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Areawide Insect Trapping Network

Vegetable IPM Updates Archive

Insect Management

Feb 18, 2015

Corn Earworm in Spring Head lettuce 2015

As the produce season begins to wind down, it would be wise to keep a look out for corn earworm (CEW); they are historically active on spring head lettuce. In the last few years, unusually high CEW abundance has been reported by PCAs on late head lettuce, particularly in the Dome/Wellton areas. Given the CEW trap catches this fall and winter, one might expect to see more CEW than normal, but then again it is impossible to predict. Nonetheless, CEW can be very damaging in spring crops where once head formation begins larvae will usually bore into the head 1-2 days upon hatching. Corn earworm is much more likely to bore into lettuce heads than other Lepidoptera larvae, rendering the heads unmarketable. Larvae may enter the head from any point on the plants, but can often be found burrowing in from the top half of the head. If fields are not watched closely, infestations may not be noticed until the head is harvested. Once inside the head, it is almost impossible to control the larvae with insecticides. Thus, pay careful attention for newly oviposited eggs (laid singly) on lettuce plants. If you are beginning to find eggs and suspect that CEW are active in the field when plants are beginning to head, it would be a good idea to treat. The UA nominal threshold for CEW in head lettuce from early heading to harvest is 1-2 larvae / 100 plants. Repeated insecticide treatments may be required to maintain low population levels near harvest. Most contact insecticides recommended for Lep larvae are active against CEW. Furthermore, the addition of a pyrethroid with thrips, aphid and/or fungicide sprays may be cheap insurance against larvae infesting heads as you approach harvest. For more information on CEW management and control recommendations see Insect Management on Desert Produce: Corn earworm / Tobacco budworm and the 2015 Lep Control Chart.

To contact John Palumbo go to: jpalumbo@ag.Arizona.edu

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Soil Science

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Plant Pathology

Jul 10, 2024

Virus transmission: Part III (2024)
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!
To contact Bindu Poudel go to: bpoudel@email.arizona.edu

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Mechanization

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Weed Sciences

Apr 17, 2019

Summer Annual Grass Identification

It is better to be a month early when applying preemergence herbicides for summer annual grass control than it is to be a day late. They have begun to emerge so don’t wait. It is important to know which grass or grasses you have but that is not possible without prior knowledge when making preemergence applications. There are more than 25 annual grass species that are found here during the summer although only about 10 are common. Most of these look very similar at early growth stages and identification can be difficult. There is a tendency to lump them all together and call them water grass, jungle rice barnyard grass or several other names. There are differences between them, however, and it is important to accurately identify them at early growth stages. This is important because many of them respond differently to herbicides and have different growth habits. For example, sprangletop is only controlled by the highest rates of Select (clethodim) and generics of this herbicide and missed by all of the other selective postemergence herbicides like Poast and Fusilade and sandbur is tolerant to all of them. By the same token, sandbur and sprangletop can over winter, come back from crowns and not be controlled by preemergence herbicides applied in the spring while most other summer annual grasses die in the winter and the seed can be controlled with herbicides in the spring. There are just 6 genera and 12 species of summer annual grass that are common here. These include echinochloa (water grass and barnyard grass), leptochloa (red sprangletop and mexican sprangletop), eriochloa (southwestern cupgrass and prarie cupgrass), cenchrus (field sandbur and red sandbur), setaria (green foxtail and yellow foxtail), and chloris (feather finger grass and truncate finger grass). A power point presentation can be found by clicking on Summer Annual Grass ID which contains pictures and descriptive characterics of each of these species.

To contact Marco Pena go to: marcop@ag.arizona.edu

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Specialty Crops

Areawide Insect Trapping Network

Nov 16, 2022

Area wide Insect Trapping Network (November 30, 2022)

Results of pheromone and sticky trap catches can be viewed here.

Corn earworm:
CEW moth counts are down areawide consistent with this time of year.

Beet armyworm:
Trap counts increased in most locations, and are about average compared to previous years.

Cabbage looper:
Cabbage looper counts declined  all  traps, well below average for this time of season.

Diamondback moth:
DBM moths counts have declined and well below average for this time of the year.

Whitefly:
Adult movement decreased in the past 2 weeks, and remains below average for this time of year.

Thrips:
Thrips adults decreased in most locations with the exception of Tacna. Currently, below average for Novenber.

Aphids:
Aphid movement loght, but most active in in North Yuma Valley and Gila Valley. Below average for November.

Leafminers:
Adult activity up in a few locations, but well below average.

To contact John Palumbo go to: jpalumbo@ag.arizona.edu

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