Cooperative Extension Service

Institute of Food and Agricultural Sciences

VEG ETA QIAN A Vegetable Crops Extension Publication

Horticultural &ie nces Department • P.O. 110690 • Caineaville, fL 3'2611 • Telephone 904/39'2-'2134

Vegetarian 93-11 November 15, 1993

Contents

I. NOTES OF INTEREST

A. Vegetable Crops Calendar.

II. COMMERCIAL VEGETABLES

A. Petiole Sap Test Guidelines.

B. Potato Disease Situation for 1993-94 Season.

Ill. VEGETABLE GARDENING

A. Orga nic Cucumbers and Muskmelons.

Note: Anyone is free to use the informat ion in this newsletter . Whenever possib le, please give credit to the authors. The purpose of trade names in this publication is solely for the purpo se of provid ing information and does not necessarily constitute a recommendation of the produ ct.

The lns titt1tc of Food and Agricultur al Sciences is an Equal Employment Opportunity -Affirma tive Action Employer au thorized to provid e research , edu cational info::_~~'.?!.' and other ~ rvi<=:5Aonly t~!"divi duals and institutions .that function without regard to race, color, sex, age, han dicap or national origin .

I. NOTES OF INTEREST

A. Vegetable Crops Calendar.

January 8, 1994 . Greenhouse and Field Vegetable Shortcourse at the Colosseum, Live Oak, FL. Contact Bob Hochmuth, (904) 362-1725.

February 16-17, 1994. Florida Agricultural Conference and Tr ade Show . Orange County Convention Center, Orlando, FL. Contact Larry Jackson , CREC, Lake Alfred.

11. COMMERCIAL VEGETABLES

A. Petiole Sap Test Guidelines.

Plant petiole sap testing has become popular among vegetab le growers an d crop consultants as a means t o determine plant N and K status. Fa st t urn -around of results from a calibrated sap test

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pro cedw·e can ht::lp growers make decisions about fertilizer manageme nt , part icularly for drip irrigation users who are injecting fertilizer. We have been ga th eri ng da ta on sap testing for seve ral vegetab le crops in Florida.

Some of our data for several crops are presented in this article. Although the data might be somewhat regional, I think the values might have usefuln ess at least as a starting point for trial. Users should the refor e view these values as guidelines.

Optimum sap testi ng should be based on field research where yields are meas ured for various fertil izer programs. Fine tuning of the sap testing program should be done by the grower for a particular farm and seas on . Although calibrating a sap test involves signifi cant work, I believe that sap te st ing holds promise for improving our ab ility to manage N and K fertilizat ion of vegetables.

IRISH POTATOES

Stage of growth

Plants 8-inch tall First open flowers 50% flowering 100% flowering Tops fallin g over Tops down

Sap K -------------- ppm ---------------1400-1600 4500 -5000 1200-1400 4500-5000 1200-1400 4000-4500 900-1200 3000-3800 800-1200 2500-3 000 200-800 <2000

ANNUAL - HILL STRAWBE RRIES OCTOBER PLANTING

Stage of growth

November December January F ebruary March April

SapK ---------------- ppm ----------------800-900 3000-3500 600-800 3000-3500 600-800 2500 -3000 300 -500 2000-2500 200-500 1800-2500 200-500 1500-2000

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BELL PEPPER

Stage of growth

First buds First open flowers Fruits half-growth First harvest Second harvest

SapK

--------------ppm -----------------1400-1600 3200-3500 1400-1600 3000-3200 1200-1400 3000-3200 800-1000 2400-3000 500-800 2000-2400

TOMATO

Stage of growth

First buds First open flowers Fruits 1-inch diameter Fruits 2-inch diameter First harvest Second harvest

BROCCOLI

Stage of growth

Six-leaf stage Two-inch heads At harvest

Sap K

---------------ppm -----------------1000-1200 3500-4000 600-800 3500-4000 400-600 3000-3500 400-600 3000-3500 300-400 2500-3000 200-400 2000-2500

----- ppm -----800-1000 500-800 300-500

EGGPLANT

Stage of growth

First fruit First harvest Mid harvest

SapK

---------------ppm ---------------1200-1600 4500-5000 1000-1200 4000-4500 800-1000 3500-4000

(Hochmuth, Vegetarian 93-11)

B. Potato Dise ase Si tu ati on fo r 1993-94 Seaso n.

Wet weather in portions of the midwest and northea st in 1993 and the spreadi ng of "new " strains of the potato late blight fungus, Phytophthor a infestan s around t he world and in portions of the United States have created a complex sit uation for potato producers (commer cial and garden s). Current indication s are that the quality of much of the potato seed Lu l.H:ff supply will be low. Excessi ve rain s where seed tu ber production occurred in 1993 created favorab le condit ions for invasion of potat o tube rs by bacteria that cause soft rot and black leg, fun gi that cause dri er rots , and the lat e bli ght fungus . Although speculative at this point, we think th e seed pieces from some seed pr oduct ion areas of the midw est and the nort heast will have fewer defects than those from other areas. In general, however, areas in the midw est that incurred heavy rai ns are lik ely to hav e higher lev els of both soft rot bacteria (including black let) and late blight th an othe r areas. Potatoes from some area s of the northeast are likely to be in fected with the late bligh t fungu s also, but dama ge from bacterial diseases may be less.

Considering the complex situati on, we ha ve prepared a list of considerations for anyo ne (produ cers, co-ops, garden supply operators, gardeners, etc) who will be purchasing seed tubers and growin g pota t oes . In the pa st, WE HA VE LEARNE D (often the hard way) THAT HAVING GOOD QUALITY SEED PIECES IS A MUST TO PRODUCE A HIGH QUALITY END PRODUCT .

CONSIDERATIONS FOR ACQUIS ITION AND HANDLING OF SEED TUBERS AND SEED PIECES.

1 . CERTIFI ED seed potatoes (F.0.B.) can not have more than 2% of the tubers with any kind of defects. The limi t for la te

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blight is 1 %. Th erefore , unce rtified potat oes should not be purchased or accepted. Some prob lems exist here. Some planting is underway in Florida and some growers may have already accepted defective potatoes or normal -appearing tubers with level s of soft rot bacteria that are higher than normal. Because of the uncontroll ab le weath er in the midwe st in 1993, a larg e supply of potatoe s may not be certifiable within federal law . It is advi sed that growers or grower groups cal l the see d producers in various areas to dete rmine th e quality of the seed produc tion crop. On -site visits ma y be necessary to in spect for quality. Some growe rs have already done this.

2. Before loads are accepted, they shou ld be carefully inspected for defects . It may be advisable to ask for an insp ect ion by the Florida Department of Agricu ltu re. Some private consultants may provide this service. As we und erstan d, once th e load is accepted, there is no recourse. If possible, potatoes shoul d be air-dried prior to storag e because the cool potatoes will form condensation immediat ely upon be ing expose d to our humid air. Soft rot bact eri a can enter or increase in tub ers dur ing production, storage , tran sit , planting, or emergence periods.

3. Seed tubers should be stored in a manne r whe re condensa tion does not form on the pot ato es, ba gs, or p ::i llets and moist air is dissipated as soon as possible after r ece ipt. Thi s will r equir e the establishment of forced air t hrough the storage ar ea. If the air can be warm ed, drying and suberization of skinned and bruised tu bers will be enhanced. Bag s an d pallets shoul d not be pa cked tight. Containers need to be spaced in a mann er that allow s for movement of natural or forced air . Forcin g air thr ough perforated pipes among th e stor age containers is recommend ed.

4. The land should be prepared in a way that minimizes survival of old crop and weed debris at least 30 days prior to planting (e.g. bottom plowing) to minimize young plant diseases. Rhizoctonia spp., Fusarium spp. and bacteria such as Erwinia spp. can survive in the soil and are likely to be in higher populations if old crop debris is not decomposed. Provision for drainage to minimize standing water from excessive rains is advised, as is the use of crop rotation.

