Late Season Production Meeting, 13 August 2010 Lygus IPM · Late Season Lygus Management August 13, 2010 Ellsworth 17 Ellsworth/UA 2005 - Orthene97 (1.0) 05F2L-P74 05F2L-P74 Orthene

Late Season Lygus Management August 13, 2010

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When is ‘Done is done?’Making late season insect control

decisions

Peter C. Ellsworth

Arizona Pest Management Center /Department of Entomology

University of Arizona

Late Season Production Meeting, 13 August 2010

We tend to focus much of our attention on when toinitiate controls of our pests. However, much moneycould be saved by smart decisions about when toterminate controls. When is ‘done is done’?

This presentation will focus on Lygus including thebackground research that supports new guidelinesdebuting here today. However, equally important aredecisions about when to terminate controls ofwhiteflies. However, this subject is a little morestraightforward and for once, depends much on thecalendar and your prediction on when green leaf dropwill occur in a given field. The goal is to insure thatwhiteflies are prevented from developing when thereis much vulnerable lint exposed prior to green leafdrop. Longer terms (!30 d), Stage I materials aregood choices; shorter terms, other materials might fitbest.


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Lygus IPM

For today, we’ll focus on Lygus, and everything wecover will fit within one building block of our IPMpyramid, Lygus Action Thresholds. However, by thetime I finish this topic, I think you will agree thatthere is an awful lot that goes into this building blockand that there is an extensive dialog that must occurbetween grower and PCA in order to arrive at theoptimal / best solution.


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Plant-Pest-Pesticide

Interactions

SamplingDensity:Damage

Biology & Behavior

EfficacyCost of Control

Returns ($)

Plant DynamicsYield & Quality Losses

Compensation

This topic is influenced by a 3-way interaction ofplant, pest, and pesticide. By the time a solution isformulated, a grower and PCA will need to considerthe plant’s development, potential for yield loss andcompensation; the number of Lygus present, thedamage they cause, and the timing of their entry andeventual exit from the cotton field, which occursnaturally each year as adults retreat and stopreproducing for a time; as well, the efficacy and costsof various controls and what potential returns oncontrol investment are possible.


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Plant Dynamics

Hanan, 1996

• Indeterminant growthhabit

– Susceptible plant parts at alltimes

• Redundancy

– 50% final fruit retention

• Compensation

Cotton is an incredibly dynamic plant. It is essentiallya perennial grown as an annual. As such, it has anindeterminant growth habit. This means that thereare plant parts susceptible to Lygus and other insectsat all times. We also know that there is muchredundancy in the plant machinery and a greatcapacity for compensation even under shorterseasons.

Well-fruited, maximally yielding plants will often onlyexpress final fruit retentions of 45-55%. This tells usthat physiologically, Lygus present or not, a plant willnaturally shed about half of the fruiting positions onthe plant.


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Fruit Loss• Spatial pattern of

fruiting changes

– Increased dependence ondistal sites

• Delayed fruiting shiftsproduction

– Climate, environmentmay be more or lessfavorable

• Carbon, Nitrogendynamics change

– Increased capacity forassimilation (leaf area)

– Increased storagereserves (stem)

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89 1011

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Nevertheless, fruit loss due to Lygus or other factorscan be very serious. In this example, it was 12 morefruiting branches before the first boll was set, due tothe extreme Lygus pressures through most of theseason.

Lygus attack developing squares (flower buds),causing them to shed from the plant withoutdeveloping into a boll (the source of the marketableyield, lint and seed). This disruption of fruitingchanges how yield is distributed on the plant, delaysproduction, and changes resource (C & N) use.


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Yield & Quality Effects

• Large gaps, disruptedC & N balances

• Result in taller plants

• Difficult defoliation

• More leaf trash

• Lower lint fraction

• Poorer quality

Lygus damage affects the pattern of fruiting to suchextent that large gaps can sometimes be created.These gaps represent disruptions to the allocation ofcarbohydrates. Where normally, carbohydrates areshunted to the boll sinks, now they are redirected tothe growing tip of the plant, making for a taller plant,one that is more difficult to defoliate (also because ofdisrupted / excess N-balance). This leads to more leaftrash in the harvest, which in turn, lowers lintturnouts and produces lint of poorer quality.

