Monday, August 29, 2011

Peachtree borer identification and control

 The peachtree borer, AKA peach crown borer, (Synanthedon exitiosa) is a major pest of peach, nectarines, cherries, plums and other members of the genus Prunus whether grown for fruit production or as an ornamental.  The adult is a clear-wing moth resembling a wasp.   “The female is dark metallic blue with a broad, reddish orange band around the body on the fourth abdominal segment. The male is smaller with a shiny, dark metallic blue body”. [i] 

Male and female photos courtesy of

When eggs are laid at the base of a peach or other stone fruit tree, the worms eat through the bark and feed on the cambium and inner bark (phloem) of the tree. Both the lower portion of the trunk and the upper roots are damaged.
Figure 3: The initial feeding activity of the borer will appear
as translucent goo that oozes from the ground.
 Figure 4: As the feeding continues, the goo will be colored by the frass produced by the feeding activity of the borer. This photo shows boring dust on the lower part of the trunk, black crusty goo, and pupal cases left behind when moths emerged.

Figure 5: When you remove some of the crusty goo from the base of the tree you will often find clear goo underneath.

A peach tree damaged by this insect may take years to die.  The tree may die one branch at a time, or the whole tree may collapse over night.  The leaves on a limb with damaged roots may yellow one day and drop to the ground the next day.  The Fruit on a borer-infested tree will become dried up mummies.
Figure 6: Nutrient uptake is hampered by the feeding activity of the borer causing chlorosis as shown on the left side of this tree.

The Soil Drench Method

An insecticide drench with a relatively lengthy residual needs to be applied to the base of the tree in sufficient quantity to soak the ground. Since the entry point of this insect can be up to 8 inches above the soil line soaking the trunk to at least that height is important. Applications of carbaryl, permethrin, and esfenvalerate are recommended at the first of July and again at the beginning of August. If other products are used the length of time between applications will need to be adjusted based on the residual effect of the product. Do not apply these products within 14 days of harvest. When these sprays are missed, you can expect damage to your peach trees and other stone fruit trees and shrubs.

Para-dichlorobenzen (PDB)

Prior to 2009 the root systems of peach tree borer infested trees were fumigated using para-dichlorobenzene (PDB). This crystalline material is sold as moth balls and moth flakes. The crystals were placed in a shallow trench several inches out from the base of the tree or shrub and covered with a shallow layer of soil to contain the fumes. The fumes found their way through the goo to the borers feeding on the tree. This procedure was done in the fall when soil temperatures were above 50 degrees Fahrenheit. PDB can also damage plant tissue if placed directly against the bark of the tree. PDB did not replace the basal drenches recommended above but was a great way to clean up an infestation when a spray was missed or inadequate. PDB should not be confused with the moth balls and flakes containing naphthalene.

On October 31, 2006, Fertilome voluntarily requested US EPA terminate all uses of Fertilome Tree Borer Crystals. The product was registered for use on fruit trees but was no longer being produced in the United States. [2]

The Label is the Law

“Using a registered pesticide like mothballs against a pest not listed on the label is legal unless (1) the pesticide is used on a site not specified on the labeling or (2) the label specifically restricts the pests against which the pesticide may be used (e.g. “for use only against ants”). [3]

The container of Enoz Moth Ice Crystals I purchased on August 29, 2011, at the True Value Hardware store on Orchard Mesa does not specifically specify a site or restrict the products use against a specific pest. Based on the EPA statement at the beginning of this paragraph it appears this product can be legally used to fumigate the roots of peach tree borer infested trees.

Hand Worming

Hand worming is accomplished by removing the soil and goo around the base of the tree, finding the tunnels and pushing a flexible wire into the burrow to kill the borer. Hand worming is a major task especially when there are several hundred borer-infested trees to treat.

Mating Disruption

Some of the commercial peach orchards I walked this summer had globs of goo erupting from the soil at the base of their trees. Some growers have tried using pheromones to disrupt the mating flight of the moths and the reports are favorable as long as neighboring orchards are treated in the same manner. [4]


The use of insect parasitic nematodes such as Steinernema carpocapsae, S. feltiae, S. glaseri, Heterorhabditis heliothidis and H. bacteriophora are effective control options. The wrong type of soil, the wrong pH, chemicals in the soil, improper soil temperature, and many other factors affect the success of nematodes in their hunt for these borers.

