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September 2007


Peach fruits have three fairly discrete stages of growth. The first stage (Stage I) lasts from full bloom until about 50 days after bloom. During this time the fruits grow fairly rapidly and growth is primarily due to cell division. Most of the cell division probably occurs during the first 30 days after bloom, but the length of stage I may be influenced by temperature. There is an increase in both fruit size and fruit dry weight. During stage I, shoot growth begins but there is too little foliage on the tree to support the growth of the fruit and shoots. Therefore much of the carbohydrates for early fruit and shoot growth come from reserves stored in the tree during the previous season. If your peach crop was a big one this year chances are that your orchard is out of gas and low on reserves! Trees move nutrients from the leaves back into the buds and wood prior to leaf drop. Research in California shows that a foliar spray of urea on peach begins to move into the leaf within two hours, with over 80% of the applied N moving into the leaves within 24 hours. The efficiency of N recovery through a foliar urea application is four-fold greater than through soil application. This nitrogen is mobilized and moved into other plant parts such as shoots and buds within one week. It remains there until spring when it is available for early use during cell division (more cells = larger fruit)! Urea is known to enhance the uptake of other micronutrients when sprayed in combination. Adding zinc, iron, manganese or any other element your tree requires will help boost bud strength and tree health. No detrimental effects have been found on winter hardiness, quite the opposite, research has shown that healthy buds with good nutrient reserves are the most winter hardy. Now is a great window of opportunity to put a bit of fuel back in the tank for next year.


The most common timing to apply ground fertilizer has been to make an application in the late fall. Research has shown that uptake and movement into the tree of a dormant application is greatly reduced and subject to winter leaching (recovery of soil-applied N by fruit trees typically ranges from 25-35%, Khemira, 1995). Moreover, a late fall application will not be available till late, (too late) in the spring, past the cell division period when soil temps warm up. A dormant application contributes most toward summer vegetative growth. Consider a different timing. Mid-August to mid-September most terminal growth has ceased, the temps are still warm and the tree is maintaining a high rate of respiration. Fertilizer applied at this time, followed by a light irrigation will quickly be moved up into the tree. It’s then stored, ready for cell division the next spring. The “sweet spot” to aim for is the period when the tree is between it’s summer work and winter sleep. Be cautious about late maturing varieties, they stay active later in the season.


“Don't quit playing when you get old, you get old when you quit playing”


Pacific Biocontrol (one of our suppliers of pheremone products) approached me this season about conducting a trial with their new Peach Twig Borer mating disruption product. Prior to biofix we applied Isonet A (Pacific Biocontrol) and Checkmate PTB (Suterra) on two seven acre blocks with an untreated block next to them. All three blocks were treated with the growers “standard” spray program. As expected, both pheremone products shut down trap catch throughout the season. A survey after harvest showed no damage from PTB in the two pheremone treated blocks. The untreated block next door showed significant PTB damage (even though it was sprayed). If you have a block that you're struggling with to maintain control of PTB, consider using one of these mating disruption products next year.


Every spring I get questions about residual herbicides. It's usually from growers with furrow irrigation and bad weed pressure. Fall is the best time to apply next year's residual materials. These materials need incorporation. Making a late fall application greatly increases the odds that a rain or snowfall will set them in place. There's a number of materials available, give us a call this fall to take care of next year's weeds!


“If winter is slumber and spring is birth, and summer is life, then autumn rounds out to be a reflection. It's a time of year when the leaves are down and the harvest is in and the perennials are gone. The drapes are drawn on another year and it's time to reflect on what's come before.” Mitchell Burgess – Northern Exposure

How was your year? What needs to change? Don't repeat this seasons mistakes!


It's fast approaching the season for Coryneum blight control. If you're farming under organic standards, fall or early spring applications of copper is your only means of controlling this disease. The first autumn rains can start the spread of the disease. Infection can also take place in the dormant season if proper moisture and temperature conditions occur. Spores, spread primarily by splashing water can remain viable several months. The key to control is PREVENTION. The label rate for Nu-Cop 50DF (same as COCS) is 8 – 16 lbs/ac for control.


There are many factors that affect the efficacy of copper in the control of bacterial plant pathogens. The most important property contributing to the biological activity of copper is its ability to exist in what is termed the “free” or “ionic” state. In nature, copper almost always is combined with other elements or minerals. When conditions become such that copper exists in the ionic or in the free copper state, it is very reactive. It is this reactive nature that gives copper the ability to kill bacteria. Also, it is this reactiveness that is responsible for phytotoxicity. The amount of copper in the ionic state is greatly influenced by pH of the solution (eg. droplet of water on the leaf). The more acidic (pH below 7.0) the solution the more free copper and the more bactericidal but potentially the more phytotoxicity it becomes. In contrast, the more basic (pH greater than 7.0) the solution the less free copper and less bactericidal but less potential for phytotoxicity. The goal is to achieve a balance between these two extremes. Copper-containing materials have been used on peaches for many years and its use may be increasing. It should not be forgotten that peaches can be very sensitive to copper and if improperly used serious phytotoxicity can occur. Be sure that the correct rate of copper is used and that sprayers are correctly calibrated. Phytotoxicity is more likely to occur when conditions are slow drying (more than 20 minutes) and cool (less than 55F). Injury is usually to leaves resulting in discoloration, shot-hole, and defoliation.


If your organic (or conventional) pear block suffered this season from rust mite or pearleaf blister mite, now is a great time (immediately post-harvest) to control them. Both species of mite move under the bud scales at this time of year to overwinter and will be somewhat protected until they re-emerge next spring. Blister mites can reproduce during winter, and all growth stages are found under bud scales. When buds start to grow in spring, the mites attack emerging leaves, from green tip through bloom stage, and developing fruit. Lime-Sulfur @ 5gal + oil @ 1gal per 100 gallons works well. As always...... good coverage is essential!


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