Every spring I get asked “How cold is too cold to spray dormant oil?” The text book answer is 45°F. A bit of common sense also figures in. Is the temperature on the rise, or decline? Is it windy, damp, cloudy, etc. Pay attention to freezing temps during the 48 hour period before application and for 24 – 48 hours after. Having said all of that, remember that we farm in Colorado, some days you just have to push the envelope a bit.
Horticultural oils have been in use for over a hundred years. They are a unique tool in our arsenal from the perspective that no pest species has ever developed resistance to them. Brought down to simplest terms, the results one will obtain with oil sprays are governed by three basic factors: the oil used, how well it is applied and when it is applied.
Oils cover insects with a suffocating film that kills both larva and eggs by a mechanical interference with the normal gaseous exchange. Coverage is essential!
As eggs get closer to hatching they become more susceptible to killing with oil. Research shows that oil sprays applied at the begging of hatch using a lower percentage of oil concentration are just as effective as earlier applications at a higher concentration. Timing is essential!
So what’s the point? We need to know what our target is and when it’s most vulnerable. Whether it’s Green peach aphid, European red mite, or Pear Psylla, missing the optimum timing by a week can make a significant difference in control.
OK, so what’s the optimum timing?
- Two Spotted Spider mite: This critter overwinters as an adult female that emerges about the same time as leaf emergence. Delayed dormant on peach and tight cluster on apple are the best timing.
- European Red Mite: Red Mite overwinters as an egg. Time sprays just prior to tight cluster on apple.
- Pear Psylla: Pear psylla overwinters as an adult. A large portion of the population exit the orchard to overwinter on surrounding vegetation. They return to the orchard in the spring to mate and lay eggs. The purpose of oil in this program is TO PREVENT EGG LAYING. Research shows that proper timing can suppress egg deposition by as much as 50% and delay it for three to five weeks. Time sprays at the beginning of egg laying. Give me a call, I can help you with timing for your area.
- Green Peach Aphid: Overwinters both as eggs and adults. Hatch occurs before bloom. Time sprays for delayed dormant period.
It's common to make an application with a tank mix of several different pesticides and formulations. There's a specific mixing order that will help keep you out of compatibility problems. 1) soluble packets, 2) wettable powders, or water dispersible granules, 3) flowables, 4) emulsifiable concentrates, 5) oils. Always , Always , Always add oils last!
Spring is the most stressful time of the year for any fruit tree. Your orchard is drawing from reserves as it progresses through bloom. Soil temps are cold and limit nutrient availability. Fruit size is partially determined by the number of cells each fruit contains. Cell division occurs immediately after bloom (from 14 to 28 days) when the stress is at it's peak. Healthy, well fed, trees are better able to handle and size large crops, survive winter injury, and pull buds through spring frosts. Next years’ flower buds will be developed this season. Keeping a tree well fed is a year round program. Properly timed foliar applications of nutrients can help relieve the stress!
Delayed dormant: Zn, Mg & B; Pink, Petal Fall & Summer: N, P, K, Zn, Mn & CA; Fall: Zn, B, & N
Are pests resisting your management? -
An individual organism's genes determine its physical and behavioral traits. When individuals reproduce, they pass along unique combinations of genes to their offspring. Different environments favor individuals with different physical and behavioral traits. Individuals with genes that improve their survival will be more likely to pass along these genes compared to the rest of the population. The mix of genes in a population is called the gene pool. The composition of the gene pool continually changes over time through a process called natural selection.
Repeated use of the same class of pesticides to control a pest can cause undesirable changes in the gene pool of a pest leading to another form of artificial selection, pesticide resistance. When a pesticide is first used, a small proportion of the pest population may survive exposure to the material due to their distinct genetic makeup. These individuals pass along the genes for resistance (survival) to the next generation. Subsequent uses of the same pesticide increase the proportion of less-susceptible individuals in the population. Through this process of selection, the population gradually develops resistance to the pesticide. (Excerpt from Fruit Crop Ecology and Management )
The practice of “resistance management” is an endeavor that each of us should be involved in. As we plan our pest programs (both insect and disease) we need to pay attention to a few key components.
- The class or group of chemistry a material belongs to.
- The number of times we use it against a pest, are we using the same class of material against succeeding generations of a pest.
The goal is to avoid “selecting out” any pest group by doing the same practice over and over.
