Fruit Crops Edition - Blueberry Section

Seasonal updates on diseases, insects, weeds impacting small fruit (blueberry, cranberry, and wine grape). Fruit Pest Alerts are also available via this category feed.
 
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July 1, 2025 , and

Fruit IPM Report June 30, 2025

Peach:

Diseases: Bacterial Spot: This disease is still present, and has increased in severity in some orchards. Brown Rot:  With the recent rains, sulfur should not be part of the spray program. Most growers should be relying on a captan based program for mid-season covers, followed by better materials during the last 3 weeks pre-harvest. See the NJ Commercial Tree Fruit Production Guide for more information.   

Oriental Fruit Moth: A biofix point for OFM was set on 4/2 for southern counties and 4/17 in northern counties. We are past treatment timings targeting the second generation.

Japanese Beetles: Japanese beetles have been observed feeding on fruit across the state. Products containing imidacloprid (Admire Pro, Leverage 360) are effective and have a short preharvest interval.

Tarnished Plant Bugs; and Other Catfacing Insects: Catfacing insects remain very active. Very little recent fruit feeding has been observed.

Thrips: Flower Thrips have been observed feeding in highly colored ripening fruit, especially in poorly managed ground covers that contain clover or other flowering weeds. Thrips damage appears as “silvering” and usually appears on fruit close to harvest. If populations are high damage can be extensive. Presence of thrips may be scouted for using a beating tray to detect the presence of adults and nymphs in the tree. Flowering weeds and shrubs on orchard edges may also be scouted by shaking flowers onto a beating tray or a sheet of paper. Delegate or Entrust at the highest labeled rate are the usual recommended materials for thrips in stone fruit. Lannate may be effective in some orchards but has not worked well in recent years. These materials all have short PHI’s and may be applied close to harvest when damage typically appears. Damage is different than peach and appears as a dark streak in a similar pattern as silvering. See the NJ Commercial Tree Fruit Production Guide for more information.

Apples and Pears:

Figure 1. Bitter rot lesions on apple. Photo by Kaitlin Quinn.

Diseases: Now that primary scab has ended, the focus turns toward summer diseases such as fruit rots (esp. Bitter rot), and sooty blotch and fly speck. Bitter rot control has been difficult at best in recent years even where management programs have been rigorous. Research has suggested products such as Merivon, Luna Sensation, Inspire Super, Omega, and Aprovia may be effective, and longtime reliable broad spectrum fungicides such as captan and ziram should provide control. Experience has suggested that the addition of phosphorous acid products such as Prophyt or Rampart to captan sprays may improve control. Observations are that these products improve control of other summer diseases such as sooty blotch and flyspeck, and may help suppress scab infections where present. Bitter rot symptoms were observed last week in southern and northern counties (Figure 1).

 

 

 

 

Codling Moth (CM): A codling moth biofix was set in southern counties on 4/28 and in northern counties on 4/30. The first generation codling moth timings have ended. Second generation timings are updated below. Rimon is not recommended for this and later generations.

Codling Moth Degree Day Timing – Second Generation
Application and Insecticide Type
County Area Biofix Rimon:

75-100DD + 14-17 days later

 

 Intrepid

1150 + 1450 DD

Diamides – Altacor, Voliam mixes: (150-200 DD)

 Madex

1250 DD + every 7-9 days during brood hatch (later if first spray is an IGR)

 Standard Insecticides –  Delegate, Avaunt, OP’s, carbamates, pyrethroids

1250 DD + 1550 DD

 
DD 1150 1450 1250 1250 1550
Southern April 28 N/A N/A 6/29 7/9 7/2 7/2 7/13
Northern  April 30 N/A N/A 7/3 7/18 7/8 7/8 7/23

 

Phenology Table: Based on annual observations made in Gloucester County.

