In this Issue
- Fruit aphids: rosy apple aphid, green peach aphid, woolly apple aphid
- Apple, Pear: codling moth updated spray dates table; fire blight
- Peach/Nectarine, Apricot, Plum: peach twig borer spray dates
- Cherry: western cherry fruit fly treatment starts when fruits turn salmon blush color
Rosy Apple Aphid and Green Peach Aphid
Aphids thrive in cooler temperatures and their eggs easily survived our mild winter of 2021. As a result, their populations are high this season. They are almost at their peak now on apples, peaches, and other fruit trees. On apples, we are primarily seeing rosy apple aphid and on peach and plum, it is green peach aphid.
Both species cause tightly curled leaves, and also cause leaves to turn yellow and drop. Of the two, rosy apple aphid is more of a concern for commercial growers because their feeding near fruit causes the fruit to become flattened and distorted.
The good news is that both aphid species will migrate away from fruit trees in a few weeks to spend the summer on weeds, vegetables, and other host plants. In addition, a new flush of growth will “hide” the damaged foliage.
If the damage is not bad, ignore the aphids and let natural enemies such as lady beetles and lacewings have their meals.
- Residential: insecticidal soap (organic; many brands), horticultural oil (organic; 1%), pyrethrin (organic; many brands), Spectracide Triazicide, GardenTech Sevin
- Commercial: Admire Pro (or generic), Beleaf, Assail
Woolly Apple Aphid
Woolly apple aphids were spotted in Davis and Utah counties this week, and the coming warm weather will provide conditions for increased population growth.
Look for these aphids in old pruning cuts, tree wounds, or cracks and crevices in the bark. They also feed on roots, and some aphids stay on roots year-round, while others migrate up the bark in spring and summer, and then migrate back in fall.
This aphid is much more difficult to manage that the aphids discussed above, in that they produce a waxy, cottony secretion that protects their bodies from pesticides and predators. They are also different in that they feed on twigs, bark and roots, rather than foliage alone.
We are finding that this aphid is becoming more and more common in backyard trees due to our milder winters. So it is very important to scout your own trees to determine when and if a treatment is needed. Again, look for them around old pruning scars or wounds, and on root suckers.
If woollies are a problem every year, it is best to treat them early! Otherwise, treat them when they are covering more than 10% of the tree.
Because of the aphid’s thick, waxy coating, it is important to spray the trees to dripping to reach and penetrate the aphid colonies.
- Residential growers can use insecticidal soap mixed with 1% horticultural oil, aimed directly at the colonies, or Spectracide Triazicide mixed with 1% oil.
- Options for commercial growers: click here.
Codling moth dates of “greatest egg hatch” are coming up for northern Utah locations.
View a pdf of the updated spray timing table. Be sure to read the instructions at the top of the page, for how to read the table.
Soon, codling moths in most northern Utah locations will be in the “period of greatest egg hatch.” What this means is that 75% of all eggs for the first generation will be hatching over a 2 to 3 week period. So if you applied a treatment for the start of egg hatch, be sure to re-apply once or twice during the date range shown on the table.
If you have not sprayed or want to spray minimally, keep fruit protected during this period of rapid egg hatch.
- See the May 14, 2021 post for a table of products (under Codling Moth)
- Options for commercial growers.
In northern Utah, we are now seeing damage from fire blight (infections happened during bloom) in orchards. Be sure to inspect flower clusters on your trees for wilting and brown/black tissue.
If infected fruit clusters are found, prune out the tissue right away. At this time of year, prune out twice the length of the symptomatic twig or shoot.
Infections that are not pruned out will continue to expand within the plant tissue, killing a greater portion of the branch. In this case, the branch will need to be pruned out up to 12 inches beyond the infected area. So it is best to prune now!
Peach Twig Borer
Treatment dates for early June in northern Utah locations
View a pdf of the spray timing table.
Peach twig borer affects peaches, nectarines, and apricots. Unlike codling moth on apples, this pest is more sporadic in Utah, and some locations have a low enough population that does not need to be treated.
The treatment table shows when to start treating the first generation for additional northern Utah locations. In general, just a single application is sufficient for the first generation. This spray will lower the population, and prevent shoots from being attacked.
But during the second generation (which can attack the fruit), you may need to apply insecticide regularly so that your tree is protected throughout the egg-hatch period.
- Residential: Use the same options provided for Codling Moth, found in the table of the May 14, 2021 post.
- Commercial: Treatment options are found in the Intermountain Tree Fruit Guide.
Western Cherry Fruit Fly
We captured western cherry fruit flies on the USU Research Farm in Kaysville, UT this week. The traps are in an orchard with a very high population, so it is the earliest site that we see them active in northern Utah.
The time to treat for the “worms in the cherry” is based on the development of your own tree. Watch the fruit color. It will go from green to yellow, and then quickly develop a rosy blush. Once that rosy blush forms, then the female flies are able to penetrate the fruit skin and lay eggs inside.
Therefore, treatment should begin as soon as cherries develop the salmon blush color. Base this off the fruits in the sunniest location of the tree, which is often toward the top or on the south side.
Treatment Options – Residential
- Malathion (malathion): every 7 days
- Bonide Fruit Tree Spray (carbaryl): every 14 days
- GardenTech Sevin or Spectracide Triazicide (pyrethroids): every 14 days
- Fertilome / Gardens Alive / Bull’s Eye / Monterey (spinosad): every 7 days
- Safer BioNEEM (azadirachtin): every 7 to 10 days
Treatment – Commercial Growers
- Commercial growers, click here.