The blanket aerial spraying in California of malathion occured in a bygone era. It would never be permitted today.
Here in SA we are the only mainland state free of fruit fly. But every year there are outbreaks that cost millions, due to illegal fruit importation.
The government certainly doesn't do enough. Other states have all but cut funding for fruit fly measures.

Millet, the issue is complicated by the fact that the fruit fly causing the major damage is native to Australia and has a wide list of hosts.

Citrus leprosis virus is not present in Australia. However I would agree with millet that it does look like you have mite damage.

I would be interested to see the genetic difference between two Satsuma varieties.  It is probably not dissimilar to this case.  Also, as Greg mentioned it is no secret that Tango is an irradiated W. Murcott Afourer.  The genetic make-up should be nearly identical, however the lack of seeds in one is a major difference and a unique attribute of Tango that is highly valued by this market.  Tango has been around for quite some time now.  Why is this legal endeavor happening now?  This whole thing seems a bit frivolous.

-Brett

Tango is not unique in being seedless.
Seedless Afourer mandarins are grown and sold here and in the US under the tradename Delite, which is licensed to Mulholland Citrus, California.  Grown in isolated blocks away from other pollen sources the fruit is seedless.
Seedless being defined by industry as no more than one seed per fruit in any 20 fruit sample.

Pancrazio, I cannot comment specifically on Xie Shan as it has not been imported here.
But satsumas in the main are not a sweet mandarin; yes, lower in acidity but not sweet.
It takes controlled water stress by growers here to get Okitsu significantly above brix 10°. Afourer/Tango will easily reach 14° brix no problem. Gold nugget which many members rate, even higher levels.
Here is data from UCR. Low numbers for SS means lower sugar levels.
http://www.ccpp.ucr.edu/variety/621.html

From a growers perspective, GN won't challenge Afourer/Tango as the most important commercial variety to arise in the last 10-15 years.
GN has a reputation here as an alternate bearer and requires greater management input to produce quality fruit.
Flavour wise I prefer Afourer for the higher sugar and acid levels at maturity.

It never was a new variety.  They gave it a fancy marketing name so it would sell and to avoid paying royalties.
From UCR, "Fruit of 'Tango' are similiar to W. Murcott in all appearance, quality and production characteristics with the exception of seed numbers."

The others mandarin varieties that were the result of the same gamma irradiation treatment to induce a seedless version all kept their original name. Eg. DaisySL, KinnowSL, EncoreSL, etc. 

Agree, it's hard to beat the richness of a Washington navel, especially after a good winter chill.
As a juicing orange in the winter I prefer Salustiana. No bitterness, seedless and rich flavour. Very underrated variety outside Spain.

The listing at http://www.citrusvariety.ucr.edu/citrus/salustiana.html is very muddled and should be corrected.
Whoever the author EMM is, says the fruit is seedy and small. Neither is true.
The description below that from the citrus bible is accurate.

Know exactly how you feel Mike. Such a destructive bird. In the process of eating a single grapefruit, will knock a dozen off the tree. Their numbers seem to have gotten out of hand.

This guy can't tell the difference, really?

Hasn't the seedless Eureka arrived over there? Both Australia and South Africa have bred their own strains and have been around for quite some time now.

Based on brix readings the Cal Honey is sweeter.

A friend down the road has completed a new planting of late navels.
He intends to use pheromone lures supplied by ISCA technologies in the establishment years.
Anyone have any field experience with these, as to whether they make any significant difference?

Gary, sounds like your trees are on rough lemon, which is very drought hardy, but very sensitive to Phytophthora. One of the shortest lived rootstocks on a commercial basis and fruit quality is sub par by most measures.

I'm not surprised.
I tried Chinese oranges when I was in HK.
They were terrible with a chemical after-taste.