All pesticides have been grouped by their class of chemistry and assigned a group number by FRAC (fungicide resistance action committee) or IRAC (insecticide resistance action committee). Pesticide labels now contain the group or class number for each product on the label right above the name.
Asana, Danitol, Warrior and Ambush all belong to the same class of insecticide known as Pyrethroids. Changing from one of these products to another will not help you with resistance management. It’s not enough to change names, you have to change classes.
The same issue is true with fungicides, it’s important to have a thorough understanding of the types and capabilities of the fungicides you use to manage plant diseases. Using the correct fungicide at the right time in the proper amount can often mean the difference between a clean, high quality crop or a significant loss in yield or quality.
Don't let powdery mildew catch you flat footed. Control is best obtained early in the season, not once you notice it! Cherries are best treated by starting at petal fall & shuck fall; peaches from bloom to pit hardening and apples before bloom. There's a wide selection of materials with various modes of action available. Don't fall into a rut and build resistance in you orchard. Rotate classes of materials and start early!
FONTELIS, a new fungicide introduced this season by Dupont.
- The active ingredient is Pentothiopyrad and belongs to the FRAC group 7.
- It has excellent activity on Coryneum blight and Powdery mildew.
- It’s rainfast within 1 hour of application.
- Has translaminar movement – in other words it will move from one side of the leaf to the other, and within a local region of the plant it will move within the xylem up and out to the tips.
Here’s a few links for more info:
Fungicides can be grouped into three use catagories:
- Preventative – must be applied BEFORE disease presence.
- Curative – can be applied after infection but before visual symptoms.
- Eradicant – can control after symptoms are present.
Fontelis is classified as an eradicant.
Here’s the scoop on an old favorite. Ziram, whose chemical name is zinc dimethyldithiocarbamate, is a broad spectrum protectant fungicide. On peaches and nectarines, it is most commonly used for coryneum blight. Zinc dimethyldithiocarbamate itself is not the compound that is actually toxic to the fungus. Instead, ziram must first break down into its degradation products, which then exhibit fungicidal properties. These products kill the fungus by reacting with its proteins, particularly the enzymes within the cells. This multi-site activity, similar to copper fungicides, is of extreme practical significance. There is little concern of developing resistant fungal strains. In fact, ziram has been available for many years with no known reported resistance development. Secondly, the non-specific action of ziram makes it a candidate for mixing or alternating with other fungicides that are at-risk for resistance development.
“The best argument against democracy is a five-minute conversation with the average voter.”
- Winston Churchill
12’ & 14’ treated trellis posts for sale. Interested? Give Pete Eastman call at 970-872-3875.
Entrust SC - Dow AgroSciences has made a change to Entrust (at last). The small 4 ounce packets of hard to measure (very expensive) powder are no more. Entrust is now a soluble concentrate formula, a liquid in a quart bottle. Yes it’s certified organic!
Here’s the conversion to change from the powder to the liquid:
- 1 oz of the powder = .8 oz of active ingredient.
- 3.2 oz of the liquid = .8 oz of active ingredient.
Just remember 3 : 1 and you should be in fine for most applications. If you’re mixing a tank using low water volume and covering a lot of acres you should do the math or round up a bit. I have a chart that shows the exact conversion ounce by ounce. Give me a call or email and I’ll get you a copy.
“A man's character may be learned from the adjectives which he habitually uses in conversation.”
- Mark Twain
I’ve had a number of organic growers call and ask me what’s going to replace streptomycin as a tool against fireblight when it is removed from the NOP list in October of 2014. There are a couple of new materials being tested that show promising results. Blossom Protect a yeast product and Previsto a copper compound that can be used all season along. Included in the program is a not so new material, lime sulfur. The following link is to a webinar that was conducted by Ken Johnson of OSU, Rachael Elkins of University of Cal, and Tim Smith of WSU on fireblight and the use of these materials.
Are bees a critical member on your team? If so here’s a few tips to help them out.
- Hive to tree proximity is not an issue, but where you place the hive is.
- Turn a bin upside-down in a sunny location and place the hives on top.
- Additional hives won’t make up for a lack of pollen in the block.
- Have a source of water close by, mud puddles are best. If you use a water bucket place a few sticks inside for the bees to land on.
- Don’t place hives where sprinklers will spray them.
Please give me a call.