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Kentucky Apple Integrated Crop Management Manual


Tree Examination
During the early part of the season, the orchard needs to be examined at least once a week. Always look for obvious problems as you move through the orchard. Select a minimum of five trees per block. If the block is larger than 25 acres, select a minimum of one tree for each five acres. Select trees so that they are representative of the different cultivars in the block. Do not select trees just for scouting convenience. Select five limbs on each tree to be examined. Select the limbs as follows: equal distance around the tree, three at chest level, one at head level, and one below your belt. On each limb, examine 20 leaves and 20 bud clusters, blooms or fruit whichever is present. Repeat for each of the five limbs. This means you will have examined 100 leaves and 100 bud clusters, blooms or fruit for each tree.

Pheromone Traps
The basic principle of pest management is that you do not take action against a pest unless you are certain the pest is present and will be a threat to your crop. Insect traps are a good method of determining if an insect is present and can also give an estimate of their concentration and distribution. Food, light, color or chemicals can be used to attract insects to a trap. However, if you are interested in only one species of insect, such as only the codling moth or only San Jose scale, a pheromone would be the best choice to attract the pest. A pheromone is a chemical produced by an unfertilized female insect that attracts only males of the same species.

The traps consist of a plastic top and bottom that are held together by a wire hanger. The tops of the traps can be reused and the disposable bottoms are coated with a sticky gel to hold the insects once they land in the trap. The trap hangs from a scaffold limb near the outside of the tree.

Traps catch the adult stage of their life cycle because this is when males are attracted to the pheromone. By knowing that the adult stage of a pest is present the producer knows when to control for damaging stages that are sure to follow. Pheromone trap information is used as starting point for calculating the number of day degrees before the emergence of the damaging stages. This tells the apple producer the best time to spray for insect control. Producers use this strategy to control codling moth and San Jose scale. Initial catches of San Jose scale or the fifth codling moth in their respective traps determines the timing and/or need of insecticide treatment.

Pheromone traps need to be examined at least once a week. On each visit, the producer counts and records the number of captured insects in each trap. Captured insects are removed and disposed of outside of the orchard. It is extremely import to keep the trap in good working condition or it may produce false information. The pheromone lure and the trap bottom must be replaced each month. Replace the complete trap if discolored or drooping. Do not dispose of the lure or trap parts in the orchard, as this may attract pests away from the trap.

Avoid contaminating the lures. Do not touch the pheromone lure in one type of trap then handle a different lure without first washing your hands or changing gloves. Otherwise, traces of the first bait will contaminate the second bait making it useless. Replacement lures should be stored in the freezer until needed.

Predicting Insect Development Using Degree Days
Temperature plays a major role in determining the rate at which insects develop. Each insect has a temperature range at which it is the most comfortable. Below that temperature they will not develop and, likewise, above it development will slow drastically or stop. Each insect also has an optimum temperature at which it will develop at its fastest rate.

By using this relationship you can make predictions on the rate of development of insects. By being able to predict when an insect will appear, you can estimate when your crop is most likely to be damaged. This method of estimating time is called the day degree method. The degree day method can be used to predict when insects will reach a particular stage of their life cycle if you know three things: the threshold temperature, the average daily temperature, and a thermal constant.

Each insect has a threshold temperature. Below this temperature no development of the insect occurs. A degree day is the number of degrees, above the threshold temperature over a 24 - hour period. For example if the threshold temperature of an insect is 50 degrees F and the average temperature for the day is 65 degrees F, then 15 degree days would have accumulated on this day. (65 - 50 = 15)

The accumulation of degree days can be used to predict when insects will hatch, pupate and emerge as adults. However, for degree days to be used to make these predictions researchers must have determined the number of degree days necessary for the event to occur. That is called the thermal constant. The thermal constant, just like the threshold temperature, will be different for different insects.

The easiest way to calculate degree days for a date is to subtract the threshold temperature from the average daily temperature. The average daily temperature can be determined by simply averaging the high temperature and low temperature for the date (maximum temp + minimum temp/2). For example, if the high temperature for the day was 90 degrees F and the low was 50 degrees F, then the average temperature for the day would be 70oF (90 + 50 / 2 = 70). If the threshold temperature for an insect were 50 degrees F, the degree days accumulated on this day would be 20 (70 - 50 = 20).

