Inspector Findings in Kentucky

Gypsy Moth Egg Masses Found in Trees

Last week (8/23) we found some gypsy moth egg masses on blue spruce trees that had been shipped from Strathmeyer Forests, Inc. of Dover, Pennsylvania earlier this year.  So far we have found the egg masses at two different nurseries located within Kentucky.  The egg masses were empty which means the eggs had already hatched. The egg masses did not appear to be old (from last year or before) so they probably hatched out at the nursery or quite possibly on a job site somewhere.  Since this insect only has one generation a year, there is not much that we can do this year.  Next year we will trap the area around the nurseries that received this infested stock.   If you have received any conifers of any sort from this nursery, please let us know.  This is a very serious pest and we need to do all we can to prevent its establishment in our state.

Rose Diseases Are Here

by John Hartman, Extension Plant Pathologist

Roses, with their diversity of varieties and types and their often spectacular blooms make them a favorite for many gardeners.  Roses in Kentucky are subject to several foliar diseases such as black spot, powdery mildew, downy mildew, and rust. 

+Black spot caused by the fungus Diplocarpon rosae, produces dark, circular spots with fringed borders on either the top side or the bottom side of the leaves.  Infected leaves often turn yellow and drop from the plant, thus reducing the number and quality of the flowers.

+Powdery mildew, caused by the fungus Sphaerotheca pannosa, attacks leaves, stems, and flower buds.  Fungal signs, the white powdery growth of the fungus are easily seen on the infected plant surfaces.  Infected leaves may be small and deformed. 

*Downy mildew, caused by the fungus Peronospora sparsa, produces lesions that are at first an off-color, then purplish brown.  Infections lead to defoliation.

*Rust, caused the fungus by Phragmidium mucronatum, is less common than black spot or powdery mildew.  Rust appears as rusty spots on leaves and stems.  Severely infected leaves may shrivel and turn brown.

Of these black spot and powdery mildew are the two most important.  They are almost always a serious problem every year under our warm, humid growing conditions.  Thus, with our warm, humid summer, a rose disease control program using fungicides should have been a summer-long project this year.  Old leaves, winter-damaged canes, and debris which are sources of fungal inoculum should have been removed and destroyed earlier this spring.

Rose growers can plant disease tolerant roses and benefit from improved performance and reduced fungicide use.  Disease-resistant cultivars have been listed in previous issues of this publication, as well as in many nursery catalogs. 

If disease-susceptible roses are being grown, a partial list of appropriate fungicides is presented here. 

Chlorothalonil (Daconil 2787) and mancozeb (Fore) will control black spot, downy mildew, and rust.  Fenarimol (Rubigan), myclobutanil (Eagle, Immunox), propiconazole (Banner), and triadimefon (Bayleton), are quite effective against powdery mildew and rust.  Azoxystrobin (Heritage), copper sulfate (Phyton-27), mancozeb plus thiophanate-methyl (Zyban), thiophanate-methyl (Cleary's 3336, Domain, Fungo-Flo), and triforine (Funginex), are labeled for the control of both powdery mildew and rust.  To maintain disease suppression, repeat fungicide applications at 10-14 day intervals throughout the growing season.

Rose growers who wish to observe how good roses can look when given proper care and diseases are controlled need only look at the rose collection at the U.K. Arboretum on campus just off Alumni Drive.  This assortment of over 400 roses is very likely the largest and best-maintained rose collection in the Midwest and is worth a visit when traveling to Lexington.

Twig Girdlers Active - Oaks

Flagging

by Lee Townsend, Extension Entomologist

Female twig girdlers are laying eggs in lateral or terminal twigs of many trees, including hickory, pecan, oak, and many others.  After depositing a single egg, the female chews a continuous notch around the twig, girdling it.  These twigs, usually over a foot long, die quickly and fall to the ground.  The egg in the broken twig hatches and the legless white larva feeds some before winter.  Development resumes in the spring and the adult emerges in early fall.  Sanitation is the key to managing this pest. Pick up and destroy the fallen twig to kill the developing generation.

Stress Can Predispose Landscape Trees To Hypoxylon Canker

by John Hartman, Extension Plant Pathologist

This summer's dry weather has created difficult times for mature landscape trees in many areas of Kentucky.  The problem is compounded by the fact that many areas endured dry weather most of the second half of last growing season as well.  Branch breakage from periodic high winds have left wounds that allow ingress of weak parasites and even aggressive saprophytes that are often indicators of the final stages of tree decline.  The fungus Hypoxylon atropunctatum and to a lesser extent relatives, H. mediterraneum, and H. punctulatum, are fungi that attack injured oaks and other trees growing in stressful conditions.

Hypoxylon canker is commonly seen on oaks as patches of brown, gray, silvery gray or black fungal stromata in the cambial zone of affected trees.  These smooth, hard patches are revealed when the tree bark is loosened and sloughs off the affected trunk or limb.   By the time the patches of fungal stromata are revealed, the fungus has decayed much of the adjacent inner bark and outer sapwood.  Discoloration and decay are often accompanied by black zone lines in the sapwood, similar to that seen for other sapwood decays.

Hypoxylon fungi are quick to colonize weakened bark and wood, and stromata may develop within a few months after infection.  Oaks and other trees are very quickly attacked because it seems that in some instances, the fungus may already be present as a latent colonist of even healthy trees.  Injuries of any kind, and now warm, dry weather, favor the fungus and rapid decline can be expected.  Tree trunks and major limbs with Hypoxylon canker and dieback should be considered hazardous and need to be removed where they represent a danger to people and property.

Look for Hypoxylon canker and dieback on all oaks, sycamore, linden, hickory, maple, beech, dogwood, hornbeam, elm, and willow.  Although in some cases, the fungus is pretty much saprophytic, attacking trees already declining, the fungal stromata are sure indicators that the tree or tree parts will not recover.  These fungi are most active under our warm growing conditions; some of them are thought to compete with the oak wilt fungus, a primary and highly destructive pathogen of oak, for nutrients, thus suppressing this more destructive disease.  This might account for the relatively minor role of oak wilt disease in Kentucky.

Lawns---Parched Or Killed

by A. J. Powell, Jr., U.K. Extension Specialist-Turf

For much of Kentucky the drought, heat and irrigation restrictions have been severe enough to seriously injure or kill many, many home lawns.  A lot of people believe that Kentucky bluegrass and tall fescue lawns will just become dormant (brown) and then recover when cool nights and good rainfall occur.  Unfortunately this is not usually the case when the heat and drought is as severe as it has recently been in many parts of Kentucky.

To determine the extent of injury, consider the following:

(1)When lawns go completely brown, with little or no green leaves showing, you can expect kill or severe thinning of the grass.

(2) Kentucky bluegrass is more quickly injured than tall fescue but both grasses may die.  Although tall fescue is more heat and drought tolerant than Kentucky blue, it usually is growing on poorer soils and it has few underground tillers to aid recovery.  Also, because of the heat and humidity this summer, brown patch disease has been an extra stress on most tall fescue lawns. Perennial ryegrass lawns will seldom survive such heat and drought, but bermudagrass and zoysiagrass lawns should have no problem.  Fine fescue growing in semi- shady locations will usually become dormant and recover before the following spring.

(3) Low maintenance lawns that have a mixture of turfgrasses and weeds, and/or lawns that almost never get fertilized with N, will usually recover.  They certainly won't get better, but you will not likely need to reseed.

(4) Almost never will the complete lawn die.  Portions of the lawn that have good soil, protected by moderate shade and north facing slopes are more likely to survive.

(5) Proper irrigation will greatly aid the lawn during very hot weather.  However, if the lawn is over-watered and then suddenly the water is cut-off (during the heat and drought), that lawn is usually doomed.  When this type of lawn turns brown, make plans to reseed.

(6) Very sandy and heavy clay lawns suffer the most damage.

(7) The longer the heat and drought, the more the damage.  Unfortunately one cannot look at the lawn or closely examine individual grass plants and positively determine if it is alive or dead.  Even when a lawn does recover it may be October or November before one can tell for sure how much turf has been lost and how bad renovation is needed.

It is obvious that hundreds of lawns throughout Kentucky will need renovation this fall.  Consider the following:

---Tall fescue is much easier to establish from seed than is Kentucky bluegrass.  To get good establishment of Kentucky bluegrass, a conventional seedbed is usually necessary.  Tall fescue can be established using a conventional seedbed or by slit (no-till) seeding.

---Timing is critical.  The optimum timing for Kentucky is mid August through September, and no later than October 15.  However, one should not consider seeding until a good, soaking rainfall has occurred and the drought is officially `over'.

