Spray for Apple trees

Fruit Tree Care: Spray & Weed Control

A properly executed schedule for maintaining fruit trees and their growing site is key to success. Plan ahead: the rewards are worth the effort!

Summer is finally upon us, and it’s time to take a good look at our fruit trees. Pest and disease control – in the form of a well-maintained growing site, as well as sprays (either natural or synthetic) – are things to practice on a year-round basis. Keeping a growing site clear of debris and weeds will help keep down the risk of fungal infections and environments suitable for pests. Dormant-season sprays are a great preventative, and growing-season sprays help provide prevention and control as needed. After the very unusual spring experienced in most parts of the country, the best defense for the fruit crop is a good offense in the form of a well-executed spray schedule. Here is a timeline for a full year’s worth of advice for maintaining fruit trees. In summer, you can begin by implementing Step 4.

Pest & Disease Control: Build a Spray Schedule

Step 1: During winter pruning (or anytime before spring bud-break): the first step in a good spray routine is to use a dormant spray. I recommend applying a horticultural dormant oil in late winter or early spring. Applying this dormant-season spray protects apple trees, pear trees, pie cherry trees, and grape vines from scale, mealy bugs, aphids, mites, and pear-psylla. It may also be used on dormant plum trees, peach trees, blueberry plants, strawberry plants, apricot trees, pecan trees, and your asparagus patch for various overwintering pests/eggs. The first spray of the season is a crucial component for your tree. It’s important to spray thoroughly — coat the entire tree — and follow the label for specific instructions. Step 2: During bloom time: I recommend applying a fire blight spray (on apple and pear trees). This is one rare application that should be made while trees are in bloom. Fire blight is a bacterial disease that infects fruit trees like apples and pears and bloom time is the best time for an effective spray application. The control contains streptomycin sulfate. While it’s intended to use at bloom time, we still urge you to spray at dawn or dusk while bees and other beneficial insects are not frequenting your trees as a food source. Step 3: After petal drop: Copper Fungicide works to control rots, spots, and other fungus affecting grape vines, strawberry plants, apple trees, pear trees, apricot trees, cherry trees, almond trees, and rose bushes. Copper-based sprays are recommended as an effective and natural means of control for things like peach leaf curl as well. A copper spray can be mixed, but some may be applied as a dry dust. Follow the printed label instructions for application methods and other necessary information for the diseases you are trying to control on your plants and trees. Step 4: After the pollination period is over and before daytime temperatures exceed 80-85ºF, you can use growing-season pest and disease-control sprays. Before applying, always make sure to read and follow the instructions on the product label. Use cautiously around small children and pets. Since pest-control sprays contain an insecticide that also will harm flower-loving beneficials like bees, be sure to only apply after every flower petal has fallen. Bees will be less likely to frequent your trees after this time. Bees are very active during the day, so spraying during the twilight hours of the morning or evening (when there is still enough sunlight to see) will also help avoid contact with bees. For an organic fungicide: Use Garden Disease Control for most fungal issues on fruit and nut trees, ornamentals, trees, shrubs, flowers, and tropical plants. For an organic insecticide, miticide, and fungicide: Use Neem Oil for vegetables, herbs, roses and other flowers, fruit trees, and berry plants. Can also be used as a dormant spray for overwintering pests. Find more natural pest and disease control options here. Again, you’ll be most successful if you read and follow the directions on each label.

Weed Control: Prevention & Maintenance

Weeds plague both the garden and fruit trees. They compete for the same nutrients and water intended for the desired plants. If allowed to go unchecked, weeds can completely nullify your planting efforts. The best way to get rid of weeds is to physically remove them on a consistent basis. Consider using a Typar® Tree Circle to prevent their presence around trees in your garden. If you consider using chemicals to eliminate weeds, try to find a solution that isn’t harmful to you, your plant, or the environment. Because weeds are plants too, anything that may harm or kill them could potentially affect the very plants you’re trying to save.