Pest Event or Growth Stage Approximate Date 2025 Observed Date
 Bud Swell (Redhaven/PF-17)  March 23 +/- 15 Days March 30
1/4″ Green Tip Red Delicious March 31 +/- 13 Days March 30
Pink Peach (Redhaven/PF-17) April 4 +/- 15 Days April 1
Tight Cluster Red Delicious April 9 +/- 13 Days April 5
Full Bloom Peach (Redhaven/PF-17) April 9 +/- 14 Days April 10
Pink Apple (Red Delicious) April 14 +/- 12 Days April 16
Full Bloom Apple (Red Delicious) April 22 +/- 11 Days April 25
Petal Fall (Redhaven) April 22 +/- 10 Days April 19
Petal Fall (Red Delicious) April 27 +/- 13 Days May 2
Shuck Split (Redhaven) April 30 +/- 11 Days April 26
Pit Hardening June 15 +/- 9 Days June 15

 

Tree Fruit Trap Captures – Southern Counties

Week Ending STLM TABM-A CM BMSB OFM-A DWB OFM-P TABM-P LPTB PTB
4/5/2025 0 0 0 0 0 0 0 0 0 0
4/12/2025 0 0 0 0 6 0 0 0 0 0
4/21/2025 0 0 0 0 36 0 1 0 0 0
4/27/2025 25 0 0 0 24 0 5 0 1 0
5/2/2025 517 0 4 0 12 0 6 0 13 0
5/9/2025 159 4 10 0 3 16 5 4 46 0
5/16/2025 91 11 6 0 1 36 2 14 69 0
5/23/2025 299 21 3 0 1 23 1 26 23 0
5/30/2025 399 14 2 0 0 41 1 11 10 3
6/6/2025 733 13 1 0 0 36 2 12 29 1
6/13/2025 684 19 2 1 0 81 2 17 22 8
6/20/2025 724 24 2 0.5 1 60 1 23 19 12
6/27/2025 932 5 1 0.8 1 40 0 5 24 14

 

Tree Fruit Trap Captures – Northern Counties

Week Ending STLM TABM-A CM BMSB OFM-A DWB OFM-P TABM-P LPTB PTB AMBROSIA BEETLE
4/5/2025 387 0 0 0 0 0 0 0 0 0 0
4/21/2025 435 0 0 0 0 0 1.3 0 0 0 0
4/27/2025 26 0 0 0 0 0 25 0 0 0 72
5/2/2025 86 0 0.33 0 72.5 0 47.2 0 0 0 136
5/9/2025 56 0 5.3 0 58.8 0 22.9 0 0 0 145
5/16/2025 13.75 2.6 7.3 0 4 0 5 0 0 0 50.5
5/23/2025 4.8 10.3 10.5 0 0.6 31.25 4.2 0 14.6 1 22.2
5/30/2025 2.2 4.8 1.8 0 0 12.4 9.6 0 9.6 1.9 22.1
6/6/2025 3 4.83 2.8 0.25 0 20 4.1 0 21.2 1.8 40.3
6/13/2025 65 20 11.4 0.6 0 12.3 4 0 10.5 1.5 59.2
6/20/2025 26 26 8 0.75 1 13 4.5 0 11 0.75 52
6/27/2025 145 19 6 1.3 6 35 5.4 0 16 1.6 38

 

Grape: The biofix in southern counties for Grape berry moth (GBM) was 5/24. Model timing will predict IGR and diamide materials for the second generation. The model works best when growers record their own bloom dates and use the Grape Berry Moth model at NEWA. The timing is set at 810 degree days base 470F for the second generation treatments using Diamides or Intrepid, which was approximately June 27 for southern counties. Other materials may be applied 2-3 days later. As we enter the summer period of disease management the focus shifts to cultural controls including leaf pulling, along with well-timed fungicide applications for downy mildew and powdery mildew management.

Blueberry: Spotted-wing drosophila (SWD) and Oriental beetle (OB) captures decreased from previous weeks likely due to heat. Blueberry maggot and sharp-nosed leafhopper trap counts remain low. For weekly reports on blueberry pests and recommendations read the Rutgers Blueberry Bulletin. For information on insecticides labelled for SWD control in small fruit crops, see the attached Table 1.

Filed Under: Blueberry, Fruit, Tree Fruit, Wine Grape
June 30, 2025 and

Late June Peach Varieties for New Jersey– New and Standard

The many peach varieties grown in New Jersey were developed in different breeding programs from several peach-growing regions, including the Rutgers Tree Fruit Breeding program. Recent evaluations have examined the known characteristics and challenges growers face in growing these varieties. These are important for making planting, thinning, harvesting, post-harvest handling, and marketing-related decisions. Understanding these differences is important for selecting varieties or replacing existing ones.

