Plum tree treatments, most common diseases and pests of this fruit tree, Nexles

Plum tree treatments, most common diseases and pests of this fruit tree

The plum tree (Prunus domestica) is a fruit tree that is part of the Rosaceae family. Their fruits are used for the preparation of the jams, compotes and brandy. The plum is not very pretentious to the vegetation factors, valorising very well the soils from the hill area. They don’t like the drought and compacted soils. The plum produces fruits after 4-5 years from planting, and its longevity is about 30-40 years. It is a medium tree, the leaves are oval and the flowers are white. The plums can be valorized in different ways. They contain: carbohydrates, organic acids, albumin, cellulose, vitamins (A,B,C), iron, calcium, magnesium, phosphorus, sodium.

Main diseases

Viruses:

Plum pox virus

On the leaves forms some circular spots of discoloration, that will cover all the leaves. On the fruits will appear circular, yellow spots, very well visible on the unripe fruit. The attacked fruit will fall from the tree before its time. If the attack is severe, the circular spots appear on the seed. The virus spreads through the infected planted material, through cicadas, aphids and pollen.

Prevention and control measures:

  • Usage of healthy graft;
  • Spatial isolation between the orchards cultivated with stone fruit trees;
  • Destruction of the weed and shrubs close to the orchard;
  • Usage of insecticides to control the population of insects.

Bacteriosis:

Bacterial canker of stone fruits (Pseudomonas syringae pv morsprunorum)

This disease manifests on the young sprouts, leaves and fruits. On the leaves appears small, circular spots with a watery look. When the humidity is high, on the surface of the spots appears the bacterial exudate as a white-yellow viscous pellicle. When is dry, the attacked tissue dries and comes off the leaf. So, the leaves will have a pierced look. A powerful attack determine trees defoliation. On the fruits are presented small, red-brown spots. The attack produces fruit deformation and crack of the pulp. Due to that the apricots lose their commercial value. On the sprouts appears long spots, the bark brunifies and its destroyed. On the produced wounds appears viscous liquid, specific bacterioses. The wounds grow from year to year and can evolve in open cancer. The bacteria penetrates the tree through the stomata, but most of the infection are produced during grafting.

Prevention and control measures:

  • Usage of healthy graft;
  • Treatments on burgeoning: Bouillie Bordelaise WDG, Copernico Hi-Bio, Melody Compact 49 WG, Funguran OH 50 WP, Champ 77 WG.

Crown gall produced by Agrobacterium radiobacter pv. Tumefaciens

On the roots and on the stem develop tumors, at the start small and soft, and after a while becomes like a wood. The tumors are having different sizes and forms. This tumors generate formations like leaves, buds or sprouts. The cells that compose this tumors are big and deformed. This bacteria penetrates into the tree through the wounds produced by the nematodes, hail etc. The appearance of this disease is favored by the temperatures between 22 and 30 degrees Celsius and atmospheric humidity of 80%.

Prevention and control measures:

  • Sorting seedlings before planting;
  • The orchard will be founded on the lands that were prepared properly;
  • Disinfection of scissors and tools, before passing from a tree to another;
  • Cutting the affected branches up to the healthy area, appliance of a treatments with Bouillie Bordelaise 4-5% and covering the wounds with cicatrisant mastic resin;
  • The seedling roots will be bathed in a solution of Bouillie Bordelaise 1% or Topas 100 EC 0.025%;
  • Treatments in the vegetation period with products based on copper.

Micosis:

Bladder plum gall produced by Taphrina pruni

The young fruits become yellow-green and are bigger than the healthy ones. After the attack, the fruits are deformed, and the shell of the stone is destroyed. On the surface of the fruits appears a grey fluff, that represents the fructifications of the fungus. After 3-4 weeks the fruits wrinkle and fall massively. The fungus winters as a mycelium on the bark of the trees. The appearance of the disease is favored by the wet and cold springs.

Prevention and control measures:

  • Usage of resistant varieties;
  • If the environmental conditions are favorable you should apply 4 treatments. You should this products: Bravo 500 SC, Score 250 EC, Polyram DF, Merpan 50 WP, Systhane Plus 24 E.

Shot hole disease produced by the fungus Stigmina carpophila

The disease is common in the unkept orchards and produces important losses to the stone fruit trees. On the leaves appears circular spots in whose right the tissue brunifies, and finally it breaks away from the rest of the leaf. On the fruits it can be observed some dot-like formations, surrounded by a red-lilac border. The pulp of the fruits losses its texture and taste. On the sprouts, the fungus produces brunifications, followed by wounds from which glue leaks. This form of attack is very dangerous, because dries the sprouts that has fruit buds. The spores assure the spread of the fungus and resists through the winter in the glue that leaks from the wounds. Also, the fungus can winter as a mycelium on the surface of the branches.

