Symptoms on Vegetable Crops Harold M. Kempen, Bill Fischer, Clyde Elmore, Carl Bell and Harry Agamaliant Introduction: Two or more are used in most of Califc;>rnia's field and vegetable crops and the danger is always present that vegetables may be injured by one of them. This does not happen very frequently, fortunately, but knowledge of which herbicide it is that caused the injury is information worth recording in one's mind. Very little is published which shows the symptoms on most of the vegetables that we grow in California because colored photos are essential and therefore the publication would be so expensive, only lawyers could afford it Some would think that knowing the different symptoms associated with herbicides from drift, off-target spraying, persistence from previous crop herbicides or inadvertant use of the wrong herbicide would be difficult. But the number of herbicides used has been considerably reduced in the past five years. From the UC Weed Science Training Gwde, publication 3056, (revised, 1980) 146 herbicides are listed in various herbicide families, such as the triazines, the substituted , the thiocarbamates, etc. Of these 85 are no longer registered in California and 61 remain. Fourteen more will no doubt be eliminated or prevented, if the Environmental Protection Act of 1990 initiative is favored by California's voters. These are on either an EPA "cancer list," on the Proposition 65 list promolgated by the Governor's Scientific Advisory Panel since that proposition was passed, or are considered to be human carcinogens from human epidemiological studies. For the record they are: , , amitrole, asulam, , , , , , oryzalin, pronamide, tridiphane and . Some of these have not been registered in California and others have already been dropped. When comparing to the 1989 Crop Protection Chemicals Reference, 258 herbicide formulations are listed; of these 128 are (in all probability) not registered in California. This says that many products are not being targeted for California use. The slides for this presentation are from several areas of the state and the symptoms are similar, which should reassure some that they are reproducible. So the blame shouldn't be put on Maine, boys. They occasionally occur from normal usage but often are from off-target spray drift, carryover from previous crops, inadvertant selection of the wrong material, or contamination of equipment. Symptoms are reasonably characteristic for each family or class of herbicide.

The dinitroanilioes Included in this class are products like Treflan, Prowl, Balan, Surflan, Sonalan, Cobex and Endurance. The dinitroanilines (often called DNA's) are mitotic inhibitors and prevent cell division. Symptoms usually show on the root system but can show elsewhere on the plant. Trifluralin causes this characteristic twisting of white beets but will cause damage to red beets also. This Clyde Elmore slide of Surflan carryover from a removed orchard to sweet com is a classic, showing the enlarged root tip. If you take a plant and put it into clean, pure water, roots will return to normalcy. Drift of Prowl here to the edge of the lettuce field before emergence, reduced this Fresno County lettuce stand, even though sister DNA ,Balan, is registered on lettuce, but preplant incorporated. We know that Balan pre-emergence will kill or damage stands of both alfalfa and lettuce. Monterey spinach growers sometimes see streaks in their spinach from overdosed trifluralin; spinach is sensitive like beets. Treflan is registered on transplant tomatoes, but placement is important. A small placement difference can mean that roots will not grow out of the treated zone. We noted this effect in Monterey as well as Kem County. DNA's can affect the shoot at the soil line some times. A Sutter County situation shows the impact of a DNA, probably Paarlan on tomatoes, and the effect of Treflan on, the roots of broccoli planted in lighter Kern County soils, though normal rates were used, but sprinkled repeatedly in our 100° summer planting period. On broccoli, either the Treflan rate must be reduced or Dacthal should be used; it works well under sprinklers in the summer. Rarely on potatoes do we see symptoms from Prowl or Treflan postplant bed-incorporated, but when we do it often manifests itself as a thickening of the stem at the soil line or below, many times with a splitting of the underground stem. Yield loss rarely occurs. A disorientation of stem tissue causes enlargement of stems of plants such as in tomato or broccoli to where they can snap off from winds or gentle prodding, but otherwise recover, heal and produce a normal crop. t University of California Cooperative Extension in Kern, Fresno, UCD-Botany, Imperial and Montery CoMnties, respectively.