---The heat and drought has greatly increased the growth of crabgrass but a heavy crabgrass population is not usually a problem when renovating a lawn in the fall with tall fescue.  The summer increase of perennial grassy weeds such as bermudagrass, nimblewill and dallisgrass is however, a serious problem.  These need to be sprayed with RoundUp at least a few days prior to seeding; however you will not get good control of the perennial weeds unless the proper rate of RoundUp is applied and these grasses have enough soil moisture that they are actively growing.

Especially for bermudagrass, spray as soon as soil moisture is adequate to get good growth, then wait about 3-4 weeks and spray again with RoundUp.  Removing the dying sod a few days after the first spray will help encourage escaped, underground bermuda to re-grow; then the second spray will be more effective.  With only one spray on bermuda, expect only 80- 90 % control.

Dense areas of living Kentucky bluegrass will also deter tall fescue establishment.  To truly get a monostand of tall fescue and quality turf, thick areas of Kentucky bluegrass should likewise be sprayed with Roundup a few days before renovation.  If the lawn is truly devastated by the heat and drought, and perennial grassy weeds are not prevalent, certainly you can omit the Roundup.

---Seed about 5-6 pounds of tall fescue per 1000 sq. ft. of lawn.  If using a slit seeder, that slices through the thatch and drops the seed into the slits, apply about one pound of seed per 1000 sq. ft. for each pass.  If you go over the lawn two times, then you would want to also broadcast about 3 pounds per 1000 sq ft before the last pass with the slit seeder.  Just broadcasting the seed, without some surface disturbance / preparation, will result in almost no soil-seed contact and poor survival.

Traditional dethatching equipment can be rented at most rental agencies.  With the knives set to penetrate through the thatch and about ¼ inch into the soil, go over the lawn two or three times.  Then broadcast the seed, and lightly go over the lawn again with the dethatcher.

---Improved turf-type tall fescue varieties include: Jaguar 3, Houndog V, Guardian, Renegade, Rembrandt, Southern Choice, Falcon II, Crossfire II, Apache II, Genesis, Lancer, Marksman, Rebel Jr., Pyramid, Pixie, Eldorado, etc.

---It is very important to regularly water the newly seeded lawn to keep the surface wet.  If you cannot water and the weather remains dry, you will not have much success.  If you can water 2 or 3 times a day, then you should have green turf beginning to show in about 10 days to two weeks. 

---You can apply the first Nitrogen fertilization prior to seeding but it is often better to wait until after germination.  If nitrogen is applied at the time of seeding, it may force growth of weeds that compete with the young seedlings of fescue.  Fertilizing immediately after germination gives the desirable grass an advantage.

Factors Critical to Pesticide Performance

by David J. Shetlar, Extension Landscape Entomologist Ohio State University

Application Timing

Pest control should be initiated only after the pest has been identified accurately and its presence threatens either the aesthetic quality or the vitality of the plant. If a decision has been made to use a pesticide, timing of the application must coincide with a stage of the pest that is vulnerable to the application.

Many pests, including borers, armored scales and gall formers can be contacted with pesticidal sprays for only a short time during the growing season. For example, armored scales can be controlled best by attacking the newly hatched nymphs (called crawlers) are active or have recently settled on their host. Borer sprays must be applied either before egg laying begins (e.g., bronze birch borer and other flatheaded borers) or before egg hatch (e.g., dogwood borer and other clearwing moths borers). Pesticide applications at any other time during the life cycle of these pests will be ineffective and should not be implemented.

Understanding Pest Life Cycles and Movement

Many insects and mites complete only one life cycle (=generation) each year. A single, well-timed, thoroughly covering spray with an effective pesticide should provide season-long control. Other pests, including aphids, mites and some scales and bark beetles complete two or more generations each year. These pests may require more than one spray during the growing season.

Most adult insects have wings and can fly. After spraying, new insects may fly in and reinfest a plant making it appear that the insecticide applied didn't perform well. For this reason, repeated applications are needed to protect some plants from incoming insects.

Selecting the Correct Insecticide/Miticide

Although many insecticides/miticides are effective against a number of different kinds of pests, it is always important to choose a product that has been proven to provide excellent results against the pest you are trying to control. General purpose sprays and pesticides are not the best approach to pest control. Instead, choose a product that has been rigorously evaluated for its effectiveness against your target pest. Then, use it according to directions on the container label, using only the amount specified. Do not use adjuvants (i.e. spreaders and stickers) unless specified on the label.

