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Apple Virus Detection

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Virus and Other Graft-Transmissible Diseases and Disorders of Apples

Virus diseases cause economic losses through lower yields and reduced quality of apples and apple products. In general, virus diseases in perennial crop plants, such as apples, are more potentially damaging than in annual crops. Viruses can remain latent, spreading through an orchard and inflicting damage, often without the growers' knowledge. Latent virus infection can produce small to moderate losses in fruit production. Often growers can maintain the productivity of diseased orchards at a profitable level by removing infected plant parts and replacing dead trees to limit the spread of the virus. Sometimes, however, losses are severe, and an acute viral infection can require tree removal.

How Virus Diseases Are Spread

Apple virus diseases are mainly spread thorough vegetative propagation. Because of this, in apple production, two methods are used to control virus diseases: adoption of virus-free propagation materials and eradication of contaminated trees. In addition, in areas where tomato ringspot virus is endemic, practices may be employed to minimize alternative virus hosts (i.e., deciduous weeds) and reduce nematode vector populations.

Some virus infections cause incompatibility between apple rootstock and scion cultivars, affecting yields and profitability of apple nurseries. A low success rate of successful grafting in nurseries may be attributed to virus infection. Reductions in bud survival have been reported to range from 20% to 67%. The degree of impact depends on the pathogen or its strain in combination with fruit type, cultivar, rootstock, nutrient supply, and tree age.

Virus Testing

Virus testing of imported propagation materials into the United States has been the most important measure used to prevent the introduction and spread of unwanted viruses.

The testing and use of virus-free materials have different benefits for each of the three sectors involved: nurseries, growers, and consumers.

Growers and nurseries benefit from virus testing in three ways:

  • reduced yield losses from viruses.
  • no need to invest in other virus control measures.
  • reduced risk of virus spread.

Consumers benefit from lower prices and more abundant fruit.

National Virus-Testing Facility

There are two facilities that tests for viruses in fruit trees in the United States. One is the National Research Support Project 5 (NRSP-5). The NRSP-5, located at the Washington State University Irrigated Research and Extension Center in Prosser, Washington, implements the nation's virus protection program for all deciduous fruit trees. NRSP-5 is responsible for providing sources of deciduous fruit tree propagation materials free of virus and virus-like diseases. NRSP-5 also develops, evaluates, and implements new technologies for virus detection and the elimination of viruses and virus-like agents from commercially important cultivars. Prior to the establishment of NRSP-5, viruses abounded in every fruit-growing region in the United States. The success of this project has resulted in a dramatic reduction in the incidence of viral diseases. The other, according to Renee DeVries, is the Plant Germplasm Quarantine Office (PGQO), Beltsville Agricultural Research Center, Beltsville, Maryland. For more information on Plant Quarantine Programs Managed by APHIS-PPQ, click here.

List of Potential Viruses

A short list and description of potential viruses are provided in Table 1. The list is not exhaustive, as many other viruses and strains of known viruses are not listed here. In addition, many unconfirmed graft-transmissible causal agents may ultimately be shown to be viruses or phytoplasma. Table 2 provides information on yield reduction caused by virus diseases in apple.

The National Clean Plant Network has recommendations for minimum testing standards for foundation and certification materials (test recommendations marked with an asterisk below are those acknowledged by the International Working Group on Fruit Tree Viruses (Acta Horticulturae 657:2004, pp. 575) and for which adequate testing exists with ELISA, PCR, or PT-PCR. Items identified as agents are graft-transmissible but are incompletely characterized.

