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Areawide Insect Trapping Network

Vegetable IPM Updates Archive

Insect Management

May 2, 2018

Spider Mites on Melons 2018

In the past several weeks I’ve had a number of calls concerning spider mites on melons. Two spotted spider mites, Tetranychus spp, are widespread on melon crops throughout the southwestern U.S, and in my experience, outbreaks are more common on watermelons than other netted and mixed melon varieties. However, problems can certainly occur on all melon types. Under ideal condition, mite populations can increase dramatically. The hot dry weather we are now experiencing can be favorable for mite infestations. For example, mites can go from egg to adult in about 37 days when temperatures average about 60° F, but at average temperature of 86° F, it only requires 7 or 8 days for them to complete their lifecycle. Several natural enemies (including predatory mites and thrips, minute pirate bugs and lacewings) play an important role in regulating mite populations below economically damaging levels. Predators can maintain mite populations in check by feeding on slowly developing mite populations. However, when temperatures become hot and dry, the mites can quickly out run the predator population due to their rapid reproduction. Good irrigation and fertilization management can enhance plant tolerance to mites. Although economic thresholds have not been adequately established for spider mites in the low desert, treatment with an acaricide is recommended when significant webbing can be found on leaves and predatory mites and thrips are absent. A number of effective miticides are available for melons including Agri-Mek, Oberon, Acramite, Miteus, Zeal and sulfur. If leafminers are present in the field, Agri-Mek is a good option. If whiteflies nymphs are beginning to build on older leaves, Oberon may be an effective option. For more information on mites and their management please visit: Spider Mites on Melons.

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

May 29, 2019

Preharvest Weed Control in Wheat Before Vegetables 2019

Although wheat is ready to harvest ,weeds can still be a problem and control measures should be considered. They can add moisture in the tank, cause contamination to the grain and add weed seeds in the field and grain. There are some herbicides that can be used but there are potential problems with all of them and they all can only be used when the grain is in at least the hard dough stage and essentially done. There are contacts, growth regulators and glyphosate that are registered as preharvest aids in wheat.

Contacts: These include Aim/Shark Sharpen and Valor) Paraquat ( Gramoxone) is not registered for this use. Sharpen is not accepted by all markets so check the label closely. Good coverage and an adjuvant are necessary and these will be weak on grasses.

Growth regulators: These include Dicamba( Clarity) and 2,4-D). These are both volatile, slow and weak on grasses. The volatility and potential injury to sensitive crops at this time of year will be a major drawback. Ally ( metsulfuron) is not a growth regulator but is systemic and registered for this purpose in some regions. It can have soil residual and may not be a good option when rotating to vegetables.

Glyphosate (Roundup): Registered for this use although contamination of the grain has become a major issue and this is not recommended for use here.

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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