Introduction to Organic Brassica Production
By Richard C. McDonald, Ph.D.
Symbiont Biological Pest Management
Tabs (I, II, III, etc.) with headings/photos –
I. Introduction to Organic Brassica Production - A. Organic Caveat. B. Organic Certification Costs/Agencies. C. Start at the End. D. Why Broccoli? E. Taking Stock of Broccoli's Growth Habits.
II. Organic Brassica Production - A. Current System – schedule and planning; Enterprise budgets and necessary equipment. B. Varieties. C. Soils/Rotation/Fertilizer/Lime/Water Requirements, D. The Plant - seed, float trays, materials, transplanting, field plants (6 to 12 leaves), cupping plants (12-20 leaves), heading plants.
III. Farmscaping/IPPM Concepts. A. Introduction. B. Principles. C. IPPM vs. IPM. D. Top Farmscaping Plants.
IV. Insect Pests and Natural Enemies A. Introduction. B. Pests. 1. Imported Cabbageworm. 1.a. Cotesia glomerata. 1.b. Pteromalus puparum. 2. Diamondback Moth. 2.a. Diadegma insulare.
V. Pesticides. A. Microbials 1. Bacillus thuringiensis (Bt). 2. Impact of Bt on Natural Enemies. B. Soaps, and other harsher controls.
VI. Weed and Disease Control – no till production.
VII. Harvest/Post Harvest Handling - when to harvest? Harvest, cooling, boxing, storage, transport.
By Richard C. McDonald, Ph.D., Symbiont Biological Pest Management, 194 Shulls Hollar, Sugar Grove, NC 28679. phone/fax: 828-297-2884; email: firstname.lastname@example.org; web: www.drmcbug.com
A. Organic Caveat - All outcomes are based on a complex set of systems - your management practices, weather, and other factors may be different and have different results. What we are showing within has been demonstrated to work in both scientific research/demonstration tests and direct field application over the last 20 years. For the purposes of this guide, most examples will be of broccoli.
B. Organic Certification - For a list of current Organic Certification Agencies and costs, please contact the Carolina Farm Stewardship Association at: www.carolinafarmstewards.org, e-mail email@example.com, or call (919) 542-2402.
C. Start at the End, and Work Backwards
The ultimate goal of this guide is to assist tobacco growers in producing a bountiful, healthy crop of organic brassicas, especially broccoli. To ensure the end product is up to the standards of a discriminating organic market, all elements of the growing system must be in place and functioning from the moment the seeds hit the ground. To identify what the essential elements of that system are, let's start at the end of the process--with the product--and work backwards.
D. Why Broccoli?
Broccoli - brief history and description, relation to other plants. Broccoli, Brassica oleracea var. italica Plenck, is a cruciferous vegetable forming a short erect stem, which produces a large green head of succulent flowers. Broccoli, cabbage and the other cultivars of Brassica oleracea evolved from the colewort, a stout, weedy perennial of the seacoasts of Great Britain and southwestern Europe. The present day broccoli was developed by the Italians in the Middle Ages from bunched kale.
Currently, across the country this green, leafy cole crop is a hot agricultural commodity. As food scientists, researchers, nutritionists, and consumers alike have become aware of broccoli’s healthy food benefits, it has been in high demand. That demand has created an excellent opportunity for farmers. In addition, for those who have the experience and equipment for growing tobacco, the growing system and equipment required to grow broccoli are very similar: 1) Equipment currently used to produce tobacco can also be used to start, transplant and cultivate broccoli; 2) The season of broccoli (spring and fall) does not interfere with burley tobacco production; 3) Broccoli is a high value crop (for example, organic broccoli is consistently wholesaling for more than $1.00/pound); and 4) Many farmers in this region are already acquainted with growing cabbage as a cash crop, and thus the switch to broccoli would be easier to make.
Caption: This cruciferous plant of branching florets is the product that drives the system that creates the market that makes farmers smile!
E. Taking Stock of Brassica Growth Habits--The key to producing a bountiful, healthy crop is learning the tricks behind each crop. Take the broccoli example below:
If you're considering growing organic broccoli or other brassicas, you'll be pleased to know that by taking stock of the growth habits of the plant--and of pest damage within the crop--you can increase your yield, and the presence of beneficial insect populations. Here's how it works for broccoli (and cauliflower):
1) About 2/3rds of the way through a broccoli plant's life cycle, it begins to cup or to attain a convex shape. At the cupping stage, plants typically have about 15 leaves. Cupping is the precursor to the plant heading or bolting.
2) Research has shown that, once broccoli plants have at least six leaves and up to 15/16 leaves (just prior to cupping), they can withstand up to 50 percent defoliation without a decrease in yield. In fact, moderate defoliation of the plants--around 20 to 30 percent--actually increases yield.
3) Defoliation causes certain plant chemicals to be emitted; these chemicals beckon parasitic wasps and predatory insects to the plants.
4) By allowing for a certain amount of defoliation, you encourage beneficial insects to establish a foothold in the cropping system. They then begin foraging in the area.
5) As the plants cup, you want the fewest numbers of pests around and the most beneficials. Cupping is the time to get particular about pest levels, and not before.
6) If pest levels at cupping time are above 2 caterpillars per plant, you can spray a biopesticide, such as the microbial pesticide Bt (Bacillus thuringiensis - see Microbial pesticides below). This will reduce pest numbers to an acceptable level with minimal harm to the beneficials.
Budget 2002-BR-1 Broccoli, Fresh Mkt,, Organic, Field Grown: Est. Revenue, Operating Exp., Feb. 02 Ann. Ownership Exp., & Net Rev./Acre/Crop.
Packman (50 days) - least amount of pest pressure in studies at Virginia Tech. Blue green color. ($240/# of seed). In our experience, this is the early season workhorse; dependable – excellent side shoot production. We’ve seen seedlings take 3 weeks of windy, 20-degree weather and still perform. Head shape tends to be more flat; in very wet years – can get bacterial soft rot (Low pH can also cause this - see soil section for liming).