Reminders

For those of you who haven’t read Fruit Tree Care: Watering & Fertilizing, I’d like to point you over there. I generally do not recommend fertilizing past June 15th here in the Midwest, and stop most fertilizer applications by July 1. Consistent watering is especially necessary during the heat of the summer months — whether it’s provided by you or by nature in the form of rain. Summer is a time of both maintenance and harvest. With proper care, your young trees should mature healthy and strong, giving you crops of delicious fruit for many enjoyable years! — Elmer Kidd, Stark Bro’s Chief Production Officer (retired)

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Spraying Fruit Trees

Dormant sprays can help reduce pests & disease in home orchards.

Prevention is the first step in controlling diseases and insect pests in home orchards. Many problems can be avoided by choosing resistant fruit tree varieties and providing them with proper care. That care includes removing all dropped fruit and leaves that might be harboring pests.

But even the most vigilant gardeners may need to spray their trees during the dormant season to reduce over-wintering pest and disease organisms.

Spraying fruit trees during the cool seasons, November through March, can help control pests that take up residence in the cracks and crevices, according to Ross Penhallegon, horticulturist with the Oregon State University Extension Service. Such dormant spraying is more effective than waiting until the weather warms and pests become active.

Below are some least toxic sprays and treatments for fruit trees. These products are widely available at garden centers. Always follow label directions.

Dormant Oil: Apply when trees are dormant, November through March, after all the leaves have fallen. Mix with water as directed and spray to all surfaces of the trunk, branches and twigs. Apply when the temperature is expected to rise during the day; temperatures below 35 degrees can damage the bark. Dormant oil controls aphids, scale, spider mites, and many other insects by desiccating or smothering eggs and larvae.

Lime-Sulfur: Spray to control fungal and bacterial diseases such as peach leaf curl, fire blight, scab and anthracnose. Do NOT apply sulfur sprays to apricots.

Fixed Copper: Spray on apples, pears, cherries, peaches, and plums to control canker. Allow two weeks between applications of copper and any sprays containing sulfur. Add a spreader-sticker product to help copper adhere to the tree surface.

Latex paint: Coat the trunks of young trees with white latex paint mixed half-and-half with water. The paint reflects strong sunlight that, once the leaves fall, can cause cracking, a favorite place for pests to overwinter and can cause substantial winter damage.

Here are some tips for specific fruit trees:

Apples: Spray copper before fall rains; dormant oil once or twice from January through March; lime-sulfur in January or February (just before buds open) and wettable sulfur just after petal fall.

Apricots: Spray copper before the fall rains and dormant oil in February.

Cherries: Use wettable sulfur or lime-sulfur applied weekly during blooming for brown rot. Information on synthetic sprays to control cherry fruit fly is available at your local county office of the OSU Extension Service.

Pears: Spray copper before the fall rains; spray lime-sulfur two to three times beginning in fall, again during winter, and finally in March just before buds open; spray dormant oil in early spring before buds open and wettable sulfur just after petal fall.

Peaches: Spray copper or a good dormant fungicide three to four times between December and bud break. Spray copper or lime-sulfur before fall rains and in spring just before bud break; apply sulfur weekly during blooming and again after all petals have fallen.

Author: Peg Herring
Source: Ross Penhallegon / University of Oregon Extension Service

Home Fruit Insecticides

Pesticide label

Karen Delahaut, UW-Madison Fresh Market Vegetable Program
Revised: 4/26/2004
Item number: XHT1098

Recently, several commonly-used insecticides for the control of insects in home fruit trees and berries have been taken off the market. As a result, it’s becoming ever more challenging for home gardeners to find suitable insecticide products at garden centers, discount stores, and hardware stores. This listing will help identify some of the suitable products that may replace products that are no longer available. Please be sure to note the product names carefully as several products have similar names, and make sure you check that the active ingredient on the product label is what you’re looking for.

Fruit insecticides that have lost their registration include diazinon and chlorpyrifos (Dursban). The following products are still available and effective for the control of the insects listed. Control recommendations for pests such as aphids, leafrollers, and plum curculio that are common to several tree fruits are listed under apple only.

