Viruses vectored by insects 
 
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: 
 

1. 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. 

Viruses transmitted in non-persistent manner:
 Papaya ringspot virus 
Zucchini yellow mosaic virus 
Watermelon mosaic virus

1. 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. 

1. 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 
 

1. 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 29^th 8AM-12 PM ( breakfast and Lunch provided by Gowan Company and BASF) 
Where: Yuma Ag Center, 6425 W 8^th 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! 

Keeping up to date with the latest developments in automated weeding machines is challenging. It’s a very fast-moving space with significant private and public investment. At the 2024 Southwest Ag Summit “Ag Tech: Innovations in Weed Control Technologies” breakout session, university experts and cutting-edge innovators will provide updates on laser weeding, high precision smart spot sprayers, robotic/automated weeders and band steam (agenda below).The session will be held TOMMOROW Thursday, February 22^nd from 1:30-3:30 pm at Arizona Western College in Yuma, AZ.
As I mentioned in the last newsletter, there will also be a Field Demo where several of these technologies and other state-of-the-art automated weeders will be demonstrated operating in the field. The Field Demo is scheduled for TODAY, Wednesday, February 21^st. Breakfast will be served at 7:00 am and demonstrations begin at 8:00 am. The event will also be held at AWC.
We will also have our 3^rd generation prototype steam soil disinfestation machine on display at the event (Fig. 3). It is a self-propelled machine designed for commercial field scale operations. The device injects steam into the soil prior to planting to raise soil temperatures to levels sufficient to kill soilborne pathogens and weed seed (typically 140 °F > 20 minutes). We have had very good results with our previous prototypes and would like to demonstrate soil steaming to interested growers next season with the new machine. In addition to obtaining grower feedback on the viability of soil steaming, a second objective is to validate our small plot research results at the field scale level. If you are interested in the technique and would like a demo on your farm, please let me know. I would be happy to collaborate with you.
For more information about the Southwest Ag Summit, visit https://yumafreshveg.com/southwest-ag-summit/.

Fig. 1. Agenda for the “Ag Tech: Innovations in Weed Control Technologies”
educational session at the 2024 Southwest Ag Summit. The session will be held
Thursday, February 22nd at Arizona Western College, Yuma, AZ.


Fig. 2. 2024 Southwest Ag Summit Field Demo agenda. The event will
be held at Arizona Western College in Yuma, AZ.


Fig. 3. Self-propelled machine designed for injecting steam into the
soil prior to planting to raise soil temperatures to sufficient levels to
control soilborne pathogens and weed seed. Unit will be on display at
the 2024 Southwest Ag Summit, Yuma, AZ. (Photo credit: Peter de
Groot).

The SW Ag Summit is taking place in Yuma this week. We will have the Weed Control breakout session on Thursday, 22 February 2024 at 1:30 pm in room AS 115 of  the AWC campus. Here’s what are we going to cover:
Do you know what the IR-4 Project is? 
Established in 1963 by the U.S. Department of Agriculture and land-grant universities this project helps ensure that specialty crop farmers have legal access to safe and effective crop protection products and contributes to developing data necessary for the registration products for best pest management. Do we have this project in Yuma?
A Weed Scientist and Principal Biologist from IR-4 and NC State University will explain what this process of making more tools available to growers takes.
 
Additionally, we will have a representative from BASF chemical company who will present NEW WEED CONTROL TECHNOLOGIES as well as active ingredients developed by his company.
 
We all know with the loss of DCPA (Dacthal) herbicide our weed management tools were reduced. You asked the Veg IPM Team to look for ALTERNATIVES for Broccoli and Onion. We are doing some Trials at the UA Yuma Ag Center with products Such as Napropamide (Devrinol), which has the Devrinol DF XT dry formulation and the Devrinol 2-XT liquid. 
Which one is more aggressive? How does water incorporation affect it? How good is it on goosefoot, lambsquarter, knotweed?
Other treatments we are looking at on broccoli are Goal Tender, Prefar, Prowl, Treflan, Enversa, Rinskor.
For direct seeded onion we are testing Prefar, Etothron SC, Dual, a combination of PREFAR+PROWL PREEMERGERGENCE at low rates, Outlook+Prowl.
 
We would like to share our observations if you honor us coming to our session. Again, it is TOMORROW Thursday, 22 February 2024 at the Arizona Western College AS 115 room. This session will start at 1:30 pm.

Get your free copy of the Weed Seedling Identification Pocket Guide at the Yuma Agricultural Center.