Arcadia (62 days) – heat tolerant variety. Use in summer months or in hot weather. Produces massive heads/huge plants. Heads are medium green and have a frosted appearance. Big globular heads. Supposed to work well with no-till. Varieties Gypsy and Nomad are similar derivates of this cultivar that work well in no-till and are resistant to soft rot.
Premium Crop (62 days) - very tasty! Beautiful, globular heads, decent side-shoot production. Dark green color. ($250/# of seed). Our favorite fall crop. Resistant to soft rot.
Yield - should be close to 1-pound heads per plant, with a six-inch stem below the head.
Early Flat Dutch/Flat Dutch –
Cauliflower: you may prefer self-blanching varieties. Otherwise, the heads must be tied shut – use different color rubber bands for different weeks.
C. Organic Brassica Production - Soils, Lime, Fertilizer, Water Requirements and Crop Rotation:
grow best on well-drained, fertile soils that are rich in organic matter and
soil life. They dislike light, sandy, droughty soils, and very tight, compacted
or poorly drained soils. However, they can thrive in a fairly clayey soil
provided that the topsoil is biologically active and has good crumb structure.
Brassicas prefer a slightly acid to neutral soil, with a pH between 6.0 and
7.0, and liming is important if the pH falls below this range.
Although broccoli and related crops are not particularly deep-rooted, it is important to be sure there is not a hardpan restricting root growth. Hard pans often form at a depth of 6 to 12 inches as a result of repeated tillage operations to the same depth. This reduces the accessibility of moisture and possibly nutrients to the crop, and can restrict yield and cause apparent "nutrient deficiencies" that are not corrected by fertilizer. If a hard pan is present, it can be broken up by chisel plowing when the soil is moderately dry. Follow chisel plowing with a deep rooted cover crop to encourage biological activity deeper in the soil profile. This may significantly enhance brassica yields, especially in dry years.
Broccoli, cauliflower and other brassicas are heavy feeders, and require plenty of available soil nitrogen (N), phosphorus (P) and potassium (K). They also need ample soil moisture, sufficient sunshine, and moderate soil temperatures (55 to 75 F) to sustain the rapid, steady growth that is essential to support good yields. Boron (B) is a critical micro-nutrient for brassica crops, and a B deficiency can cause "hollow stem" in broccoli or cabbage (interior of stem cracks and turns brown), and can lower marketable yields. Since soils in our region are often low in B, a boron supplement may be needed.
Recent research suggests that broccoli, cabbage and other brassicas prefer a "bacteria-dominated" microbial community in the soil, and the roots of many varieties secrete anti-fungal compounds to tip the balance in favor of bacteria. This contributes to resistance to soil borne fungal diseases, but it also inhibits the symbiotic mycorrhizae ("root fungi") that help many other crops absorb moisture, and insoluble forms of P and micronitrients. For this reason, sufficient amounts of readily available P and other nutrients are needed for optimal growth in broccoli, cabbage and related crops. Rapidly-decomposable organic materials (animal manures, young green vegetation, legume cover crops), and finished compost made from a starting mixture that is rich in such materials, will encourage a bacterial-dominated soil microbial community.
Several months before
planting broccoli or other brassicas, obtain a soil test through your Extension
office or a reputable private soil testing lab to evaluate your need for lime,
organic matter inputs and fertilizers. A&L Eastern Agricultural Laboratories
(7621 Whitepine Road, Richmond, VA 23237; tel. 804-743-9401), offers a standard
soil test (pH, organic matter, major nutrients) for $7.35, and a Boron test
for $3.50. To sample a field, take cores (surface to 6 inch depth) from at
least a dozen points evenly distributed through the field, mix thoroughly
in a clean plastic bucket or ceramic crock, and send a pint of soil to the
testing lab. You can use a soil corer (about $20, available through several
mail-order seed and farm supply companies) or a shovel and trowel to get the
samples. Dig out a shovelful, leaving a nearly-vertical surface, then use
the trowel to take an even slice from 0 to 6 inches from this surface.
Different soil labs use different methods and different units to report the test results; however they will consistently indicate whether each nutrient is present in low (deficient), medium (may be yield limiting), high (optimum), or very high (ample, possibly excessive) quantities. If the pH is below 6.0, apply lime at rates recommended by the lab. NOTE: when you lime, you are also adjusting the balance of calcium (Ca) and magnesium (Mg) in the soil. Both are essential elements for brassicas and other crops. If Mg is "low" or "medium" on the soil test, use dolomitic limestone (widely available). However, if Mg is "high" or "very high", and Ca is "low" or "medium", use a calcitic or high calcium limestone. You can obtain high-Ca lime through Seven Springs Farm (contact Ron Juftes at 540-6512-3228 or visit www.7springsfarm.com).
Your soil test will not directly tell you how much available N is present, since levels of soluble N fluctuate widely through the season in both conventionally and organically managed soils. However, the A&L test report includes an "estimated nitrogen release" based on the percentage organic matter (OM) and soil texture (sandy, loam, silty, clay). N is constantly released by the biological decomposition of organic matter in the soil. If soil organic matter levels are good (2% for a very sandy soil, 3-4% for a loam or silt loam, and 4-6% for a clayey soil), the soil is well-drained and biologically active, and it receives substantial annual organic inputs (compost, cover crops, organic mulches, aged manure, etc), it can release 100 to 150 lb available N per acre per growing season.
Soil test recommendations
for broccoli and cauliflower may include as much as 150-200 lb/acre N, and
perhaps 100-110 lb/acre each of phosphate (P2O5) and potash (K2O) for a soil
that tests "medium" for these nutrients. Although these amounts
may be needed for a "tired" soil, or one in transition from conventional
to organic production, much less may be indicated for a fertile, biologically
active soil receiving a sufficient amount and diversity of organic inputs
(5 tons dry weight per acre per year). A biologically active soil will have
numerous earthworms (several to a dozen per shovelful), often shows fungal
networks and/or numerous small insect-like critters, and has a soft, crumbly
structure. It will show moderate to high OM levels on a soil test. Very sandy
soils may support few worms, but will become noticeably darker and better
aggregated (crumb structure) as biological activity increases.
