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Update from the field: San Jose scale and Mites


San Jose scale:

San Jose scale has been a little quiet this year…almost too quiet. This heatwave has probably slowed their development down a little bit, so I am anticipating seeing an increase in activity soon. This timing may be particularly important for blocks that have had a history of scale problems. Looking at the degree day timing for Fort Valley, at this rate I expect the second large peak of crawler activity to occur within the next 7-10 days in middle Georgia. Thus, the SC ridge has about two weeks and upstate SC has about three weeks from now until we would expect to see a peak in crawler activity.  As a reminder, scale crawler activity can me monitored with electrical tape and double-sided tape (or vaseline).

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San Jose scale crawler.

If you have blocks where you have had a history of San Jose scale issues or have noticed problems this season, with the overlap of San Jose scale and PC activity, there is an opportunity to synergize management efforts for these pests. Please note the PHI for the listed chemicals.

In blocks with fruit on the trees, a combination of Imidan (3.5-4 lb; PHI=14 day) with Esteem (6 oz; PHI=14 days) or Centaur (34.5 oz; PHI=14 day) is likely our best (albeit expensive) option, with high efficacy for both PC and scale. Alternatively, another effective option is to tank mix Esteem or Centaur with either Belay (6 fl oz; PHI=21 days), Actara (4.5-5.5 oz; PHI=14 days), or Avaunt (5-6 oz; PHI=14 days). I cannot recommend mixing scale chemistries with a pyrethroid at this time, as the pyrethroids will have a larger negative impact on our natural enemy communities that may provide some natural control of San Jose scales.

In terms of scale-only management Esteem or Centaur alone are good options, or Venerate XC (2 qt applied twice over 7 day period; 4 qt total; PHI=0 days), which is most effective when targeting peak crawler emergence, is an alternative option.  

Lastly, in blocks that have already been harvested, consider applying 2% summer oil in at least 200 gallons of water/acre.

Please note that that while crawlers seem to be active all season long, there will be a third peak of activity in early August. That may be another option for a knocking the scale population back prior to our normal dormant management options.


Mites:

While San Jose scale may not be the biggest fans of this heat, the hot, dry weather is perfect for spider mite reproduction and development. A little rain will help suppress populations, but until then just in case anyone is having issues with mites, I wanted to update everyone with some management options.

Mite damage is primarily foliage based. Damage to leaves appears as a general “bronzing” of the leaf, as the mites puncture and ingest the contents (including the green chlorophyll) of the plant cells.

Leaf bronzing due to mite feeding.

Spider mites also construct webs, which can be extensive in heavily infested trees. 

Example of spider mite webbing on peach tree.

Thankfully, peaches in general, are much more tolerant than other orchard fruits to mite pressures. They can withstand mild to even relatively high mite infestations, but significant bronzing and webbing can lead to defoliation. If heavy mite pressure continues for a long period without control, and moderate to substantial defoliation occurs, trees can potentially experience a reduction in vigor, a markedly lower fruit yield, and a overall decline in health the following year.

The University of California has an excellent monitoring and treatment decision model, which can be found here: https://ipm.ucanr.edu/PMG/r602400111.html

In addition, mite infestations can be a nuisance to fruit pickers. In this case, management may be needed regardless of potential injury to the trees/fruit.

As such, targeted applications of miticides can be used as needed. The preferred choices are curative miticides (e.g. Acramite, Nexter, or Envidor) used in rotation. If adults are well managed, but eggs are still present, then a preventative miticide (e.g. Zeal) may be used to help control the remaining eggs. If multiple miticide applications are made, BE SURE TO ALTERNATE/ROTATE active ingredients, as mites readily develop resistance to miticides.

Although easier said than done, avoid over-application of pyrethroid in the summer, as these sprays have a tremendous negative impact on predatory mites, while minimal long-term impact on pest mite populations, which can lead to subsequent mite flareups.

For more information about mite management, please check out the peach management guide.

I hope everyone is doing well and staying hydrated!