These are effects above and beyond the major yieldloss possible when Lygus densities are high andpersistent.


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Sulfoxaflor UTC

The good news is that there are and will be goodproducts to help control Lygus efficiently.

Here is an example of a new, experimental compoundsprayed to control Lygus adjacent to a an UntreatedCheck (UTC). Note the large difference in boll load(yield) and the differences in height of the crop.

Registration of sulfoxaflor by Dow is expected in2012.


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Carbine UTC

Carbine, registered 5 years ago, has continued toperform outstanding in control of Lygus andprotection of yield.

However, over-reliance on this single compound is ofconcern as well, because of the potential forresistance development. Belay, registered this yearby Valent, is a neonicotinoid with excellent Lyguscontrol potential. While not a main whitefly controlproduct, Belay will also reduce whitefly numbers andfits well as a rotational alternative to Carbine inArizona cotton.


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UTC-LygusOberonEndigo

Leverage360HAgriFlex

Leverage360LHero

AgrimekBAS320

EXP32R1Orthene

CarbineLoBelay+Orthene

DiamondMedBelayMed

DiamondHiDiamondLo

Diamond+CarbineBelayHi

EXP32R2C-V-O

EXP32R4EXP32R3

CarbineEXP32R5

0 0.5 1 1.5 2 2.5 3

Yield (Bales / A)

Here are the Carbine containing treatments. Note thevery low rate (1.7 oz) of Carbine is too low for thiskind of pressure. But also note the extreme Lyguspressure that reduced yields 5-fold to less than 0.4bales / A in the UTC. Carbine, sulfoxaflor, and Belayled the trial.


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Cotton Lygus Insecticides

Acephate

Endosulfan

Flonicamid

57

Acephate

Endosulfan

Flonicamid

91

66%

81%

2008 2009

In a random survey of central Arizona cotton fields in2008 and 2009, we can see this pattern of cottoninsecticide use.

Two thirds of the sprays targeting Lygus wereCarbine in 2008 and grew to 81% in 2009! This hasbeen at the expense of the cheaper, but much morebroad spectrum insecticides, Orthene and Endosulfan.


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Cotton Lygus Insecticides1st Use

Acephate

Endosulfan

Flonicamid

35

Acephate

Endosulfan

Flonicamid

45

87% 91%

2008 2009

Our guidelines specifically suggest using Carbine firstagainst Lygus as a way of deferring the use of anybroad spectrum insecticides.

Your industry has embraced this approach with 87%of Lygus 1st sprays being Carbine in 2008 and 91% in2009!

Of course the risk remains that we could over-rely onthis single class of chemistry for Lygus control. In2010, the availability of Belay gives growers arotational alternative to Carbine where Lyguspopulations require multiple sprays over time.


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Lygus Management Studies

• First opportunity for field studies usingselective controls for PBW (Bt cotton) &whiteflies (IGRs)

A real-world experimental example. By using Btcotton to control pink bollworm selectively (andhaving no effect on Lygus) and by using whiteflyselective IGRs, we were able to isolate the controlsystem just to the pest of interest, Lygus. Historically,it is rare to be able to isolate on one pest’s action in afield situation. Consider that 40 years ago in AZ andin CA, growers, ag-chem suppliers and academicscientists vociferously debated whether Lygus was apest or not! But also consider, there were many pestsat that time that required sprays including bollweevil, pink bollworm, bollworm/budworm, evencotton leafperforator. As a result, it was very difficultto parse out the impacts of each in the system. Not sohere, where we have had the first ever opportunity toexamine Lygus-specific effects in this system.


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Adults fly; Nymphs don’t

00F3threshold

First some important biology:

We all know that only adults have wings andtherefore only they can move any significantdistances. In fact it is unlikely that nymphs moveacross or down rows very much. They are plant-bound.