On most soils, a starter organic fertilizer with an analysis of 5-4-5 or 5-5-3 (often based on composted poultry litter) should be used at time of planting to supply up to 50 lb/a N (and corresponding amounts of P2O5 and K2O). This will boost growth early in the season, when cool soil temperatures can retard nutrient release from even the most fertile and biologically active soils. If the soil is also low in boron (B), be sure to include a boron supplement to supply 1-2 lb B per acre. Mix the B supplement thoroughly with the starter fertilizer, and do not exceed 2 lb elemental B per acre, as this can be toxic to other crops in your crop rotation. Boron can also be applied in transplant water. If additional N is needed during crop growth, you can side-dress with any of several organic N fertilizers, or use liquid fertilizers based on fish and seaweed (applied as foliar spray or through drip irrigation).
If the soil tests low in P, K and organic matter, incorporate some nutrient rich manure compost or aged manure prior to planting broccoli. Aim to supply perhaps 100-150 lb P2O5 and 150-200 lb K2O. This can be achieved with applications of 5 to 10 tons per acre of aged manure (depending on manure source - get a nutrient test on the manure so you can fertilize more precisely). Remember that, for organic certification, "raw" manure (which includes aged manure that has not gone through a rigorous composting process) must be applied at least 120 days before first harvest - so either get it on early, or compost it thoroughly first.
If just P is low, another way to boost soil P level is to apply Rock Phosphate or Colloidal Phosphate at 500 to 1000 lb/acre. This is somewhat expensive but you will only have to do it once. Soil tests may show only a slight increase in available P, but the element is there, and it will gradually become more available to the crops if you enhance soil biology through cover crops and high quality compost. If K is low but P is sufficient, remember that hay mulch is a particularly rich source of K. Spread hay mulch at 5 to 10 tons per acre once the broccoli is well established. The mulch also retains soil moisture, suppresses weeds and feeds soil life.
Calcium (Ca), magnesium (Mg) and sulfur (S) are also important nutrients for brassicas. Proper liming (see above) should take care of Ca and Mg needs. Crop limiting S deficiencies are relatively rare, but if one is suspected, you can get a test for S included in the soil test for a few extra dollars per sample. S can be supplied with gypsum (calcium sulfate), sul-po-mag or Epsom salts (magnesium sulfate). Use gypsum if Ca is low to medium, sul-po-mag if Ca is ample and neither K nor Mg is "very high", and Epsom salt if Mg is low relative to K and Ca.
Too much P and K can be a problem too!
Soils managed organically
for a number of years with heavy inputs of manure, compost and applied mulch
can accumulate very high or excessive P and K levels. Soil test labs often
recommend some P and K even when test levels are high to very high, but this
may be unnecessary on organically managed, biologically active soils. In fact,
continuing to apply these nutrients, either as organic or mineral amendments,
can upset nutrient balance and harm crop yield or quality.
Another common situation during transition from conventional to organic methods, is a soil that is depleted of organic matter (less than 2.5 percent on medium textured Appalachian soils) but very high in P and K. This results from intensive applications of chemical NPK fertilizers - all the N gets used up and/or leached out, but the P and K accumulate.
Growing legume cover crops is the best way to replenish and maintain N and OM levels in soils that already have ample or excessive P and K. Other than a light application of starter fertilizer to get the brassica crop off to a good start, manure-based composts and organic fertilizers and hay mulch should be avoided, as they will aggravate the nutrient imbalance. Plant a mixture of hairy vetch and winter rye, or for early spring brassicas plant a non-hardy cover crop mix such as oats + lana vetch or berseem clover, or millet + soybean or cowpea. For the OM-rich soil that has built up too much P and K, the cover crop may be sufficient. For the tired "dead" soil that got its P and K overload from conventional fertilizers, use a high quality compost (1-3 tons/acre), vermi-compost (worm castings), biodynamic preparations, and/or other soil microbial inoculants to introduce a diversity of beneficial soil organisms. These are just as important as NPK and B for success with brassicas. If the crop appears hungry for NPK, foliar feed with a fish fertilizer at recommended rates. You will get a significant response and it won't overload the soil with these nutrients.
This may be the last thing on your mind after the Great Monsoon of 2002-03, but remember that brassicas are not all that deep rooted, and may require irrigation during warm dry spells. These crops generally need about one inch of water per week, and require irrigation if rains do not provide this moisture. Drip irrigation is strongly recommended for delivering moisture and nutrients directly to the crop row. If you do not have a drip setup, overhead sprinkler irrigation is much better than none at all during a drought. An organic mulch of hay, or an in-situ rolled-down cover crop mulch can help conserve soil moisture, reducing irrigation needs, and potentially saving a crop for farmers that do not have access to irrigation.
Since brassica crops
are subject to a number of insect pests and fungal diseases, a sound crop
rotation is important. Crops in the crucifer (brassica) family should be planted
only once every four years (minimum 3 years) in a given bed or plot. This
plant family includes cabbage, broccoli, cauliflower, collards, kale, kohlrabi,
radish, turnip, rutabaga, arugula, mustards, bok choy, Chinese cabbage, and
several other specialty Oriental greens. Brassicas can be rotated with beans
and other legume vegetables, tomatoes, potatoes, corn, squash family, lettuce,
onion family, carrots, beets or spinach. Include cover crops within the rotation
scheme to rest and rebuild the soil, and encourage beneficial insects. Brassicas
thrive particularly well after legume cover crops, and/or onion-family (garlic,
leeks, onions, scallions), all of which have subtle beneficial effects on
the soil. The legumes also provide extra N, on which the brassicas thrive.