5. Planting should be timed so that the seed pieces and young plants are not exposed to excessive moisture . Warm soils that are wet are more likely to have inoculum for bacterial soft rot diseases.

6. For this season, IT IS ADVISED THAT ALL SEED-PIECE LOTS BE GRADED ON THE FARM PRIOR TO CUTI'ING, preferably at the time of arrival, by rigorously separating defective tubers from the intended planting stock. CULLS SHOULD BE DESTROYED AND NOT LEFT AROUND FIELDS OR HANDLING FACILITIES. THOROUGHLY BURY OR BURN CULLS. CULL PILES ARE NOTORIOUS FOR PROVIDING INOCULUM FOR PLANTINGS. SEPARATE PERSONNEL SHOULD BE USED FOR THIS OPERATION. THIS MAY SEEM TO BE AN UNCOMFORTABLE AND EXPENSIVE TASK, BUT IN THE LONG RUN IT WILL BE ADVANTAGEOUS. FURTHER, PLANTING FEWER ACRES OF QUALITY SEED PIECES WILL BE EASIER TO MANAGE OVER THE SEASON THAN A GREATER ACREAGE WITH EXCESSIVE DISEASE PROBLEMS.

7. After culling, seed tubers should be handled with a minimum of bruising and treated with a labelled DRY seed-piece fungicide immediately after cut ting. If handling equipment becomes obviously contaminated from mushy seed tubers, the

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time should be taken to at least clean (preferably disinfest) knives and other equipment as often as practical. If a lot of seed tubers has a high incidence of disease, the equipment should be disinfested before the next lot is processed. Diluted bleach and commercial disinfestants are available.

Seed tubers and pieces should not be wetted. Do not use wet gibberellic acid for sprout stimulation unless necessary (as in Dade County) where freshly harvested seed tubers have to be used.

Dust formulations of captan and Tops-2.5D are available for seed piece treatment. Although not thoroughly tested, it has been observed that treatment with captan as a dust may reduce bacterial seed piece decay at least slightly. Mancozeb products such as Dithane M45, Penncozeb, Maneb Plus Zinc F4, Manex II, and Manzate 200 DF are labelled for seed piece treatment as aqueous dips. Because the seed pieces need to be treated wet with the mancozeb products, it may not be a good practice this year because of the lower quality seed tubers.

8. Seed pieces should be planted as soon as possible after the seed is cut and treated with a fungicide. If seed pieces need to be stored, they should be kep t dry as outlined above .

CONSIDERATIONS FOR SUPPRESSION OF LATE BLIGHT ON EMERGED PLANTS.

It is highly likely that late blight, a disease of potatoes and tomatoes, will occur in the 1993-1994 crop. Severe outbreaks occurred in last year's crop in Florida and in some of the seed tuber production areas up north. In addition to the inoculum that might be introduced via seed tubers, the late blight fungus may have survived in some fields in Florida from the last crop. With the introduction of the second mating strain last year or sometime in the past, the overall

populatio n may now have the ability to produce a thick- wall ed spore (oospore) that can survive in our fields. Prior t o last season, we have generally regarded survival of the late blight fungu s through the hot summer to be minimal. It is a cool-weather pat hogen (55° to 65° F is near optimal).

In addit ion, a strain(s) of th e late blight fungus that is resistant (insen siti ve) to metalax yl (e.g. Ridomil 2E) was foun d in Florida and elsewhere in the U.S. last season. Below are some consid erati ons for the chemical cont rol of late blight.

A. Ridomil 2E is not labe lled for use on potatoes any more !!! It was labell ed for use as a soil t rea tment at seeding only . It was nev er labell ed as a foliar spra y because of the ri sk of creating ideal conditio ns for buildup of resis tant strain s.

B. Metalaxyl -containing produ cts (MCP's) form ulate d with a COMPANION FUN GIC IDE SUCH AS MANCOZEB, CHLOR OTHALONIL , AND COPPE R ARE AVAILABLE. We st rongly advise that these pr oducts be used within the overall spray program for potato produ ction an d tomato productio n this season. Examples of such products ar e RIDOMIL MZ-58 and RID OMIL BRAVO 81W.