Prevention and control measures:

  • Cutting and burning the affected branches;
  • The wounds resulted after the cutting will get covered with mastic resin;
  • After the cuttings,to the trees will be applied a treatment with Bouillie Bordelaise 4-5%;
  • Treatment application in the vegetation period with Sore 250 EC, Folpan WDG, Rovral 500 SC.

Powdery mildew produced by the fungus Podosphaera tridactyla

This disease is not dangerous, but in the dry and hot years can affect the sensitive years.The attack appears on the leaves of young sprouts through the appearance of some white spots. Those will extend and will cover the whole leaf. The disease will evolve, and the mycelium will become grey and dusty. The attacked tissue wrinkles and dries. The fungus attacks the young fruits too. This are covered by a white mycelium felt. The fruits crack and rot.

Prevention and control measures:

  • Balanced fertilization;
  • Usage of resistant varieties;
  • The attacked sprouts and fruits will be burned;
  • Treatments with Systhane Plus 24 E, Thiovit Jet 80 WG, Kumulus DF, Topas 100 EC, Karathane M 35 CE.

Brown rot produced by the fungus Monilinia laxa

This disease attacks all the aerial organs of the trees, producing significant losses in the cold and rainy years. The attacked leaves hang without falling, the flowers brunify and dry, and the branches bend as a hook. The young fruits wrinkle, brunify and fall massive. The pulp of the mature fruits rots and on their exterior appear yellow-grey pillows. Finally, the fruits are mummified and remain in the trees, ensuring the transmission of the disease in the next year. The fungus winters on the mummified fruits and in the bark of the attacked branches.

Prevention and control measures:

  • Gathering and destruction of the attacked fruits;
  • Cutting and burning the affected branches;
  • Cutting the affected branches up to the healthy area, appliance of a treatments with Bouillie Bordelaise 4-5% and covering the wounds with cicatrisant mastic resin;
  • Chemical treatments in the vegetative rest with products based on copper (ex: Bouillie Bordelaise) and preventive treatments applied in vegetation with Switch 62.5 WG, Score 250 EC, Topsin 500 SC.

Blackthorn dotty produced by the fungus Polystigma rubrum

On the leaves appear some circular, yellow spots, that evolve and become orange and finally red. The tissue in the right of the spots thickens, become crispy and are swollen to the lower side. Finally the attacked leaves fall, producing premature defoliation of the trees. So, the tree is sensitive to the frost, and the differentiation of the fruit buds won’t develop normally.

Prevention and control measures:

  • Gathering and destroying the leaves from the orchard;
  • Usage of resistant varieties;
  • Treatments with Folpan 80 WDG, Falcon 460 EC, Topsin 70 WDG.

Peach rust produced by the fungus Tranzschelia pruni-spinosae

On the upper side of the limb will appear yellow spots. On the lower side in the right of the spots will appear the brown spores, and later (at the end of the vegetation) will appear the spores of resistance, which are black. The attack of this fungus determine low resistance to frost and the appearance of fructification once at 2 years. The fungus has its first stages of development on the Persian buttercup, and after that passes on the fruit trees. Also, Blackthorn (Prunus spinosa) is an intermediate host in which the fungus multiplies, and after that migrates on cultivated species. Winters as a mycelium in the subteran organs of the plants from the Anemone genus (Persian buttercup).

Prevention and control measures:

  • Gathering and destroying of leaves from the orchard;
  • Destruction of the Prunus spinosa and Anemone spp which are near the orchards;
  • Treatments with Bravo 500 SC, Topas 100 EC, Score 250 EC, Falcon 460 EC.

Main pests

Codling moth (Cydia pomonella)

It is a polyphagous species that attacks many species of fruit trees. The larvae attacks the fruits. The females lay their eggs directly on the fruit or on the leaves close to the fruit. After hatching, the larvae diggs galleries in the attacked fruits, leaving inside faeces.

Prevention and control measures:

  • Using the pheromone traps to identify the flight of the adults;
  • Treatments with Reldan 22 EC, Novadim Progress, Laser 240 SC, Affirm, Calypso 480 SC.

Brown-tail (Euproctis chrysorrhoea)

It is a polyphagous species that attacks some shafts and fruits trees. It has a generation a year and winters as a larvae in a cocoon on the top of the sprout. The larvae attacks the buds and the leaves and can produce tree defoliation. For detecting the presence of this pest, the trees should be examined very well.

