesley R. Autio, Assistant Professor
James T. Williams, Ph.D.

Ontario Author:
C.L. Chu, Ph.D.

The soluble solids level in the fruit refers primarily to the fruit sugar level. The equipment needed includes a refractometer, paper towels or toilet paper and a squeeze bottle of water. Clean the prism and cover it with water then, look through the instrument, and adjust the refractometer to read 0 for the water if necessary. Clean and dry the prism and squeeze a few drops of apple juice on the prism from the bottom portion of an apple not used in the starch-iodine test. Read and record the soluble solids (SS). Note the correction for the present temperature. Rinse and dry the prism between each reading. Usually, the instrument will only need calibration once a day. It should be checked with water at the start of each site, record one SS per apple pressure tested. Ripe Delicious apples usually have soluble solids of greater than 10%.

Seed color is recorded from the apples that are sampled above. Record seed color as white, light brown, dark brown or black. Seeds from mature fruit will be dark brown to black.

Sampling the Apples from the Grading Line

Note when a cull has more than one defect, record only under the major defect.

<< Prev Next >>

[ Ky IPM Home ] [ Apple IPM Home ] [ Apple Scouting Manual ] [ Consumer Information ] [ Grower Information ] [ IPM Final Reports ]

Apple IPM web site created by Kerry Kirk - 2001 - Maintained by Pat Dillon