In This Issue:
New Website for Trap Reports
Widespread Drought Reports
Drought Conditions Persist
Strawberry Renovation in a Drought
Drought Effects on Apple Trees
Ohio Apple Scab, Fire Blight and Sooty Blotch Activity - SkyBit Products
Degree Day Accumulations/Phenology
The states east of Ohio in Maryland, Pennsylvania and New Jersey have drought equal or greater than Ohio. Governor Ridge of Pennsylvania has declared as of last week 55 out of 67 counties on emergency water restriction on non agricultural use . A few apple trees on M9 with good to full crop are collapsing under the stress in Adams County, the top county in the state This region received some showers on Wednesday of last week, with 1 to 2 inches in Gettysburg. Reports in New Jersey say that ponds and wells have gone dry from irrigation use, and therefore unable to continue to protect crops from drought just as the peak of the peach harvest will start in one to two weeks. In Canada, strawberry growers have not renovated fields because the ground is too hard to cultivate.
In Columbus, peaches are ripening and are of average size and have had no irrigation for two weeks. Last week we received about one inch of water. Peaches are under heavy bird damage and hornets and bees are also destroying the fruit, with 10 to 25 % of the fruit being eaten. About 5% of the current crop is affected, with more expected this week I have spotted a ground hog at high noon standing on his back feet trying to eat the peaches as well. I was not able to take some non chemical action on him. In past dry seasons these animals and insects, seeking moisture, go for the ripe fruit and are difficult to control. Picking the fruit early can help reduce the overall damage; also, attempts to control birds has been difficult.
Conditions in Ohio as of July 24, 1999
|Region||Category of Drought|
|NW Ohio||Near Normal|
|NCentral Ohio||Near Normal|
The answer is based on information from people who have worked on renovation research and other small fruit experts in several northeastern states and Canada. First, the consensus was that if growers had not yet mowed the plants, they would be better off just skipping that step this year. Since foliage is needed for flower bud development, it may be better to keep what leaves you have, especially if you do not have irrigation (or cannot use it) as is the reason this question was asked in the first place. Mowing too late (past mid-July) in any year hurts more than helps.
A number of growers have been using Gramoxone to narrow the rows, rather than tillage, with good results. In addition, tillage could be used in the fall if we get rain. One individual had been using Scythe herbicide, rather than Gramoxone, also with good results. Thanks to Marvin Pritts, Dick Funt, Deborah Breth, Kevin Schooley, and Stan Hokanson for their input.
Source: Kathy Demchak, Fruit Times Newsletter
Over the growing season, for adequate tree growth, flower bud formation and fruit quality, apple trees need roughly 1 - 1.5 inches of rain per week. Most areas of the state are way below this for the 1999 season. Obviously, a deluge of rain in September won't make up for dry conditions encountered in July.
Elena Garcia of the University of Vermont put together a nice, general overview of apple trees and water relations http://orchard.uvm.edu/uvmapple/newsletter and some of that information is presented in the next paragraphs. Then I will deal with some specific effects of drought that Ohio fruit growers are likely to have to deal with.
".. Even though fruit trees are made up of mostly water (table 1), only about 0.15 acre inches of water is harvested in the crop. About 95-95% of the water taken up by a fruit tree is lost to the atmosphere through transpiration.
Table 1. Loss of water by transpiration
|Shoots and wood||10-20%|
|A mature tree||85-87%|
Transpiration, the loss of water from the leaf tissue into the atmosphere, has two important functions in the plant. First, the cells in the leaves are cooled because water is being evaporated. This maintains the cells at an optimum temperature for metabolic processes such as photosynthesis to take place. If transpiration is limited due to water stress in the plant, photosynthesis will be limited and reductions in plant growth, fruit quality and yield will result. Secondly, since water is moving from the roots to the different parts of the plant, this movement facilitates the passive movement of important minerals and dissolved chemicals throughout the plant. Nutrient deficiencies are likely to be present under water stress situations.
During the winter months, apple trees use very little water. Water absorption from the soil by roots increases as leaf surface of the plant increases in the spring and most of the water comes from the upper soil layer which is warmer and has greater feeder root penetration. The "potential" water available to the plant depends on the root volume and the soil water holding capacity.
The roots of deciduous trees such as apples are usually extensive and have been found at depths of six feet. In sandy soil, roots have been found to extend laterally two to three times the branch spread and 1.5 times in loam or clay soils. When roots are deep and extend well laterally and there is a good supply of winter precipitation, there is usually no need for irrigation. However, where rooting is shallow, such as the root systems of growth-controlling rootstocks of high-density plantings, the need for irrigation will be higher than for standard, low-density plantings. Today, many orchards, particularly those with the shallow-rooted dwarf trees, provide some means of water application to protect the trees from water stress.
The ability of the soil to retain water is called the water-holding capacity and this capacity to hold water varies with the different textures of the soil. Table 2 shows the relationship of soil type to its water holding capacity and the moisture available to the plant.
During the growing season, the water status with a tree changes from day to day and hour to hour, whereas the soil water changes slowly. Tree water usage increases mainly with increased air temperature, air movement, sunlight intensity and with lower relative humidity. Table 3, which appeared in the March issue of Cornell Northeast Tree Fruit Newsletter (K. Lugerman) gives you an indication of how much water is needed when canopy size and evapotranspiration (evapotranspiration is the total loss of water by evaporation from the soil surface and transpiratin from plants from a given area, and during a specified period of time) are considered.
Stomata Activity. Stomata are pores on the leaf epidermis through which gas exchange (carbon dioxide, oxygen and water vapor) takes place. Since these gases are involved in respiration, photosynthesis, and transpiration, the opening and closing of the stomata regulate these processes in the plant. Stomata are open less wide and for a shorter duration on trees (a) in dry soils vs. those in a moist soil and (b) on plants during high temperatures and low relative humidity vs. Those on a cool, humid day. When dryness is severe, stomata may not open at all to prevent water loss from the leaves. When stomata are less active or closed due to drought, both photosynthesis and transpiration are reduced as much as 40% before the leaves show any wilting and over 90% at wilting. When the stomata are closed, food and energy loss by respiration are increased.
Vegetative growth and water. If there is not adequate stored soil moisture early in the season, a drought at this time will result in reduced shoot length and leaf size. However, if there is sufficient soil moisture early in the season followed by a late season drought, shoot growth may be a good in a non-irrigated tree as in an irrigated one because shoot growth is completed within six weeks after growth began. Trunk diameter may be reduced by a mid or late summer drought.
Nutrient supply. When less water is available to carry the nutrients from the soil particles into the tree, nutrient deficiencies are aggravated. Uptake of water soluble nutrients, such as nitrogen, boron, magnesium or potassium is most affected.
Fruiting. Reproductive growth is usually more sensitive to water stress than vegetative growth. Because flower bud initiation and differentiation is a photosynthate requiring process, water stress occurring during mid-summer and fall may result in decreased cropping the following year. In Washington state, severely drought stressed trees failed to bloom, and if they bloomed, the flowers had many abnormalities. Fruit set is also sensitive to water stress. In a study conducted in England on Cox's Orange Pippin, fruit set was reduced 65% for trees receiving no rain or irrigation from March to June.
Fruit growth. Under adequate moisture conditions, apple fruit growth occurs at an almost linear rate during the entire season. During the first three to five weeks after bloom, fruit increases in size due to cell division, with some cell expansion beginning at this time. The growth of the fruit 25 - 30 days after petal fall is mostly due to cell expansion. This cell expansion is highly dependent upon an adequate supply of moisture which provides weight and diameter increases of the fruit, and one of the first responses to water deficit by an apple tree is that fruit growth slows down. As a matter of fact, fruit circumference growth is used as a sensitive and practical measurement of water stress in the tree. Water stress during any time of the season may impair the ability of the fruit to increase in size.