A Quick Summary

Peach growers, whether backyard or commercial, will need to ensure they don’t miss the treatments necessary to control the peach tree borer, or they run the risk of losing their trees to this pest.





Wednesday, August 24, 2011

Lavender Research at Bob Korver's

Bob Korver of Palisade Colorado irrigates this field by running water down the furrows on either side of the lavender beds. The furrows are about six inches deep. The field was planted this spring and has only been watered 4 times. This field contains 10 cultivars in a completely randomized block design. Each block consists of 10 plants of one cultivar. Each block is replicated 6 times. The flower stalks are being cut off five of the plants in each block with the other five being allowed to develop and mature their flowers.
This research project will provide the data necessary to compare the production of Bob’s 10 cultivars and determine if there is a significant difference in production when the flower stalks are removed vs. when they are left to develop. At this time there does not seem to be a difference in plant size between those plants that have had the flower stalks removed and those plants where the flower stalks were left on. A difference in yield however, may appear sometime over the next two years.

Shawn Douglas and Kay Stucker-Shilts cut off flowers and
collect data

Data will be collected through 2013 on growth rate and yield. The results of this research will be posted on my blog and web site. If funds are available the quality of the oil of the various cultivars will be determined by gas chromatography-mass spectrometry after the 2012 harvest.

This project is a cooperative venture of Bob and Elaine Korver, the Lavender Association of Western Colorado, and Colorado State University Extension. If you are interested in learning more get in touch with me at

Fall Webworms appearing in Cottonwoods and other Populus species

Fall Webworms are showing up in cottonwoods throughout western Colorado. This insect overwinters as a pupa in debris at the base of trees with the adults emerging, mating, and laying eggs in late summer on the twigs and branches where the caterpillars form their tents.

While cutting off the branches and burning the tents might seem like a good idea there are only so many branches you can remove without causing root damage. Cutting off branches also creates wounds through which pathogens can invade. Burning the tents while still on the tree is likewise not recommended as the damaged tissue can be highly susceptible to disease infection and insect attack. It would be better to let these caterpillars continue to feed than to remove or burn branches to control them. The tents are unsightly but unless the tree is severely stressed from some other malady, fall webworm infested trees most likely are not going to suffer from these beasties feasting away on a few leaves.

A spray of Bacillus thuringiensis (BT) and Pyganic are organic options. Pyrethroids such as permethrin, cyfluthrin and esfenvalerate are also recommended. Adding a non-ionic surfactant or a couple drops of liquid dishwashing soap per gallon of spray helps the spray penetrate the tent and reach the caterpillars within. Aspens are particularly sensitive to soaps and liquid concentrate sprays so test a small patch of leaves a day or so prior to spraying the complete tree to determine if the spray is phytotoxic.  Or, leave out the soap.
Imidacloprid does not work on this insect as it is not effective on Lepidopteras (moths and butterflies).

The BT strains that work on lepidopteras are aizawai and kurstaki. See the web page at for more info on the various strains of BT and the insects they are effective on.

The PyGanic label can be found at

Dr. Cranshaw’s publication on tent-forming caterpillars is at

Tuesday, August 23, 2011

Three-leaf Sumac and eriophyid mites

Lower Leaf Surface
Upper Leaf Surface
 If you have a three-leaf sumac, Rhus trilobata, and it takes on a purple cast as seen in the above photo it most likely has an infestation of eriophyid mites. These tiny carrot-shaped creatures feed on the leaves and cause them to change color. With some trees, they cause the leaves to curl or roll. They are very hard to see as they are one-fifth of a millimeter in size (twenty-five millimeters in an inch).

A spray of plain or soapy water usually is sufficient to wash these six-legged critters off the leaves. Be sure to wash both sides of the leaves paying more attention to the underside. See  for more info on these mites.
The orange carrot shapes to the left of the pin, the black line, are the mites.

Tuesday, August 9, 2011

Increase the effectiveness of glyphosate herbicide by adding nitrogen

Shawn weighs out ammonium sulfate in the Mesa County CSU Lab.
Glyphosate, the herbicide ingredient most commonly known as Monsanto’s Roundup went off patent several years ago. As a result many companies now produce and sell this herbicide sometimes at a lower cost than previously.

While this herbicide is much more effective on grassy weeds than broadleaf weeds (dandelions, purslane, bindweed, etc.) you can increase the overall effectiveness of this chemical by adding nitrogen to the spray. A spray mix containing 0.5 to 1% nitrogen is recommended.