Table 1. Taxonomic groups, isolates designations of major apple tree viruses, and some of their biological characteristics
GroupVirusAcronymSymptomsTransmission*References
CapillovirusApple stem grooving virusASGVStem grooves, abnormal graft unionMe/Gr/SeUyemoto and Gilmer, 1971; Plese et al., 1975
IlarvirusApple mosaic virusApMVMosaic, mottling, necrotic ring spotsMe/Gr/PoGotlieb and Berbee, 1973; Wood et al., 1975
NepovirusTomato ringspot virus (apple union necrosis)ToRSVMosaic or ringspots, rasp leaf, yellow bud or vein, ringspots and chlorosisMe/Gr/Se/Po/NeStouffer et al., 1977; Parish and Converse, 1981
SobemovirusApple latent virusALV (type II)Latent infectionMe/Gr/Se/Po/InFranki and Miles, 1985
TrichovirusApple chlorotic leaf spot virusACLSV (ALV type I)Chlorotic leaf spots or rings, stem pitting, stunning, line patterns, chlorosisMe/Gr/NeChairez and Lister, 1973; Dunez et al., 1975
FoveavirusApple stem pitting virusASPVDie back, inner bark necrosis, decline, epinasty, vein yellowing, latent infectionMe/GrFridlund and Aichele, 1987; Kogenezawa and Yanase, 1990
PhytoplasmaApple rubbery woodCausal agent is a phytoplasma and is included here because it was first investigated as a possible virus diseaseAbnormal flexibility of stems and branches, shortened internodes, reduced or stunted annual growth, rootstock productivity, tree vigor and yield may be reducedMe/GrNRSP-5
*Possible transmission patterns:

Me = mechanical.

Gr = grafting.

Se = seeds.

Po = pollen.

In = insects.

Ne = nematodes.

Table 2. Yield reduction effects on apple production due to viral diseases.
Apple CultivarsVirus StrainYield Reduction (%)References
Golden DeliciousApple mosaic virus (AMV)46Baumann and Bonn, 1988
Golden DeliciousAMV, rubbery wood disease agent (RW)21-67Baumann and Bonn, 1988
Golden DeliciousRW46Wood, 1978
Golden DeliciousApple stem grooving virus (ASGV), apple stem pitting virus (ASPV), apple chloritic leaf spot virus (ACLSV)12Meijnske et al., 1975
Golden DeliciousASGV, ASPV, ACLSV30van Oosten et al., 1982
McIntoshAMV9Zawadzka, 1983
McIntoshRW8Zawadzka, 1983
Red DeliciousAMV42Zawadzka, 1983
Red DeliciousRW20Zawadzka, 1983

Web Resources:

Apple Virus Detection

References:

  • Baumann, G., Bonn, G E., 1988. Einflub von Apfelmosaik und Gummiholzkrankheit auf Die Vegetative und Generative Leistung von Apfelsorten auf M 9 bis zum 13 Standjahr. (The influence of apple mosaic virus and rubbery wood on growth and cropping of apple trees on M 9 till the 13th orchard year.). Erwerbsobstbau 30:162-165.
  • Chairez, R. and Lister, R.M. 1973. A comparison of two strains of apple chlorotic leaf spot virus. Phytopathology 63:1458-1464.
  • Dunez, J., Marenaud, C. and Delbos, R. 1975. Bark split disease of prune trees and its association with strains of apple chlorotic leaf spot virus. Acta Hortic. 44:81-91.
  • Francki, R.I.B. and Miles, R. 1985. Mechanical transmission of sowbane mosaic virus carried on pollen from infected plants. Plant Pathol. 34:11-19.
  • Fridlund, P.R. and Aichele, M.D. 1987. Reactions of crabapples considered as potential apple pollinizers to latent virus infection. Fruit Var. J. 41:17-18.
  • Gotlieb, A.R. and Berbee, J.G. 1973. Line pattern of birch caused by apple mosaic virus. Phytopathology 63:1470-1477.
  • Koganezawa, H. and Yanase, H. 1990. A new type of elongated virus isolated from apple trees containing the stem pitting agent. Plant Dis. 74:610-614.
  • Meijnske, C.A.R., van Oosten, H.J., Peerbooms, H. 1975. Growth, yield and fruit quality of virus-infected and virus-free ‘Golden Delicious' apple trees. Acta Hortic. 44:209-212.
  • Parish, C.L. and Converse, R.H. 1981. Tomato ringspot virus associated with apple union necrosis and decline in Western United States. Plant Dis. 65:261-263.
  • Plese, N., Hoxha, E. and Milicic, D. 1975. Pathological anatomy of trees affected with apple stem grooving virus. Phytopathol. Z. 82:315-325.
  • Stouffer, R.F., Hickey, K.D. and Welsh, M.F. 1977. Apple union necrosis and decline (tomato ringspot virus as possible cause). Plant Dis. Rep. 61:20-24.
  • Uyemoto, J.K. and Gilmer, R.M. 1971. Apple stem-grooving virus: propagating hosts and purification. Ann. Appl. Biol. 69:17-21.
  • van Oosten, H.J., Meijnske, C.A.R., Peerbooms, H., 1982. Growth, yield and fruit quality of virus-infected and virus-free ‘Golden Delicious' apple trees, 1968-1982. Acta Hortic. 130:213-220.
  • Wood, G.A., Chamberlain, E.E., Atkinson, J.D. and Hunter, J.A. 1975. Field studies with apple mosaic virus. N.Z. J. Agric. Res. 18:399-404.
  • Wood, G.A. 1978. Effect of rubbery wood disease on growth and yield of ‘Golden Delicious' apple trees. Orchardist N. Z. 51:66-67.
  • Zawadzka, B., 1983. The effect of mosaic and rubbery wood infection on the growth and yield of apple trees. Zesz. Probl. Postepów Nauk Roln. 291:385-390.

