KENTUCKY PEST NEWS
Lexington, KY 40546
ENTOMOLOGY • PLANT PATHOLOGY • WEED SCIENCE
Online at: www.uky.edu/KPN
Number 1369
March 11, 2014
FRUIT -Backyard Fruit Spray Guides
SHADE TREES & ORNAMENTALS -Polar Vortex Effect Varies With Insect
FRUIT
Here are links to the backyard fruit pubs: • Simplified Backyard Peach and Stone Fruit Spray Guide (PPFS-FR-T-20) http://www2.ca.uky.edu/agcollege/plantpatholog y/ext_files/PPFShtml/PPFS-FR-T-20.pdf • Simplified Backyard Apple Spray Guides (PPFS-FR-T-18) http://www2.ca.uky.edu/agcollege/plantpatholog y/ext_files/PPFShtml/PPFS-FR-T-18.pdf • Simplified Fungicide Guide for Backyard Fruit (PPFS-GEN-08) http://www2.ca.uky.edu/agcollege/plantpatholog y/ext_files/PPFShtml/PPFS-GEN-08.pdf
Backyard Fruit Spray Guides Nicole Ward Gauthier, Extension Plant Pathologist As the weather warms, questions regarding backyard fruit production are likely to arise. In response, Extension Specialists in Plant Pathology, Entomology, and Horticulture have co-authored a simplified backyard peach spray schedule to complement last year’s backyard apple spray schedule. Both documents, as well as other plant disease factsheets, can be found on the plant pathology publication page at http://www2.ca.uky.edu/agcollege/plantpathology/ex tension/pubs.html
SHADE TREES & ORNAMENTALS Polar Vortex Effect Varies With Insect Lee Townsend, Extension Entomologist Unusual blasts of polar air swept across Kentucky this winter. What was the effect on Kentucky arthropods? These creatures are a hardy lot with effective mechanisms that allow them to survive some harsh conditions. First, a few species are vulnerable but many are not likely to be affected. Second, the air temperatures stated in weather reports are often quite different from those occurring in sites where these creatures are spending the winter. Factors such as snow cover, mulch, and orientation can provide enough protection to allow survival. Even the impact on species that are affected can be temporary because of the high reproductive capability of arthropods. Here are some observations and reports on some of our common species. Time will tell if they reflect what actually happened.
Eastern tent caterpillars There was little apparent effect on the eastern tent caterpillar (ETC). This insect spends the winter as tiny, fully developed caterpillars in distinctive egg masses that encircle twigs of wild cherry and related species. ETC is one of the first insects to become active in the spring and is well-adapted to survive our often-erratic winter and early spring weather. Hardy may be too mild a term for them. Laboratory studies have shown that caterpillars in the egg can withstand temperatures down to minus 31° F. It has been a cold winter, but temperatures have not been low enough to expect a significant reduction in egg hatch this spring. Dissections of some eggs collected in early March of this year show nearly 80% survival, the same rate determined several years ago in studies by UK entomology researchers during the ETC/Mare Reproductive Loss Syndrome outbreak. The growth and development of many insects is directly dependent on temperature. Usually, this allows relatively accurate predictions of egg hatch and development. Unfortunately, the ETC is an exception. Predictive models using degree-day information can provide a general idea of when egg hatch can occur but actual hatch in the field is variable. In fact, eggs from a single mass usually hatch over about a 2-week period, not all at once. This is an important survival mechanism that protects the species from high mortality. Prolonged egg hatch increases the chances of species survival even if some early caterpillars are killed by freezes or heavy rains during early spring.
Certified Arborist Larry Hanks has tracked ETC egg hatch in central Kentucky since 2001. His earliest observation was March 13, 2012; the latest was April 4, 2013. Typically, the caterpillars first appear during the second or third week of March. It is still too early to provide a general prediction for 2014. Continued cold will slow development but a string of 70° F days can cause egg hatch to begin in a short time. ETC populations seem to have increased over the past 5 to 7 years with numerous tents visible along fence line wild cherry trees in some areas of the state. Regrowth and sprouting of new trees may have resulted in increases in host trees and the caterpillars. Watch for information on the ETC’s development this spring and monitor fence lines accordingly. Scale A recent sample of willow oak from Jefferson County had live oak lecanium scale nymphs on twigs. Soft scales, such as this one, spend the winter on twigs and small branches. Development resumes in the spring and adults are present in early summer. The reproductive capacity of soft scales (hundreds of eggs per female) can mean quick recovery, even if winter mortality is high.
Figure 2. Live nymphal oak lecanium scale nymph
Bagworms Bagworm is a species that appear to be susceptible to cold temperatures. Research indicates that 24 hours at minus 1° F can kill more than 75% of the eggs in a bag. Their northern distribution in the U.S. extends to southern Michigan, indicating winter temperature is a limiting factor for this insect. It is one species that might be reduced by our winter weather. Figure 1. Tiny ETC larva waiting in egg
Figure 3. Bagworm larvae may be reduced due to winter weather.
Wooly adelgid Personnel from the Office of the State Entomologist sampled hemlock woolly adelgid populations at several locations in eastern Kentucky. Their findings indicate very high average mortality (greater than 90%). This may be a significant setback for the insect but a high reproductive rate and re-infestation should mean a rebound in time. A reduction in adelgid populations also is likely to affect survival of the beetle that has been introduced as a biological control agent.
Figure 4. Hemlock woolly adelgid egg sacs
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.