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February 2014


Last season Cropworx introduced to the area a new insecticide certified for organic production named Grandevo.  It is a bio-pesticide that has activity on chewing and sucking insects and mites.  I was impressed with the application results I observed last year on green peach aphid and pear psylla.  While at the Washington State Hort show in December I met the technical service manager for Marrone Bio Innovations the manufacturer of this product.  What follows is part of an email he sent to me in response to questions I asked him about Grandevo:


There are three proteins that are produced in chemical analysis of the soluble fraction of the Grandevo fermentation process.  One of the peaks behaves like a Bt protein and produces a stomach toxin type of lethal result in lepidopteran species.  The other protein peaks create a variety of other effects including contact kill of immature life stages, feeding cessation, reduced fecundity (egg laying), reduced viability of eggs that are laid, and repellency.  Sometimes the repellency feature gets in the way of really understanding mode-of-action on some target pests because the adults can fly away to untreated refuges.    With spotted wing drosophila for example, Grandevo is lethal to the larvae but we need to kill the adults before eggs are laid.   So I have been working with various groups to test baits + Grandevo to induce feeding, thereby increasing ingestion and mortality.


You are also right with recall about what I have learned from a variety of field applications:  I would rather make two applications of 1.5 lb/ac than a single application of 3.0 lb/ac.  


I believe the feeding cessation is a big key to Grandevo efficacy in a variety of pests.  It makes sense that this feeding cessation is also a reason why Grandevo works best with sequential applications rather than a single application.   In strawberry and raspberry production areas of southern California, the crop consultants taught me that their best results resulted from 2 to 3 sequential applications of Grandevo @ 1.0 to 1.5 lb/ac followed by release of predatory mites for control of two spotted spider mites and McDaniel mites.  We all began to witness that treated two spot adult mites would feed on Grandevo, then become lethargic and much less motile.   I believe this feeding cessation impacts the plant feeders and subsequent egg laying is also reduced.   They go into a stress mode based upon observed behavior.   When the two spot mites slow down, they are more easily captures by predatory mites.   The overall result is a big decline in two spot populations below economic thresholds



“The only sure bulwark of continuing liberty is a government strong enough to protect the interests of the people, and a people strong enough and well enough informed to maintain its sovereign control over the government.”               Franklin D. Roosevelt


During the Hort Show I had lunch with Terrance Robinson and Todd Einhorn.  I asked them the question “To grow large Bartlett pears, what’s the single most important task a grower can do?”  Their response – Use MaxCel at a high rate one to two times just past bloom.   



As of October of this year antibiotics will no longer be allowed in certified organic production (They are still registered for use in conventional systems).  There are a lot of lessons to be learned in how to combat Fire Blight (FB) without the use of antibiotics. The following are excerpts from a paper entitled “Grower lessons Learned in the Development of Non-Antibiotic Organic Options for Successful Fire Blight Control”  written by David Granatstein and Harold Ostenson of WSU Extension.  While the focus is on organic production there’s a number of points that will hold true and advantageous in all orchard systems.


  • A chain saw to lower the tree canopy in half, and a tower sprayer which applies the chemical sprays downward onto the tree canopy and flowers would probably reduce the fire blight potential almost more than any other action regardless of the product mix utilized.

  • Pre-bloom nutrient sprays play an important role in an integrated FB control program because these pre-bloom sprays accelerate tree leaf expansion and the startup of photosynthesis, resulting in a more compact, shortened bloom period, faster fruit set, and a reduction in FB infection exposure.

  • In addition to standard orchard sanitation practices to control FB infection levels, consider a fall application of dilute lime sulfur and oil and/or copper just prior to leaf drop. This action will reduce overwintering pests, scab, and FB inoculum levels.

  • Sulfur applied in low concentration with full canopy coverage in early June will help to promote tree shoot terminal growth and less shoot blight, especially on pears.