Desiree is a very attractive yellow-fleshed, clingstone peach variety, ripening during the last week of June. The fruit is beautiful and medium to moderately large, which is impressive for the early-season variety. The flesh is firm with a very sweet and tangy flavor. The tree is vigorous, and its leaves have low susceptibility to bacterial spot. The fruit is also having low susceptibility to Bacterial Spot. [Read more…]

Filed Under: Blueberry, Cranberry, Fruit, Strawberry, Tree Fruit, Uncategorized, vegetable, Wine Grape Tagged With: , , , ,
June 17, 2025 and

Fruit IPM Report June 17, 2025

Peach:

Bacterial Spot: Fruit symptoms from this set of infections have begun to appear in southern counties. So far fruit symptoms are very low and only in highly susceptible varieties. Peaches are at or past pit hardening and fruit now has some resistance to bacterial spot. Infections can still occur but will be less unsightly and may still make grade. Growers should continue to manage using Oxytetracycline and lower rates of copper, especially around rainy periods and severe weather.

Rusty Spot: Rusty spot infections are appearing on fruit across New Jersey and ongoing until pit hardening. Maintain coverage through second cover with effective materials such as Rally, Rhyme, or potassium bicarbonate products. Other choices include Flint Extra, Inspire Super, and Luna Sensation.

Peach Scab: Maintain good coverage with captan or other effective fungicides until July in orchards where scab was an issue last year.

Oriental Fruit Moth: A biofix point for OFM was set on 4/2 for southern counties and 4/17 in northern counties. Treatment timings targeting the second generation are shown in the table below.

OFM 2nd Generation Timing
Insecticide Type
County/Region Degree Days by 6/16 base 45 Conventional

1150-1200

1450-1500

 Intrepid/Rimon

1050-1150

1300-1400

 Diamides/Virus

1075-1150

1375-1450
Gloucester – Southern 1265 1st –past

2nd – June 23-26

 1st –past

2nd – June 17-20

 1st –past

2nd – June 20-23
Middlesex – Northern 1110 1st – June 18-20

2nd – too far off

 1st – June 13-18

2nd – too far off

 1st – June 14-18

2nd – too far off

Tarnished Plant Bugs and Other Catfacing Insects: Tarnished plant bug and other catfacing insects are active, and activity is increasing with dry weather and summer temperatures. There has been very little recent fruit feeding observed.

Green Peach Aphid: Green peach aphid counts have decreased significantly at most farm sites, but a few scouted blocks had pressure above threshold. If more than 1 colony of aphids are found in nectarines, or 2-3 colonies are found in peaches, an insecticide for aphids is needed. See the NJ Commercial Tree Fruit Production Guide for recommended materials and rates.

Scale Insects: White peach scale and San Jose scale crawlers began emergence around May 26 and will continue emergence for up to 6 weeks (Figure 1). Control options during crawler emergence include Neonicitiniods (suppression only), Sivanto, and the IGR’s Esteem and Centaur. See the NJ Commercial Tree Fruit Production Guide and the product labels for more information.

Figure 1. Scale feeding on apple.

Thrips: Increased thrips activity was recorded last week. Thrips damage appears as “silvering” and usually appears on fruit close to harvest. If populations are high, damage can be extensive. Delegate or Entrust at the highest labeled rate are the usual recommended materials for thrips in stone fruit. These materials all have short PHI’s and may be applied close to harvest when damage typically appears. Thrips have also been observed to mark cherries. Damage is different than peach and appears as a dark streak in a similar pattern as silvering. See the NJ Commercial Tree Fruit Production Guide for more information.

Apples and Pears:

Diseases: Now that primary scab has ended, the focus turns toward summer diseases such as fruit rots (Bitter rot), and sooty blotch and fly speck. Bitter rot control has been difficult at best in recent years even where management programs have been rigorous. Research has suggested products such as Merivon, Luna Sensation, Inspire Super, Omega, and Aprovia may be effective, and longtime reliable broad spectrum fungicides such as captan and ziram should provide control. Experience has suggested that the addition of phosphorous acid products such as Prophyt or Rampart to captan sprays may improve control. Observations are that these products improve control of other summer diseases such as sooty blotch and flyspeck, and may help suppress scab infections where present. Scab symptoms are appearing in some orchards statewide.