Apples

Aphids
• Carbaryl, Malathion, Methoxychlor (Bonide Fruit Tree Spray)
• Dimethoate (Hi-Yield Cygon)
• Endosulfan (Hi-Yield Thiodan)
• Esfenvalerate (Ortho Bug-B-Gone)
• Malathion/Methoxychlor (Fertilome Triple Action, Ortho Home Orchard Spray)
• Permethrin (several products)
• Phosmet (Bonide Imidan WP)
Apple Maggot
• Carbaryl (Sevin)
• Esfenvalerate (Ortho Bug-B-Gone)
• Malathion/Methoxychlor (Fertilome Triple Action, Ortho Home Orchard Spray)
• Phosmet (Bonide Imidan WP)
Codling Moth
• Carbaryl (Sevin)
• Carbaryl, Malathion, Methoxychlor (Bonide Fruit Tree Spray)
• Esfenvalerate (Ortho Bug-B-Gone)
• Malathion/Methoxychlor (Fertilome Triple Action, Ortho Home Orchard Spray)
• Permethrin (several products)
• Phosmet (Bonide Imidan WP)
Leafrollers
• Bacillus thuringiensis (Dipel, Thuricide, Others)
• Carbaryl (Sevin)
• Carbaryl, Malathion, Methoxychlor (Bonide Fruit Tree Spray)
• Esfenvalerate (Ortho Bug-B-Gone)
• Malathion/Methoxychlor (Fertilome Triple Action, Ortho Home Orchard Spray)
• Permethrin (several products)
• Phosmet (Bonide Imidan WP)
Mites (Includes Pear Rust Mite)
• Dormant Oil
• Insecticidal Soaps
Plum Curculio
• Carbaryl (Sevin)
• Carbaryl, Malathion, Methoxychlor (Bonide Fruit Tree Spray)
• Esfenvalerate (Ortho Bug-B-Gone)
• Malathion/Methoxychlor (Fertilome Triple Action, Ortho Home Orchard Spray)
• Permethrin (several products)
• Phosmet (Bonide Imidan WP)
Scales
• Esfenvalerate (Ortho Bug-B-Gone)
• Insecticidal soap (Safer’s, Concern)
• Dormant oil

Pears

Pear Psylla
• Esfenvalerate (Ortho Bug-B-Gone)
• Permethrin (several formulations)

Raspberries

Aphids
• Insecticidal Soap (Safer’s, Concern)
• Malathion
Cane Borer
• Carbaryl (Sevin)
• Rotenone
Fruitworm
• Carbaryl (Sevin)
• Rotenone
Leafrollers
• Carbaryl (Sevin)
Picnic Beetles
• Carbaryl (Sevin)
• Malathion
• Rotenone
Sawfly
• Carbaryl (Sevin)
• Malathion
• Rotenone

Stone Fruits
(Apricots, Cherries, Peaches, Plums)

Cherry Fruit Fly
• Carbaryl (Sevin)
• Carbaryl, Malathion, Methoxychlor (Bonide Fruit Tree Spray)
• Phosmet (Bonide Imidan WP)
• Rotenone
Cherry Fruitworm
• Carbaryl (Sevin)
• Phosmet (Bonide Imidan WP)
Peachtree & Lesser Peachtree Borers
• Endosulfan (Hi-Yield Thiodan)
• Esfenvalerate (Ortho Bug-B-Gone)
• Permethrin (several products)
Tarnished Plant Bug & Stink Bug
• Carbaryl (Sevin)
• Endosulfan (Hi-Yield Thiodan)
• Esfenvalerate (Ortho Bug-B-Gone)
• Permethrin (several products)
Strawberries

Aphids
• Endosulfan (Hi-Yield Thiodan)
• Insecticidal Soap (Safer’s, Concern)
• Malathion/Methoxychlor (Fertilome Triple Action, Ortho Home Orchard Spray)
Cyclamen Mites
• Endosulfan (Hi-Yield Thiodan)
• Malathion
Leafhoppers
• Endosulfan (Hi-Yield Thiodan)
• Malathion
• Rotenone
Picnic Beetles
• NONE
Plant Bugs
• Carbaryl (Sevin)
• Endosulfan (Hi-Yield Thiodan)
• Malathion/Methoxychlor (Fertilome Triple Action, Ortho Home Orchard Spray)
Slugs
• Iron Phosphate (Escar-Go, Sluggo)
• Metaldehyde bait (several products)
Spittlebugs
• Carbaryl (Sevin)
• Endosulfan (Hi-Yield Thiodan)
• Malathion/Methoxychlor (Fertilome Triple Action, Ortho Home Orchard Spray)
Strawberry Leafroller
• Bacillus thuringiensis (Dipel, Thuricide, Others)
• Carbaryl (Sevin)
• Endosulfan (Hi-Yield Thiodan)
• Malathion/Methoxychlor (Fertilome Triple Action, Ortho Home Orchard Spray)
• Rotenone
Strawberry Bud Weevil
• Malathion/Methoxychlor (Fertilome Triple Action, Ortho Home Orchard Spray)
White Grubs
• NONE