  • Dormant Stage to Tight Cluster Stage -
    • Use active organic coppers, combined with or separate from lime sulfur and oil in dilute sprays of 200-500 gallons/acre with full coverage on every row. This period offers the best opportunity to effectively control overwintering pests, scab, and damaging fungi for the remainder of the growing season. During this time, more water with less spray material is a better control investment than less water and more concentrated levels of spray materials.
    • This is the time to be bold with all your orchard control sprays. This is also the time when sprays will have a minimal impact on beneficial insects.


  • Pink Bud Stage through 50% Bloom -  These stages are critical to an integrated control program because: (1) warmer temperatures and conditions including bloom favor FB infection; and (2) exposure of the flower and young developing fruitlets to the strongest FB control materials also lead to fruit russet and potential loss to the organic fresh market. We have to move to ‘softer’ materials which generally address a single orchard horticulture problem category: only pest control, or fungal control, or crop load management. The following statement is germane to the integrated FB control program during these stages:

    • Spray water volumes need to move from dilute [200-400 GPA] to semi-dilute volumes [100-200 GPA] to reduce the potential for leaf/flower burn and fruit russet.  Using different nozzles for higher rates in tree tops continues to be a good plan even with lower total spray volumes.

  • Full Bloom Stage -  There is neither an antibiotic or non-antibiotic cure for FB. If the FB control plan has been to wait until FB models indicate an infection period has occurred, then it is going to be difficult to suppress FB infection during bloom, especially in younger fruit tree blocks. One of the main purposes of the integrated FB control program is to initiate a multiple spray program early in the spring growth cycle that has an accumulated effect on minimizing the potential for FB bacteria to infect during bloom. It is during this stage [full bloom] when the FB bacteria have a direct route into the plant via the flower nectary.

    • Lime sulfur or lime sulfur + oil with 200 GPA spray volume are considered one of the best spray mix options during bloom. This mix suppresses scab, overwintering insect pest emergence, mildew, scale, and fire blight, while compacting the bloom window (shortening FB nectary infection periods), and reducing tree flower populations (especially late bloom). Experienced growers use 2-3 applications in the 200 GPA spray volume range every 3-4 days to cover an 8-12 day bloom window. Even at low lime sulfur percent by volume, especially with low volumes of oil, good results in addressing the multiple challenges have been regularly achieved. Complete tree canopy spray coverage has been the differentiating factor.

    • While lime sulfur applications greatly reduce the beneficial organisms in FB biocontrol products,  in most cases, the lime sulfur option trumps these and other FB control options because of its multiple simultaneous actions on various diseases,  insect pests,  bloom window compaction, and crop load reduction.

    • Soluble coppers might be the option of choice after lime sulfur bloom applications rather than biologicals to reduce the russet potential from high accumulations of bacteria/yeast on russet prone apple cultivars under extended wet and humid conditions. The new soluble coppers, like the OMRI-approved CuevaTM [not available in all states], have much lower rates of copper [metallic copper equivalent 1.8%].  In most cases these new soluble coppers will provide better FB control with a lower risk of late bloom fruit russet compared to standard metallic copper materials. There is probably no spray material option applied during this time that does not carry some risk of fruit russet., In most cases, spraying apples post bloom more often with higher rates of water, and lower active spray material concentrations, compared to spraying higher rates of spray material in lower water concentrations, sprayed over a longer window, will help to minimize russet.
  • Petal fall - Post Petal fall [+30 days] Stage.

    • If shoot blight after petal fall is a major threat to the orchard, multiple applications of soluble copper are probably the best approach even at the expense of fruit russet. Controlling overly vigorous new growth via horticultural practices should also be a high priority.  Control of chewing and sucking insect pests during this stage (e.g., aphids, stink buds, white flies) is important as they are a major factor in the spread of the FB bacteria that will cause shoot blight.


David’s full paper along with a number of other resources can be found at:




“Agriculture not only gives riches to a nation, but the only riches she can call her own”

Samuel Johnson


Questions?  Please give Dan or me a call!


Larry                            Dan

970-234-3424              480-254-3025

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