Dear All,
White peach scale(Pseudalacaspis pentagona, Diaspididae) is a poliphagous pest of fruit and ornamental trees. Its parasite, Prospaltella berlesei was efficient against it earlier however recently many garden owner brought samples (Juglans regia, Syringa vulgaris etc.) infested heavily with this pest to me and asked what to do to cure their plants.
How is the infestation and damage of white peach scale in your country? What do you use to control them?
Hi Andras,
White peach scale has not traditionally been a problem in Pennsylvania peach orchards, but has started showing up in isolated areas over the last couple of years. I think it may have to do with the increased number of pyrethroid, methomyl, endosulfan and neonicotinoids used to control the Brown Marmorated Stink Bug which are probably knocking out any biological control. Traditionally in the Eastern US it has only been a pest in New Jersey and further south for some reason - possibly their IPM programs of clean tilling the ground cover to control Lygus. In PA, we keep a nice grass strip and tolerate more weeds which may allow more biocontrol. Damage in PA at this point is spotty, but can cause severe damage, especially to young trees.
For small-scale (sorry for the pun!) gardeners or growers try summer horticultural mineral oil to suffocate them. For commercial peach growers, try dormant oil spray at 2-3% concentration or if you are still allowed to use it chlorpyrifos at 2 qt/A. Some growers are trying buprofezin at 35 oz/A pre-bloom, but I think post-bloom for the crawlers would be best and not impact the bees. Most expensive, but most effective has been spirotetramet (Movento) at 9 fl oz/A post-bloom. Pyriproxifen (Esteem) should also work but have not tested it in peach and it has been unreliable in controlling our San Jose Scale in apple. I will let you do the conversions to metric, which I also prefer, but growers and pesticide companies don't. Will have to check and see if we have that particular parasitoid. Good luck. David
Dear David,
Many thanks for your distinguished and thorough answer. About 20 years ago Pseudalacaspis pentagona was much less important but slowly its density started to increase mainly in commercial orchards parallel with the decrease of San José scale. Many think that it was partly the consequence of the use of pesticides killing P. berlesei, its parasitoid. However, one should note that its primary host plants Morus alba and M. nigra can be found everywhere and they grow spontaneously.
For small-scale gardeners I used to suggest also summer horticultural oil not to harm themselves.
Hi Andras,
The pest is a serious pest of Mullberry in north of Iran (The place I live) and cause severe damages. It is now a key constraint on SIlk worm rearing.
Cheers,
Hallo Andras,
In South Africa it is considered an economically important pest species which occur on mulberry, stone fruit and some ornamentals such as Crassula sp.
Not much R&D work on Pseudalacaspis pentagona has been reported in Malaysia. I reckoned it is not a serious or even a pest in the tropic. The institute responsible for R&D on fruits & orchard in Malaysia is MARDI.
Dear Arash, Sonnica, Konstantinos and Siti,
Many thanks for your contributions and characterizations on this pest. I feel we got some useful information mosaics on the role and importance of P. pentagona in various countries.
Nice answer Konstantinos and good information to have. Fenoxycarb was tested in the US for many years on tree fruit and other crops, but never made a food registration because of some tox problems and effects on aquatics. Only registered for termites and ants as baits. I would expect it to be more effective than pyriproxifen. Not sure, but I think we have 3 generations in Pennsylvania as well. Trials in other states like New Jersey where it is more of a problem on peach show spirotetramat to be extremely effective for 1st generation crawlers as you mentioned. You have one of the more interesting department titles I have seen in awhile.
Dear All,
Unfortunately, P. pentagona appeared on a peach tree at our orchard.
Dear András,
The occurrence of P. pentagona is currently limited on Catalpa bignoides and a few other ornamental trees in the Czech Republic. P. pentagona has not been found on fruit trees yet but considering global warming and situation in neighbouring countries its occurrence on peach plants is probable in following years.
Dear Tomáš,
Thanks for your contribution on the Czech situation. Global warming seems not to be stopped. How frequent are peach plantations in your country?
Dear András,
In total the area of peach orchards is about 584 ha but peaches are frequently grown in gardens.
Used to only be a pest of peaches in New Jersey, but now expanding into Pennsylvania peach orchards and enough of a problem to warrant pesticide control in some cases. Chrlorpyrifos at dormant is probably the cheapest and most effective, but toxic and with many restrictions on applications. Also effective is spirotetramat from Bayer, but is expensive and needs a penetrant to make it work reliably. Don't know if we have that parasite in the US, but many other parasitic wasps such as Aphytis sp. are effective on our other scale pests.
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