This is an aerial photograph of my 2000 Thresholdstudy. In the outlined area you can see severalborders of cotton each with 3 harvested strips takenfrom them. However, in addition to the 3 dark stripesdown each border, we can also see some darker areasof growth.

This is photographic evidence that adults are notmajor damagers of cotton. If they were…


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UTC

Adults fly; Nymphs eat!

We would expect a halo of damage (as drawn in onplot in center) to develop around these UTC plots dueto the frequent movements of Lygus adults fromthose plots. However, the demarcation betweenunprotected v. adjacent protected areas is distinct.This indicates damage by a plant-bound life form,nymphs. Lygus were well-managed in all areasaround these untreated plots. Yet, no pattern ofdamage occurs around these UTC plots.

Indeed, adults do move and probably do eat as well,but comparatively they are in this world to move andreproduce, whereas nymphs have one objective inlife, to eat and grow.

So nymphs have become the basis for development ofour threshold system.


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0 Sprays3 Sprays

Note height difference

As further evidence, these effects occur over theshortest spatial scale. That is in adjacent rows, shownhere in a commercial trial where cotton was sprayed3 times on the left for Lygus and not at all on theright. The height and eventual yield differences wesee are as a result of Lygus feeding and damage, asthese plots were planted to Bt cotton and all otherpests were selectively controlled.


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2005 - UTC05F2L-P75

05F2L-P75 UTC

Now consider the control system:

From a ground view, one can see the UTC and howtall the crop is (over my head), and how even the lateproduction failed to result in opened, harvestablebolls (delayed maturity effects). See the green(unopened) bolls on top.


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2005 - Orthene97 (1.0)05F2L-P74

05F2L-P74 Orthene 1.0 + Penetrator

In contrast, the adjacent plot of Orthene is muchshorter and comparatively well-loaded withharvestable yield.


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Seasonal Densities : Yield

Let’s review the threshold information starting withan examination of seasonal densities of Lygus lifestages vs. yield. Our goal has been to find arelationship where bug numbers are “predictive” ofyield. For adults there are examples of 25-30 adults /100 sweeps being related to 1 bale / acre yields atone end, and related to 3 bales / acre at the otherend. This is NOT a good basis for developingthresholds that support decision-making.

Nymphs / 100 sweeps show a good relationship toyield, supporting the importance to monitoring theirnumbers.

Note “R2” pronounced R-square is a measure of fit ofthe line (or curve) to the points or data it isestimating. The higher the number (closer to 1), themore “perfect” the fit.


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Yield : Density

• Regression ofstandardizedyields from twoyears

• Excellent fit

After two years of study, we conducted regressions ofstandardized yields using a 2nd degree fittedpolynomial (quadratic). The fit was excellent…


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Yield : Density

• Regression ofstandardizedyields from twoyears

• Excellent fit

• Maximum Yield @1.7 nymphs / 100

From this relationship, we can examine the point ofmaximum yield, which occurred at 15 total Lyguswith ca. 1.7 nymphs per 100 sweeps. Of course, yieldis only partly the answer,…


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Revenue : Density

• Regression ofstandardizedrevenues from twoyears


To understand the point of diminishing return, wedeveloped this regression that shows the relationshipbetween standardized revenues and our testedthresholds.


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Revenue : Density

• Regression ofstandardizedrevenues from twoyears


• MaximumRevenue @ 5.2nymphs / 100

Following this curve to its maximum, we see thatmore money is made when a threshold of 15 totalLygus with 5.2 nymphs per 100 sweeps is observed.Furthermore, this basic relationship held up under ahuge variety of cotton economic conditions ($0.20-1.20 / lb). So these studies have given rise to ourcurrent recommendation which is intentionally set tobe somewhat conservative to guard against excessiveyield loss and to accommodate the normal time-lagbetween sampling, decision-making, andimplementation of the action (spraying)…


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Quality, Impact of Compensation

• Revenue did notconsider risks toquality

• Micronaire ~ fiberthickness (>5 =discounts)

• 1 grade lower inseverely damagedcotton

4.84.8 4.74.7 4.94.9 55 55 5.55.5 <== micronaire<== micronaire

Quality was not modelled. But the relationship shouldprotect any quality loss (high micronaire), too.