Temperature extremes add variables to this simple method of calculating degree days. To overcome these and more accurately predict when insects will be present follow these rules:

1.) If the maximum temperature for a 24-hour period is not greater than the threshold temperature, no degree days are accumulated.

2.) If the high temperature for the day is greater than the optimum temperature, the temperature at which the insect will develop at the fastest rate, then you use the optimum temperature as the high temperature for the day when calculating the average temperature for the day. For example:

maximum day time temperature = 98 degrees F
optimum temperature = 95 degrees F

The optimum temperature of 95 degrees F would be used as the high temperature for the day when calculating the average temperature for that day.

With apple IPM, degree day models are used primarily for two insects, San Jose scale and codling moth. Degree day accumulations are used to predict when certain biological events, such as egg laying, egg hatch, or scale crawler movement, they also indicate optimum periods for insecticide applications. For both of these pests, degree days are accumulated after certain events, termed "biofixes". These occur in the early spring.

Weather Monitoring
Several commercial orchards in Kentucky are using computer-based weather stations in the orchard to provide data to predict the occurrence of fire blight and apple scab infections. These monitoring devices record temperature, leaf wetness, rainfall, and humidity. Computer models direct producers to bactericides and fungicides only when needed to control these diseases. Generally, these systems reduce the number of pesticide applications. However, during long periods favorable for disease infection, producers may be directed to make more applications than would be required using a standard spray schedule.

Time of Year
Daily weather observations of temperature and precipitation should be taken during the growing season (March l5th to October 1st). In addition, from the start of green tip (near April 1st) until the end of 2nd cover (near June 30th) daily leaf wetness observations are also needed.

Stations should be set up about 1 week before March l5th in order to check out equipment and to take care of any problems.

Time of Day
Weather observations should be taken once a day at approximately 7:00pm. It is very important to take the observation, reset the thermometer, and empty the rain gauge at the same time each day.

To ensure accurate and continuous weather observations, one person should be designated as the weather observer. The observer should be given responsibility of taking and recording the weather observations and maintaining the equipment. Also, at least one other person (i.e., a member of the family or neighbor) should be know how to take and record observations in the event of the observer's absence.

Observation Form
The observer should enter his or her daily weather observation on the supplied Apple IPM Scouting Log. The log is designed to contain one week's weather and management data. The first section of the form is for recording all weather data, and certain insect and orchard development stages. The second half is to record all spray applications for the week, with the third part containing any management activities (i.e., pruning, mowing, etc.). The remainder of the form is for scouting information.

Weather Observations
Max/Min and Current Air Temperatures
The maximum air temperature is defined as the highest temperature that has occurred in a 24-hour period. The minimum air temperature is the lowest temperature that has occurred in a 24-hour period. Current air temperature is the temperature at the time of observation

The maximum, minimum, and current air temperatures are obtained from a "U-type" max/min thermometer. All three temperatures are representative of the past 24 hours and are indicated on the thermometer since it was last read and reset. At the time of observation, all three temperatures should be recorded and the thermometer reset. The current temperature should be read off the minimum side of the thermometer.

The thermometer should only be reset at the stated observation time. Both max/min temperatures are to be recorded on the date the thermometer is read even though the maximum or minimum temperature may have occurred on the preceding day.

Total Precipitation
Precipitation is the amount of water deposited upon the earth surface in both liquid (rain, drizzle) and solid (snow, ice pellets, hail, freezing rain) forms. Measurement is determined by the vertical depth of liquid or solid deposit accumulated over a flat surface. Since scouting begins in early spring in Kentucky, the grower might want to pour a small amount of alcohol or other liquid which does not freeze into the bottom of the rain gauge to keep the collected precipitation from freezing and busting the gauge. If this is done, be sure to subtract the amount of antifreeze from the total amount of liquid in the gauge to get an accurate measurement of precipitation. The rain gauge should be emptied only at the time of observation although additional readings may be taken at any time.

Periods of Leaf Wetness
Leaf wetness periods are the time intervals when the leaves or branches of a tree are wet with water. Rain, fog, or even dew can cause leaf wetness. For apples, a leaf wetness period is defined as a time interval of at least one hour when the leaves or branches of an apple tree are wet with moisture. Many growers use electronic instruments for measuring leaf wetness.