Fire Blight: Fire Blight symptoms began appearing in southern county apple orchards the week of 5/19. Typically it is recommended to cut out infected limbs; however, this is a practical decision that must be made. This blog post from Michigan State may be helpful to decide whether it is worth cutting out infected tissue. Once the terminal buds set, typically in July, infected wood should be removed to prevent colonization by the bitter rot pathogen.

Codling Moth (CM): A codling moth biofix was set in southern counties on 4/28 and in northern counties on 4/30. Trap captures increased in some orchards this week. Second generation timings are updated below. Rimon is not recommended for this and later generations.

Codling Moth Degree Day Timing – Second Generation
Application and Insecticide Type
County Area Biofix Rimon:

75-100DD + 14-17 days later

 

 Intrepid

1150 + 1450 DD

Diamides – Altacor, Voliam mixes: (150-200 DD)

 Madex

1250 DD + every 7-9 days during brood hatch (later if first spray is an IGR)

 Standard Insecticides –  Delegate, Avaunt, OP’s, carbamates, pyrethroids

1250 DD + 1550 DD

 
DD 1150 1450 1250 1250 1550
Southern April 28 past past too far off too far off too far off too far off too far off
Northern April 30 past past too far off too far off too far off too far off too far off

 

Figure 2. Aphids on fruit.

Wooly Apple Aphid (WAA); Green Apple (Spirea) Aphids (GAA): GAA colonies are being observed, some above threshold in some apple blocks (Figures 2 & 3). GAA is generally a pest that can be tolerated in orchards where beneficial insects are present. Generally treatment thresholds for GAA are if 50% of the shoots are infested where no beneficial insects are present. WAA aerial colonies are also forming in orchards statewide. See the NJ Commercial Tree Fruit Production Guide for more information on effective products at this time.

Figure 3. Green apple aphid colonies on younger branches.

Pear: Pear psylla are still actively laying eggs and nymphs continue to hatch. Options for control include spinosyn products such as Delegate and Entrust, and the neonicotinoids (IRAC group 4A). The addition of 0.25-1 gal of summer oil may improve control. Other options at this time include products containing abamectin. Be sure to read and follow the label instructions regarding the addition of penetrants for abamectin products.

Grape: The biofix in southern counties for Grape berry moth (GBM) was 5/24. Model timing will predict IGR and diamide materials for the second generation. The model works best when growers record their own bloom dates and use the Grape Berry Moth model at NEWA. The timing is set at 810 degree days base 470F for the second generation treatments using Diamides or Intrepid. Other materials may be applied a few days later. Given the current weather patterns, this should be about the last week of June in southern counties. As for diseases we are seeing low levels of phomopsis on older leaves in some vineyards.

Blueberry: Spotted-wing drosophila (SWD) and Oriental beetle (OB) captures increased from the previous week. The first catch of Blueberry Maggot (BBM) was recorded on June 12. For weekly reports on blueberry pests and recommendations read the Rutgers Blueberry Bulletin.

Phenology Table: Based on annual observations made in Gloucester County.

Pest Event or Growth Stage Approximate Date 2025 Observed Date
 Bud Swell (Redhaven/PF-17)  March 23 +/- 15 Days March 30
1/4″ Green Tip Red Delicious March 31 +/- 13 Days March 30
Pink Peach (Redhaven/PF-17) April 4 +/- 15 Days April 1
Tight Cluster Red Delicious April 9 +/- 13 Days April 5
Full Bloom Peach (Redhaven/PF-17) April 9 +/- 14 Days April 10
Pink Apple (Red Delicious) April 14 +/- 12 Days April 16
Full Bloom Apple (Red Delicious) April 22 +/- 11 Days April 25
Petal Fall (Redhaven) April 22 +/- 10 Days April 19
Petal Fall (Red Delicious) April 27 +/- 13 Days May 2
Shuck Split (Redhaven) April 30 +/- 11 Days April 26
Pit Hardening June 15 +/- 9 Days June 15