Pl ant Protection Poin ter NO. 6 should be consulted for details on the use of the above listed fungicides as well as other available ma te rials. Limitat ions rela ted to application numbe rs and ra tes are presented. When Ridomil MZ-58 is us ed, tank mixing additional mancozeb ( up to legal limi ts of to tal mancozeb) to th e spray mix is advi sed so that ampl e mancoze b is availabl e for control of late blight and other foliar diseases. The use of non - MCP 's such as man cozeb and ch lorot hal on il without MCP 's or alternati ng th em with Mr.P 's are additional options. With non -MCP's spray

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int erv als may need to be redu ced Lo 5-10 days.

FOR ECASTIN G THE FUTURE IS RISKY BUT WE BELIEVE THAT GROWERS NEED TO BE ADVISED OF POSSIBLE PRODUCTION PROBLEMS. HOPEFULL Y THEY WILL KEEP IN CONTACT WITH COUNTY EXTENSION FACULTY FOR NEW DEVELOPMENTS . WE WISH THEM LUCIC Scruti niz e TAILGATE RUMORS, no doubt there will be plenty.

(Kuchar ek, Weingartner , and Bart z, Plan t Pa thologists. Veget ari an 93 -11)

Ill. VEGETABLE GARDENING

A. Organic Cucumbers and Muskmelons.

Over in the Organi c Gardening Resea rch and Edu cation P ark (Gainesville, UF), this past Spring Dr . Stev e Kost ewicz evaluated 15 cucumber and 42 muskmelon varieties for home gardens unde r organic culture . He appli ed 40 ton s per acr e of poultry manure (th at included some bedding as a pre -plant fertilizer). The aged poultry lit ter, which had bee n stored under a tarp for seve ral mon ths pri or to applicat ion, was br oadcast/i ncorporat ed 30 days before seedin g. As the crops grew, they wer e sidedre ssed weekly with an applica tion of fish emu lsion (1 pin t/10 00 sq ft) until harves t. Seeds wer e pla nt ed on March 23, 1993, using the "hill" system (1 plant per 20 sq. ft.) .

Results

Cucumber s were h arves ted 14 times. Twelve of the vari eti es yielded heavy outputs of fruits. The highest yie lds (lb/pl ant ), were obtained from 'S lice Nice', 'Poinsett 76', 'Tasty Gr een', an d 'Supersett' . Th e most fruits per pl ant came from 'Sl ice Nice'.

Muskmelons: In sp ite of unfavorable cool, wet growing conditions, several varieties did develop some good­size fru it s. However , daily showers resulted in foliage diseases and fruits with low sugar content and growth-cracks. The best early me lons (80-90 days) were 'Sweet 'N Early', 'Easte rn Star', and 'St ar Headliner'. The highest mid-season (90-100 days) yielders were 'Magnum 45', 'Ambrosia', 'Pri mo ', and 'Ta ngiers'. The best of the late season (100+ days ) va rie ties we re 'Grande Gold', 'Durango', an d 'Lusciou s Plus '.

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In sub je ctiv e te sts to ev alua te the degree of sweetne ss , muskmel on varie ties that tasted moderatel y· sweet were as follows: 'Sw eet 'N Earl y', 'E aste rn Star', 'Ambrosia ', 'Grande Gold', 'Primo', and 'Luscious Plus '.

Readers wishing to know more about these trials under organic growing conditi ons are referred to the article by S. R. Kostewicz on page 267, Pro c. Fla. State Hort. Soc. 105:1992 .

(Stephens, Vegetarian 93-11)

Prepared by Exten sion Vegetable Crops Specialists

Dr. D.J. Can tliffe Chairman

Dr. S.M. Olson Assoc. Professor

Dr . G.J. Hochmuth Professor

Dr. S.A. Sargent Assoc. Professor

Dr. C. S. Vavrina Asst . Profe ssor

Dr. D. N . Maynard Pr ofessor

Dr . W.M. Stall Professor

Dr . J. M. White Assoc. Professor