July 2, AppleTalk Blog Post

AppleTalk Blog Post
Monday, July 2, 2018
Questions or comments: Peter Werts, IPM Institute of North America, pwerts@ipminstitute.org

There will be no AppleTalk conference call on Tuesday, July 3, 2018. The next call will be held on Tuesday, July 10, 2018.

Wisconsin Apple Growers Association – 2018 Summer Field Day
Wednesday, July 18, 2018 – Oakwood Fruit Farm, Richland Center WI

Pheromone trap maintenance
Visit last week’s AppleTalk blog post for a reminder on pheromone trap maintenance, http://www.ecofruit.wisc.edu/appletalk/june-26-appletalk-conference-call/

Apple maggot
Red spheres should be going up in all orchards across the region. Apple maggot (AM) emergence is often spotty in early July and we expect trap captures to increase as we move into mid-July and through the month of August.

There is not anything new regarding the timing of AM sprays. If we are relying on baited or unbaited spheres, the narrative suggests that if you are catching maggot flies on red spheres, they are laying eggs and there is no safe interval to wait to spray. In practice, if the numbers we are catching are fairly low and if most traps are zero and only catching a few, you are probably okay, however, as numbers increase, the urgency to spray increases. The threshold developed by Cornell is an average of one fly per sphere, where three unbaited spheres are used per ten acres. When using a baited trap, this threshold increases to an average of five flies per sphere.

We will discuss AM management in greater detail during next week’s AppleTalk call.

Japanese beetle
Japanese beetle (JPB) is moving into the areas of our region that have had historic pressure, e.g., Eau Claire, Chippewa Falls, southeast Wisconsin and northern Illinois. Insecticide options for this pest are rather limited. Neonicotinoids, e.g., Assail (acetamiprid), will offer good repellency if applied before large aggregations of JPB begin to appear. If populations are large, applying a “knock-down” or contact insecticide, e.g., organophosphate or PyGanic (pyrethrins), may offer good control. Last year John found that a combination of 1 – 2 lb. of Imidan (phosmet) tank mixed with a neonicotinoid may give us much better management of this pest. Carbamates, e.g., Carbaryl, also work, but are much more disruptive to biological controls and other natural enemies that may be active in the orchard. If you are avoiding organophosphates, carbamates or pyrethroids, then it is very critical to make an application of a neonicotinoid at the first sign of their feeding injury and before the aggregations appear. If imidacloprid products are applied for AM or leafhoppers, e.g., Wrangler, Alias, Montana, these should also offer some repellency and anti-feeding properties for Japanese beetle.

Organic producers have the option of applying neem (azadirachtin) oil products, e.g., Azadirect, Neemix, Trilogy, or PyGanic. It is important to be aware that a botanical insecticide such as neem may be phytotoxic if tank mixed with other pesticides. Additionally, several years ago a new product called beetleGONE! (Bacillus thuringiensis galleriae) was introduced to the market. Trials done at UW Madison on roses found that beetleGONE! performed decently on roses. When we looked into pricing in 2016, it was still quite expensive, but worth investigating and organic producers should keep it on their radar.

Sequential sampling of mite populations offer a quick and easy way to assess mite populations. The sampling method uses a presence or absence count which correlates to an assumed average number of mites per leaf across the entire block being sampled. When we can sample frequently, this is often the quickest method to identify if a block needs to be treated with a miticide. This sampling method does not account for the days mites have been on the leaves or if any predators are present. For example, mites can be below threshold, but still causing bronzing, which means we have economic damage. Prolonged feeding can stress the tree by impacting photosynthesis and can lead to reduced shoot growth and fruit bud set the following year and in severe cases impact winter hardiness.

Sequential mite sampling July 1-31: http://newa.cornell.edu/uploads/mites50.pdf

If you are going to apply a miticide as rescue treatment (populations are over threshold or bronzing is occurring) look for a miticide that controls all motile forms, as there are miticides which only affect eggs or adults. All miticides should be rotated between applications and seasons. Please note, miticide rates may vary between two-spotted spider mites and European red mites, and not all miticides will control apple rust mites. Apple rust mites do not have thresholds and are generally not a concern on large semi-dwarf trees, but may be of concern for trees that are newly planted or on trellised systems. Populations of 200-500 per leaf are often needed to cause injury, and may justify treatment.

For a more in-depth discussion on mite management visit: Red Mite Building in Gala and Red Delicious. June 31st, 2018, The Jentsch Lab, http://blogs.cornell.edu/jentsch/2018/07/02/red-mite-building-in-gala-and-red-delicious-june-31st-2018/.

Return bloom in apples
For information on promoting return bloom visit the following article by Janet van Zoeren and Amaya Atucha in last week’s Wisconsin Fruit News (page 12), https://go.wisc.edu/y70yf3.

Happy Independence Day! See you next week.