Weather-Related Problems

Sprays should always be applied to dry foliage and bark when rain is not expected for several hours. However, as long as sprayed surfaces dry before rainfall occurs, reapplication is usually unnecessary. Sprayed plants should be monitored in five to seven days to determine treatment effects, especially if rain occurs soon after the application. If the treatment was not effective, and if the pest is still in a vulnerable stage, the application should be repeated. It is a good policy to spray when the temperature is between 50 and 90 degrees F (10-32 degrees C). Many pesticides are less effective below this range, and some products may cause plant damage above the upper limit.

Storage Life of Pesticides

Many insecticides/miticides may tend to lose their killing power over a period of time, once they have been opened. This process may be speeded up with improper handling and improper storage. Therefore, it is always best to buy only the amount of insecticide/miticide you expect to use in one season.

Pesticides can be used from one year to the next. Remaining product should be stored in a safe, dry place that does not experience freezing or extremely high temperatures. Refer to the label for specific instructions on long term storage.

Pest Resistance

Resistance is a general term which, in the broad sense, means pests that were previously killed by a pesticide have produced offspring that are no longer killed by it. To illustrate, let's suppose that an insecticide is applied and that it kills 95% of the insects in a population which contact it, but there are 5% of the insects which received the same dosage but survived the treatment. This 5% is considered resistant to the insecticide. They live to produce another generation, and this generation, having had resistant parents, passes on to its offspring the resistance factor. Most likely there will be a greater number of the new individuals carrying resistance to the insecticide compared to the first treated population. As repeated insecticide applications are made and more generations produced, it is only a matter of time before the majority of the insects in question will survive the insecticidal application. A possible explanation is that the insecticide has acted as a selecting agent, killing those members of a population which are susceptible to the chemical and leaving those which are resistant. Survivors breed and produce subsequent resistant generations. Resistance develops fastest in insects which have high rates of reproduction. This is another reason why pesticides should be used only when and where necessary to prevent damage to valuable landscape plants.

Pruning Field Grown Shade And Flowering Trees

by T.E. Bilderback, R.E. Bir and M.A. Powell, Extension Horticultural Specialists Department of Horticultural Science North Carolina Cooperative Extension Service, North Carolina State University

INTRODUCTION. Every nurseryman should know how to prune trees and the reason for the various pruning practices. Many landscape problems can be avoided if correct pruning is performed, while the tree is growing in the nursery. Incorrect pruning practices or lack of pruning diminish the quality of the plant material.

EARLY STAGES. The most important aspect of early growth during the first year after planting is in root initiation and establishment. Unless large whips have been planted, pruning is generally not a critical practice at this time, as many of the smaller lower branches can aid in stem taper or trunk caliper and thus should be left on the tree. General pruning should be confined to large lateral branches which are out-of-scale and with maintenance of a main leader. Large lateral branches may be pruned back to 2-3 buds to help caliper development of the lower stem.

Terminals of leaders may dieback during the first season. For mis-shaped seedling trees, often the best choice is to cut them off approximately 1 inch above the ground just before bud break the second season. This takes considerable courage, however shoots soon develop at the base of the stem. For single leader trees, the one most vigorous and straightest is selected and the others removed. For clumped or multi-stemmed trees such as river birch, and crape myrtle 3 to 5 stems should be left.

The species growth habit generally dictates pruning requirements during the second and third growing seasons. It is easiest to work with the natural growth habit of a species than to change the natural form. Trees such as oaks, 'Bradford Pear' or maples are usually pruned to maintain a single leader and well spaced, wide angled branches. Other trees such as crabapples cultivars may be pruned to form 3 to 5 modified leaders with wide scaffold branches.

SUMMER PRUNING. Summer pruning in deciduous trees would include 1) the removal of watersprouts (small shoots) along the trunk and base, and 2) the maintenance of a single straight leader. Theoretically, most pruning of deciduous trees is best performed during the dormant season, but corrective shaping is essential and should be done at the first possible chance. Broken, damaged and dead branches are best removed when observed.

Broadleaved upright plants such as `Nellie R. Stevens' and `Fosters #2' hollies need attention throughout the summer months. The terminals should be tip pruned to increase branching density. A strong vertical terminal should grow 8-10" long before being pruned. Later on in the season as the growth develops, another central terminal should be selected.

