In a recent edition of this newsletter on 20 April 2022, I presented a cantaloupe phenological (crop growth and development) model based on heat units accumulated after planting (HUAP, 86/55 F^o thresholds) as shown in Figure 1.
 
The benefits of working with and using a model like this include being able to describe and predict important stages of crop growth and development (crop phenology) and harvest dates.  This can also be a good tool for improving crop management (e.g., fertilization, irrigation, harvest scheduling, pest management activities, labor and machinery management, etc.). 
 
Included in our work with the development of this phenological model, we have also conducted nutrient uptake studies and water use studies to develop a better understanding of nutrient and water demand for desert cantaloupe production (Silvertooth, 2003; Soto et al., 2006; and Soto, 2012).
 
Figure 2 presents the nitrogen (N) uptake and portioning patterns for desert cantaloupes (melons), Silvertooth, 2003 and Soto et al. 2006.  This data describes total N uptake for cantaloupes at ~ 140 lbs. N/acre.  From this data, maximum N flux (N uptake/day) period extends from early fruit development to the netting stage.
 
Water use by desert cantaloupe production was also measured in these studies and patterns of water use followed the crop coefficient (K_c) patterns provided by the Arizona Meteorological Network (AZMET) and conformed to the K_c values from FAO 56 (Allen et al., 1998) and Grattan et al. (1998). 
 
Considering N uptake and water demand patterns in relation to cantaloupe crop phenology, we can insert the overlaps as shown in Figure 1, with the red and blue lines for N and water management, respectively.  Maximum N demand occurs from approximately 500 to 1,000 HUAP, which coincides with primary fruit development.  Accordingly, the N application window for optimum N uptake is from approximately 300 to 800 HUAP, which is from early flowering to the netting stage of the crown fruit.  The N application window is recommended in advance of the optimum N uptake period to provide for N mineralization and the plant-available forms of N for plant uptake and utilization.
 
Considering the N application window described in Figure 1 and a maximum seasonal uptake and demand of ~ 140 lbs. N/acre, early and split applications during this period of cantaloupe crop development can help achieve optimum utilization of fertilizer N inputs.
 
The period of maximum water demand extends from early fruiting stages of development through the maturation of the crown fruit, 300 to 1300 HUAP.
 
Considering the conditions we are experiencing these days in desert crop production with water shortages and extremely high prices of fertilizers, we have an abundance of motivation to manage our crop production systems with the highest efficiency possible.  Understanding crop water and nutrient demand for each crop we are working with and using that knowledge to manage our crops most effectively, is to our benefit agronomically, economically, and environmentally.
 
Nitrogen is the plant nutrient required in largest amounts by most non-leguminous crops and it is important for us to manage that nutrient for a crop in a careful and deliberate manner.  Water and N interactions are a critical aspect of crop growth, development, and management in any system, but particularly in an irrigated crop production system.  Thus, the focus offered in this article on water and N management for desert cantaloupe production.
 
I encourage those who are working with spring cantaloupe production this season to test and evaluate this crop phenology model, particularly in relation to nutrient and water management under field conditions with various planting dates, varieties, and soil types.  We appreciate your feedback.

Figure 1. Heat Units Accumulated After Planting (HUAP, 86/55 ^oF)



 Figure 2.  Cantaloupe (melon) N uptake and partitioning patterns.  (Soto, Silvertooth, and Galadima 2006).  Note: kg/ha * 0.89 = lbs/acre

References:
 
Grattan, S.R., W. Bowers, A. Dong, R.L. Snyder, J.J. Carroll, and W. George. 1998. New crop coefficients estimate water use of vegetables, row crops. California Agriculture 52(1):16-21.https://doi.org/10.3733/ca.v052n01p16
 
Allen, R.G., L.S. Pereira, D. Raes, and M. Smith.  1998. Crop evapotranspiration - Guidelines for computing crop water requirements - FAO Irrigation and drainage paper 56. Food and Agriculture Organization of the United Nations. Rome (FAO). https://www.fao.org/3/x0490e/x0490e0b.htm
 
Silvertooth, J.C. 2003. Nutrient uptake in irrigated cantaloupes. Annual meeting, ASA-CSSA-SSSA, Denver, CO.
 
Soto, R. O. 2012. Crop phenology and dry matter accumulation and portioning for irrigated spring cantaloupes in the desert Southwest.  Ph.D. Dissertation, Department of Soil, Water and Environmental Science, University of Arizona.
 
Soto-Ortiz, R., J.C. Silvertooth, and A. Galadima.  2006.  Nutrient uptake patterns in irrigated melons (Cucumis melo L.).  Annual Meetings, ASA-CSSA-SSSA, Indianpolis, IN.

We have learned a lot about viruses in the past few newsletter articles and one of the striking features of most plant viruses is that they always need a host. And the relationship between a virus and its host plant is very specific. So where do the viruses go when we do not have lettuce or melon in the field? And how do they come back at the right time to infect the crops?  (clue insect vector). The answer is weeds. A lot of the most economically important viruses are economically important viruses not just because of the losses they cause, but also because of the losses they cause in variety of plants. Viruses have small genome size that allows them to evolve faster. Viruses over time have evolved to adapt and increase their host range.
Below are some common viruses in agriculture and the number of plants they infect/overwinter. Keep in mind that there are many plants that can act as a reservoir for virus but have not been reported yet, so this is not an exclusive list. 
 
Alfalfa mosaic virus (AMV): Alfalfa, lettuce,indive, sunflower, datura, amaranth, different species of pigweed, milkweed, annual fleabane, ixeye daisy, hairy galinsoga, smallflower galinsoga, different species of mustards, common lambsquarters, hedge bindweed, field bindweed, cucurbits, different species of clover and vetch, beans, broad beans, lima beans, lupine, pea soybean, ground Ivy, healall, okra, purslane, pimpernel, black nightshade, pepper, tomato, petunia, eggplant, potato, garden pansy etc. 
 