Crop rotation is an essential component of pest control for cabbage root maggot, flea beetle, and possibly caterpillar pests. Rotation breaks up the life cycle of flea beetle and root maggot, both of which have a key part of their life cycle in the soil. If these are serious pests, plant next year's brassicas at some distance from this year's crop, rather than in an adjacent bed or plot, into which pest larvae may migrate.
Clubroot is a particularly stubborn fungal disease of brassicas. A four-year rotation is a good preventative, but if clubroot appears in a field, you will need to exclude brassicas from that field for at least seven years. Keeping soil pH at about 7.0 also deters clubroot fungi. Fortunately, clubroot does not appear to be very common in our region - but some vigilance and good rotation may be needed to keep it that way!
Water needs: Broccoli needs roughly one inch of water per week.
D. The Plant – Broccoli featured here. Photos with captions:
Seeds/starts – plant in 288 cell “Speedling” flats (200 cell flats would work well, too) in a raised float bed in heated greenhouse.
Transplants - These plants were scouted and cared for until they reach the 6-leaf stage (8 to 10 weeks old) in one inch Speedling flats; 4 to 5 weeks in three quarter inch Speedling flats. Plants are then hardened off outside for a week or so prior to planting.
Direct set in the field with12-16 inch centers on 30-inch rows.
Field plants (6 to 12 leaves) – this is when you can tolerate some damage in order to get beneficials established. Scout at least 20 plants/acre in an X pattern in the field and release beneficials if necessary. This ensured a favorable beneficial to pest ratio of 25% to 33% of scouted plants with beneficials present (see Table 1).
Cupping plants (12-20 leaves) – Usually 10 to 14 days out before harvest; depends upon temperatures. Time to make sure plants are clean of pests just prior to harvest. Use Bt variety kurstaki for most caterpillars. You will need to rotate Bt varieties and other microbials (CLV) – viruses; otherwise you’ll get resistance.
Heading plants – watch closely for signs of insects. Cut heads open to check for cabbage aphids and other insects. If lots of rain, harvest early to avoid brown spot and other wet rots.
Bearing in mind that the growing system for brassicas starts with a field of healthy, fertile soil, the next most crucial element of the system is the incorporation of an effective pest management strategy. By planting specific beneficial plants, you will create an environment that entices the good insects to be there when you need them to battle the bad insects. Research has shown that incorporating specific plants into the borders and some pullout rows of your broccoli will ensure the continuous presence of beneficial insects in your field throughout the growing season. By working backwards to identify the types of insect pests that typically attack crucifers in this region, you can fortify your field with adequate numbers and varieties of natural enemies. When the pests do arrive, your beneficial insects will meet them at the gates. In order to keep these good bugs around, you need to have AT LEAST 5 percent of your broccoli field planted with beneficial farmscaping plants. This doesn’t have to be IN the field; it can be right next to it, if you have ditches, banks or other areas you can plant. My motto regarding the incorporation of beneficial insects into the field is: If I lay a banquet for them, they will come.
B. Principles of Organic Brassica Integrated Parasite and Predator Management (IPPM).
First, start at the end and work backwards, as we said before-
The ultimate goal of this guide sheet is to be able to help you produce a bountiful, healthy crop of organic brassicas (focusing on broccoli as our example) and at the same time, build an organic system of beneficial border plants and beneficial insects into your field to ensure that you will get a healthy productive broccoli crop every time.
So, the first thing (after making sure your soil is fertile and healthy) you want to do is begin to have areas along and in your field that your beneficial insects can live and reproduce in. You need to have around 5% of your broccoli field planted with beneficial farmscaping plants in order to keep the good bugs around. Farmscaping: So, the area to be planted - i.e. for an acre at 5%: 43,560 sq.ft = 2200 sq. ft. of farmscaping plants). More small plots spread out is better than one big plot. Second, some interesting facts about broccoli that will come in handy.
PHOTO: Broccoli plant at the cupping stage.
You can take advantage of the growth habits of broccoli to increase your yield and your beneficial insect populations. Researchers learned that broccoli plants could withstand up to 50% defoliation without a decrease in yield. In fact, moderate defoliation (around 20 to 30%) actually increased yield! So by being able to allow for a certain amount of defoliation, you can help your biological control prospects. Your natural enemies will have 'food' and other requisites in order to stay where you want them.
A broccoli plant will grow to a certain point and then 'cup'. This cupping occurs about 2/3rds of the way through the plant's life cycle, and is the precursor to the plant 'heading'. Once the plant begins to head, it is extremely important to keep pests out of the head area.
So, we can closely monitor the growth stages of a broccoli plant. We know that we can tolerate some defoliation before the plant cups in order to make sure our beneficials are established and working. We also know that defoliation will not hurt, and in most cases, actually help yield.
As the plant begins to cup we know that we want the fewest amount of pests around and the most amount of beneficials as the broccoli heads begin to mature. This is the time to get particular about pest levels, and not before! If pest levels at cupping time are above your economic threshold, then you can consider spraying a specific biopesticide (like the microbial pesticide Bt (Bacillus thuringiensis) that will reduce pest numbers to an acceptable level with minimal harm to the beneficials. Otherwise, by wisely planning ahead and using some farmscaping principles to encourage beneficial insects, you will have a healthy population of beneficial insects, such as ladybugs, parasitic wasps, predatory beetles, bugs and flies that can suppress pest populations all season long.
C. IPPM vs. IPM.
Imagine you've just received an invitation in the mail to attend a banquet being held in your honor. The menu accompanying the invitation lists all your favorite foods. Are you going to come? You bet you are!!
The gist of this analogy is that just like us, beneficial insects need sources of food and shelter in order to stick around. You can weave 'web of life' in your field by planting specific plants. Also, by thinking ahead and anticipating the types of pest problems you might have, you can encourage the right beneficial insects to be there when you need them to attack the pests. My motto is: If you plant it, they will come. Or, I will buy them (beneficials) once and have them here forever after...'