Fire blight susceptible trees such as crabapple, pear, and other rosaceous species may require extra spring and summer pruning. Tips of branches are blackened as the disease moves down the branch. To control the disease, prune at buds or branches well below the discolored area. (This may be 12-15 inches on infected branches.) Pruning equipment should be disinfected by wetting all cutting surfaces with isopropyl alcohol, 10% chlorox solution, or saturated copper sulfate solution. This disease is easily spread by non-disinfected pruning shears.

WINTER PRUNING. Extensive pruning of deciduous nursery stock is best completed before plants break dormancy. The branch structure is more easily seen and pruning at this time will stimulate growth on remaining branches. Pruning should be limited to removal of no more than a third (1/3) of the total bud and leaf bearing branches. Otherwise extensive water sprouting may result.

Depending upon the intended use, customer demand and market, deciduous shade trees are usually limbed up from 36 to 60 inches.

Smaller flowering trees usually branch lower than larger trees and may be as low as 24 inches. Boulevard and parking island trees need higher clearance than specimen and residential trees.

To maintain a dominant leader, prune competing lateral branches or the tree will develop multiple leaders. If one leader is straight, prune angled branches. Approximately one-half their length may be removed by cutting to an outward facing bud. If neither leader is straight, remove one and consider staking. It is also possible to tie them together and cut one back, then cut off the short one at the end of the growing season.

When cutting back a leader on opposite budded trees a double leader will develop unless one bud is eliminated. To remove one bud, make a slanted cut above the bud to be left, trying not to expose the stem directly behind it but removing the opposite bud or roll out (pinch out) one bud.

Extra large or long lower branches also suppress terminal growth and should be removed or cut back to at least one-half their length. Some growers cut small branches less than one-fourth inch back to 1 or 2 buds and allow shoots to grow until the end of the season. This helps increase lower stem caliper during that season and then they are removed during the next dormant pruning cycle.

Prune out crossing, inward growing, parallel and competing branches. Branches growing in the center of multi-leadered trees such as river birch and crapemyrtle should be removed so that attention is focused on exfoliating bark.

Scaffold branches are permanent branches which make up the frame of the tree. When trees are small, tiers of branches may be 3 to 6 inches apart such as in Pyrus cultivars. During the next two years in the field, pruning to develop spacing between whorls to a foot or more is desirable. Branches should also be well spaced around the trunk. Acutely angled limbs are weaker than more horizontally growing branches and should be eliminated. Parallel branches growing in the same plane, one above the other should also be eliminated by removing one of them. Branches growing back toward the trunk or across other branches should be removed. By making these choices well spaced branching may be accomplished.

The height of the first branches is usually determined by the market sought and size of tree being sold. The bottom branches for small flowering trees like dogwood or kwanzan cherry may be left low at 1 ½  to 3 feet. Small residential shade trees may begin at 3 feet in height. Large caliper trees for boulevard or street use may be pruned to 4 feet or higher to reduce maintenance conflicts.

Buds left on the end of pruned branches form the next tier branches. Pruning influences their direction. On opposite budded trees it is good practice to prune back to buds facing to the side rather than up and down. This can be used to stimulate branching on light branched trees. If branches are cut back to side buds it can double the number of branches when the tree starts to grow.

Current research indicates that flush cuts are no longer recommended. Cut just beyond the branch collar perpendicular to the branch being pruned rather than as close to the trunk as possible. This minimizes the size of the wound.

An identifiable quality of nursery grown shade trees is a straight leader and good branch structure. Along with other management skills and good pruning practices, a grower should be able to improve the quality of field grown trees and increase the percent of marketable plants in his fields.

Horticultural Oils--Control Soft-Bodied Pests with Less Toxicity

From Oregon State University Extension & Experiment Station Communications web site

Horticultural oils are an effective, "least toxic" method of pest control that can be used safely and effectively if used carefully.

 They are most effective in controlling over wintering insect eggs, larvae such as caterpillars, and soft-bodied adult pests including aphids, mites, scales, mealybugs, psylla and whiteflies on perennial plants.

People may be more familiar with the use of horticultural oils as "dormant oils," applied during the winter to control pests. These oils are used on woody plants during the dormant season, before buds swell. They can also be sprayed on the leaves during the spring or summer to control pests.