Alan R. Biggs, West Virginia University

Think your Mac is infected? How to detect and remove viruses and malware on Mac computers

Many Mac computer users believe that Apple computers are perfectly protected from any type of malicious software or virus code. This situation might have been true for some considerable time, however, the prevalence of malware has increased with the growing popularity of Apple products. On the other hand, mobile devices such as iPhone, iPad, and iPod touch remain relatively safe, since most malicious software and viruses are developed to infect the macOS operating system. Despite this, some of these infections transfer from Macs to iOS devices when they are connected via a USB cable.

As compared to the Windows operating system, the Mac operating system includes an increasingly effective protection system. System updates are delivered with a new version of a database including the list of known malware and viruses. This allows computers to search and block these infections automatically. In the past, Mac computers remained virus free for long periods because malicious software developers predominantly targeted Windows computers. Today, however, Mac computers might be affected by many of the viruses now present on the internet. Built-in protection tools now automatically deal with threats, and often it is more difficult to notice if your Mac system is infected, whether performance is reduced, etc. In this article, we describe common cases of computer infections, how the system behaves in response to them, and how to diagnose existing threats.

Table of Contents:

It is recommended to run a free scan with Malwarebytes - a tool to detect malware and fix computer errors. You will need to purchase the full version to remove infections and eliminate computer errors. Free trial available.

What is the difference between a virus and malware?

First, we will clarify the definitions of malware and a virus. Malicious software (malware) usually behaves like various applications and often appear to do little when opened. In fact, these applications add extra applications that might display pop-up ads, and change the home page and default search engine settings. These infections are mostly used to display advertisements, however, they sometimes also track browsing history, most used queries, etc. Viruses are small portions of computer code designed to go unnoticed, however, they often reduce Mac performance. Checking the activity monitor will enable you to see the kernel task consuming extensive computer resources due to the prevalence of a virus, since it is designed to protect the Mac from overheating.

Most common signs of an infected computer

There are many symptoms of Mac infection, but these might vary with the type software installed on your computer. Here we describe the most common scenarios to alert you of the need to check for malicious software.

