I am often asked what cold weather does to insect populations. It depends on the insect, the stage it is in and where it is located on the tree. For moths such as citrus leafminer, the pupae survive, but many of the larvae inside the mines of tender flush leaves are killed as the flush is burned by the cold. For California red scale, the younger instars tend to die off, leaving mostly the adult stages. Citricola scales are in the 2nd instar stage deep inside the tree infesting twigs and experience very little mortality. Earwigs are deep in the ground waiting out the cold. Asian citrus psyllid immatures would be killed by extended cold periods, but the adults would survive the cold and feed when the temperatures warm during the day. I guess the answer is that even in a freeze year, the cold never gets them all!
I was asked recently to put together a photo identification sheet for Asian citrus psyllid adults, nymphs and eggs. To obtain a copy, see my web site under Citrus Insect Pests/Asian Citrus Psyllid/Monitoring- Recognizing ACP Stages or click on this link: http://ucanr.edu/sites/KACCitrusEntomology/Home/Asian_Citrus_Psyllid/Monitoring/
It is very important that PCAs go beyond relying on yellow sticky cards and learn to recognize the psyllid stages and monitor orchards using visual surveys of flush and tap sampling. These methods will speed up detection of the psyllid in new areas and determine if treatments are effective in areas where the psyllid has established.
Citrus growers and other Ag professionals are invited to attend the Univerity of California, Lindcove Research and Extension Center Annual Citrus Fruit Display and Tasting on Friday December 14th starting at 9:00 A.M. During the Citrus Fruit Display day, you can see and taste more than 100 citrus varieties that are grown at Lindcove.
Education Building Activities 9 am - Noon
Walking tour starts at 10 am
- 10 am: Tour the Citrus Clonal Protection facilities that produce budwood with Dr. Rock Christiano
- 10:30 am: Tour the demonstration orchard with Dr. Tracy Kahn who will discuss new citrus varieties
- 11:30 am: View the action of the new fruit grading system in the packline that provides researchers with detailed information about fruit size, weight and quality demonstrated by Therese Kapaun and Don Cleek
Grafton-Cardwell and Morse have held off suggesting that growers should spray citrus groves in the fall to control bean thrips. There are several reasons for this: (1) to date, bean thrips has been a problem mainly for shipments of navel oranges to Australia and New Zealand and it is difficult to know which fruit will be destined for this market, (2) levels and timing of bean thrips flying into citrus in the fall can vary greatly from year to year (depends a lot on when weed hosts and other plants dry up, when the weather turns cold, etc.; some years, bean thrips move in early and feed on the fall flush, other years this movement is later), (3) bean thrips typically fly into citrus over a 3-6 week period and it would be difficult to maintain an effective pesticide residue on citrus without multiple applications, (4) once the bean thrips are inside the navel of navel oranges, they are difficult to control, and (5) we are looking forward to the registration of ethyl formate as a post-harvest treatment (hopefully in time for the 2013-14 shipping season). An effective post-harvest treatment would be a much more practical means of dealing with this problem than field sprays - only loads of packed citrus destined for AU/NZ would be treated.
The graph below shows the male California red scale pheromone trap catches (green) and the crawler tape catches (red) for a citrus orchard at Lindcove. The scale activity is finally starting to wind down as the night temperatures cool. Male flights peaked at Lindcove this year during March, mid-mid June, late July and early September. Four generations of crawler activity occurred during Mid May, early July, mid-August, and late September. The male flight and crawler activity seems to be winding down now. It may pick up a bit if the daytime weather stays warm, but usually the females stop producing crawlers around November 1.