13"4 Dinitroanilines such as Cobex and Prowl, if sprayed to the green stems of several crops will cause stems to be brittle and subject to snapping off. Treflan doesn't generally do this, but infrequently it will affect the foliage of pepper in Monterey, or melons in Fresno. Such symptoms are caused by absorption in young leaf tissue or buds, is not systemic and rarely affects production. Balan rarely shows a strapped leaf appearance on lettuce. Prowl is much more likely to cause foliar damage to young growth and buds, as on squash in Imperial County and post-emergence on potatoes. It does this to young cotton, grape buds, tomatoes,' and other crops, but it is the 4 EC formulation that does it. The ornamental dry formulation label does not do this, I am advised by Dr. Elmore. Should we have to switch labels due to Hayden's Environmental Protection Act of 1990, we would have to re-evaluate this effect on weeds in onions and garlic, and other crops. Not all crops are impacted by Prowl. Carrots, which are very tolerant to all dinitroanilines, are not impacted preplant, pre-emergence or post-emergence from them at rates as high as 4 lb ai/a. Yet it will control Russian thistle quite well at 1or2 lb ai/a post-emergence, in comparison to the check. And Treflan is safe when incorporated 10 inches deep preplant with a rototiller.

The Iriazjnes The triazines are photosynthetic inhibitors and and include such herbicides as (Sencor/Lexone), (Princep/Caliber 90, ~d other names), atrazine (AAtrex, Atrazine, etc.) prometone, and prometryn (Caparol or Prometryne). 1be symptoms from them are characteristically none to the root system, but chlorosis or yellowing on the leaf tissue of plants. Norqially it appears on fully expanded but newer leaves when absorbed from the soils with transpiration water. If high rates .are applied, leaves may tum brown (bum) quickly but usually some yellowing occ\Jrs on some leaves. Mostly the chlorosis is interveinal in contrast to the substituted types of herbicides. When interactions with nutrient excesses or shortages occur, all bets are off. Prometryn is a methylmercaptotriazine, and symptoms fromit tend to be more splotchy. Asparagus is rather tolerant to simazine but on high calcium soils, symptoms are more frequent than diuron, causing the tiny leaves to yellow. Sencor causes these kind of symptoms on tomatoes in the Sacramento Valley, but it can be additive to other triazines such as carryover from atrazinc. Melons in Fresno show symptoms of a bit of simazine carryover, it being very persistent Potatoes are moderately susceptible to Sencor or Lcxone, with some varietal differences, Centennials being very susceptible but the new russet Nortotah not different than White Rose. In Kem County the low organic matter (0.1-0.5%), low clay content of soils (about 12%) and the high transpiration rates in the summer make it very marginal on potatoes. Tomatoes are also marginally tolerant to labeled use rates and un~ some conditions such as drip irrigation, show temporary symptoms. Grape leaves (sometimes eaten as vegetables by ethnic groups) can show extensive simazine interveinal chlorosis on some varieties under sprinkler and high calcium soils, but prometryn (Caparol) carryover from layby cotton looks vivid yellow on squash in Imperial County.

The substituted ureas The substituted ureas include herbicides such as diuron (Karmex, Direx or Diuron), linuron (Lorox) and (Spike). Veinal clearing (chlorosis) is mostly commonly present when from root uptake. If applied to foliage, more browning (bum) occurs as from a spray contaminant on melons. Carryover sometimes occurs since they persist in soils, with linuron being shortest and tebuthiuron lasting for several years when used at non-crop rates. Lorox on asparagus is widely used on young plantings (recently getting a Kern County label) and causes some foliar browning from over the top sprays of speedling rootings. Historically it has worked very well as a chemigation treatment on carrots before the new EPA regulations prevented that as an option unless specifically labeled. Mixtures of Lorox with Fusilade + COC surfactant induces greater symptoms on 2-3 fem leaf c811'0tS. Kern County potato varieties show different susceptibilities to Lorox as with Sencor, again with the russet Centennial variety being sensitive, even to CaITyover from use in carrots. Lorox is extremely effective as a contact foliar spray, damaging broccoli in Imperial county. If methamle (Probe) is registered on onions, you may see damage like chloruxuron (J'enoran), now discontinued. Probe, too has contact activity at rates about 1/4 of those showing soil activity.