So how do you figure out the amount of a nitrogen fertilizer to add to the glyphosate/water spray?

Let’s say you are mixing up five gallons of spray for a backpack sprayer. One gallon of mixed glyphosate and water weighs about 8.35 pounds, thus 5 gallons of this spray will weigh 41.75 pounds. The steps are as follows:

1. We first need to convert 0.5% to a decimal by moving the decimal point over two places to the left. This gives us 0.005.

2. We next multiply 41.75, the weight of the five gallons of spray by 0.005. (0.005 X 41.75 pounds = 0.209) That is the weight in pounds of nitrogen we need to add to the five gallons of spray.

3. We then can convert 0.209 to ounces. There are 16 ounces in a pound and 0.209 X 16 ounces = 3.34 ounces. Now we know the amount (3.34 ounces) of Nitrogen in ounces we need to add to the each five gallon tank of spray, but not the amount of fertilizer.

4. Fertilizers contain varying amounts of Nitrogen depending on their formulation. Ammonium sulfate contains 21% N; Ammonium nitrate 33%; and Urea 48%. For this exercise I’m going to use Ammonium sulfate.

5. We next have to convert 21% (the percentage of nitrogen in ammonium sulfate) to a decimal. WE do that by moving the decimal point two places to the left. (21% = .21 – there is a decimal between the 21 and the %, you just can’t see it.) We then divide 3.34 ounces (the amount of nitrogen we need) by .21. This gives us the amount of ammonium sulfate needs to be added to every 5 gallons of glyphosate spray. (3.34 divided by 0.21 = 15.9 ounces or one pound).

If you have an eight ounce cup handy, you would need to add two of these, full to the top, to the 5 gallons of spray. This will give you the 0.5% nitrogen mix you need.

To figure out the amount of ammonium nitrate or urea to use, divide the amount of nitrogen needed by the percentage (changed to a decimal) of nitrogen in the fertilizer.

Monday, August 8, 2011

Algae and Turfgrass

Curtis Swift, Ph.D., Colorado State University, Tri River Area

A mass of algae collected from a lawn.
Masses of greenish to brownish globs of algae that form on the soil surface can damage turf by suffocating grass plants and their roots. As these gelatinous deposits dry they form tough black crusts that crack and peel off in sheets. This problem is more common in thin, shaded, over-fertilized, and over-watered turf than in well-drained, healthy turf. Compacted areas, especially where water stands, are especially susceptible. Proper soil preparation prior to seeding or laying sod, selecting the proper grass for the site, fertilizing properly and following other proper cultural techniques helps reduce problems with algae.

Maintaining a thick turf even in areas where shade is a problem, and avoiding water-logged soil and over-watering reduces problems with algae. Watering in late afternoon or early evening has been reported to increase problems with algae. Improving drainage through a vigorous aeration/core cultivation program is recommended. Top dressing to fill the aeration holes will improve drainage if the proper material is selected to fill the aeration holes. Applications of diluted solutions of sodium hypochlorite or liquid household beach (0.01%), copper sulfate (2 to 3 ounces per 1000 square foot area) are recommended treatments. Daconil (chlorthalonil) and Fore (mancozeb) are fungicides labeled for the management of algae.

When algae seal the soil surface and/or the spaces between the soil particles it fosters the development of a condition called anaerobiosis (an anaerobic environment caused by the presence of biotic/living organisms). In sandy soils this creates ‘Black Layer’, a film of bacteria an inch or so below the soil surface. This oxygen depleted environment, results in a toxic situation and subsequent root death. Deep aeration along with proper watering helps correct ‘Black Layer’, a widespread problem in sports turf management.

Smith (1988) reported the development of these anaerobiotic layers were more prevalent when urea was used as a fertilizer when compared with either ammonium nitrate or ammonium sulfate. Smith also found the addition of sulfur to a urea or ammonium sulfate application increased the severity of Black Layer.

As with the correction of algal formations on the soil surface, alleviation of problems with Black Layer is through proper turf management to include aeration.


Beard, J.B. 1973. Turfgrass: Science and Culture. Prentice-Hall Inc. Englewood Cliffs, N.J.

Couch, H.B., 1995. Diseases of Turfgrasses: Third Edition. Krieger Publishing Company, Malabar, FL.

Schumann, G.L., Vittum, P.J., Elliott, M.L., Cobb, P.P. 1998. IPM Handbook for Golf Courses. Ann Arbor press, Inc. Chelsea, MI.