  • Computer performance has noticeably decreased. It becomes sluggish and the activity monitor displays various mysterious process running in the background, consuming Mac resources.
  • You notice a new toolbar on the web browser, that you have not intentionally installed. In most cases, these toolbars encourage you to shop or search faster by typing a search query directly into toolbar.
  • Casual Internet browsing loads unexpected results, or redirects to irrelevant websites. Search queries appears within an unfamiliar search engine.
  • Websites that you open displays many advertisements, including those that should be ad-free (for example Wikipedia).
  • Your favorite websites (that you normally visit daily) do not load, or you are randomly redirected to advertising webpages.
  • Advertising windows continually pop up on the desktop and you cannot find any association with websites that you browse or programs you run.

If you have noticed any of these symptoms, do not panic - performance is often reduced for a number reasons, and it may not be the result of a virus or malware on the system. Additionally, some developers attach ads to their software with intention of introducing you their other products. Nevertheless, it is always safer to scan your computer for possible threats. Bear in mind, however, that if you simply enter a query describing your problem and download the result, it might be malware or a fake application.

Most common methods of computer infection

Knowing how malware and viruses infect your computer will help you to diagnose or prevent possible threats. The methods vary with the type of threat, however, there are a number of common ways that unwanted software can infiltrate your computer. Check the list below to ensure that the threats have not infiltrated your Mac.

Malicious software

As mentioned above, malware and malicious software are merely synonyms for a type threat that is introduced as 'free' (or sometimes paid) software that supposedly cleans or protects your computer from viruses. In the most frequent cases, this software appears when the search query contains keywords about fast, easy and free viruses removal. To avoid these threats from malicious software, check independent reviews of applications or ask for personal recommendations from other users. These threats are spread by downloads, emails, or even instant messages.

Fake files

Malicious software and viruses are frequently hidden within common files, such as images and Word or PDF documents. Many computer users are aware of the dangers of opening executable files such as .dmg on Mac computers and .exe on Windows, but few believe that simple image or document files might also contain threats. The best precaution is to open files from trusted or known sources only, and avoid opening data that appears on your desktop randomly or together with installation of untrusted software.

Fake updates or system tools

Another popular and confusing method used to spread malware is through various pop-up dialog boxes. These encourage you to upgrade your software and apply additional tools to access the content. The Adobe Flash Player browser plug-in is a popular way hide threats within its installation files. We strongly recommend that you add and update this plug-in through their official website only.

Randomly contacted by 'technical help'

Occasionally there are cases whereby users receive calls from people claiming to be Apple or Microsoft 'technicians'. They often state that your computer is likely to be infected and you should follow some steps to clean it. Following their guidance will add malicious software to your system.

Built-in protection tools

Apple Flashback Virus

Together with system updates, Apple includes tools that work in the background to protect users from malware and viruses. You are advised to check how they are invoked and what actions they perform.

File Quarantine or Gatekeeper

Most Mac users are familiar with this tool, but not all are aware of how it is invoked and what function it actually performs. When attempting to open an application you have downloaded or installed from external storage, you will see a warning message that displays information about the source from which it was downloaded. You must manually choose to open the file, unless the application is downloaded from Mac App Store, since these apps are acquired from a trusted Apple source. If you are trying to launch an application that was not digitally signed by the developer (a condition enforced by Apple), the File Quarantine/Gatekeeper tool will block the access to this particular application.

Xprotect

This tool contains a slightly more aggressive prevention policy against files that are recognised as possible malware or virus infections. When trying to open files for the first time after download, this tool checks the entire package and compares it with the database of known malware or viruses. If it finds any matches, you will see a message stating that files are infected or damaged and the only option offered is to move the file to trash. The Xprotect tool works very successfully and is one of the main reasons why infected Mac computers are rare. This tool might sometimes block older versions of legitimate software, such as Java or Flash plug-in, since it was proven that these plug-ins are vulnerable to malware attacks.