Micronaire relates to the thickness of the fiber.Generally, micronaires higher than 5 are undesirable.


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‘15:4’ Threshold Recommendation

100 sweeps

This so-called ‘15:4’ threshold represents 15 totalLygus per 100 sweeps with at least 4 nymphs per 100sweeps. I should add here that a 15 inch sweep-net isa standard method used by our consulting communityin Arizona.


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When to stopspraying?

• Plant factors?

• Bug factors?

• Season?

Threshold work is not done, however. Once athreshold is established, at a minimum, one has toconsider under what conditions should spraying bestopped. Decision-making could potentially be basedon plant factors, bug factors, or elements related tolength of season remaining (an environment byvariety interaction).

In fact, information in all 3 areas are needed to makethe best decisions.


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Cotton’s Fruiting Curve

NAWF = 5

This is a graphical depiction of Cotton’s Fruiting Curveexpressed as blooms per unit area over time (HUs).In AZ cotton, we do have the capacity in somevarieties to grow a second or true top crop after cropcut-out. Some growers manage irrigations to matureout the primary fruiting cycle only, while others electto continue irrigations to mature out the top crop.

So experimentally, we set-out to examine 4 differentLygus chemical control termination timings centeredaround initiation of cut-out, where cut-out is definedas NAWF " 5. (NAWF = Nodes above upper-most,first-position white flower, a standard measure ofcotton phenology).


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Lygus Termination Studies

• Obj: Determinetiming of lasteffective spray

• Compare 12 differentproduction scenarios(3 x 2 x 2)

– Variety (E, M, F)

– Planting (Opt., Late)

– Irrigation termination(Opt., Late)

Given this 3-way interaction, it is important toconsider different production scenarios that influenceseason length and fruiting potential. So we looked at12 production scenarios in a factorial arrangement ofvarieties (early-, medium-, or full-season), plantingdates (optimum or “early”, and late), and irrigationtermination (optimum or “early”, and late).

Our objective is to determine the timing of the lasteffective spray for Lygus.


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Medium Maturity

We must consider the plant damage dynamics:

For a “medium” maturity variety, the fruiting curvelooks like this. We can take a width of the base ofthat curve aligned with the timing of initiation of cut-out as a measure of risk or period of vulnerability toLygus damage.


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Early Maturity (Short)

An early maturity variety, fruits more quickly andmore compactly, with little to no capacity to “comeback” and produce a true top crop. Note the width ofthe curve.


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Late Maturity (Full)

Full season varieties have the greatest potential for atop crop but fruit somewhat later and longer than theother types.

In general, full-season varieties, which grow over alonger period, have the highest yield potential(assuming no losses to pests) and early maturing orshort-season varieties have the lowest yield potential(but also the shortest period of vulnerability).


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Duration of Exposure

S

M

L

So just the choice of variety could impact the relativeduration when flowering plants are present andvulnerable to Lygus attack.


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DP555BR

14 May

Last Irrigation

1 September

Last Irrigation

16 September

Full Season / Late Planted

H a r v e s t e d H a r v e s t e d

Just to give a sense of how the experimental fieldwork was done, this is how the trial looked in thefield for one variety and one planting date.

Average yields (bales / A) for DP555BR planted late(14 May 2005) and irrigated late (left, 16 September)or optimally (right, 1 September) showing 1 replicatewhere Lygus were sprayed 5, 4, 0, or 2 times (front toback). Each subplot is 6-rows wide with the 4 centerrows already harvested; compare middle two rows.


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DP444BR

14 May

Last Irrigation

1 September

Last Irrigation

16 September

H a r v e s t e d H a r v e s t e d

Short Season / Late Planted

In this case (2005), we are looking at a 12-row wholeplot of a short-season variety, DP444B/R, that wasplanted late (14 May). This shot is after our machineharvest of the two subplots. So 4 of 6 rows wereharvested out in each case where irrigations werestopped earlier (on the right) or later (on the left).The numbers you see represent the total number ofLygus sprays made to these plots. Yields were good inthe 2-spray plots, not statistically better in the 4-spray plots, and off 1 whole bale in the UTC. You caneven see the darkened area where the UTC was muchmore rank than the surrounding cotton. Note, too,that this short-season variety did not respond to theadded water.