Tree Fruit Trap Captures – Southern Counties

Week Ending STLM TABM-A CM BMSB OFM-A DWB OFM-P TABM-P LPTB PTB
4/5/2025 0 0 0 0 0 0 0 0 0 0
4/12/2025 0 0 0 0 6 0 0 0 0 0
4/21/2025 0 0 0 0 36 0 1 0 0 0
4/27/2025 25 0 0 0 24 0 5 0 1 0
5/2/2025 517 0 4 0 12 0 6 0 13 0
5/9/2025 159 4 10 0 3 16 5 4 46 0
5/16/2025 91 11 6 0 1 36 2 14 69 0
5/23/2025 299 21 3 0 1 23 1 26 23 0
5/30/2025 399 14 2 0 0 41 1 11 10 3
6/6/2025 733 13 1 0 0 36 2 12 29 1
6/13/2025 684 19 2 1 0 81 2 17 22 8

Tree Fruit Trap Captures – Northern Counties

Week Ending STLM TABM-A CM BMSB OFM-A DWB OFM-P TABM-P LPTB PTB AMBROSIA BEETLE
4/5/2025 387 0 0 0 0 0 0 0 0 0 0
4/21/2025 435 0 0 0 0 0 1.3 0 0 0 0
4/27/2025 26 0 0 0 0 0 25 0 0 0 72
5/2/2025 86 0 0.33 0 72.5 0 47.2 0 0 0 136
5/9/2025 56 0 5.3 0 58.8 0 22.9 0 0 0 145
5/16/2025 13.75 2.6 7.3 0 4 0 5 0 0 0 50.5
5/23/2025 4.8 10.3 10.5 0 0.6 31.25 4.2 0 14.6 1 22.2
5/30/2025 2.2 4.8 1.8 0 0 12.4 9.6 0 9.6 1.9 22.1
6/6/2025 3 4.83 2.8 0.25 0 20 4.1 0 21.2 1.8 40.3
6/13/2025 65 20 11.4 0.6 0 12.3 4 0 10.5 1.5 59.2
Filed Under: Blueberry, Fruit, Tree Fruit, Wine Grape
June 2, 2025 , , and

High Temperatures Predicted this Coming Week – Ways to Prevent Heat Stress

OSHA Safe + Sound Header for Heat Illness Prevention

Heat exposure for agricultural laborers should be a consideration when working outside and even in non-airconditioned buildings. When a person’s ability to adapt to heat stress is exceeded, exposure can lead to reduced productivity, mistakes in job performance, increased workplace incidents, and/or heat-related illnesses. Each person’s heat tolerance varies and several factors including type of physical activity, fitness level, underlying health issues, temperature, sun exposure, air movement (wind), and humidity can dramatically impact the potential for heat stress. To determine the level of heat risk, employers should consider the job, the environment, and the worker.

Evaluate the Risk of Heat Stress:
Monitoring the environmental conditions during work times to make management decisions for workers is an important part of preventing heat-related illnesses. Temperature is not the only factor in implementing heat stress management. Humidity is another important consideration. The heat index is a measure of how hot it feels when the relative humidity is factored in with the actual air temperature.

An environmental heat assessment should account for the following factors: air temperature, humidity, radiant heat from sunlight or other artificial heat sources, and air movement. OSHA recommends the use of wet bulb globe temperature (WBGT) monitor to measure workplace environmental heat. OSHA provides this link to calculate the WBGT for a specific location. There is also a NIOSH/OSHA Heat App for Android and iPhone devices that uses the Heat Index as a screening tool.

Management Suggestions for Enhancing Heat Tolerance:
Acclimatization (to heat) is a process of adaptation that involves a stepwise adjustment to heat over a week or sometimes longer. An acceptable schedule for achieving acclimatization is to limit occupational heat exposure to one-third of the workday during the first and second days, one-half of the workday during the third and fourth days, and two-thirds of the workday during the fifth and sixth days. The acclimatization procedure should be repeated if a person misses workdays after days off due to illness, vacation, or other reasons for missing one week or more of job duties.

Fluid replacement:
Provide adequate drinking water for all employees. Recommend to employees they drink plenty of water before work shifts, during work, and after work. Simply relying on feeling thirsty will not ensure adequate hydration. To replace the four to eight quarts of sweat that may be produced in hot environments, people require one-half to one cup of water every 20 minutes of the workday. Potable drinking water kept at a temperature of 59°F or less is recommended.