Prevention and control measures:

  • Elimination of the branches where the larvae are presented;
  • Treatments with Karate Zeon 50 CS, Fastac Active, Laser 240 SC, Calypso 480 SC, Affirm.

Fall webworm (Hyphantria cunea)

It is a polyphagous species that attacks ornamental trees (Mulberry tree, London plane etc.) and fruit trees. It has 2 generations a year and winters as a pupa in the superficial soil layer. This insects produces defoliation of the trees and low fruit production. The caterpillars will stay on the lower side of the leaves and and will start to consume them. Also, they will weave some kind of nest, inside of which they eat.

Prevention and control measures:

  • Treatments with Faster 10 CE, Kaiso Sorbie, Affirm, Novadim Progress, Laser 240 SC.

Peach twig borer (Anarsia lineatella)

It has three generations a year and winters as a larvae under the exfoliated bark of the branches. In the spring, they leave their shelter and attacks the buds. In the young sprouts, the larvae eat holes to penetrate. The new appeared females will lay their eggs on the buds, and the larvae will penetrate in the fruits of the precocious species. The larvae of the next generations penetrate in the fruits that will ripen, where it diggs deep galleries.

Prevention and control measures:

  • Cutting and destroying of the affected branches (sprouts);
  • Treatments with Decis Mega EW 50, Karate Zeon 50 CS, Affirm, Mospilan 20 SG, Laser 240 SC.

The mites are insects that hardly can be seen with the open eye. They are polyphagous species that attack many plants and fruit trees, cultivated species or spontaneous. They feed with the cell juice. After the attack, the leaves have a parchment look, the flowers abort, and the plant stagnates from growth.

Prevention and control measures:

  • Treatments with Nissorum 10 WP, Envidor 240 SC, Milbeknock EC, Vertimec 1.8 EC.

Oriental fruit moth (Cydia molesta)

It has 3-4 generations a year and winters as a larvae in a silky cocoon in the cracks of the bark. This moth attacks the sprouts, the leaves and fruits of the fruit trees, but the most damaged are the fruits. The larvae of the first generations attacks the sprouts and feed with the inside of them, producing big losses to the newly established orchards. The larvae of the third and fourth generations produce big damage to the fruits. This penetrate into the fruit through the peduncle area and eat irregular galleries around the stone. The apricots stop from growing, rot and fall.

Prevention and control measures:

  • Cutting and destroying of the attacked fruits and sprouts;
  • Usage of attracting traps;
  • Treatments with Mospilan 20 SG, Karate Zeon 50 CS, Decis Mega EW 50, Calypso 480 SC, Affirm.

San Jose scale (Quadraspidiotus perniciosus)

It is a polyphagous species that attacks over 200 species of plants. It has 1-3 generations a year and winters as a larvae on the bark of affected trees. The females and larvae spread on all the organs of the affected plant, including the fruit, this insect feeding with the cell juice of the host plant. If the attack is severe the shield that protects the body of the insect overlap and suffocate the trees. They stagnate from growing and in 2-3 years dry.

Prevention and control measures:

  • Application of the recommended treatments in the vegetative rest;
  • Cleaning the branches with a scrub;
  • Treatments with Nuprid AL 200 SC, Actara 25 WG, Calypso 480 SC, Faster 10 CE, Movento 100 SC.

The aphids are a polyphagous species that migrates from a plant to another or from a species to another. They grow on the spontaneous flora, and after that they move on the cultivated crop. It present as a colony on the lower side of the leaves, flowers or inflorescences and young sprouts. The insects sting and suck the cell juice, causing a stress to the plant. If the attack is severe, it causes a decrease in tree resistance to disease.

Prevention and control measures:

  • Treatments with Decis Mega EW 50, Confidor Energy, Mospilan 20 SG, Actara 25 WG.

Plum fruit moth (Cydia funebrana)

This species attacks the stone fruit trees. It has 2 generations a year and winters in a cocoon or in different protected spaces. The larvae penetrates into the fruit and feed with the pulp and stone. The attacked fruit stagnates from growing and fall on the ground. The larvae will continue their feeding on the fallen fruits. After the feeding, they leave the fruit and will search for the right place to winter.

Prevention and control measures:

  • Treatments with Laser 240 SC, Karate Zeon 50 CS, Faster 10 CE, Affirm, Decis Mega EW 50.

Sciaphobus squalidus

It is a dangerous species that attacks usually the flower buds and blossoms. It has a generation every 2 years and winters as an adult in the superficial layer of the soil. In the spring the adult appear, that climb in trees and feed with flower buds and blossoms. The larvae are not dangerous to the tree, they feed on the roots of the spontaneous herbaceous plants.