Fruit cracking. Fruit cracking may result after water is supplied by rain or by irrigation following an extended dry period.
Pre-harvest drop. Apple drop just before harvest is common on trees affected by water stress. The effectiveness of "stop-drop" sprays such as NAA is reduced.
Yield and quality. Any tree subjected to water stress can be expected to have reduced yield and poorer fruit quality. Table 4 shows the effect of apple quality for varying periods of drought before harvest.
Now, let's consider some additional specific problems:
Calcium-deficiency physiological disorders. Corking is worse in apples under conditions of moisture stress. Leaf injury may occur from calcium chloride sprays during hot, dry summers. When injury is noticed, reduce calcium chloride to one-half the rate in the next spray or delete calcium chloride from the cover sprays until one-half inch of rain has fallen.
Sunburn. Sunburn occurs when fruit is exposed to direct solar radiation. Green and yellow cultivars are particularly susceptible, but even red cultivars may sunscald on hot, sunny days. If the injury is mild, the flesh itself may not be damaged, but longer exposure can result in severe injury to both skin and flesh, with sunken areas and dead tissue extending a centimeter or more into the fruit. As limbs bend under the weight of the growing fruit, the fruit in the interior becomes exposed and susceptible to injury.
Source: Dr. Diane Miller, Associate Professor, Horticulture and Crop Science
Site: Waterman Farm, Columbus
Source: Dr.Celeste Welty, OSU Extension Entomologist
Traps Used: AM = red balls, SJS = tent trap, others = wing traps
Apple: 7/22 - 7/28
Apple: 7/21 - 7/27
Other pest activity: green apple aphid, potato leafhopper, Japanese beetle, Oriental fruit moth strikes
Beneficials at work: Lacewings everywhere, orange maggot, multitudes of Stethorus punctum and other lady beetles, predatory mites
Site: West District; Huron, Ottawa, & Sandusky
Source: Gene Horner, IPM Scout
Traps Used: AM = red balls, SJS = tent traps, STLM = wing trap, Others = Multipher traps
Apple: 7/21 - 7/27
Other pest activity: Green apple aphid, two-spotted spider mite, Oriental fruit moth strikes, apple rust mite
Beneficials at work: Lacewing eggs, predator mites, other lady beetles, predatory wasps, banded thrips
|Actual DD Accumulations
July 21, 1999
|Forecasted Degree Day Accumulations|
July 28, 1999
|Location||Base 43° F||Base 50° F||Base 43° F||Normal||Base 50° F||Normal|
|Akron - Canton||2591||1767||2817||2579||1944||1736|
|Range of Degree Day Accumulations|
|Coming Events||Base 43° F||Base 50° F|
|Codling moth 2nd flight peak||1587-3103||1061-2212|
|Apple maggot flight peak||2033-2688||1387-1804|
|Obliquebanded leafroller 2nd flight begins||2124-3040||1412-2076|
|Oriental fruit moth 3rd flight begins||2172-2956||1553-2013|
|Peachtree borer flight subsiding||2230-3255||1497-2309|
|Redbanded leafroller 3rd flight begins||2389-3113||1722-2209|
|Spotted tentiform leafminer 3rd flight peak||2415-3142||1728-2231|
|San Jose scale 2nd flight subsides||2494-3257||1662-2303|
|Redbanded leafroller 3rd flight peak||2514-3225||1818-2625|
|Obliquebanded leafroller 2nd flight peak||2634-3267||1789-2231|
Thanks to Scaffolds Fruit Journal (Art Agnello)
Ted W. Gastier
Extension Agent, Agriculture
Tree Fruit Team Coordinator
Ohio State University Extension Huron County
180 Milan Avenue
Norwalk, OH 44857
Information presented above and where trade names are used, they are supplied with the understanding that no discrimination is intended and no endorsement by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.
All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.
Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Keith L. Smith, Director, Ohio State University Extension.
TDD # 1 (800) 589-8292 (Ohio only) or (614) 292-1868