Jan 24, 2024Avoid Seed Corn Maggots in Spring Melons (2024)To contact John Palumbo go to: jpalumbo@ag.Arizona.edu
Botrytis rot is not considered a major problem in lettuce but it can cause significant damage/loss when the field conditions are favorable for the pathogen. Cool wet conditions are favorable for the pathogen. Symptoms include water-soaked, brownish-gray to brownish-orange, soft wet rot that occurs on the oldest leaves in contact with the soil. Old leaves are more susceptible than young leaves and the fungus can move into the healthy parts. Fuzzy gray growth can be observed in the disease area which is characteristic of the pathogen. In worse cases, the entire plant can collapse. Romaine cultivars, transplanted lettuce that are big and have leaves touching the soil are more susceptible.
The pathogen: Botrytis cinerea
Botrytis cinerea affects most vegetable and fruit crops, as well as a large number of shrubs, trees, flowers, and weeds. Outdoors Botrytis overwinters in the soil as mycelium on plant debris, and as black, hard, flat or irregular sclerotia in the soil and plant debris, or mixed with seed. The fungus is spread by anything that moves soil or plant debris, or transports sclerotia. The fungus requires free moisture (wet surfaces) for germination, and cool 60 to 77 F, damp weather with little wind for optimal infection, growth, sporulation, and spore release. Botrytis is also active at low temperatures, and can cause problems on vegetables stored for weeks or months at temperatures ranging from 32 to 50. Infection rarely occurs at temperatures above 77 F. Once infection occurs, the fungus grows over a range of 32 to 96 F.
Masses of microscopic conidia (asexual spores) are produced on the surface of colonized tissues in tiny grape-like clusters (see picture). They are carried by humid air currents, splashing water, tools, and clothing, to healthy plants where they initiate new infections. Conidia usually do not penetrate living tissue directly, but rather infect through wounds, or by first colonizing dead tissues (old flower petals, dying foliage, etc.) then growing into the living parts of the plant.
1. Buy high-quality seed of recommended varieties. Treat the seed before planting.
2. Practice clean cultivation. Plant in a light, well-drained, well-prepared, fertile seedbed at the time recommended for your area. If feasible, sterilize the seedbed soil before planting, preferably with heat. Steam all soil used for plantbeds at 180 F (81 C) for 30 minutes or 160 F (71 C) for one hour.
3. Avoid heavy soils, heavy seeding, overcrowding, poor air circulation, planting too deep, over-fertilizing (especially with nitrogen), and wet mulches.
4. Focus on healthy plant vigor. Do not over fertilize.
5. Use drop or furrow irrigation instead of sprinklers. If sprinklers have to be used, irrigate morning or early afternoon giving enough time for foliage to dry.
6. Apply recommended fungicides when conditions favor disease development. Make sure to rotate fungicide to avoid development of resistance.
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.