For more information on insecticides: See University of Wisconsin Garden Facts XHT1095, XHT1096, XHT1097, or contact your county Extension agent.

Tags: insect, pest, pest management, pesticide Categories: Fruit Care, Fruit Problems, Fruits

Breaking news

VISIVASNC/DREAMSTIME.COM Many gardeners use neem because they view it as being “not chemical”.

More gardeners are using neem to tackle pests and diseases, but is neem itself a good guy or not?

The new century was a little over a month old when neem burst into the consciousness of New Zealand gardeners. “Editors please note,” came the herald from a Palmerston North nurseryman and garden columnist in February 2000. “The following is a great breakthrough in gardening pest control and if possible should be printed to assist your local gardeners… Incredible breakthrough in garden pest control… Recently a new natural substance has become available to the home gardener that looks like it is going to be the main solution to the control of many common insect pests.”

This great hope of organic gardening was touted as able to kill all those garden pests such as aphids and grass grubs while somehow leaving other insects and organisms unharmed.

It was no new panacea though.

* Organic pest & disease control for your favourite fruits
* Vegetable gardening guide: Part 6. Beating pests & diseases
* Q & A: How do I protect my roses from aphids?

LANDSCAPES/ADOBE STOCK A grove of neem trees.

For thousands of years, extracts from Azadirachta indica, aka neem, a medium-sized, evergreen tree native to the Indian subcontinent, had been used locally to cure or ameliorate a myriad of ailments from leprosy and respiratory disorders to constipation, rheumatism and malaria. And for just as long, farmers had been using it as a pesticide and soil conditioner, among other things.

Almost every part of the tree contains neem’s prized compound, azadirachtin, but it is most concentrated in the seeds and is extracted from them much as olive oil is from olives.

The post-extraction residue is traditionally made into neem cake, and is now sold as granules.

Neem’s effects on insects is grisly. The American National Research Council’s 1992 book Neem: A Tree for Solving Global Problems details how it disrupts or inhibits the development of eggs, larvae, or pupae; disrupts mating and sexual communication; repels larvae and adults; deters females from laying eggs; sterilises adults; poisons larvae and adults; deters feeding; blocks the ability to swallow; sends metamorphosis awry at various stages; and inhibits the formation of chitin (a primary component of the exoskeletons of arthropods). Different insects are affected differently, and more than 300 insect species can be affected one way or another, including bees, moths, flies, butterflies and grasshoppers.

123RF Neem leaves and essential oil.

The home gardener will typically spray neem oil onto foliage to kill or deter aphids, beetles, cabbage white butterflies, leaf miners, whiteflies, mealybugs and other pesky leaf-chewers and sap-suckers, leaving other insects unharmed.

The underlying theory is explained by organic gardener and former Lincoln University Biological Husbandry Unit tutor Hamish Kelland. Unlike the other main botanical insecticide, pyrethrum, which is toxic to insects on contact and is thus an indiscriminate killer of both pest and beneficial (and neutral) insects, neem oil has to be ingested to be effective, he explains. So beneficial predacious and parasitoidic insects are not affected as typically, these feed on other insects and not plant material – and so seldom get enough concentrations of neem to affect them (although research has shown that hoverfly larvae are sensitive to neem sprays).

Collateral damage is one reason why all insecticides should be used cautiously, Hamish says.

He uses pesticide sprays – of any sort – as little as possible. “Maybe once a season, and only as a last resort. Say, if the aphids are bad on our roses, I will make a mixture of garlic, cooking oil and water, and spray just the tips, where the aphids are most likely to be feeding on the tender new growth.”