Use Combo Cleaner to clear your Mac

Combo cleaner contains two virus scan engines. The first checks for Mac-based malware infections, while the second searches for PC generic security threats. This software scans the Mac and also checks web browsers for potentially unwanted plug-ins and infected emails. Although infected emails do not directly cause system problems, this option prevents possible threats spread via email messages. First, visit the Combo Cleaner developers website, and get the software. Then, launch it and select Antivirus in the left side panel. Choose Quick Scan, Full Scan, or Custom Scan. Quick Scan is the best option when you suspect that you might have threats on your computer but do not have time to perform a full scan. Full Scan will scan all files stored within the Mac hard disk. This option might take some time, depending on the amount of files your storage area contains. A Custom Scan might be the best option when you wish to check specific files or folders.

Recommended actions when Mac is infected

Following the steps below, you can decrease the risk of problems that may be caused by malicious software. Apple tv converter mac. Also, you will be able to eliminate threats to the Mac.

Apple Virus Detection

Avoid entering passwords

If you suspect that your computer might be infected by a virus or malware, do not enter any passwords or login details, due to the possibility of a hidden keylogger running in the background. This software is commonly deployed with malware and viruses. Bear in mind, that some of these infections record periodical screenshots, so you should avoid of revealing any passwords when copying and pasting from a document or clicking the Show password option.

Stay offline

Another good precaution is to disconnect from Internet. Turn off the Wi-Fi and/or unplug the Ethernet cable from your computer, until you are sure the computer is safe. This will protect your private data from any third parties, since most data that malware collected is sent to the servers, where developers are able to access it.

Activity Monitor

If the information above helped you to consider recent files you have downloaded or installed to your computer, try to remember their name. If the application is running, turn it off by using the keyboard shortcut of Command and Q or simply click the Quit button in the top left corner of the window. Further, open Activity Monitor by using Spotlight or going to Applications and then the Utilities folder through Finder. Once Activity Monitor is launched, locate the search field at the top right corner of the window and type the name of the malicious software. Often, you will find that the application is still running in the background, even though you have closed it recently. Select the running app and click the X icon at the top left of the toolbar and click Force quit. Most malware developers are aware of this situation, and thus deliver random, unused names, to make it difficult to find the particular process in this way.

Shut down and restore

If it is possible, turn off your computer and enter Recovery Mode by holding down the Command and R keys while pressing the power button - hold down these keys until you see Apple logo. Restore your Mac from a recent backup, such as Time Machine or another application. Bear in mind, that you should select the backup created prior to the point at which you believe the Mac was infected. When the restore process finishes and your computer is rebooting, ensure that external storage is not connected to the Mac (if it previously had contact with the infected device). Also be vigilant and do not open fake applications, emails, or files that contain threats. The best option is to connect external storage to a Windows computer running antivirus software (although the infection is based on a Mac operating system, these programs should be able to detect and remove it).

Protect credit card details

If you think your computer was infected with one of the methods listed above, delete the files immediately. If, however, you have made any transfers or purchases from your credit card, especially for software that appeared to be fake, contact your credit card company or bank immediately and explain the situation to ensure that your credentials are not used elsewhere. You might receive refunds for bogus money transfers.

Clear junk files

To ensure you have eliminated the infection completely, also clear all the junk files. Clear the Internet browser cache manually. Open Safari and click on Safari in the menu bar at top of your screen, then select Clear History. In the new pop-up window, select All history from the drop-down list, and finally click Clear History. Next, delete the entire download folder. Open this folder through Finder, select all files within and drag to Trash, or right-click and select Move to Trash. Finally, open Trash and select the Empty the Trash option.

Change passwords

A final option is to secure all logins. Once you are sure the computer is completely clear of infections, change all passwords, including those of websites, cloud services, applications, etc. You are advised to contact your credit card company or bank to notify them of the current situation - they might then heighten attention for attempts to access your account in future.

Apple Iphone Virus Detection

Reinstall macOS

Apple Virus News

If you have endured many unsuccessful attempts to clean the Mac, there is another option that will work in most cases: consider a complete reinstallation of the Mac operating system. Detailed instructions are in this guide.

Video Showing how to clear Mac from viruses and malware





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