Sometimes called "narrow range oil" or "superior oil," most horticultural oils are highly refined petroleum products, manufactured to control pests on plants. They are lighter than fuel products, evaporating quickly. Some vegetable oils, citrus oils and fish oils are also used as horticultural oils.

The oils kill insects and other soft-bodied invertebrates by suffocation, clogging their "spiracles," or breathing holes. The oils may disrupt the functioning of cell membranes.

Horticultural oils have advantages over chemical-based pesticides:

Ø       They degrade rapidly by evaporation. They have very low toxicity and have almost no toxicity to humans or wildlife at the rates recommended for use to control pests.

Ø       They can be useful in controlling a wide variety of soft-bodied pests. But beware - they eliminate a broad array of pests. Care must be taken not to eliminate over wintering or slow-moving larval beneficial insects.

Ø       They act as an excellent surfactant and wetting agent for fungicides such as lime sulfur and copper, also used during the dormant season.

Ø       Pests have developed little or no resistance to horticultural oils, unlike numerous other pesticides on the market.

Ø       Horticultural oils are relatively inexpensive.

Ø       They are less harmful to adult beneficial insects.

Ø       They are certified for organic use.

However, horticultural oils are by no means perfect.  Under the wrong conditions, horticultural oils may cause some damage or burning to certain plant foliage.

To ensure against harm to your foliage, spray a small area first and wait a few days to see the effects. The oils may cause some bluish plants, such as blue spruce, to loose their bluish cast, though the color should return within a couple of years.

Do not use them when it is windy or when the temperature is greater than 90 degrees or below freezing or when it is raining or extremely humid.

For dormant sprays, do not use during freezing weather. Spray when the temperature is above 40 degrees and before any green tissue is present. Do not apply horticultural oils to plants under drought or insect stress.

If in doubt about drought stress, water the plant before spraying it with horticultural oil.

Dry Weather Can Initiate Long-Term Landscape Problems

by John Hartman, Extension Plant Pathologist

A brief glance at unirrigated landscape trees, shrubs, and lawns as well as at farm crops confirms that we are experiencing a very dry period in most of Kentucky.  Although rainfall in some parts of eastern Kentucky brought temporary relief last week, the over-all situation remains grave.  Watering restrictions are in force in most areas.  Unfortunately, drought has been accompanied by higher-than-normal temperatures for much of the summer.  In the landscape, seedlings and recently transplanted trees and shrubs have been at greatest risk because they lack extensive root systems.

Most of us are familiar with wilting and leaf scorch symptoms associated with dry weather.  Leaves of drought-stressed plants close their stomata which reduces their rate of photosynthesis.  Depending on species, they may not recover their former photosynthesis capacities, even when irrigated following drought.  Reduction in photosynthesis may not kill a tree, but it means fewer carbohydrates are made and stored for future use.  In addition, leaves of many trees and shrubs are beginning to turn yellow or brown and are dropping to the ground.  Some species increase their production of leaf abscission chemicals in response to drought.  Fewer leaves means less water loss.

Diseases such as bacterial leaf scorch may show enhanced symptoms during times of drought.  In addition, there are some diseases of landscape trees and shrubs that normally do not appear until after the drought has occurred.  Drought- related predisposition to attack by opportunistic pathogens can occur even when drought stress symptoms are not obvious.  The role of water stress in encouraging opportunistic plant pathogens is unclear.  It is possible that the stress condition interferes with the plant's defense against such pathogens, or possibly, the reduced carbohydrate reserves leaves the plant little energy to fight invasion by pathogens.

Certain fungi such as Hypoxylon, an oak pathogen (see above article on Hypoxylon canker), and Armillaria, which attacks many woody plants are influenced by drought stress.  Similar relationships to drought may exist with other fungi such as Thyronectria, cause of honeylocust canker, Cytospora or Valsa, causes of cankers on prunus, poplar, willow, maple, spruce and other conifers, Sphaeropsis, cause of pine tip blight, and Botryosphaeria, cause of cankers of many woody plants. Symptoms of these cankers may not appear until the season following the dry weather.

Thus, it is important to continue watering woody landscape plants, so long as local watering restrictions allow it.  Further information on this subject is available in U.K. Extension Publication ID-89, How Dry Seasons Affect Landscape Plants which is available at your local county extension office.