In keeping with this perspective, think of two terms: 1) Farmscaping, which is the deliberate planting or modification of an agricultural environment with specific plants to encourage populations of beneficial insects. 2) IPPM - Rather than the term IPM (Integrated PEST Management), I encourage you to be thinking IPPM - Integrated PARASITE and PREDATOR Management (This term comes from Dr. Everett Dietrich, the grandfather of beneficial insect rearing).
These two comparisons are equal to the difference between Eastern and Western medical thought--Western medicine treats the illness or its symptoms, while Eastern medicine, with its use of tonics, focuses on keeping you well in the first place. It is the same with your garden or farm. By using IPPM and having the beneficials there IN THE FIRST PLACE, you can nip many of your pest problems in the bud before they ever have a chance to become a problem. So let's look at a few ecological principals to make your broccoli field more attractive to beneficial insects:
Ž ***My IPPM GOAL-you want 1/4 to 1/3 of the “target” plants you sample to have some indication of beneficial insect activity***(wasps, cocoons, mummies, partially eaten egg masses, etc.) or to be relatively pest free. Remember the goal is a “balance” tipped in our favor. Sample at least weekly or more often if a pest problem is present – if possible, sample about 1/4 to 1/3 of the plants (if you want to run statistics on your data). Farmscaping – Dr. Robert BUGG - Definition: Deliberate use of specific plants and landscaping techniques to attract and conserve “Beneficials”.
Feed your bugs – Dr. McDonald’s Baker’s Dozen: Applied Farmscaping Principles:
Ž 1) Farmscaping is part of a Multiple Redundant Systems (MRS) approach – MRS is a form of disaster preparedness – triple redundancy is desirable for plants and insects. So for both you want “guilds” of food plants and natural enemies to protect your plants. This is why we list more than 10 beneficial food plants per season – more than one natural enemy attacking each life stage is better, too. Less can lead to breakdowns. You Want A Natural Enemy for Each Life Stage of the Pest(s). Let's take the Imported Cabbageworm Butterfly (ICW) as an example. It has life stages starting with egg, larva (five different instars), pupa, and adult. So it really has eight different stages that we need to have something attack. Our best chance of sustainable suppression is to make sure we have a complex of natural enemies for each specific life stage. There are ladybugs, Trichogramma wasps, and other predators that can attack the egg stage of the ICW. Likewise, ladybugs will gladly consume ICW caterpillars and there are several specific wasp parasites that sting and lay eggs in ICW caterpillars, especially the first three instars. For the pupal stage, we know that the parasitic wasp Pteromalus puparum is very effective in eliminating at least half of all ICW pupae in a field.
[Table 1. Example listing for Imported Cabbageworm and Japanese beetle of more than one natural enemy/life stage, thus achieving Guilds of Natural Enemies for each life stage. Japanese beetle needs more natural enemies for each life stage.]
Ž 2) Anticipate Pest Problems – Think Ahead - encourage the right beneficial insects to be there when you need them to attack the pests. Ladybugs/Trichogramma wasps attack the eggs of caterpillars.
Ž 3) Specific Plants attract specific beneficials – example: fennel is great for attracting parasitic wasps, syrphid flies, and ladybugs. So one plant can bring in a guild of beneficials.
Ž 4) 5% of crop area should be planted in farmscaping plants- “lots of clumps of food plants spread out over an area is much better than one big clump” – if you take nothing else away from this session, just remember the above quote! Remember, you can farmscape right next to your field if your growing space is at a premium.
Ž 5) Consider Dispersion indices for insects when foraging – “Insect Specs”:
Different insects have different disperal rates – for example, flies can move much further, much faster than a ladybug. So WHERE you put your farmscaping has to be coordinated with the TYPES of insects you are trying to bring in. For example, we want to have syrphid flies in our broccoli fields, but because they are so mobile, we only have to plant food plants around the edge of the field to ensure that the flies will be present. However, if we are trying to attract beetles, like ground beetles or lady beetles, the plants need to be very close to the crop plants – beetles don’t like to travel far if they don’t have to.
(Stay in field)
Medium Dispersion (forage 1/4 mile)
High Dispersion (forage > 1/4 mile)
Ground Beetles (Carabids)
Ladybeetles (when happy)
Smaller Parasitic Wasps
Most Parasitic wasps
Predatory Wasps – Paper
Syrphids (Hover Flies)
Dragonflies, Tachinid flies, Large Parasitic Wasps
Ž 6) Have something blooming all the time – you have the neighborhood 24 hour Wafflehouse for beneficial insects. Flowers are prime food & mating sites for wasps. Important to have a well fed, mated female beneficial! Wild mustards and crucifer crops like broccoli have flowers that are very appealing to beneficial wasps. It also turns out that these flowers are prime mating sites for the beneficial wasps, too. This is good news, because if a female wasp is not mated, she lays all male eggs, the population crashes, and so does your beneficial wasp population. Green House – use to Jump-start garden areas.
Ž 7) Nectar – liquid sugar food + vitamins for beneficials. Nectar is critical for optimum performance of many beneficials. Many beneficials will lay over 3-fold more eggs if properly fed. Example: Parasitic wasps egg laying capacity – poorly fed – 30 eggs; if she is well fed, over 300 high quality eggs. Some of the best plants you can have for this purpose are those in the wild carrot family (also known as Umbellifera), such as dill, fennel, tansy, queen Anne’s lace, caraway, coriander, parsnip, etc.
Ž 8) Extra-Floral Nectaries – nectar glands that are not associated with flowers. Peonies, Sweet potatoes, bachelor buttons, all have extrafloral nectaries. Parasitic wasps and flies use these extrafloral nectaries as important food sources.
Ž 9) Pollen - Is an alternative form of protein. When certain predatory insects (which beneficials often are) have eaten almost all of their prey population, they will leave unless there is an alternative form of protein around. Once again, many plants in the wild carrot family can provide pollen. Another good pollen producer is the corn plant. Syrphid flies need pollen to lay eggs.
