WORMS in Fall Produce
Historically, worms (Lepidopterous larvae; -beet armyworm, cabbage looper and corn
earworm) are the most important pests of desert pruduce during September and October.
So, it is no surprise that worms are everywhere particularly in Dome Valley where
heavy beet armyworm pressure has been reported over the past week or so. Many PCAs
have reported that armyworm have been infesting lettuce as early as 8 days after
wet date, which seems quicker than usual. Corn earworm larvae have also been reported
in a few fields. Here at the Yuma Ag Center, one can easily find newly new egg masses
and neonate beet armyworm larvae on 10 day old lettuce and broccoli stands. Cabbage
loopers are beginning to show up and their populations will likely increase. Remember,
temperatures drive larval development and adult moth activity, particularly when
night time temps remain high (in the mid-70s or higher). The moths are nocturnal
and will actively oviposit when evenings are warm and winds are light. With shorter
days coming, the moths have more time to lay eggs at night. As long as the average
temperature remains around 80-85°F, worms should be active at damaging levels. Those
ideal conditions are consistent with the weather forecast for the next 10 days (daytime
highs in the low 100’s and nighttime lows in the mid 70’s). Fortunately, there are
a number of very effective insecticides that can be applied as stand-alone foliar
products that provide effective residual control of both of these lepidopterous
species. Radiant, Proclaim, Intrepid, Avaunt and any one of the Diamide products
(Belt, Coragen, Exirell, Vetica, and Voliam Xpress) can provide good knockdown and
extended residual control of armyworms and loopers. Addition of a pyrethroid often
enhances knockdown of corn earworm and cabbage looper for many of the products.
Of course, residual control will often depend on the rate applied. In general, the
higher the rate, the longer the residual. But this will also depend on plant size
at time of application and how fast the plant is growing. Before selecting a product
for worm control, be conscious of products (chemistries) previously used on the
crop. Avoid using products with the same mode of action more than twice on any given
field. More information on the insecticides available for effective control of beet
armyworm and cabbage looper can be found in this document:
Lepidopterous Larvae Management in Desert Produce Crops, 2015..
Worms are everywhere!
Remember, When in Doubt . . . . . “SCOUT”
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Managing Sclerotinia Drop of Lettuce with Fungicides
Successful management of any plant disease is achieved by targeting one or more
vulnerable stages in the disease development cycle. For Sclerotinia drop of lettuce,
caused by the fungi Sclerotinia minor and S. sclerotiorum, this point of attack
centers on the fungal bodies called sclerotia. At crop maturity, sclerotia produced
on infected plants will be incorporated into soil along with crop debris as the
land is prepared for planting the next crop. For the Sclerotinia fungi, sclerotia
serve the same purpose that seeds do for plants; that is, they allow the organism
to carry over in soil in a dormant state until conditions become favorable for their
germination and growth. Over the past several years of fungicide evaluation trials,
the traditional fungicide application to the lettuce bed surface beginning after
thinning has provided at best about a 50 to 60% reduction in dead plants compared
to plots not receiving a fungicide treatment. In a 6-year comparison of fungicide
efficacy in plots containing Sclerotinia minor, the average reduction of disease
was 61, 53, 44, 43, 43, and 38%, respectively, for plots treated with fluazinam
(Omega), boscalid (Endura), iprodione (Rovral), penthiopyrad (Fontelis), Coniothyrium
minitans (Contans), and fludioxonil (Cannonball). In soil infested with Sclerotinia
sclerotiorum, the mean reduction of disease in the same six trials was 73, 56, 49,
47, 44, and 23%, respectively, for plots treated with Contans, Omega, Endura, Cannonball,
Rovral, and Fontelis. Application of fungicides to the bed surface prevents germination
of sclerotia at or near the soil surface, thus reducing the incidence of Sclerotinia
drop. Ongoing research is focused on examining new active ingredients and methods
of application to soil with the goal of consistently increasing the degree of Sclerotinia
drop control above levels now achieved.
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Clean Your Chemigation Tank
Applying herbicides through sprinkler systems has become increasingly popular over
the past several years. The three most commonly chemigated herbicides are Kerb(
Pronamide), Prefar(Bensulide) and Dacthal(DCPA). Almost all of the Kerb, most of
the Prefar and a significant amount of the Dacthal are applied by chemigation through
sprinklers. Sprinkler systems were designed to apply water,not herbicides and care
must be taken to avoid poor or spotty weed control and/or crop injury. Care must
also be taken to clean the chemigation tank and pipe as any of these herbicides
can cause severe injury or death to other crops that they are used on. It doesn’t
take much. There are suggested cleanout procedures listed on most labels and several
products sold to accomplish this. The following table can be used as a guideline
to determine the sensitivity of some of the crops grown here to residuals of Kerb,
Prefar and Dacthal.
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Question to the IPM Team:
We received the following insect image from an Arizona Western
College student for identification. The insect was found in the crop of jojoba.
Our Entomologist Extension Specialist Dr. John Palumbo suggested to obtain specimens
for additional observations. Considering the location and crop found we believe
it is the Smoke Tree Sharpshooter Homalodisca lacerta
leafhopper from the family cicadellidae. It damages the crop by inserting its proboscis
and removing plant fluids. It has been identified to be a vector of plant diseases
like Pierce's disease of grapes. University of Arizona http://arizona.openrepository.com/arizona/bitstream/10150/215741/1/370083-103-106.pdf
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Area wide Insect Trapping Network:
September 30, 2015
Our area-wide trapping network is up and running. The project is designed to measure
the activity and movement of adult populations of a number of key pests. The project
is being funded by the Arizona Iceberg Lettuce Research Council, and will hopefully
provide an indication of when pest activity (e.g., corn earworm moth flights) is
increasing based on pheromone/sticky trap captures. The data is not intended to
indicate field infestations, as trap data is largely a reflection of adult movement.
If nothing else, the data may make PCAs aware of increased pest activity in some
areas and encourage intensified scouting in susceptible produce fields. The pests
being monitored include: corn earworm, tobacco budworm, beet armyworm, cabbage looper
using pheromone traps; aphids, thrips and whiteflies using yellow sticky traps.
A total of 15 trapping locations have been established. Traps will be checked weekly
and data will be made available in the bi-weekly Vegetable IPM updates. If a PCA
or grower is interested in weekly counts, those can be made available by contacting
Results of pheromone and sticky trap catches can be viewed
Corn earworm moth activity has increased, particularly in Wellton, Roll and the south Yuma Valley at levels comparable to this time last year.
Similar, beet armyworm moths are active in most areas, but have been particularly heavy in Dome, Roll and the south Yuma Valley.
Cabbage looper moths numbers are slightly increasing in some traps (Wellton), and should increase in the next few weeks.
Adult activity has increased a bit in some areas, but overall is still much lighter than normal.
Thrips numbers remain low in all areas.
Activity is low in all areas.
No alate (winged) aphids have been captured to date.
The Vegetable IPM Updates Archive page provides links
to updates from previous weeks.
The Vegetable IPM Video Archive page contains a collection
of educational videos from current research work in vegetable crops by University
of Arizona Researchers.
For questions or comments on any of the topics please contact Marco Pena at the Yuma Agricultural Center.
College of Agriculture, The University of Arizona, Tucson, AZ.
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