NUMBER 1189 |
March 24, 2009 |
|---|
WATCH FOR |
HOUSEHOLD |
FRUIT |
SHADE & ORNAMENTAL |
SPECIAL TOPICS |
INSECT TRAP COUNT |
Armyworm Flight Begins |
|
| Woody Plant Health & Springtime Maintenance Practices By John Hartman |
Choose the right location for plants in the landscape. Too often, perfectly good plants are located in sites that favor disease outbreaks. An important IPM concept is to choose plants that will grow well in a particular landscape site, or to modify the site so that the plants will grow at their best. Plants that must struggle to overcome the effects of a poor growing location are usually the most vulnerable to diseases.
Choose disease-resistant plants for the landscape. Where it is available, disease resistance is a most efficient means of plant disease control. When it comes to fighting diseases of landscape plants, it sometimes pays to know the name of the cultivar and how it is likely to respond to diseases that are common here.
How a tree or shrub is planted often affects its health. When trees and shrubs decline in the landscape, the cause is often thought to be one of the pathogenic fungi or bacteria seen growing in branch and twig cankers. But when one of these pathogens is observed, is it necessarily the cause of the plant’s demise? This opens up many questions for the diagnostician. Did the tree decline due to lack of space for the roots to grow? Was the planting hole properly dug to be much wider than the size of the root ball? At planting, it is best to use the same soil that came out of the hole to backfill around the root ball. Was the soil that was put back into the hole the same as the original soil dug out? Did root rot occur because the planting hole was poorly drained? Did anyone observe girdling at the base of the tree? The strangling effect of girdling roots or twine would stress the tree and invite opportunistic pathogens. If the tree or shrub was removed from the container, were encircling roots detected? Were they cut or removed before planting? What about the twine at the base of the trunk used to hold the burlap wrap in place? Was it removed and was the burlap peeled back from the top and sides of the root ball at planting? Did anyone notice that the twine was plastic? If left in place, the plant would soon be strangled.
Thus, to maintain long-term tree and shrub health in the landscape, make good decisions now. Choose the right location for new plants in the landscape, choose disease-resistant plants, and plant trees and shrubs properly in order to start them off right and to assure that they will have good health for a long time. Figure Legends: |
| SPECIAL TOPICS |
|---|
|
Where Are These Graphs? To see these graphs go the IPM web pages at: What do These Graphs Look Like? The insect weekly capture number is plotted on a graph with the vertical axis representing the number of moths captured and the horizontal axis illustrates the capture date. On each graph you may see up to three lines. The green line represents the current year and a data point will be added each week. The blue line is a rolling five year average that does not include an outbreak year. The red line (if we have available data) is the moth population in a year where we have demonstrative data that fields required treatment. We refer to this as an outbreak year. We have a much more robust data set for Princeton (14 yrs) than we do for Lexington (2 yrs.). What Do These Graphs Tell Me? We believe that these graphs can provide you with a sense of relative risk. The red line tells you what the population looked like in a year when treatments were warranted for some fields. The blue line shows you what the population looks like in years where there is little chance of needing pest control (Data from outbreak years are removed from this data set.) So, these two lines provide a sense of high and low risk for the insect. The green line then tells you what is going on in the current year. What Will These Graphs & The Temperature Model NOT Tell Me? This system will not provide absolutes. All models have an associated error, and we have a once per week sampling so we will never be able to get closer than a week when predicting events. This will not tell you what will happen in any given field. It will not tell you if an outbreak will occur. They only provide a measure of risk, (based on our historic knowledge of the insect population size) and a time window (based on the degree-day model) in which events will occur (e.g. caterpillar feeding). You must scout your fields to determine if the pest is present and if it is present in sufficient numbers to warrant control. How Can I Use This Information? Most of the time you will be taking a very brief look at the graphs. You will be looking for two items: 1.) when the counts start to increase and 2.) how large the counts get relative the “average” and “outbreak” lines. If the moth population size approaches the level of an “outbreak” year, we will begin making predictions of when the caterpillar (damaging stage) offspring of these moths will appear. These projections will be placed in the Kentucky Pest News. |
INSECT TRAP COUNT |
|||||||||||||||||||||||||
| By Patty Lucas | |||||||||||||||||||||||||
Graphs of current insect trap counts will soon be available on the IPM web site at -http://www.uky.edu/Ag/IPM/ipm.htm. |
|||||||||||||||||||||||||
NOTE: Trade names are used to simplify the information presented in this newsletter. No endorsement by the Cooperative Extension Service is intended, nor is criticism implied of similar products that are not named.
 H17-73.jpg)
For example, Rhododendrons and azaleas require well-draine N10-91.jpg)
d acid soil. If the soil is poorly drained, they are vulnerable to Phytophthora root rot, and if the soil is too sweet, they will turn yellow from iron deficiency (Figure 1). If the landscape bed is not naturally suitable, one needs to create well-drained beds with acid soil for them. The same is true for white pines. They can grow well in some Kentucky locations, but they, too need acid and sandy soil. If the roots are not provided with these good conditions, expect white pine decline to gradually take out the trees. On the other hand, Taxus also needs a well drained soil to avoid Phytophthora root rot (Figure 2), but it will perform poorly in acid soil. H17-84.jpg)
If landscape plants such as crabapples, dogwoods, roses, and other plants prone to leaf diseases are planted in shady locations or if they are planted so densely that good air movement and ventilation are not possible, the planting site has been poorly selected. In such cases, one should expect outbreaks of diseases such as scab, black spot (Figure 3) or powdery mildew when susceptible cultivars are planted to shady sites. H9-33.jpg)
For example, flowering crabapple is a popular small tree for residential landscapes. With flowers, foliage and fruit, it can be attractive in all seasons, especially during bloom. Unfortunately, it can be detrimental to the beauty of the landscape when it is diseased. Flowering crabapple FB shepherd crook enh (Hershman) H13-35.JPG)
can be plagued with scab (Figure 4), fire blight (Figure 5), cedar-apple rust, and powdery mildew. These diseases can cause spotted, wilted leaves, rotted fruit, and premature leaf fall. These diseases can be avoided by planting cultivars that are disease-resistant. Disease-resistant flowering crabapples such as ‘Prairiefire’, ‘Mary Potter’, and ‘Harvest Gold’ have been developed and are on the market; lists are available at the local Cooperative Extension Office. H19-65.jpg)
Trees often decline because the tree was planted too deep (Figure 6). When the tree was planted, were flaring buttress roots at the base of the trunk observed? Was the soil from the nursery brushed back to expose the buttress root flare at the top of the root ball? Was the tree set so deep that the root flare was covered? Newly planted trees and shrubs, with their recent root pruning, are certainly growi H19-70.jpg)
ng under drought conditions. Many canker-causing fungi develop only when plants are drought stressed. What caused the drought? Was the root ball kept moist before planting? Was the area over the root ball watered frequently after planting? Was mulch used around the base of the tree to keep the root ball moist? Were wire label fasteners removed (Figure 7)? The answers to these kinds of questions illustrate the importance of using good planting techniques to avoid tree and shrub diseases. 
How to Use the Insect Graphs from the UK-IPM Trap Lines
You may watch the seasonal progress of moth populations for six pests (armyworm, black cutworm, corn earworm, European corn borer, fall armyworm and southwestern corn borer) at two locations (Princeton, Caldwell Co. & Lexington, Fayette Co. KY). Traps are set the first week in March annually, and the numbers of captured moths are counted each Friday in the season. Data are normally posted on Friday afternoon on the IPM web pages (see below) and in the next available Kentucky Pest News (KPN) usually published each Tuesday afternoon.