Ž 10) Overwintering sites for beneficials - It turns out that many beneficials make cocoons and hibernate in or very near the plants where they find their hosts. For example, let's take broccoli again. By leaving some broccoli plants to overwinter, the cocoons of parasitic wasps can survive on the plant, and then become the starter colonies of beneficials to ride herd on the first pests that attack broccoli, like the imported cabbage worm, Pieris rapae (L.). It might look a little messy to leave the plants in the field and not compost them, but, hey, who says pest management comes without a price' If this strategy is not to your liking, another would be to pull the broccoli plants up and set them aside somewhere (until mid- to late-April or so) in order to make sure that the beneficials have emerged, before you compost the plants. Recent research has shown that yarrow and comfrey are also excellent overwintering plants for parasitic wasps.
Ž 11) Entrainment – (entomologists– Joe Lewis really opened up this field) have discovered that insects (especially parasitic wasps and flies) can perform associative learning, so if you get insects (especially young ones) happy in their environment, they will “tune in” to a particular pest. A good way to do this for a predator or parasite is to release it on or nearby the intended prey.
Ž 12) Drought/Stress – These systems can also fail! In drought years insects from all over will come to your area and can overwhelm a system. Be ready with backups additional insects, ladybugs/lacewings, Bt, soaps, diatomaceous earth. Finally,
Ž 13) Your Design Decisions Mantra: Encourage Biodiversity! - Remember that insects are part of the web of life in your garden or farm. The beneficial insect complex is not only composed of parasitic wasps and flies, predatory beetles, lacewing larvae, ladybugs and so on, but ALSO the pollinators, antagonists/competitors that occupy and compete for space and food with potential pests, and finally the saprophytes and decomposing insects that help complete the food cycle back to the soil so the cycle can start again. And remember, “If you plant it, they will come....” For further information on Farmscaping, go to my web site (www.drmcbug.com) and click on the farmscaping section. Also see ATTRA’s Farmscaping publication at their website (www.attra.org).
The gist of this message is that, just like us, beneficial insects need sources of food and shelter in order to stick around. You can weave “web of life” in your garden/farm by planting specific plants that attract specific beneficials. Also, by thinking ahead and anticipating the types of pest problems you might have, you can encourage the right beneficial insects to be there when you need them to attack the pests. My motto is: “If you plant it, they will come. Or, I will buy them (beneficials) once and have them here forever after...”
FARMSCAPING - Top Plants for Beneficials
Spring: brassicas – wild mustards, ground ivy, Tulip poplar, vetches, pussy willow, yarrow, umbels - parsley/parsnip/ coriander, buckwheat, clovers, mints, Norway Maple, grains, peonies, borage.
Summer: mints, wild carrots- cow parsnip, tansy, bronze fennel, smartweed-Vietnamese Cilantro, Jerusalem artichoke, kenafe, sweet potato, borage, smartweed, bachelor buttons.
Fall: Patrina, autumn joy sedum, vetches, chrysanthemum (Pacifica), tansy, bronze fennel, Queen Anne’s Lace/other wild carrot family plants, garlic chives, Goldenrod. Research has shown yarrow and comfrey to be very high in overwintering wasps underneath the plant’s leaves. Also pull some of the last broccoli for overwintering on/underneath – hold until May.
Now, we introduce the some of the major broccoli pests and their natural enemies: The following is a brief overview of the life histories of imported cabbageworm, diamondback moth, and their parasites. All pests that attack broccoli attack other crucifers.
Since broccoli is an introduced vegetable, most of its insect pests originated in Europe or are polyphagous species native to the U.S. [e.g., cabbage looper]. The major caterpillar pest complex of crucifers in the United States generally consists of the cabbage looper, Trichoplusia ni (Lepidoptera: Noctuidae), the imported cabbageworm, Pieris rapae (L.) (Lepidoptera: Pieridae), and the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae). The rank of species importance generally varies with latitude. In the more southern areas of the U.S.A., cabbage looper ranks as the primary pest, followed by imported cabbageworm and diamondback moth. In the more northern latitudes, cabbage looper populations become more variable (dependant upon winter mortality) and imported cabbageworm becomes the dominant species.
The biology of imported cabbageworm, diamondback moth, and cabbage looper in nearby southwestern Virginia has been studied in detail. Imported cabbageworm and cabbage looper were the predominant injurious species of unprotected cabbage in southwest Virginia in 1981 and 1982; imported cabbageworm was the major pest of unprotected cabbage in this same area from 1982 to 1984. Cabbage looper was the most injurious lepidopterous pest of broccoli in the southern Piedmont area of Virginia in 1985 & 1986 and the cabbage webworm Hellula rogatalis(Hulst) (Lepidoptera: Pyralidae), was most abundant in 1987.
B. Life Histories:
1) The Imported Cabbageworm (ICW), Pieris rapae (L.) (Lepidoptera: Pieridae)
(PHOTOs of egg, larvae (instars 1 through 5), pupa, and adult butterfly.
The imported cabbageworm, was first discovered in North America in 1860, when a single adult specimen was captured in Quebec. Nearly thirty years later, imported cabbageworm had spread north to Hudson's Bay, south to the Gulf of Mexico, and west to the Rocky Mountains. It now occurs throughout most of North America. The imported cabbageworm overwinters as a chrysalis in or near cruciferous crops. In Virginia, the adults emerge in March. Mating and egg laying occurs within 24 hours of emergence. Eggs are laid singly on the underside of the outer leaves of the host plant. Hatching occurs in 4 to 8 days. The larvae pass through 5 instars in 12 to 33 days and then form a chrysalis. Adults emerge in 8 to 20 days and have a life span of approximately three weeks. Female imported cabbageworm butterflies generally lay 200-300 eggs. In southwestern Virginia, the imported cabbageworm has 2-3 generations per year on cabbage. In the piedmont of North Carolina ICW has 5-7 generations per year.