Prevention and control measures:

  • Moving the soil in the autumn;
  • Treatments with Decis Mega, Reldan 22 EC, Fastac, Actara 25 WG, Calypso 480 SC.

Apple blossom weevil (Anthonomus pomorum)

It has a generation a year and winter as an adult in protected areas (bark of the trees). The adults appear in the spring and feed with the young leaves. The females lays its eggs in the flowers or in the blossoms. The larvae feed inside the flowers or blossoms.

Prevention and control measures:

  • Treatments with Decis Mega, Reldan, Fastac, Actara 25 WG, Calypso 480 SC.

Thrips

They are some small insects, hardly visible with open eye, they attack a high number on culture plants or fruit trees. They colonise the flowers, leaves, determining the abortion of the flowers and stagnation from the growing of the tree.

Prevention and control measures:

  • Treatments with Actara 25 WG, Mavrik 2 F, Karate Zeon 50 CS, Decis Mega 50 EW;
  • Usage of attracting traps.

Apple leaf-curling midge (Dasineura mali)

It has 3-4 generations a year and winters in the superficial layer of the soil. The first signs of attack appear in may, when twisted and discolored leaves can be observed. Inside those leaves you can find yellow-orange vermiform larvae. If the attack is strong, the photosynthesis capacity is reduced and the yield too.

Prevention and control measures:

  • Treatments with Movento 100 SC, Calypso 480 SC, Faster 10 CE, Nurelle D, Affirm.

Spotted tentiform leafminer (Phyllonorycter blancardella)

This insect attacks a series of ornamental trees and fruit trees. The larvae will feed with the tissue found between the upper and lower epidermis of the leaves. A massive attack will reduce the ability of photosynthesis and implicitly decreases production.

Prevention and control measures:

  • Gathering and burning of the leaves fallen on the soil;
  • Treatments with Actara 25 WG, Reldan 22 EC, Laser 240 SC, Coragen 20 SC, Kaiso Sorbie.

Plum scale (Sphaerolecanium prunastri)

It is a polyphagous species that attacks many fruit trees, vine etc. It has a generation a year and winters as a larvae on the bark of the attacked branches. The adults and larvae colonise the branches and leaves producing tissue necrosis. Also, they can attack the leaves, producing deformations and their fall. The attacked plants are covered with their sweet droppings, that favors the appearance of some phytopathogenic fungus.

Prevention and control measures:

  • Cleaning the branches with a scrub;
  • Treatments with Mospilan 20 SG, Nuprid AL 200 SC, Decis Mega EW 50, Calypso 480 SC, Faster 10 EC.

Winter moth (Operophtera brumata)

It is a species that has a generation a year and attacks some shrubs and fruit trees. The larvae produces heavy losses. They attack the buds, flowers, leaves and even the fruits. After the attack the fruit buds are destroyed, the flowers are consumed, and the leaves are nibbled. So, the production decreases significantly.

Prevention and control measures:

  • Treatments with Actara, Reldan 22 EC, Laser 240 SC, Affirm, Kaiso Sorbie.

Hoplocampa minuta, Hoplocampa flava, Eurytoma schreineri

The larvae of those insects penetrate the young fruits, where it consumes the stone and part of the pulp. After the attack, the fruits wrinkle, become violet and fall from the tree.

Prevention and control measures:

  • You should apply 2-3 treatments with different products, after the flowers began to fall. Examples of products: Actara 25 WG, Laser, Affirm, Movento 100 SC, Calypso 480 SC.

Got a question?

When does one spray to control pests and disease in plums and pears?

During the vegetation period, treatments are applied in certain phenophases for the control of pests and diseases. As the possible treatments are many and varied, please provide more information, even images of your trees, so that our experts can follow up with specific information and advice. Please email more details regarding your issue to [email protected]

What is the cause and nature of large sections of plum tree bark pealing apart?

There can be several causes: the attack of some pests, certain diseases, alternation of cold/sunny days during winter (depending on the area).

I have white splotches along the small branches of my plums. Mainly on the purple leaf variety. Thought it was scales but none of the pictures match. We had an extremely dry summer and now a real wet fall in NC….any ideas? Can post a pic if helps

Can you verify if these white splotches can be removed?

www.nexles.com

The Best Time to Spray Plum Trees for Worms

Worms can cause considerable damage to plums, as well as to the trees on which they grow.