In addition, he simply doesn’t get the spray out for just the odd pest. Instead, he applies patience. “I wait to see if the beneficials come and manage them, and only if they are really getting away on the plant do I spot-spray.”

This is in contrast to the usual advice dispensed to neem users, who are often told to spray at first pest sighting because as a growth regulator, it is most effective on immature insects.

123RF Neem tree, Azadirachta indica, flowers.

Nelson’s Bill Brett, horticulturalist and author of Garden Pest & Disease Control, concurs with Hamish.

“I aim to minimise pest and disease by using all science-proven cultural practices, resistant varieties where possible, and early intervention (at the beginning of the first life cycle of the pest).”

His “vegetable arsenal” includes neem, but only Naturally Neem, which he says is the only neem approved for use on vegetables by New Zealand’s Environmental Protection Agency. Bill’s preference for one neem brand over others highlights the difficulty of scientific consensus on the efficacy of neem.

The ease and variety of ways the azadirachtin and other compounds can be extracted from the tree and processed, along with genetic and differing environmental factors, makes for neem products of varying toxicity as well as quality.

Bill finds neem effective against sucking insects, including aphids, thrips, whitefly, mealybug, scale and mites, but not against chewing insects such as caterpillars, beetles and green vegetable bug.

Given the range of insects affected by the neem oil, it is common sense to only spray when the beneficial insects such as hoverfly, lacewings and ladybirds are not around at dusk or dawn. And never in spring when blossom and bees are out in force.

Remember too, that oil alone will smother many other insects.

123RF Neem leaves and fruit.

Christchurch gardener Sue Hesp has been happily using neem for eight years following her daughter’s recommendation. She uses Wally’s Secret Tomato Food with Neem Granules on her tomatoes, loves it and knows it works. “There are no insects on the tomatoes,” she observes, adding that when the whiteflies start appearing, she knows the neem is running out.

While Sue prefers to use the granules, she also uses neem oil on her fruit trees as a winter spray and is about to try granules under her apple trees to get rid of codling moth. She says she tries not to spray too much and does not use any other sprays in her garden. Sue likes the idea of using neem because “it is not chemical” and hasn’t seen any negative effects of using it in her garden.

While neem oil is pretty much all about killing and deterring pests and certain fungi, neem granules are also believed to be good for the soil as well as acting as pesticide and deterring soil pathogens, fungi and pests such as nematodes, grass grubs, root mealybugs, carrot flies and gall.

By blocking soil bacteria from releasing nitrogen, neem has the beneficial effect of reducing the rate of denitrification. Recent research has shown that neem can increase the number of microorganisms in both the soil and the rhizosphere, with other field trials revealing it can even increase the average weight of the earthworms in the soil.

Keep your tomato plants healthy for a bumper crop.

So far, all good stuff, but is there any bad that comes from its use?

Some effects do bear more thinking about. As neem degrades relatively rapidly in ultraviolet light and water, it tends not to build up in the environment. This is fortunate as neem is mildly toxic to fish and other aquatic animals – so it’s best not to be heavy-handed with it.

Some formulations of neem-based products can actually damage plants, and many suppliers suggest avoiding using it around plants in bloom, newly transplanted ones or those under stress.

Debate over its toxicity to humans and other mammals continues.

Bill Brett points out that the EPA-approved Naturally Neem actually carries a warning on the label that it may affect the reproductive systems of terrestrial vertebrates (that is, humans).

Sue Hesp says she has heard rumours that neem is carcinogenic, but discounts them.

Both, however, are among an undeniably growing number of gardeners using it. According to Christchurch garden centre Terra Viva, their neem oil and granules sales have increased 55 per cent since 2015, with the oil being more popular than the granules.

While it might not quite live up to its initial billing as the great green saviour of gardening, neem has certainly earned a place on the top shelf, albeit with a caution: use sparingly.

NZ Gardener

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Horticultural Oils for Pest Control

What are Horticultural Oils?

