For the life of me, I cannot seem to grow weeds lately for my nursery trials. Most growers would love to have my problem but when you are testing new herbicides it helps if there are some weeds coming up in the untreated pots to know whether the new materials have any effect.
At first I blamed it on the potting mix (I changed from bulk to bagged) but now I am thinking it may be due to how I irrigate. And that may be why growers have weed problems. You see, I don't put on a lot of water; after the initial watering in I only irrigate 3X/week for about 10 minutes each time. I think that I don't put on enough water to keep the media very wet. The plants look fine. Most nurseries water daily and some ever add handwatering. Could it be that if nurseries cut back on their irrigation that they could still get good plant growth and reduce their weeds?
In some work I did about 10 years ago, I found that containers irrigated based on soil moisture had considerably less weed pressure than plants irrigated using timer controllers and used less water with no loss of plant quality.
Last week I set out a rain gauge with a data logger to monitor the amount of water applied. After I get a good handle on that I think I will do a quick trial to test my theory whether it's the potting mix or if it's the water amount. Either way, if there's something that will reduce weed pressure, we need to find out what it is.
An Advisor in my office was starting some plants in potting mix. We were surprised to find the plant (see photo; for reference the pots about 4" wide and tall) come up from what assume is the potting mix but could be a seed contaminant. I've looked through a number of references and can't ID it. It is heavily covered with spines like bristly oxtongue but it is not that weed. The spines/bristles are on both sides of the leaves, including the midrib. Also on the stems and petioles. The upper side of the leaves are stippled with dots that are brownish. I am currently growing it until it flowers. That should make it easier to ID.
Any ideas are welcome!
Reprinted from the San Diego Farm Bureau Monday Update (7/13/09)
Bad news from south of the border. The first case of citrus greening (HLB) in Mexico has been confirmed. An Asian citrus psyllid found in a backyard citrus tree in the northeast corner of the Yucatan Peninsula tested positive for HLB. The nearest commercial grove is reported to be 200-225 kiolmeters from the find site. The Mexican government has implemented an emergency program and USDA has offered to help.
As a dedicated UC IPM Advisor, I took today as a working non-furlough day on a holiday. Does that sense? Today I was evaluating a herbicide trial for preemergence bittercress control and starting a new one to look at postemergence bitercress control. These projects are sponsored by the USDA IR-4 program (http://ir4.rutgers.edu/) a program with helps suport pesticide registrations in minor crops. By minor, they mean just about anything that is not corn, soybean, wheat, and rice. The request for testing can come from YOU (http://ir4.rutgers.edu/ornamental/OrnRequestForm.cfm). So if you have an idea about something you think has good potential for your crop put it here. Often pesticides that have shown good activity working in another crop where it is labled will also work on the ornametal species but efficacy and phtotoxicity trials need to be run to be sure.
Also, if you want a chart of herbicides that you can use for common nursery weeds, I have one posted. Go to http://cesandiego.ucdavis.edu/files/67580.doc. If you run your own tests, feel free to modify it. I'd be interested to know how your tests turn out and we can fill in some blanks on the chart.
Have a safe and happy 4th of July!
I travel a lot. Mostly for work but because I'm in southern California the variation in climates, situations, crops, and non-crops makes for very interesting trips. This is my entry into describing some of the things I see and do as I work in the south region.