Related Articles

A plum tree festooned with gaily-colored moths is hardly a welcome sight for fruit growers, It means that the tree will likely suffer damage from the moths while at the caterpillar stage, also known as the larvae or worm stage. The worm stage is generally the best time to treat plum trees to control populations. But if you do spray for worms in your plum trees, examine both the worms and the damage they cause carefully to determine which fruit worms are in the trees. The most effective time to spray plum trees depends on what kind of worms are causing the damage.

General Guidelines

Make sure the crawlers you see in your plum tree aren’t the grubs or larvae of beetles, which generally are treated with methods other than spraying. Many non-spray methods exist for controlling fruit worms, such as attracting and releasing natural predators or removing infested tree parts. If you do spray for worms, the bacterial spray Bacillus thuringiensis (Bt) is generally applied when the worms are at their youngest, but when to spray depends on season the worms emerge. Spinosad is also considered organic and best used when worms are young, but the time of day you spray is as important as the time of year. That’s because spinosad can harm honeybees if applied when they are active. Evening through early morning is the best time of day to spray Spinosad.

Citrus Cutworm

To control citrus cutworm, which eat plums as well as citrus, apply the bacterial spray Bacillus thuringiensis (Bt) during the spring period in which the worms are at their smallest. The worms emerge from eggs in waves, so you’ll likely need to spray Bt more than once during this period. Spinosad, another organic spray, is applied just after the petals fall, but before fruits emerge. The citrus cutworm is light green and pink or brown at one end, with a white stripe. Older cutworms are duller in color, but still have the white stripe. The worms are most evident in early spring, before they go dormant. Damage includes holes in the plum tree’s leaves and fruit.

Fall Cankerworm

Spray Bt when the larvae are young, which is around when the plum tree flowers, or just after. The fall cankerworm gets its name from the season in which it turns into a moth. But spring and fall is when the worms emerge, turning foliage into skeletons and occasionally leaving scars on fruit through their deep bites. The worms have a characteristic habit of standing on their back legs. They can also be identified through their three white and one yellow stripes running along the sides of their green bodies.

Fall Webworm

Bt is the organic spray of choice for controlling fall webworm. Spray trees as soon as you notice the caterpillars in the fall. If they have already reached the web-tent stage, follow manufacturer’s instructions for adding a wetting agent to better reach the worms inside the tent. As their name suggests, fall webworms emerge in late summer, and during the fall create tents on the branches of trees, including plum trees. They also destroy foliage. Although these webs are the clearest way to identify them, they’re also known for their orange spots on green bodies, with long white hairs giving them a fuzzy look.

Green Fruitworm

The University of California’s Integrated Pest Management program notes that the green fruitworm is often controlled by the sprays used for other pests. But if you have to treat plum trees specifically for the green fruitworm, spray Bt twice when the worms are still small. Your first application should be just after the trees are first beginning to bud. Make the second application a week to 10 days later. Spinosad is an alternative spray choice. The IPM program recommends spraying Spinosad in late spring when the blossoms are falling from the trees. Additionally, apply the spray between late evening and early morning, to avoid killing honeybees. The green fruitworm has three narrow white stripes — one on each side and one on top of its pale green body. It is notorious for causing scarred and oddly shaped plums by chewing large holes in young fruit. Holes in early foliage are also a telltale sign of the young fruitworm.

Codling Moth Worm

No organic sprays have yet been found to control codling moth worms, which tunnel their way through from the plum’s surface to the stone. Organic orchardists have reported some success by releasing a natural predator, the braconid wasp. Using a chemical spray is complicated for the home gardener because determining the necessity and the proper time for each spray relies on first setting pheromone traps to catch them at the moth stage, than calculating the number of days, at certain temperatures, will pass before the eggs hatch, in order to effectively spray the young worms. In general, the chemical pesticide spray Methoxyfenozide is applied about three times between May and August to treat the two to three generations of young codling moth worms. Aside from fruit damage, look for worms that are light pink or white, with brown or black heads.

Additional Larvae

Other larvae sometimes referred to as worms include the larvae of moths such as various leafroller moths, as well as the peach twig borer, redhumped caterpillar, Western tussock moth, Western tent caterpilla and, orange tortix moths. Bt applied when they are at their youngest is generally the first spray of choice, according to the the University of California’s IPM program. On the other hand, worms such as the young form of the American plum borer moth respond best to chemical sprays — in the case of the plum borer, at six weeks intervals starting in April.

Other Crawlers

The larvae or grubs of beetles such as the shothole borer, the Pacific flathead borer and the branch and twig borer may be mistaken as worms. Sprays are generally not indicated for these young pests. Removing damaged branches and twigs is often recommended to deal with the problem. Wrapping the trunks of trees also affords some protection from the larvae and the adult beetles.

homeguides.sfgate.com

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