Question to the IPM Team
Some Videos to Check Out
Pheromone/Sticky Trap Monitoring Network
Leafminer Management on Fall Lettuce
With the weather staying relatively warm so far this fall, insect pressure remains
steady. This is indicated in part by our counts taken from in our trap network.
Worms remain heavy in most areas, but whitefly flights are beginning to subside
except in those areas out east near fall melons. However, as temperatures begin
to cool down in the next few weeks, it is important that you not forget about Liriomyza
leafminers, particularly as the first produce fields approach harvest. Leafminer
numbers have been moderate thus far this season, but we have recently observed higher
numbers (adults and larvae) showing up on the older leaves of lettuce here at the
Yuma Ag Center. In addition, an increase in adult flies has been observed on yellow
sticky traps used for monitoring whiteflies over the past week or so. In most cases,
these traps have been located near or adjacent to fall melons, cotton or alfalfa.
The 10-day forecast calls for temperatures to be in the 90s for the next week, and
leafminer adults should continue to be active. Larval activity could easily cause
damage if left uncontrolled in lettuce or baby leaf fields where they are currently
present. These larvae can cause significant damage to older, pre-harvest lettuce
by feeding and damaging wrapper leaves of head lettuce and romaine. Pupae collecting
within the leaf margins can also be considered contaminants. In addition, baby leaf
lettuces, spring mixes and spinach are susceptible to larval feeding (mining) on
the tender growing leaves. These populations can be effectively controlled with
currently available products. Products that are presently being used to control
armyworms, loopers and thrips such as, Radiant (5-7 oz/ac), Coragen (5-7 oz/ac),
Voliam Xpress (9 oz/ac), and Exirel (15-20 oz/ac) can effectively kill newly emerged
larvae in the leaf mines before they cause significant damage. Be sure to include
a penetrating adjuvant with these products to enhance translaminar movement of the
product and larval control. For more information on leafminer biology and management
please go to:
Remember, When in Doubt . . . . . “Call John”
Click picture to listen to John’s update
To contact John Palumbo go to: email@example.com
Fusarium Wilt on Lettuce
On October 8th we received our first confirmed sample of Fusarium wilt on lettuce
for the 2014-15 production season. Since the first discovery of this disease in
Arizona during the 2001-02 growing season, Fusarium wilt has been found yearly in
some lettuce fields from mid-October through early January. The initial visual indication
of the disease is yellowing of one or more older leaves, followed by leaf wilting
and eventually plant death. The external root surface is unaffected; however, a
brown to black necrosis of the internal taproot and crown tissue will be apparent.
Disease incidence can range from a few plants up to large areas or zones of infected
plants within a field. Plants can become infected and display symptoms at any age,
ranging from very young plants just after thinning to those ready for harvest. The
symptoms of Fusarium wilt resemble two other lettuce disorders, ammonia toxicity
and the early stages of lettuce drop. To confirm disease identity, it is necessary
to bring plant samples to me at the Yuma Agricultural Center for analysis. Confirmation
of disease identity is achieved by isolation and identification of the causal fungus,
, f. sp. lactucae
, from symptomatic root tissue.
Disease incidence and severity is strongly affected by planting date and the type
of lettuce grown. The main determinant of disease severity with respect to planting
date is soil temperature. Research data demonstrate that lettuce planted in early
September can result in high levels of Fusarium wilt, whereas plantings in the same
naturally-infested field started in mid-October or early December sustain moderately
low and trace levels of disease, respectively. Of many crisphead and romaine cultivars
tested, crisphead cultivars generally are significantly more susceptible to Fusarium
wilt than romaine lettuce. There are also significant differences in susceptibility
among romaine cultivars. The lettuce Fusarium wilt pathogen can survive in soil
for many years, so minimizing the spread of infested soil both within and especially
between fields is of paramount importance. Two comprehensive research reports concerning
disease development and management of Fusarium wilt of lettuce are available. Please
contact me and I will email these reports to you.
Click picture to listen to Mike's update
Goal “Lift Off”
Codistillation is when a herbicide evaporates or changes from a liquid to a vapor
with water. This can occur from soil, water or plant surfaces and can be responsible
for substantial loss of some herbicides. When codistillation occurs with Oxyflurofen
(GoalTender, Goal 2XL and others), the concern is not herbicide loss but crop injury.
Codistillation can occur with several herbicides. It is affected by many factors
including temperature, moisture, organic matter, soil pH and other variables. In
general, codisillation is greatest when temperatures, moisture and pH are high and
organic matter is low. One of the herbicides used in this region that is most affected
by codistillation is Eptam (EPTC). A study conducted several years ago in Brawley
California found that more than 80% of the Eptam that was applied in irrigation
water was lost by codistillation. Most of this was from the soil after it had reached
the field. In our trials, we have found that codistillation may help GoalTender
and Goal 2XL (oxyfluorfen, also sold as Galligan, Oxi Flo and others) kill weeds
but it also can increase crop injury. Goal can move into plants in the vapor phase
once it has lifted off and both weed control and crop injury are enhanced. We have
seen this when Goal is Chemigated through sprinklers. Goal is primarily a contact
type herbicide and moves little in the plant. It works preemergence by killing weeds
as they emerge from the soil and contact the herbicide. It is rare for contact
type herbicides to work better when overhead water is applied but this seems to
be the case with this herbicide. Lift-Off or codistillation of Goal lift off injury
seems to be worse this season because of rain. In many cases this potential is exaggerated.
Lift-Off of Goal differs from the usual off target drift that can occur with other
herbicides. In this case it is movement of the herbicide with water vapor. Moisture
must be present and this moisture must evaporate. The vapor normally stays in the
field and it is common for a band application to the furrows, for instance, to move
across the bed top. Significant movement out of the field normally only occurs with
wind. GoalTender is not as volatile as Goal 2XL and is less prone to codistillation
but it occurs with both. The picture below is of GoalTender that was applied to
the furrows only but it lifted off and covered the entire bed. The crop grew out
of this in 2 weeks.
Click picture to listen to Barry
Area wide Insect Trapping Network Oct 1,
Oct 15, 2014
Results of pheromone and sticky trap catches can be viewed
Corn earworm moths remain very active in the Dome Valley and
have significantly increased in the Yuma Valley where numbers on i11 Oct were above
15 moths per night in both areas. Activity also increased in many of the other areas
including the Gila Valley and Wellton.
Cabbage looper/Beet armyworm:
Beet armyworm moths are active in most areas,
but have been particularly heavy in the Yuma Valley and Dome. Cabbage looper moth
activity continues to increase across most areas and was heaviest last week in the
south Yuma Valley near the River (Co. 14.5 and Levee Rd) and near Texas Hill (47E).
Activity has begun to increase in the south Gila Valley.
Adult activity continues to decline in all areas, except out east
near 47E. This trap is located adjacent to fall melons which are approaching harvest.
Thrips numbers in general are beginning to pick up in most areas,
but movement was particularly heavy 2 weeks ago in Dome Valley.
Slight increases were observed last week in most areas. However,
a very high number of adults were captured on a trap located at 47E adjacent to
Alate (winged) aphids are beginning to show up on traps, particularly
in the Yuma Valley. This is not surprising given the north winds over the past week
or so. An occasional cabbage aphid was found on the traps, all others were species
not important to produce crops.
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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