Cucumber mosaic virus (CMV): pigweed, horseweed, oxeye daisy, coffee weed, Canada thistle, bull thistle, hairy galinsoga, Jerusalem artichoke,  prickly lettuce, wild chamomile, hawkweed, groundsel, Canada goldenrod, sowthistle, endive, sunflower, lettuce, mustard, radish, chickweed, lambs quarters, morning glory, cucurbits, common teasel, alfalfa, beans, lima beans, mung beans, geranium, ground Ivy, okra, purslane, jimsonweed, ground cherry, horsenettle, black nightshade, pepper, tomato, petunia, eggplant, potato, burning nettle, garden pansy. 
 
Lettuce mosaic virus (LMV): lettuce, bristly oxtongue, spinach. 
 
Bidens mottle potyvirus: lettuce, endive, horseweed, hairy beggarticks, virginia pepperweed, Mexican pricklepoppy. 
 
Celery mosaic virus (CeMV): Celery, giant hogweed
 
Papaya ringspot virus (PRSV): Bur cucumber, creeping cucumber, balsom pear, cucumber, cantaloupe, watermelon, summer squash, pumpkin, gourd, winter squash, butternut squash, 
 
Tomato spotted wilt virus (TSWV): Tomato, potato, pigweed, hairy beggarticks, oxeye daisy, coffeeweed, prickly lettuce, annual sowthistle, ebdive, sunflower, lettuce, shepherd’s pruse, chickweed, hedge bindweed, cantaloupe, muskmelon, bean, broad bean, mung bean, cutleaf evening primerose, broadleaf plaintain, purslane, jimsonweed, bittersweet nightshade, black night shade, pepper, tomato, petunia, eggplant, potato. 
 
Tobacco mosaic virus(TMV):  White campion, jimsonweed, pepper, tomato, tobacco. 
 
Turnip mosaic virus(TurMV):  pigweed, wild carrot, bachelo’s button, Canada thistle, hairy galinsoga, smallflower galinsoga, common catsear, pineapple weed, dandelion, endive, sunflower, lettuce, mustard, brassicae crops, corn cockle, chickweed, common lambsquarter, spinach, cucumber, alsike clover, lupine, redstem filaree, ground Ivy, okra, velvetleaf, common pokeweed, purselane, jimsonweed, black nightshade, tomato, petunia..
 
Watermelon mosaic virus (WMV) :   mustard, common lambquarters, spinach, cucumber, watermelon, cantaloupe, squash, buttercup, red clover, common vetch, alfalfa, beans, lupine, pea, henbit, common mallow, okra, common pokeweed, jimsonweed, nightshade, 
 
Zucchini yellow mosaic virus (ZYMV) : cucumber, cantaloupe, watermelon, squash, zucchini, pumpkin, gourds. 
 
 
Source: Cornell.edu

Interested in the latest ag technologies? FIRA USA and a number of other entities are organizing a 3-day event October 18-20 in Freson, CA focused on autonomous ag robotics and technologies. The event includes keynote speakers, break out sessions, a trade show and in-field demos of harvesting, weeding, thinning, and planting robots. The emphasis is on specialty crops so it should be very interesting program. For more information, click here.

Last Thursday April 28, 2022 the EPA issued a notice of intent to suspend (NOITS) DCPA, which when effective, will prevent the sale, distribution, and use of the technical-grade product containing the pesticide dimethyl tetrachloroterephthalate (DCPA).
Please see all details of the NOITS by clicking the following link:
https://www.epa.gov/pesticides/epa-issues-notice-intent-suspend-herbicide-dcpa
 
Dacthal was first registered in 1958^[1] and we are constantly adjusting it to our changing cultural practices.  Recently some evaluations were done of Dacthal’s safety to iceberg lettuce applied Pre and Post-Transplanting. The product showed promising results. It is a mitotic inhibitor and kills germinating weeds by stopping cell division. This mode of action is similar to preemergence herbicides such as Prowl, Kerb, Balan, Trifluralin and others but its chemistry and how it moves in the soil differs. Dacthal is absorbed by both shoots and roots of germinating seedlings although most of the activity is from shoot absorption. When absorbed by the shoots, it will move upward into the plant. It is not absorbed by foliage and can be safely applied over the crop. Dacthal adheres strongly to soil particles. The best time to apply Dacthal is when the soil is moist but not saturated^[2]. 
We are also including in this update the statement from registrant AMVAC Corporation for more information regarding notice of intent to suspend DCPA: https://www.amvac.com/news/amvac-regulatory-issues-statement-regarding-dachtal-dcpa.
 
 
 
References:

1. https://en.wikipedia.org/wiki/Dimethyl_tetrachloroterephthalate
2. https://cals.arizona.edu/crop/vegetables/advisories/more/weed193.html

Area wide Insect Trapping Network   VegIPM Update, Vol. 15, No. 21, Oct 16, 2024

Results of pheromone and sticky trap catches can be viewed here.

Corn earworm: CEW moth counts increased in most traps; about average for early October.

Beet armyworm: Trap counts increased in most areas last week, and about average for early October.

Cabbage looper: Cabbage looper trap counts still most locations, below average for this time of the season.

Diamondback moth: Adult activity increasing, particularly in the Yuma and Dome Valleys.  Above average for this time of season.

Whitefly: Adult movement increasing Tacna, Dome Valley and Yuma Valley; overall about average for early October.

Thrips: Thrips adult movement picking up in all areas, overall activity above average.

Aphids: Winged aphids beginning to show up the north Yuma and Gila Valleys; about average for early October.