Shurtleff, M.C., Fermanian, T.W., & Randell, R. 1987. Controlling Turfgrass Pests. Prentice-Hall, Inc. N.J. 449 pages.

Smith, J.D. 1988. Black plug layer on Saskatchewan golf courses. Greenmaster 24(8): 6-11, 21.

Friday, August 5, 2011

Tuber Diseases of Irish Potato

Tuber Diseases of Irish Potato

The presence of Rhizoctonia and scab on Irish potatoes is an indication of soil conditions that need to be corrected before you plant your next crop of potatoes. The following explains how to identify these problems and provides the necessary guidance to prevent and correct problems with these diseases in the future.

Rhizoctonia – ‘the Dirt that Won’t Wash Off’

Photos Courtesy of
Rhizoctonia solani on potato tubers is often called the “dirt that can’t be washed off” due to the formation of hard black raised specs and spots (sclerotia) on the skin of the tuber. This fungus also attacks and causes lesions on the stems and roots of the plant causing plant death or reduced yield. Once in the soil this fungus can remain for years, hence the reason for following a rigorous crop rotation program. This means not planting potatoes in the same area for at least two to three years. If the soil is contaminated with Rhizoctonia planting a crop of grass or cereal in the rotation schedule helps reduce the presence of this plant pathogen.
Tubers selected for planting can be already infected with Rhizoctonia so check them carefully prior planting. Certified disease-free tubers should be free of this disease. Tubers being sold for table use, i.e. from the grocery store, may be infected with this and other potato pathogens.

The Rhizoctonia fungus survives in soil on infected tubers remaining from the previous year’s crop as well as on decomposing plant residue. Using finished compost free of animal waste is critical to preventing problems with this disease. Since the fungus is less likely to attack potato plants that have formed green leaves, the faster the potato plant emerges from the soil, the less likely the plant is to be infected. Planting when the soil is cool (55 – 60oF.), planting tubers deeper than two inches, and wet soil increase problems with this disease. Warming the soil prior to planting with clear plastic sheeting is suggested. Planting shallow encourages rapid emergence resulting in less infection. Hilling up the plants to ensure there is adequate depth of soil for tuber formation will still be necessary but only after plants emerge.

‘Common Scab’ of potatoes

Infection by scab creates roughly circular, raised, tan to brown, corky lesions on the tuber. Pits up to one-half inch deep on the tubers can result. Tubers infected with this disease organism are safe to consume but have a lower quality in the market place.

Common scab, caused by the bacterium Streptomyces scabies, is the scab organism of soils with a pH above 5.0. Acid scab caused by Streptomyces acidiscabies occurs in soils below a pH of 5.0. A third acid-loving Streptomyces species, S. turgidiscabies, along with S. acidiscabies, have only been reported in the northeastern Unites States and Japan. The scabby appearance of the tubers is due to the plant toxins produced by these bacteria. Other Streptomyces species are known in Europe and elsewhere causing russet or netted scab. Unlike the Streptomyces species of North America, these species are known to cause root rot and yield reduction.

Choosing disease-free tubers for planting, as with Rhizoctonia, is critical with this disease as scab can be introduced into the soil by planting scabby tubers.

Scabby potatoes are more common in areas where high soil organic content is the norm, especially when unfinished compost or animal manure is used as soil amendments. Even in soils where low organic content (the native soils in Western Colorado typically have less than 1% organic matter) is normal, potatoes can suffer from scab when the tubers develop in contact with pockets of organic matter. This scab-forming bacterium is a saprophyte surviving on fresh dead organic matter as well as seedlings. To prevent scab thoroughly work compost into the soil breaking up any clods in the process. Lasagna gardening and the use of straw or hay in which potatoes are grown often results in more problems with scab.

Maintaining adequate moisture (80 – 90%) during tuber development has been shown to reduce scab formation. A three to four year rotation with grasses and cereal crops helps reduce the incidence of scab. Rotations with carrot, beet, spinach, turnip, and radish should be avoided as these crops can increase scab problems with potatoes.

The use of scab resistant cultivars of potatoes is recommended.

Table 1 - Scab Susceptible and Resistant Cultivars

Susceptible Cultivars

Scab Resistant Cultivars

Centennial russet










Irish Cobbler








Red Pontiac

Norgold Russed







White Rose


Yukon Gold


Russet Burbank




Table contents in part extracted from Rowe, R.C. 1993. Potato Health Management, APS Press.