Feb 7, 2024Keep an Eye Out for Corn Earworm in Spring Head LettuceTo contact John Palumbo go to: jpalumbo@ag.Arizona.edu
With melon season on full bloom, you will also start seeing diseases on melons. Cucurbit yellow stunting disorder is more of a problem on fall melons but they can also occur in summer melons. Cucurbit yellow stunting disorder is a cucurbit disease caused by a plant virus named Cucurbit yellow stunting disorder virus (CYSDV; genus Crinivirus, family Closteroviridae). This virus was first detected in southern California and Arizona in 2006 and infects cantaloupe and honeydew melon, watermelon, and various types of squash. CYSDV is transmittedexclusively by the whitefly, Bemisia tabaci. Symptoms always start from the oldest leave which is a diagnostic feature of the virus.
All biotypes of B. tabaci known to exist in North America can transmit the virus efficiently, including biotypes A, B and Q. Whitefly transmission is responsible for virus spread over short distances (e.g., within and between fields). However, with high winds whiteflies can move long distances and transport the virus. The virus can stay infectious within whiteflies for up to 9 days. As virus infection is systemic (meaning they have to be circulated inside the plant system to show symptoms) it can take 3 to 4 weeks for disease symptoms to develop following infection. This gives a window for infected symptomless plants can be unknowingly transported and can lead to epidemics. The virus is not transmitted mechanically (by touch, mechanical damage, cuts etc) or via seed. However, the virus can be efficiently transmitted even if there is low whitefly pressure in the field.
The best management approach is to monitor the whitefly population and be proactive with insecticides application. Rotate insecticides with different modes of action Group numbers to minimize development of insecticide resistance. Practice good weed management in and around fields to the extent feasible. Remove and destroy old crops/volunteers, enforce regional cucurbit -free period to eliminate the virus from the cropping system.
Sweet Shield and Novira varieties seem to do well in Yuma area.
Due a lack of effective post-emergence herbicides, most vegetable crops are hand weeded following cultivation to remove in-row weeds. This operation is costly and finding labor to perform the task has become increasingly difficult. Precision micro-sprayers for delivering herbicides have been developed, but lack sufficient speed, accuracy and off-target spray control to be commercially viable. To address this, a high speed, centimeter scale resolution sprayer that can spot apply herbicides to weeds with minimal off-target spray while traveling speeds that are viable for commercial farming operations was developed. The objective of this research was to evaluate the performance of the device in terms of spray delivery accuracy, off-target spray quantity, weed control efficacy and crop safety. The spray assembly comprised 12 custom-built spray modules spaced 1 cm apart. The device was tested with lettuce in the laboratory at a travel speed on 2.0 mph while targeting three weed species at three stages of growth. Results showed that targeting accuracy of spray delivered was ± 2 mm and that the percentage of off-target spray was less than 3%. Weed control efficacy exceeded 95% and there was no observable crop injury. Improvements to the original design were identified and the enhanced sprayer was found to provide sub-centimeter precision. Practical applications of the technologies developed include precision spot spraying of weeds in lettuce, carrot, onion, spring mix and other vegetable crops. A remaining technical challenge for the realization of an automated precision weeding machine is the development of a camera imaging system capable of reliable crop/weed differentiation. Field testing of the precision spot sprayers is also needed.
Click the following link to watch presentation on Centimeter Scale Resolution Spot Sprayer.
The Yuma IPM Team has received requests for herbicide efficacy data generated locally for Onion and Broccoli.
We are currently doing some evaluations for direct seeded broccoli. Some of the treatments suggested by PCAs and growers are Devrinol DF XT at the rate of 1.0 and 2.0 lb, also Devrinol 2-XT at the rate of 1.0 and 2.0 qt. Additional preemergence herbicides included in the trials are Prefar 6 qt, Trifluralin 1.5 pt. Other treatments included are Goal Tender and Prowl with a directed application at 3-5 leaves. In a separate broccoli test we are looking at different incorporation timings of Devrinol due to some stunting issues reported. Our trial includes 12, 24, 36 hour sprinkler irrigation incorporation times for the liquid and dry formulations. Phytotoxicity will be evaluated and reported to you in this newsletter and University of Arizona Workshops.
For onions we established trials including treatments suggested such as Ethotron SC at 32 fl oz to a fine soil. Also included Prefar, Dual Magnum and Treflan preemergence. We will compare with Outlook plus Prowl and Goal Tender at 3 leaf stage.
Additionally, Corteva Agriscience is also focused in providing some options for weed control in both broccoli and onions. Some of their products been evaluated at the Agricultural Center are Rinskor (Hulk) and Enversa at post and preemergence.
We thank you for your treatment suggestions, which are incredibly helpful for designing the experiments we are conducting. We are looking forward to sharing the results with you.