135 The thlocarbamates The thiocarbamates include such widely used herbicides as Eptam, Sutan +, RoNeet, Tillam and Far-go. These are cell growth inhibitors but work primarily on the shoot meristems rather than the root tissues as use rates. Often.they cause epinasty (distortion) and leaf clasping not unlike Nortron. In carrots we have been attempting to find a replacement for carrot oil, which was not a large enough product to pennit doing all the toxicology requirements, and EPTC is the candidate. It was registered but caused periodic injury in 1960. Our extensive recent studies continue to support that, but carrots seem to outgrow symptoms from use rates. The thiocarbamates generally do less well on emerged weeds but will cause deformity in growth and retard grasses and nutsedges for about two weeks. Cucumbers and onions show these types of distortion. Vemam sometimes caused severe foliage "arthritis" to sweet potatoes and is not longer used for weed control here in California.

The ace~ Theace ~des include Lasso, Dual and Antor. These are also cell growth inhibitors but seem to damage root as well as shoot meristems. Symptoms are usually distortion of new leaves. Note that the seed leaves, which are already developed in the seed, are less apt to show distortion as the new developing true leaves. Lasso preplant on cucumber and on lettuce show the characteristic distortion of new growth. On roots damage can sometimes be severe, often causing reddish or purple discoloration when plants contain red pigments. This may be confused with root pathogenic damage. Miscellaneous herbicides Many herbicides don't fit our classification system, but are important. Let's look at Gramoxone Super (). It is seen from time to time on crops from drift. The symptoms usually are chlorotic circles or spots, often becoming tan but not with a ring or halo as is common for some fungi. On cucumber at 1/8 lb ai/a in the Sacramento area, drift on spinach in Yolo or Monterey Counties, and on lettuce in Monterey, the typical tan lesions are apparent without systemic effect on new growth. On sweet com, , an analog, showed similar symptoms in a Fresno County situation. With Roundup on broccoli in Yolo, on tomatoes in Fresno, the symptoms from foliar applications can show a yellow spotting or very yellow new growth, often with flowers aborting, but later there is usually stunting to new growth. New leaves show a more "shattered" appearance than 2,4-D. Stunting and multiple bud shoots may occur and usually normal regrowth occurs eventually, if low rates are drifted on crops. The oldest systemic herbicide, 2,4-D and other phenoxy products cause delayed distonion that causes more "strapping" to leaves with leaf veins in a row than does Roundup. Often 2,4-D will cause tubular effect on young plants (lettuce), or twisting of older plants (onion), and often gross deformity and cracking of the roots of highly sensitive plants (carrots). While systemic, portions of plants often return to normal growth while maintaining the symptoms on the plant, unlike Banvel, which like Roundup, is readily retranslocated to new growing meristems. Goal is a contact herbicide, as a directed spray on older onions shows or over young onions with concentrated sprays showing white lesions. When spotted, tissue kill occurs on older onion leaves or asparagus stems, and they will twist in the direction of the lesion. When it causes tiny black speclcle lesions on expanding broadleaf or grass plant leaf tissue, especially sensitive crops such as lettuce or spinach will show entire outside leaves browned by it without systemic effect. Not all strange symptoms are induced by herbicides. Diseases like Cucumber mosaic virus can be credited to a herbicide on potatoes. Wind blown sand can cause lesions like Goal making onions twist toward the direction of the sand. Birds can peck out the growing meristem of seedling vegetabl~ and induce lateral buds, being blamed on stunting herbicides. And ammonium gas, injected too near roots of plants before planting the crop can kill crops (but usually leave a black center in the root). Liquid fertili7.Crs applied with injectors, can cause black necrosis, brown necrosis or chlorosis not unlike too much salt damage. And foliar applications of nitrogen fertilizers by fertigation, can SCOICh foliage of crops if not washed off, or if applied with some otherwise hannless herbicides. References: ------Crop Protection Chemicals Reference. 5th Edition. 2266 pp. + supplement. John Wiley & Sons. Kempen, H. M. 1989. Growers Weed Management Guide, 2nd Edition. Thomson Publications,

136 Fresno. 250 pp. Kurtz, E. 1989. Principles of Weed Control in California. 2nd Edition. Thomson Publications, Fresno. 490 pp. Derr, J. F. & B. L. Appleton Herbicide Injury to Trees and Shrubs. A Pictorial Guide to Symptom Diagnosis. Blue Crab Press. P. 0. Box 5055 Virginia Beach, VA.72 pp.

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