Horticultural oils are petroleum-based or vegetable-based pesticide oils which are used to control insects and mites. Being non-toxic, they work by smothering the pests and suffocating them, and as such, they’re a direct contact pesticide, meaning that you have to spray the pest directly at the time of application for the pesticide to be effective. Horticultural oils are also non-selective, that is, they kill whatever insect or mite you spray them on, regardless of whether they’re pests or beneficials.

Both natural and synthetic horticultural oils are mixed with water for spraying, but as we are all well aware, oils don’t normally mix with water. To allow them to mix with water, horticultural oils also contain emulsifiers, soap-like substances which break up the oil into tiny droplets, allowing them to evenly disperse through the water, forming what us called an emulsion (basically oil mixed in water).

A Brief History of Horticultural Oils

The use of oils to control pests is not a new technology by any means. In 200 BC, the Roman senator and historian Marcus Porcius Cato (also known as Cato the Elder) advocated oil sprays for pest control. Before the era of fossil fuels and petroleum refinement, natural oils were historically used to control pests, and with industrialisation, there was a shift towards synthetic petroleum-based oils.

The early petroleum-based oils were called dormant oils, because they were heavy, unrefined oils which contained substances that were toxic to plants and damaged their leaves, and could therefore only be used on dormant deciduous plants and trees (which have dropped their leaves).

Manufacturers eventually refined the petroleum-based oils to remove toxic impurities, such as compounds containing sulphur, nitrogen or oxygen and aromatic compounds. By the additional processes of filtration, distillation and dewaxing, manufacturers were able to produce the very light and highly purified petroleum-based horticultural oils available today, which can be used in all seasons of the year and do not cause leaf burn.

With the trend back to natural pest control methods, we’ve seen increased interest in the use of vegetable-based oils for pest control in recent years. Some of the vegetable-based pest oils also contain additional plant oils such as neem oil, an extract from seeds of the neem tree (Azadirachta indica), which contains the compounds Azadirachtin A & B, which have insecticidal and fungicidal properties.

Which Pests and Diseases Do Horticultural Oils Control?

Traditionally horticultural oils were developed for hard-to-control pests on fruit trees that overwintered in crevices in the bark while the trees were dormant, such as mites, scale, aphids, mealybugs and the eggs of some caterpillars.

Modern horticultural oils can be used all year round and are effective in controlling scale, aphids, two-spotted mite, mealybug, whitefly and citrus leafminer. They can possibly be used on plant bugs, lace bugs and some caterpillars.

Horticultural oils may also be used to prevent certain fungal diseases such as powdery mildew and rose black spot.

Additionally, horticultural oils do have some deterrent effect, as pest insects don’t like laying their eggs on oily leaf surfaces, so spraying may deter early outbreaks of aphids, scale and mites on fruit trees.

When horticultural oils also contain other plant oils such as neem oil, they may be effective against a broad range of chewing and sucking insects, killing pests which ingest the oil after it has been sprayed.

Advantages of Horticultural Oils

Horticultural oils are relatively non-toxic, and are quite safe to humans and wildlife. They don’t have an objectionable smell, and can be used indoors as well as outdoors. In terms of cost, horticultural oils are fairly cheap compared to other pesticides. Additionally, they will not harm non-target beneficial insects such as bees, parasitic wasps and ladybirds if you don’t spray them directly! Horticultural oils evaporate quickly, and once they dry they have little residual toxic activity to beneficial insects.

Disadvantages of Horticultural Oils

The biggest problem with horticultural oils is that they have to contact and cover the pest to be effective. This means that you have to be very thorough when spraying, being sure to spray the whole plant or tree, including areas such as the undersides of leaves and cracks in the bark, as these are places where pests often hide. It also means that immobile, slow moving and very small pests are easier to control than larger, faster moving and flying ones.

How to Use Horticultural Oils

As horticultural oils work by direct contact, sprays must be evenly applied, covering all plant surfaces including both the tops and undersides of all leaves, as well as stems, branches and bark.

Horticultural oils are commonly sprayed in winter on deciduous fruit trees and roses to control pests such as scale, aphids, mites and mealy bugs. The first winter application is usually carried out after pruning and a second application just before bud burst occurs. Spraying can also be done at any other times when pests are observed.