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03F4LT

12 Production Scenarios

So let’s look at the yield data (in bales / A) for these12 production scenarios, early planted for the 6 cellson the left and late planted for the six on the right.Yields are plotted for each lygus termination timingand the number of sprays are shown above; for thetwo irrigation termination timings, either with morewater (on left) or less water (on right) sides of eachcell.

As we reveal each cell, you can see how yieldpotential was consistently greater as we adopted amore normal planting date and as we moved to moredeterminant (shorter season) varieties.


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Yield : NymphsRelationship

03-05LT

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ns ns 0.40 0.28 0.76 0.74 0.82 0.69 0.74 0.74 0.92 0.84R2

!

In 2005, we hit yields as high as 4 bales and as low as0.5 bales. And the yield : nymph relationships held upwith very high degrees of fit. Wherever seasonalnymph densities were high, yields were low; andwhere nymph densities were low, yields were high.

Of course, yields are only part of the answer. We needto look at revenues as well, broken down byproduction scenario. These data are complex andbased in “bug” factors, plant factors, the season andof course economics.


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$ Compensation $

$

$$$

$

$

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$

$

$

0.75

Lygus control termination guidelines are presentedhere as a family of curves for one cotton price (75¢).We also assumed ca. 17$/lygus application and 12$ /late season irrigation — the absolute returns areaffected by these latter two variables, but thedecisions within a line do not change as a result.

For these parameters, the ultimate best pay-off pointvaries by planting date, variety and irrigationtermination timing. Early season varieties plantedearly saw no economic benefit of controlling Lygus.However, planted late and irrigated late (darkershades), the early season variety should be sprayeduntil LT4 (= ca. one week after initiation of cut-out).

The decisions are in fact very dynamic!


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What’s the right decision?

NAWF = 5

Grower Facts8/7/07

ST4554Planted in AprilGood fruit loadNo prior sprays

NAWF = 5-617:8

So what happens in the real world? Here are a set ofgrower facts. What would you do? Spray or not?[Think of ST4554 as a medium to full season maturityvariety; and April as a timely, early planting].


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Grower DemonstrationKevin Rice, Pinal Co. Agent

Let’s find out what should have happened by splittingthe field in half and treating one side and leaving theother alone.


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$ Compensation $

$

$$$

$

$

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$

$

0.75

This variety is a bit between medium and full season.As a full season variety (blue lines) not carried latewith extra irrigation(s) (light blue line), the propertermination timing would be LT3 (green circle) orwhen the crop is at NAWF ~ 5.

[As a medium maturity variety (purple line),irrigations terminated normally (lighter shade),cotton should not benefit by these late Lygus sprays.However, as cotton prices go up 85–90¢, as they aretoday, the decision to terminate sprays advances toLT3).


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What’s the right decision?

Grower Facts8/7/07

ST4554Planted in AprilGood fruit loadNo prior sprays

NAWF = 5-617:8

Carbine Spray8/9/074595 lbs

UTC4392 lbs

203 lbs increase32%T.O. @ 50¢

33$ return

The spray returned over 200 lbs of seedcotton. At32% turnout to lint, that is about 65 lbs of lint. Evenat 50 cents / lb, the grower made about 33$ morewhere he sprayed. What did the spray cost? In thiscase, probably about $17.

Was the spray a good choice? An investment of $17that returns almost double that is in fact an excellentinvestment. But in the world of Lygus, that is only asmall savings as compared to a miss-timed mid-season spray when even larger potentials for lossexist. This decision was truly on the edge ofprofitability, but clearly it was a better decision tospray.


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2010 Lygus Demo’s

$

$$$

$

$

0.75

2 AugustDP1044

Well-fruitedYuma Co.