1.a. Cotesia glomerata (L.) (Hymenoptera: Braconidae)
Cotesia glomerata (L.) (formerly Apanteles glomeratus) was the most common larval parasite of imported cabbageworm in southwestern Virginia. It attacks the first three instars of imported cabbageworm, ovipositing 20 to 50 eggs per host. Parasite larvae emerge en masse from the late fifth instar, and spin characteristic yellow cocoons. You will see masses of yellow cocoons on brassica leaves – a good sign.
1.b. Pteromalus puparum (L.) (Hymenoptera: Pteromalidae)
Photos of wasp adult, stinging chrysalis, parasitized chrysalis, parasite larva in broken open chrysalis.
P. puparum was accidentally introduced into the United States in the late 1800's It is the most common parasite of imported cabbageworm in southwestern Virginia. In surveys conducted from 1981-1984, parasitism of imported cabbageworm by P. puparum in southwestern Virginia was greater than 50%. P. puparum is a gregarious internal parasite of the imported cabbageworm, attacking the newly formed pupa. Larvae develop within the host and emerge as adults through a small hole cut in the pupal case.
2. Diamondback Moth: Plutella xylostella (L.) (Lepidoptera: Plutellidae)
Photo; Moth, eggs, larva, pupa, adult
The diamondback moth, is a cosmopolitan species, apparently originating from the southern Palearctic region bordering the Mediterranean Sea. It overwinters in the pupal stage, with adults emerging in early- to mid-May. Mating occurs at dusk on the day of emergence and lasts about one hour. Egg laying begins shortly after dusk and reaches its peak about two hours later. Eggs are oviposited singly or in small groups (two to eight), mainly on the upper surface of the host plant leaves. Hatching occurs in four to eight days. The larval period varies from 9 to 30 days, during which the larva passes through four instars. The mature larva constructs its cocoon typically on the lower leaves. Adults emerge in 5 to 15 days. The life span of the adult averages two weeks and during that time the female oviposits an average of 159 eggs. In Virginia, three generations of diamondback moth are known to occur on cabbage; however, the potential for more generations exists in areas of southwestern Virginia or the Carolinas where cabbage is in continuous cultivation or wild cruciferae are present.
2.a. Diadegma insulare (Cresson)(Hymenoptera: Ichneumonidae)
Photos; adult, adult stinging caterpillar, wasp pupa inside moth pupal case.
D. insulare (=insularis), is the major parasite of diamondback moth in Virginia. The female attacks diamondback moth larvae, especially the later instar larvae. A solitary parasite emerges from the prepupa shortly after the host has spun its cocoon. This parasite can control diamondback populations.
3. Cabbage Looper: Trichoplusia ni (Hubner) (Lepidoptera: Noctuidae)
The cabbage looper is the predominant southern pest of unprotected crucifers like broccoli. It is mainly a late season pest in northern climes. In mild winters, this insect can become a significant pest even in northern climes. During harsh winters, this insect cannot survive and must migrate up from the south in during the late spring/early summer to reestablish populations.
The cabbage looper has several specific natural enemies. Trichogramma species attack the egg stage; a parasitic fly named Voria ruralis attacks the larval stage and there are several parasitic wasps that attack the larva.
4. Harlequin Bugs/ Stink Bugs
Harlequin bugs are brightly colored orange and black bugs with some white spots. These bugs are problems wherever crucifers are grown continuously. There needs to be an interruption of the crucifer crop in order to reduce populations of these bugs. One of the best ways to control bugs is by using a trap crop. Our field experience has shown that harlequin bugs are attracted to mustards and radishes. By monitoring a trap crop of these plants alongside the regular crop, you can see whether harlequin bugs are present. If they are, then a soap spray on the trap crop will kill them. Also squish or spray their egg masses – they are usually found on the same plant as the adults. There are egg parasites of the bugs that would be good to establish. More work needs to be done in this area.
1. Bacillus thuringiensis Berliner
Microbial photo of Bt with sporulation crystal, dead caterpillar on leaf, dead parasite larva inside a dead caterpillar.
B. thuringiensis is a gram positive, spore-forming bacterium, which is very pathogenic to a large number of lepidopterous larvae. Different caterpillar species exhibit varying responses when fed these crystals and/or B. thuringiensis spores. The imported cabbageworm is highly susceptible to B. thuringiensis in both the field and laboratory.
We use OMRI approved Bt products; there are also some very effective viral products that work well on caterpillars and would be recommended in rotation so that resistance to Bt is minimized. Example – Gemstar – attacks Helicoverpa (Heliothis) larvae; also CLV – Certis product active against loopers, earworms and budworms.
Weeds – best weed control is suppression, hoeing ($300/acre), no tillage. Our common weeds are lambsquarters, pigweed, hairy gallasoga, bindweed, and some grasses.
The main diseases we have encountered are:
Seedlings in flats – Rhizoctonia – causes wire stem – plants grow slowly and never perform. Usually caused by lack of healthy microbs in flats/soil. We want a mix that is FULL of microbes - the friendly kind about which I write under the Soil section. The mix should either contain about 10% by volume Worm Castings, or anywhere from 10 to 75% by volume of a high quality compost. These will provide millions of friendly bugs that will tend to occupy the root surface and tend to exclude the bad guys. Anaerobic conditions in the float water can also do this, so be sure to completely change out plastic and water between seasonal crops.
Field Plants – Black Shank – Sclerotinia – caused mainly by monocropping crucifers in the same field – prohibited under Organic Standards. With proper composting, you can suppress most diseases. We are currently examining no-till systems for weed and disease suppression.
