The overall goal of this procedure is to distinguish between beach bark disease resistant and susceptible American beach trees. This is accomplished by first collecting adult beach scale insects and their eggs directly from American beach trees. The second step is to obtain a homogenous batch of eggs by cing them away from the adults and other debris.
Next, the eggs are counted out laced on foam pads and affixed to the bark of the test trees. At the same time tests to confirm the viability of the eggs are set up. Approximately one year later, the test pads are removed and the number of adults and egg clusters are counted.
Ultimately, this technique to artificially infest beach trees with the beach scale insect is used to identify trees that are resistant and susceptible to beach bark disease. The advantage of this technique over the one previously developed by Dave Houston for artificial scale infestation is that our technique employs control trees and egg viability assays and is quantitative and reproducible enough for genetic studies. This method can help with beach bark disease management decisions by determining which trees are resistant to the disease and should be retained during harvest, or might make the best candidates for inclusion as seed orchard, American beach trees with a heavy infestation of the beach scale.
Insects are easily identified by their whitewashed appearance. Use a hand magnifying glass to confirm the presence of eggs, which are typically abundant from mid-July to mid-August. Tape a plastic sealable one gallon collection bag to an infested tree trunk and use a paintbrush to gently brush the white waxy clumps of adult scale insects, eggs, and other debris into the bag.
Collect eggs from a minimum of three different trees at least 12 meters apart. Dampen a 2.5 centimeter square piece of polyethylene foam and tape it to the inside of the bag to prevent the eggs from drying out. Then seal the bag.
Breathe into the bag to add a protective cushion of air for transport of the eggs. The eggs can be stored in the sealed collection bag for up to two weeks at four degrees Celsius. To separate the scale eggs from the adults and debris, construct a sieve by sandwiching.
A square piece of 250 micron nylon mesh between a short piece of two inch PVC pipe and a coupling. Place a glass petri dish under the sieve and then empty the mixture of adults wax eggs and debris from the collection bag onto the sieve. Then use a small paint brush to gently encourage the eggs to pass through the mesh into a glass Petri dish below.
To prevent the eggs from drying out. Tape a damp piece of foam to the lid and seal with parfum purified eggs can be stored in the Petri dish at four degrees Celsius for at least a week. In order to obtain viable scale insects, first you have to be able to identify the adult egg laying insects and separate them from the eggs using the sipping process.
Finally, you need to be able to confirm the viability of these eggs using a viability as egg. To assess egg viability, use a 10 cc syringe to apply a thin ring of petroleum jelly around the circumference of the bottom of a 60 millimeter glass Petri dish. Scoop up approximately 100 eggs into a spatula and transfer them to the center of the ring.
Then place the lid on the Petri dish and seal with perfil. Allow the sealed petri dish to remain undisturbed at room temperature for two weeks or three weeks if the eggs had been stored at four degrees Celsius. After two to three weeks, use the dissection microscope to count the number of hatched nymphs, which often can be found stuck in the petroleum jelly.
Then count the number of unhatched eggs, which are opaque and yellowish, and the number of hatched eggs which are lighter in color and translucent. Calculate viability by dividing the number of hatched nymphs by the sum of the empty eggs plus the remaining unhatched eggs. Good viability should be in the 75 to 90%hatched eggs.
Range field testing for resistance to the beach scale. Insect can be done quantitatively by counting out 500 eggs using a portable dissecting microscope if only a qualitative test is needed. Place the 500 eggs in a small vial with a fill line that can be used to measure additional batches of approximately 500 eggs.
Next dampener rectangle of open cell polyethylene foam, and then squeezing out as much water as possible. Using a small metal laboratory spatula, gently sprinkle the 500 eggs across the center of the dampened foam. Now the eggs are ready to be used for artificial infestation.
Select mature, healthy American beach trees that show no signs of scale, infestation or disease. Tie a nylon rope around the test tree, then place the foam pad onto the tree with the egg side facing against the bark. Slide the rope over the pad to secure it.
Slide a second pad under the rope on the opposite side of the tree. A minimum of two pads should be placed on each tree. Plastic or metal-based material should be used rather than rope, string or twine because the latter are more readily scavenged by wildlife.Precut.
A 23 by 30 centimeter piece of vapor, permeable, waterproof house wrap and line the top and sides with acetate based silicone adhesive. Then place the house wrap over the foam test pad and press the edges to the tree to create a waterproof seal. Place nylon twine or plastic coated hardware wire around the tree and house wrap to hold the wrap in place while the adhesive sets select visibly susceptible trees to be used as controls.
Use a firm bristled brush to remove any natural occurring scale insects or eggs from the area where the test pad will be placed. Then place test pads on at least two susceptible trees at each test site. Begin by growing seedlings or graphs in an augmented potting soil mix.
The testing of potted seedlings or graphs is done in a shade house later in the growing season. Fertilize the plants weekly as needed during the growing season, keep the plants in a shade house. Allow the plants to go dormant outside in the fall prior to moving them to a four degree Celsius storage.
From November through April after one to two years, when the trunk is tall enough to have at least two separate test pads placed on it and has a minimum diameter of one centimeter as measured with a caliper five centimeter above the soil line. It is ready for testing, prune any small side branches as necessary to make room for the test pads. Use a dissecting microscope to count out 150 eggs and scatter them over a precut and dampened open cell polyethylene foam pad.
Affix the foam pad to the seedling with the egg side against the bark using plastic coated wire. Wrap a small square of house wrap around the seedling just above the foam and seal it with acetate based silicone. For controls, attach egg containing foam pads to known susceptible seedling families or grafts.
About one year. After placing the foam pads on the trees, carefully remove the foam pad from the seedling or from the mature tree. Then use a hand lens or 10 x magnifying glass to count the number of adult scale insects established on the bark.
When the foam pad is removed, it is not uncommon for some adults and most egg clusters to be pulled off of the tree with the foam. Under a dissecting microscope count the egg clusters and adults that are attached to the foam pad. A resistant seedling is shown here.
The black lines indicate the extent of the foam pad. No infestation of the bark is seen. The two susceptible seedlings seen here exhibit different degrees of susceptibility.
A susceptible mature tree 57 weeks after artificial infestation is shown here. Trees were artificially infested with beach scale eggs in the Allegheny National Forest and Pennsylvania, and in Luton State Park in Michigan. This graph compares resistant trees to susceptible control trees.
The number of trees tested in each group is listed in parentheses. Adult counts per 100 eggs supplied were averaged across all trees within the group. Although there is a lot of variation in the number of adults established on the susceptible trees, clear differences are detected between susceptible and resistant trees.
While attempting this technique, it's important to make sure that the house wrap is sealed firmly to the tree. This will prevent too much moisture build up on the foam pad, which could ruin your assay. After watching this video, you should be able to collect and purify scale insect eggs and use them to set up tests to determine if a beach tree is resistant or susceptible to the scale insect.
The scale insect is part of a causal complex with a fungus that actually leads to beach bark disease.