No previous spraysPlans to terminate optimally

NAWF ~ 3

Spray or No Spray?14:1

1 Week later,NAWF ~ 2.5Lygus, 4:1

In another example (Yuma, 2010), a full-seasonvariety was planted timely (Early, blue line) andirrigations projected to be timely (light blue) so as tofacilitate rotation of the ground to vegetables. Hereagain the last effective spray should be around LT3 orNAWF ~ 5.

In this case NAWF was already well less than 5,probably at least one week beyond the cut-off point.

Should he spray? Probably not. Besides, there werenot threshold numbers present to begin with. Lyguswere only 14:1 instead of 15:4 or higher. At this stageof growth and population levels, adult Lygus willleave a field seeking more vigorously floweringagricultural fields. In fact, one week later Lyguslevels continued to decline naturally.


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2010 Lygus Demo’s

$

$$$

$

$

0.75

27 JulyDP164

Good fruit retentionPinal Co.

No previous spraysPlans to terminate late

NAWF ~ 4.4 & 5.1Lygus, 17:6 & 14:5

Spray or No Spray?

In a central AZ example, the grower was growing afull season variety (blue line) and intending to carry itvery late (dark blue line) to maximize yield potential.This shows that LT4 or about 1 week after cut-out isthe appropriate termination timing for Lygus controls.

Should he spray? His NAWF for 2 different fields wereclose to 5, and Lygus were near or over threshold inboth cases.

He did elect to spray. In fact, 20 days later hemanaged to turn the plant development around (adifficult thing to do as a crop approaches cutout) andNAWF was now 5.5 (16 August) and Lygus wereagain at threshold. The decision was to spray onceagain because NAWF > 5.


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Carbine UTC

So again, effective products are needed, but theknowledge about when to use them effectively iscritical to squeezing out the maximum profits fromcotton production. Carbine remains an important andfully selective (safe on beneficials) product to useagainst Lygus (and even late season aphids).


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LygusSample adults &

nymphs per100 sweeps

‘15:4’ – ‘15:8’actionthreshold

Use Carbine asselective 1stoption

Terminate basedon guidelinesfor plantingdate, variety &irrigation plans

UTCProtected

Our guidelines for Lygus control are based insampling both adults and nymphs in 100 sweeps perfield, in observing research-tested and commerciallyvalidated thresholds, and in responding with Carbineas the first selective option for control of Lygus thatextends the period over which beneficials contributeto overall pest management.

These most recent guidelines provide research-basedinformation on how to decide when to terminateLygus controls based in planting date, variety andirrigation plans.

Representative plants (2) from the Carbine (2.8 oz) plot on the left v.the same from the UTC from our 2005 trial. Photo credit: John Braun.


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Blo

om

s p

er

Are

a

Heat Units After Planting (86° / 55°F)

PrimaryFruitingCycle

‘Top’crop

cut-out

Bt CottonEradication

Stage I: Fully SelectiveStage II: Partially Selective

Stage III: Broad Spectrum

Fully Selective: Carbine

Broad Spectrum Insecticides

Secondary pests heldunder natural control

Partially Selective: Belay*Broad: Orthene, Vydate

DiscontinueLygus sprays@ NAWF ~ 5

0 3000 HUAP1000 2000

Technology Use Plan

15:4

Our overall technology use plan for cotton looks likethis. It emphasizes selective approaches to thecontrol of our three key pests supported by well-defined sampling programs and decision-making.Sprays for whiteflies depends on sampling of adultsand nymphs and implementation of chemical-usestage-specific thresholds. For Lygus, adults andnymphs are also measured. Sprays are madeaccording to a two-component threshold. Additionalsprays are made as needed when Lygus areincreasing and above threshold, but discontinued at atime in crop development based on variety, plantingdate, and irrigation plans. Carbine is a good 1st useproduct; Belay is an excellent rotational alternative(our non-target assessments are still pending); andthe broad spectrum materials are still available foruse.

Documents

Late Season Production Meeting, 13 August 2010 Lygus IPM · Late Season Lygus Management August 13, 2010 Ellsworth 17 Ellsworth/UA 2005 - Orthene97 (1.0) 05F2L-P74 05F2L-P74 Orthene