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OBLR - Obliquebanded Leafroller (Choristoneura rosaceana) 

Wednesday May 20, 2020

Early leafroller damage on Gala
OBLR larvae on apple leaf

OBLR - Obliquebanded Leafroller (Choristoneura rosaceana) 

Why is it a problem?
Leafrollers are common pests in treefruit orchards, causing damage to developing leaves and green tissue by their distinct 'leaf-rolling', as well as by their feeding habits on the fruit itself. Leafroller feeding damage is the main cause for concern for growers, as it can lead to significant damage to the fruit, both in the form of small "pin pricks" size holes (summer damage) as well as large malformations which affect the entire shape of the fruit (early feeding damage), making it unmarketable. Both are a concern for growers, as either can greatly limit the amount of return from the packinghouse to the grower.    
 
Where do leafrollers come from?
Leafroller larvae overwinter on the trees, and become active when the trees break dormancy. Developing leafrollers can be found by scouting orchards for signs of egg masses, or for feeding damage caused by leafroller larvae on the developing buds and shoots. Leafroller larvae have the appearance of a large worm, with tiny feet arranged in pairs as fore- and hind limbs. OBLR larvae have a distinct light coloured band across a black head, with a pale yellow-green body. Once mature, leafroller larvae will develop into adult greyish moths which will either have 2 generations per year (OBLR and Budmoth) or only one in the case of Fruittree and European leafrollers. What this means is, growers should be concerned about leafroller populations in their orchards from Green tip to Petal fall, and into the summer months as fruit develop. For OBLR, monitoring should include timing of the second generation emergence during the summer (usually in July and August).  
 
How the BC DAS system can help: Keeping you Informed + Equipped
The BC Das system allows growers to be informed about where we are in the larval development of leafrollers in the growers' specific geographic location. Using degree days based on the local weather stations that the grower has selected as being reflective for their orchard, the BC DAS system will then provide the grower with up to date information regarding the probable larval development stages of leafrollers, allowing growers to better time sprays and control measures. Information such as instar and pupae percentage, maximum and minimum temperatures, and the upcoming forecast will prompt the system to send out notifications to alert growers for when control measures are best used according to when the pest will be most susceptible. The BC DAS system also includes information on the natural enemies of leafrollers, which allows growers to make informed choices to avoid disrupting the natural beneficial control of other insects in the orchard during this time.    
 
In addition, the BC Das system has control measures incorporated into the OBLR model webpage. What this means is, when the development of larvae reaches the optimum timing for control sprays, the grower is then supplied with the tools needed to ensure coverage against this pest. The DAS Spray Guide offers different spray options, rates and timings, allowing growers to plan their sprays for coverage against multiple pests, as well as allowing the grower to select for product options currently registered for either conventional or organic use. By following along on the BC DAS model, the grower will have timely information and knowledge of the tools currently available to control leafroller populations in their orchard.    
 
Still interested in finding out more? Check out our BC DAS OBLR model video on YouTube to connect horticultural knowledge from the field with the online DAS program: