Areawide Diamondback Moth Trapping Network Established in Yuma
In response to the recent outbreaks of Diamondback moth (DBM) , Plutella xylostella in Yuma, we have established a pheromone trap network designed to monitor the activity and movement of adult populations of DBM. PCAs have had difficulty controlling DBM in cabbage, broccoli and cauliflower since October. Wing Traps with DBM pheromone lures have been placed in Roll, Wellton, Dome Valley, Gila Valley and Yuma Valley in locations where Cole crops are presently being grown, or in areas where infestations were known to occur this fall. The data we collect is not intended to indicate field infestations, as trap data is largely a reflection of adult movement. The data may reflect emergence/ activity of adults in adjacent fields with known infestations, or provide an indication that DBM may be moving into fields not previously infested. If nothing else, the data may make PCAs aware of increased pest activity in some areas and encourage intensified scouting in susceptible produce fields. DBM are still active in many fields, and most recently we’ve observed that populations are beginning to spread into direct-seeded crops that were not previously effected by DBM. For this reason, we are tracking moth activity to monitor their activity relative weather conditions and crops sources. We have a historical perspective of DBM activity in Yuma. From 1998-2000, we established a pheromone trap network during the winter and spring in Yuma which included DBM. Not surprisingly during that 2-year trapping period DBM counts never exceed 6 moths/trap/day at any time during the spring season. DBM have historically been a secondary pest, that may cause issues in spring cabbage crops. However, in just the few weeks we’ve been trapping DBM since Dec 20, we’ve had four trap locations where DBM counts have exceeded 10 moths/trap/day and in one location (Co. 9th and Ave F) over 25 moths /day were recorded. These traps were all located in the Yuma Valley, stretching from Co. 21st up to Co. 9th street. We will continue to monitor DBM trap activity throughout the season, as well as trap population activity throughout the summer to determine whether DBM is active when brassica crops are not available. This may give us an indication of the potential for more problems going into next season. From a historical perspective, trap counts during the summer of 1999 in the Yuma Valley occasionally caught DBM moths in traps at low levels (0.2-1.2 moths/trap/night from July-August). We concluded at that time that many of the DBM captured may have come in with transplants, as we were uncertain whether DBM was capable of over summering in the desert in the absence of brassica crops. We hope to gain more insight into the pest’s activity during summer months in Yuma this year by actively trapping throughout the area. For access to DBM trap counts please visit Areawide Diamondback Moth Trapping Network.
We are on the final section of virus transmission. Virus transmission by insects is one of the most efficient and economically important transmission in agriculture. When you have insects in your crops, not only you are losing your crops because of feeding/chewing by insects, a lot of insects also act as a vector of plant viruses.
Seven out of 29 orders of insect feeding on living green land plants are vectors of plant viruses.
Insect transmit viruses in 4 distinct modes:
Non persistent transmission: The insects can acquire the virus in a matter if seconds/minutes and they are immediately viruliferous. The virus in retained in the stylet of the insect and are transmitted to the next plant the insect feeds on. The virus is retained in the vector only for few minutes and is lost after insect molting. Most viruses transmitted by aphids are non persistent. So when you see few aphids in your melon field and see cucumber mosaic virus symptoms 1-2 weeks later in your field, don’t be surprised. Aphids are efficient vectors, and since viruses are systemic it takes anywhere from few days to 2-3 weeks for the plants to show symptoms. Thus it is very important to manage insects in the field even if you don’t think the ‘pressure’ is not as high.
Semi-persistent transmission: The insects can acquire the virus in minutes/hours and there is no latent (incubation) period in the insect. The virus can stay in the insects foregut for hours and is lost after insect molting. Some species of aphids and whiteflies fall in this category. Example: Cucurbit yellow stunting disorder virus in melons transmitted by whiteflies.
Persistent circulative: Insects have to feed on virus infected plants for hours/days to acquire the virus and the virus has to incubate for hours/days in the insect. After insect can transmit the virus for weeks. Virus can be present in the vectors hemolymph but there is no multiplication of virus in the insect body. Vectors in this transmission includes: Aphids, leafhopper, whiteflies, treehopper.
Example: Beet curly top virus transmission by beet leafhopper
Persistent propagative: Insects have to feed on virus infected plants for hours/days to acquire the virus and the virus has to incubate for hours/days in the insect. After insect can transmit the virus throughout its lifespan. The virus can multiply in the vector system and often times the virus particles are also passed on to the insect offspring. Tomato spotted wilt virus is transmitted on persistent propagative manner by 9 different species on thrips.
Save the Date : 2024 Plant Pathology Workshop
When: August 29th 8AM-12 PM ( breakfast and Lunch provided by Gowan Company and BASF)
Where: Yuma Ag Center, 6425 W 8th Street
What will covered: Plant Pathology program Updates, past season field trial results (we
have some exciting results to share), Q&A to help better Plant pathology program,
Industry panel discussion for all your industry related questions! See you in few weeks!
Controlling Fusarium Wilt of Lettuce Using Steam Heat – Trial Initiated
Earlier this week, we initiated a trial examining the use of band steam for controlling Fusarium wilt of lettuce. The premise behind this research is to use steam heat to raise soil temperatures to levels sufficient to kill soilborne pathogens. For Fusarium oxysporum f. sp. lactucae, the pathogen which causes Fusarium wilt of lettuce, the required temperature for control is generally taken to be > 140°F for 20 minutes. Soil solarization, where clear plastic is placed over the crop bed during the summer, exploits this concept. The technique raises soil surface temperatures to 150-155˚F, effectively killing the pathogen and reducing disease incidence by 45-98% (Matheron and Porchas, 2010).
In our trials, we are using steam heat to raise soil temperatures. Steam is delivered by a 35 BHP steam generator mounted on a custom designed elongated bed shaper (Fig. 1). Preliminary results were encouraging. The device was able to increase the temperature of the top 3” of soil to over 180°F at a travel speed of 0.5 mph as shown in this video of the machine in action (shown below). These temperatures exceed that of those known to control pathogens responsible for causing Fusarium wilt of lettuce (> 140°F for 20 minutes).
Stay tuned for final trial results and reports on the efficacy of using steam heat to control Fusarium wilt of lettuce.
If you are interested in evaluating the technique on your farm, please contact me. We are seeking additional sites with a known history of Fusarium wilt of lettuce disease incidence to test the efficacy and performance of the device.
References
Matheron, M. E., & Porchas, M. 2010. Evaluation of soil solarization and flooding as management tools for Fusarium wilt of lettuce. Plant Dis. 94:1323-1328.
Acknowledgements
This project is sponsored by USDA-NIFA, the Arizona Specialty Crop Block Grant Program and the Arizona Iceberg Lettuce Research Council. We greatly appreciate their support.
A special thank you is extended to Cory Mellon and Mellon Farms for allowing us to conduct this research on their farm.
Weeds are one of the most visible of all agricultural pests. They can’t move or hide and once established often stick up over the crop. Just one weed in a 10 acre field is annoying to look at. With insects and diseases, the damage is often more visible than the pest. That is not the case with weeds. A moderate weed infestation is approximately 10 weeds per square foot. If a herbicide produces 90% control, that leaves 1 weed per square foot or 43 weeds per acre. Without an untreated check, this can look like the herbicide failed! It is easy to leave an untreated spot in a field and it is well worth doing. Many applicators do so unintentionally because of skips, powerlines and other causes. They help determine crop injury and weed control. Here are some examples of what various levels of control looked like from one of our cole crop trials:
Corn earworm:
CEW moth increased in Tacna/Roll/Dome last week, and areawide about average for mid-October.
Beet armyworm:
Trap counts highest in Tacna, Wellton and Dome, but below average for October.
Cabbage looper:
Cabbage looper numbers increased in Tacna/Roll/Wellton but still below average.
Diamondback moth:
DBM moths are beginning to appear in traps in Yuma Valley, trending below average for early October.
Whitefly:
Adult movement increased in the past 2 weeks and above average for mid-October.
Thrips:
Thrips adult activity down over the past week, and trending below average in October.
Aphids:
Winged adults continue to be captured for the season, consistent with heavy winds from W-NW. Can expect aphid flights to increase in the coming weeks.
Leafminers:
Adult activity increased significantly in Tacna associated with maturing melons. Trending above average for mid-October.