Physical Fitness: Physical fitness is extremely important. The rate of acclimatization is a function of the individual’s physical fitness. The unfit worker takes 50 percent longer to acclimate than one who is fit.

Increasing Safe Work Practices:
To find management and guidance tools for determining whether to implement heat stress management plans refer to the CDC documents on Heat Stress and Work/Rest Schedules.

The following list of management options should be considered to prevent heat stress for workers:

  • Limit exposure time. Schedule as many physical work activities as practical for the coolest part of the day (early morning or late afternoon). Employ additional help or increase mechanical assistance, if possible, to lighten individual workloads.
  • Minimize heat exposure by taking advantage of natural or mechanical ventilation (increased air velocities up to 5 mph increase the rate of evaporation and thus the rate of heat loss from the body) and heat shields/shade when applicable.
  • Take rest breaks at frequent, regular intervals, preferably in a cool environment sheltered from direct sunlight. Anyone experiencing extreme heat discomfort should rest immediately and be provided with first aid for heat stress.
  • Wear clothing that is permeable to air and loose fitting. Generally, less clothing is desirable in hot environments, except when the air temperature is greater than 95°F or a person is standing next to a radiant heat source. In these cases, covering exposed skin can reduce the risk of heat stress.
  • A buddy system may also be helpful. It depends on a fellow worker’s ability to spot the early signs of heat stress, such as irritability, confusion, or clumsiness. A ready means of cooling should be available in work areas where heat illness might occur.
Filed Under: Blueberry, Commercial Ag Updates, Cranberry, Field, Forage & Livestock, Fruit, Landscape, Nursery, & Turf, Nursery, Organic Production, Strawberry, Tree Fruit, Turf, vegetable, Vegetable Crops, Wine Grape Tagged With: ,
May 16, 2025 and

Deer Damage Control in the Vineyard

New Jersey’s high deer population significantly threatens vineyards, particularly those near wooded areas. Deer are a pest, especially on young vines and in the early growing season when food sources are scarce, and tender shoots are emerging. If the vineyard is close to the deer population, management is needed for the long-term productivity of the vineyards.

Identifying the deer damage: Deer browse on leaves and tender shoots using the lower front teeth. Deer do not have upper incisors, so the leaves browsed by deer have a rough, torn, and shredded appearance but no tooth marks (Figure 1). This can cause substantial crop loss and even compromise the health of the vines, specifically if the same vine is damaged over the years (Figure 1). Fortunately, secondary buds of grapevines can grow and produce replacement shoots when the actively growing shoot tip from the primary bud is damaged. A new shoot from a basal bud may not be as productive, however, it will ensure new vegetative growth, sustaining the canopy of the grapevine. [Read more…]

Filed Under: Blueberry, Cranberry, Fruit, Organic Production, Strawberry, Tree Fruit, Uncategorized, vegetable, Wine Grape Tagged With: , , , ,
May 15, 2025 and

Crown Gall in Grapevines – Early Symptoms and Management.

What is Crown Gall?

Figure 1. Early symptoms. Young soft galls developing on the graft union during early spring (L) and cracking of bark by growing crown galls (C and R).

Crown gall is a serious disease affecting grapevines, particularly in cool-climate viticulture. It is caused by the soil- and plant-borne bacterium Agrobacterium vitis (A. vitis). This pathogen induces tumor-like growths (galls) that disrupt the grapevine’s vascular system, reducing the flow of water and nutrients from roots to shoots. If left unmanaged, crown gall can stunt vine growth and eventually kill the plant.

Diseases Symptoms

The earliest and most distinctive symptoms are abnormal, soft, whitish swellings (see Figure 1, Left). As these galls grow, they cause the bark to crack and peel due to pressure from underneath (Figure 1, Center and Right). Galls can initially be mistaken for benign growth, and therefore, detection requires careful inspection.

Figure 2. Crown gall on the graft union and trunk of the grapevine.