To control citrus leaf miner on citrus trees, spraying is done when new flush growth is present, and application is repeated every 5 to 14 days.
With vegetables and ornamental plants, to control mites, aphids and greenhouse whitefly, spraying is done when pests first appear and then repeat applications are carried our as directed on the product label.

Horticultural oils can also be used on Indoor plants to control scale insects, mealy bugs and spider mites. Some indoor plants, such as maidenhair ferns, are more sensitive to leaf damage so it is recommended to test any horticultural oil on a small area of foliage before using to avoid yellowing or leaf burn.

The withholding period is the amount of time to wait before consuming any produce that has been sprayed. With petroleum oils, do not apply to edible crops later than 1 day before harvest. Plant based oils are safe for use on vegetables with no withholding period, so you can spray and eat on the same day, just wash thoroughly before eating as you normally do.

Precautions

  • Do not spray when temperatures are near or above 35°C because heat increases risk of leaf injury through drought-stress.
  • Only use on healthy, unstressed plants, do not apply to plants suffering from heat or moisture stress.
  • Do not use on citrus trees in late autumn/winter, as this can sometimes cause increased susceptibility to winter injury, wait until after winter hardening has occurred before spraying.
  • Do not spray directly on to sensitive flower heads to prevent oil spotting.
  • Do not combine with sulphur or sulphur-containing sprays such as lime sulphur as they can react with oils to form phytotoxic compounds (substances toxic to plants). Also, do not mix with fungicides such as Captan (which contains sulphur) or pesticides such as carbaryl.
  • Do not use horticultural oils within 30 days of a sulphur application because elemental sulphur can persist for long periods, check label directions as most oils prohibit their use.
  • Do not use on plants that tend to be sensitive to oils.

Environmental Impact of Synthetic and Natural Horticultural Oils

Synthetic horticultural oils such as ‘White Oil’ list their active ingredient as petroleum oil, paraffin oil, or sometimes as naphtha, it’s all pretty much the same thing, just a refined petroleum oil mixed with an emulsifier to make it mixable with water. By comparison, natural horticultural oils are emulsified plant oils.

Environmental impact of any garden product can be broken down into the categories of toxicity, soil mobility, persistence and bioaccumulation potential.

If we compare the toxicity of the natural and synthetic petroleum oils, we see some differences. In general, they’re both classed as low in toxicity to animals, birds, bees and fish, but moderately toxic to earthworms and some other aquatic organisms such as molluscs.

If we have a closer look at human toxicity, we see that the petroleum oils do present a higher toxicity hazard in terms of chronic toxicity hazard in the areas of reproductive and developmental toxicity.

According to the review by Thurston County Health Department in the US, “When evaluating petroleum oils for potential for reproductive and developmental toxicity, there were some effects that suggest that fetal toxicity can occur at doses without maternal toxicity. The EPA concluded that the very high doses used in the toxicity tests were so much higher than those expected from pesticidal uses that there are no concerns for potential sensitivity of infant and children to mineral oils and aliphatic petroleum hydrocarbons” (Reference: USEPA. Office of Pesticide Programs, Special Review and Reregistration Division. Revised Reregistration Eligibility Decision, Exposure and Risk Assessment on Lower Risk Pesticide Chemicals. CASE: Aliphatic Solvents (3004). Active Ingredients: Mineral Oil (063502) & Aliphatic Petroleum Hydrocarbons (063503). Revised: November 29, 2007.)

Thurston County Health Department qualify their statement by explaining that they lowered the risk rating from high to moderate in light of the US EPA assessment: “Thurston County pesticide review system typically rates reproductive or developmental toxicity without maternal toxicity as high in hazard but since the EPA has determined that the concentrations that toxicity was observed was much greater than those expected from pesticidal use that the hazard is rated moderate.”

So, overall, petroleum oils are moderately toxic to humans, as compared to natural plant oil formulations which are often used in foods, and are considered low in toxicity.