No-tillage (NT) systems. No-till systems for production of cabbage and broccoli have been developed in recent years by Dr. R.D. Morse at Virginia Tech that enable high crop yields without application of herbicides. During the past decade, extensive research and field experiences have shown that, to successfully produce NT, no-herbicide broccoli and other transplanted crops, growers must (1) properly establish and manage high-residue (6-10 t/ha) cover crops and (2) use transplanters that can effectively set transplants in high-residue in situ mulch, and precision place in-row organic fertilizer and install in-row drip tubing with minimum disturbance of surface residues. Advantages of NT systems (compared with conventional plow-disk systems) include conservation of soil and water, increased yields, improved soil quality, and weed suppression.
Harvest - When to harvest? Market may dictate preferred head size. Like tight, bunched heads. IF YOU CAN LET THE FLORETS GET TO THE SIZE OF POPCORN KERNELS; YOU’VE MAXXED HARVEST WEIGHT. Medium sized heads are best – too large or too small can be a problem. Try to harvest away from the heat of the day. Otherwise, you must hydro-cool the head to get the field heat out of it. When in doubt, invoke the ‘popcorn rule’.
Ice and hydro-cooling – ice, ice and more ice - access to massive amounts of flake/cube ice a must. Get ice machines. Tubs to cool harvest. Wash heads if you find insects; insects will fall out of ice slurry if broccoli is left in tub for about 15 minutes or so.
Packing/boxing – custom boxes – 20 pounds of broccoli/box. $1/apiece for broccoli boxes.
Storage – walk in cooler set at 34 degrees; reefer and park on site.
Transport – cooler to transport or use silver tarp, insulation board, and protect from wind. Use a truck camper shell or equivalent.
Most crucifers like broccoli, cabbage, cauliflower, kale, etc. can naturally withstand a certain amount of cold weather. By blocking the wind and cold from these plants, you can dramatically increase the season of these plants. They will grow well during the winter in cloches, or even hoop houses.
P.O. BOX 1555, VENTURA, CA 93002
800-248-2847 (BUGS) * 805-643-5407 * FAX 805-643-6267
RINCON-VITOVA'S Beneficial Blend Seed Mix
Beneficial blend is a seed mixture produced by Lohse Mill that yields a wide variety of plants known to harbor beneficial insects. One method of attracting predators and parasites is to provide a food source such as some aphids. Providing nectar, pollen and/or a little aphid honeydew also increases longevity of beneficials and may improve their reproduction.
Many of the components of Beneficial Blend's grain, legume and flower seed mixture are very susceptible to insect pests--this keeps pests off the nearby crop concentrating the food source for beneficials. Some of the plants used are also susceptible to common plant diseases, however the stand is never affected all at once. Beneficial Blend has a certain amount of tall plants, such as cereal rye grain and mustard, to catch aerial spiders and provide structure for webs.
Eighteen Diverse Plant Species that Bloom Sequentially: Cereal rye grain, barley, subclover*, common vetch, yellow blossom sweet clover, white blossom sweet clover, crimson clover*, LM 331 alfalfa*, mustard, carrot, coriander, baby's breath, buckwheat, baby blue eyes, bishop's flower, fennel, celery white yarrow, sweet alyssum.
*All small legume seeds are inoculated with Rhizo-Kote to assure effective nitrogen-fixing nodulation.
Tolerates and Improves Most Soil Types: Rincon-Vitova's Beneficial Blend has excellent drought resistance and tolerance for variable, low fertility soils with high or low pH and non-tillable, compacted soil. It is good for soil building and erosion control.
Planting Instructions: A light planting rate of 10 lbs/acre will establish 2-4 plants of each species on a square foot. In orchards and vineyards only one row of the Blend out of every 8-10 rows is needed to provide the beneficials a place to live where the planting will not be disturbed or mowed.
In field crop situations Beneficial Blend should be planted on the borders and row ends as a barrier to incoming pests. A program for pest management with cover crop interplantings is described in a new manual "CEC Naturfarm Conversion Project: IPM Using Pest Break Strips for Insect Pest Management."
The Beneficial Blend should be planted 1/4 -1/2 inch deep in a good , fine seedbed since many flower and herb seeds are small. Broadcasting and ring rolling or using a brillion seeder are preferred methods of planting. Drilling is the next best method, ensuring that the small seeds are not planted too deep. Fertilizer should be applied on infertile soil types, such as sand or shale. On loam soils fertilizer is not necessary because the objective is a diversity of plants and not an abundance of plant material. Planting dates are between October 1 to November 15.
Management: After planting, Beneficial Blend is not normally mowed or disced. It will sometimes have a sparse weedy appearance as different plant species flower and mature during the season. Partial mowing might offer some advantage in concentrating beneficials and also reducing woody material, which sometimes attract a lot of lygus bugs. Mowing or discing should always start farthest away from the Beneficial Blend row and mow or disc toward the row over a period of several days. This allows time for the mower to herd insects into the blend rows for protection. At least half of the planting should always be left to stand as tall as possible, unless the planting interferes with cultural operations or harvest.
A well-established stand will reseed and can last several years, which will add vigor to the perennial and biennial plants in the blend. Irrigation is desirable to extend the period of bloom, however a dry land planting will also be productive until it exhausts the soil moisture.
Evaluation and Testing: The components of Beneficial Blend were planted at Kearney Agricultural Center of the University of California and vacuum collections indicate high populations of insects and beneficials. Dr. Robert Bugg and others from the Sustainable Agriculture Program have established the value of many of the plants in the mix. Dr. Bugg's recommendations are followed in each year's upgrade of the formulation.
Altieri and Schmidt, "Cover crops affect insect and spider populations in apple orchards". Cal. Agriculture, Jan-Feb, 1986, pp 15-17.
Bugg, "The Ecology of Cover Crops," 1994. UC-SAREP, Davis, CA FAX 916-752-8550.
Dietrick, Phillips and Grossman, "CEC Naturfarm Conversion Project: IPM Using Pest Break Strips for Insect Pest Management," 1995. Nature Farming Research and Development Foundation, Lompoc, CA. FAX 805-736-9599.