Spotted Wing Drosophila
Spotted wing drosophila numbers began about when we expected this year, but trap catches remained low, and numbers rose more slowly than last year. Numbers are significantly higher now, but still lower than last year at this time. Blueberries and brambles that are ripe or ripening seem to have the highest numbers now. Plums and some peaches are also attacked, as they ripen. In grapes, I don’t expect attack until verasion. Numbers should continue to climb through the month. They have the shortest life cycle during the hot temperatures of August. Once temperatures cool in September, the population continues to rise, but more slowly, since growth and development takes longer at cooler temperatures. Trap designs, identification photos, bait formulas, cultural management information, and a pesticide list are on the SWD page of our website. Did you see my note earlier, about a new SWD pesticide, called Exirel, from DuPont?
Leaf Tissue Testing for Nutrient Analysis
The time to do leaf sampling for nutrient analysis in tree fruit is late July through early August. Don’t wait too long! Forms and instructions for plant tissue testing are on the Soil Testing page of UNHCE’s website
X-Disease of Peach, Nectarine, Sweet Cherry
Late July and early August is the easiest time of year to locate and eliminate X-disease infected choke cherries. They stand out from most other vegetation by the bronze foliage color. In early stages of infection, choke cherry foliage is yellow-green. In addition to the color clues of infected choke cherries, you can tell the species (infected or not) from others in several other ways, including looking at the leaf edges, the point of stem-to-fruit attachment, and arrangement of fruit on the twigs. I have both close-up photos and descriptions in my fact sheet Identifying Choke Cherry – Source of X Disease. Keeping the peach/cherry orchard mowed also helps discourage high populations of the leafhoppers that pick up the disease agent from infected choke cherries, and transmit them to your trees when they feed. That’s in the publication, too.
Peak attack for this species usually is in August. They have preferences, and in New Hampshire we see the most injury in Delicious, Cortland, Red Astrachan, Yellow transparent, and a few other varieties. The amount of injury is likely affected by our pattern of spraying, not just by preferences of the flies to lay eggs. Based on my 35 years of fruit evaluations, injury is rare on Paulared and Macoun.
Red sticky sphere traps are still the best to monitor AM. In some sites with heavy pressure, the attack period extends into September. The fly on this fruit is a female, recognized by the four white bands on her abdomen, and the pointed tip to the abdomen. Males have blunt tipped abdomens, and only three bands. Both have the same pattern of black bands on the wings.
Pesticide Applicator Training Recertification Credits On Line
Recently my colleague Rachel Maccini (in the pesticide safety education program) announced that there are now materials at UNH Cooperative Extension’s website that allow you to obtain recertification credits without going to a meeting. You can get the credits by studying materials on line. For those of you who are shy a credit or two, this might be really worthwhile for you to investigate! Some modules are up & running, and others are coming. Here is the link to the information.
Brown Rot on Peaches, Plums, Nectarines
As stone fruit begin to ripen, they become much more vulnerable to brown rot infection, compared to green fruit. The disease is favored by warm, wet conditions. Please remember that the SI fungicides (like Indar, Quash, Rally and Tilt) should not be used through the season to control BOTH the blossom and fruit rot phase of the disease. That could easily lead to the fungus developing resistance. So switch around a bit and use Captan, Gem or Pristine in your spraying.
Using Retain on Apples
If you plan to use the growth regulator Retain, the time to apply it is three to four weeks before the anticipated harvest date. For many growers, McIntosh is the variety that makes the most sense to treat. That means application time is close. The label warns not to spray during the heat of the day. It says that best results come from slow drying conditions, to maximize absorption (early AM or night application). Pome fruit plants under stress don’t show a good response.
I usually see the first few webs of this insect in mid-July. This year I saw several on blueberries and apples July 18th & 19th. Early signs are several leaves webbed together, with dozens of yellow, hairy caterpillars inside. New webs continue to appear through September. I see the most problems in rows that are close to woodland borders. Predators and parasites reduce the numbers somewhat, but not enough to prevent losses in some sites. We even have two birds that specialize in eating hairy caterpillars (black-billed cuckoo and yellow-billed cuckoo), but they are not very abundant. If the damage is objectionable, you could spot-spray webs with an insecticide. In addition to a huge range of chemical insecticides, the Bacillus thuringiensis-based sprays work on these. If the caterpillars are large, though, chemicals are more effective. Some blueberry growers ignore the webs here & there, and point them out to customers as proof that they don’t nuke things with sprays. The critters feed on the surface of fruit, as well as foliage that gets webbed up. I find that a relatively coarse spray and a wetting agent help to penetrate the webs.
Alan T. Eaton, Extension Specialist, Integrated Pest Management
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