As the disease progresses, galls may become woody, rough, and brown, growing to several inches in diameter (Figure 2). They most often appear at the graft union or sites of mechanical injury on the lower trunk. The graft union is especially susceptible due to: (i) its irregular shape, which is prone to cracking, and (ii) potential contamination by A. vitis during the grafting process. Galls may also form on cordons and canes. Early scouting and removal of affected trunks can help limit the spread of infection. If the gall encircles the vine’s vascular system, the entire plant may collapse and especially in young vines, which have thinner trunks.

Another indicator of severe infection is the emergence of multiple new suckers from the vine base (Figure 1, Left). Additionally, leaves of affected vines may show green wilting and reddening due to restricted water and nutrient flow (Figure 3). However, similar symptoms can also result from viruses or nutrient deficiencies, making diagnosis challenging. In such cases, inspect the trunk visually for physical signs of gall formation or vascular disruption.

 

Why does wounding cause gall formation?

Figure 3. Leaf of crown gall-affected grapevine showing green wilting and reddening.

Wounding is a key point of infection in crown gall development. In early spring, grapevines attempt to heal sites of winter injury by producing callus tissue. These masses of undifferentiated cells with soft cell walls are particularly vulnerable to infection. A. vitis, which may already be present in the vine, exploits these wounds to inject its DNA into the callus cells. This bacterial DNA contains a tumor-inducing gene that integrates into the plant’s genome, leading to uncontrolled cell division, resulting in the characteristic gall.

Management of Crown Gall

An integrated pest management (IPM) approach is essential for effective crown gall control. Strategies include:

1, Avoidance
Site selection is the best decision to avoid cold injury. Avoid planting in low-lying areas where cold air settles. Gentle slopes are preferable for air drainage but beware that cold air may still collect at the lower end of a slope. Avoid planting in such spots unless you have excellent air drainage practices.

Figure 4. Grapevine in a year after hilling and damaging winter. Notice the graft union and trunk a few inches above it, unaffected by winter damage due to hilling-up, while the unprotected trunk shows crown gall.

2. Exclusion
Start with clean, certified planting material to reduce the chance of introducing A. vitis into your vineyard. Ideally, use 2010 Protocol-certified stock, which is propagated using advanced screening techniques to minimize bacterial contamination.

3. Resistance
Different grapevine species vary in susceptibility. Vitis vinifera cultivars are generally more susceptible. Hybrids and some vinifera varieties show moderate tolerance. Native species and certain hybrids tend to have better resistance. Consider planting more resistant varieties in areas prone to cold injury.

4. Protection
Hilling up soil around the base of vines during winter is highly effective. The soil acts as insulation, protecting the graft union and lower trunk. While this won’t shield unburied parts of the vine, it can preserve enough tissue to allow regrowth from protected suckers (Figure 4). Training these suckers as new trunks and using multiple trunks per vine can reduce the risk of total vine loss. For detailed guidance, refer to Rutgers NJAES Factsheet FS1264.

5. Eradication
Remove and destroy infected vine sections (Figure 5). This is the most effective post-infection strategy. Scout during early spring or winter pruning. Any removed vine parts should be taken out of the vineyard entirely. If removing an entire vine, extract it with the root system, as A. vitis can persist in root debris for years.

6. Chemical Control Options

Figure 5. New trunks and cordons were developed after removing the old, infected cordon.

A few commercial treatments are available, including:

  • Galltrol-A (AgBioChem, Inc., Provo, UT)
  • Gallex (AgBioChem, Inc., Provo, UT)
  • Copper-based compounds
  • Antibiotics

However, their effectiveness varies. Once the bacteria establish themselves systemically, eradication becomes extremely difficult. Always follow label instructions and integrate chemical treatments with cultural practices for best results.

References
Burr T. and Martinson T. 2015. Start Clean, Stay Clean Grape Crown Gall. National Clean Plant Network. Factsheet.

Moyer M. 2013. Grapevine Crown Gall. – Disease Management White Paper. Wine.wsu.edu/research-extension/

Gohil H., Nitzsche P., and Ward D. 2017. Hilling up to Prevent Winter Injuries in Vineyard. Rutgers NJAES Factsheet 1264. https://njaes.rutgers.edu/fs1264/

Todaro T. and Longstroth M. Managing Grapevine Crown Gall. Michigan State University Extension.

Filed Under: Blueberry, Fruit, Strawberry, Tree Fruit, Wine Grape Tagged With: , , , ,