The presence of leaf wetness can also be determined by direct observations of leaves and branches of an apple or comparative vegetation. The tree should be in the general proximity of the station. Depending on weather conditions, direct observations of leaf wetness may or may not be necessary. If rain, snow or fog has occurred in the past 24 hours, then observations of wetness should be taken and recorded, along with supplemental temperatures. Leaf wetness observations include the beginning and ending times of precipitation periods. On the Scouting Log, there is a row for this information. Simply circle the time of the observed leaf wetness period in either the am or pm column. If the wetness begins or ends upon a half of an hour, start or end the circle halfway through the corresponding number. If it starts upon the hour, circle the entire number.

There are many brands of electronic instruments useful for measuring weather conditions in the orchard, calculating disease risks, recording insect degree-days, and keeping records of orchard conditions. Some units are self-contained microcomputers that stand alone in the orchard with built in sensors for temperature, relative humidity, rainfall and leaf wetness. These units measure the weather, calculate risks, and keep orchard records. Other weather monitoring approaches place only the weather sensors in the orchard, with the weather information transmitted to a personal office computer indoors either by direct radio or telephone connection, or via data storage devices which can periodically be connected directly to a computer to which the weather information is downloaded. It is the office computer that contains programs for calculating disease risks and keeping orchard records.

Prices for these instruments may range from a few hundred to a few thousand dollars. For gaining a better understanding of orchard biology, they may be worth the money. For the latest information on weather monitoring and predictive instrumentation, consult with your county extension agent. Less costly lower-tech weather monitoring instruments, discussed below are also useful.

Record Management
It is very important that all weather observations and management operations be recorded for the success and implementation of IPM in your orchard. Be sure to keep up with the daily weather observations at the correct time.

Maximum/Min Thermometer
1. Before resetting each day, make sure all bubbles are out of the thermometer mercury. If there are breaks in the mercury, grasp the top of the instrument and shake it downward until it is normal. 2. Always read the minimum side of the thermometer to obtain the current temperature. 3. Read and record the maximum, minimum, and current temperatures at approximately 7:00pm every evening once scouting begins. 4. It is very important that the thermometer does not come into contact with direct weather elements, i.e., direct sunlight, rain, etc. 5. The thermometer needs to be mounted very securely onto the 4"x4", as any vibration of the instrument will cause an inaccurate reading and separation of the mercury.

Rain Gauge
1. The rain gauge may be placed either on top of the temperature shelter, nailed up above the 4"x4", or placed on a separate wooden post about 1-3.3 feet above the ground. This should be about 20 feet from the temperature shelter. 2. If the gauge is affixed atop the temperature shelter, make sure the mouth of the gauge is high enough up to avoid collecting extra precipitation that splashes or runs off the top of the shelter. 3. If there is a chance of freezing weather, place a small amount of anti-freezing liquid, such as alcohol, in the bottom of the gauge to keep the precipitation from freezing, expanding, and busting the gauge. 4. Be sure, when recording a measurement with alcohol, to subtract the amount of anti-freezing liquid from the total amount of collected liquid for an accurate reading. 5. The rain gauge needs to be read, recorded, and emptied at approximately 7:00pm daily. 6. Both instruments should be checked daily for breakage and inconsistent measurements. Such signs may suggest that separations are present in the thermometer or leaks in the rain gauge.

Thermometer Shelter

1. Facing the front of the shelter, both left and right sides and the top dimensions of the shelter are all equal, 1"x7"x12". Several small holes are to be cut out of the sides for proper ventilation in the shelter.

2. You may opt to slant the top to prevent the accumulation of water on the top of the shelter, but it may be level as well.

3. The back wall of the shelter is a 1/2"x12"x12" piece of plywood.

4. Insert the 4"x4" deep enough into the ground (1-2 feet) to be very sturdy.

5. Mount the thermometer very securely onto the 4"x4"; any vibration of the instrument will lower the magnets and produce an inaccurate reading.

6. The thermometer is to be placed in the shelter approximately 5 ft above the ground.

7. The shelter should be on the side of a gently sloping terrain with a southerly exposure (not a ridge or depression).

8. The shelter should be at an elevation which is representative of the grower's farm.

9. Place the shelter at least 100 ft from non-vegetated surfaces (dirt roads, extensive concrete or paved areas, etc.); also it should be far from any obstructions such as buildings, trees, etc. (any nearby obstructions should be at least twice the distance from the outside edge of the site as the obstruction is tall).

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Apple IPM web site created by Kerry Kirk - 2001 - Send questions or comments to Patty Lucas