The routes of exposure are typically through inhalation or skin contact. According to the safety data sheets for petroleum-based horticultural oils, to minimize risk:

  • Avoid skin and eye contact and inhalation of vapour, mist or aerosols.
  • Use personal protection equipment: Overalls, Safety Shoes, Safety Glasses, Gloves.
  • If risk of inhalation of exists, wear organic vapour/particulate respirator meeting the requirements of AS/NZS 1715 and AS/NZS 1716.
  • Consumer Use: Wear gloves. Wash hands after use.
  • Hygiene measures: Keep away from food, drink and animal feeding stuffs. When using do not eat, drink or smoke. Wash hands prior to eating, drinking or smoking.

While some of these measures sound overstated (overalls and safety shoes for spraying horticultural oil?), exercise common sense and take the necessary measures required to avoid breathing in petroleum oil or getting it on your skin!

Both natural and synthetic oils have low soil mobility, being poorly soluble in water they are expected to bind well to soil and vegetation, so there is little to no risk of run-off and contamination of groundwater and waterways.

If we look at environmental persistence, how long it takes for the product to break down, we find that natural oils have a low persistence, they break down very quickly into natural substances being plant-based, while synthetic oils have a high persistence, and tend to remain in the soil for a long time. Most synthetic petroleum oils aren’t broken down by sunlight or hydrolysis (breakdown through interaction with water), and are likely to take over 60 days to biodegrade to half of the applied concentration.

The synthetic petroleum oils are poorly absorbed when ingested, inhaled, or through skin contact, and are quickly eliminated from the body, unchanged and not metabolized, so their potential to bioaccumulate is low – that is, the levels of pesticide do not build up in plants, animals and other living things.

By comparison, natural plant oils, being harmless food products, if ingested, are likely to be absorbed and metabolized by humans, animals and fish, but exposures from uses in pest control are unlikely to accumulate to a toxic level, so the risk of bioaccumulation is also rated low.

In SGA’s Garden Product Guide – Safe for You ‘n’ Nature, which rates garden products on a 6-star rating (where 6 stars indicates a very low environmental impact and 1 star indicates a very harmful product environmentally and for humans), natural horticultural oils typically rate well with 5 out of 6 stars, while synthetic petroleum-based horticultural oils rate less favourably at 4 out of 6 stars.

Fruit Tree Spray Schedule: Tips On Proper Fruit Tree Spraying Times

When you first chose your fruit trees, you probably picked them from a tree catalog. The shiny leaves and gleaming fruits in the pictures are enticing and promise a delicious result after a few years of minimal care. Unfortunately, fruit trees aren’t the carefree plants you might hope they’d be. Pests and diseases affect fruit trees in every part of the country. Spraying fruit trees is the best way to avoid these problems, and they work best when they are done at the right time of the year. Let’s learn more about when to spray fruit trees.

Fruit Tree Spray Schedule

Tips on proper fruit tree spraying times are normally dependent on the types of sprays used. Here are the most common types for spraying fruit trees and the best time for spraying trees to prevent future issues.

  • General-purpose spray – The easiest way to take care of all possible pests and problems with your fruit trees is by using a general-purpose spray mixture. You won’t need to identify every pest and disease that is bothering your tree, and it will cover those you might even miss. Check the label and use a mix that is labeled for fruit tree use only.
  • Dormant sprays – To take care of scale insects, apply a substance called dormant oil. Dormant oils should be used early in the spring, before the leaf buds begin to open. They can cause damage to trees if you use them when the temperature drops below 40 degrees F. (4 C.), so check the weather for the next week before using these oils. Most fruit trees only need dormant oils applied about every five years, unless there is a large infestation problem in the area.
  • Fungicide sprays – Use a fungicidal spray early in the season to eliminate scab disease, such as with peaches. You can wait a bit longer in the spring to use this spray, but do so before the leaves have opened. These general purpose fungicides should always be used when the daytime temperatures are steadily around 60 degrees F. (15 C.).
  • Insecticidal sprays – Use insecticidal spray when the flower petals fall to take care of most fruit tree pests. The only exception to this rule for home use is probably the codling moth. To take care of this common insect, spray the trees again two weeks after the petals fall, and one final time in the middle of summer to take care of the second generation of moths that often arrives.

No matter what type of spray you’re using on your fruit trees, take care to never use them just when the blooms are opening. This will avoid damaging the bees that are so important for pollination and fruit development.

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