Kehilangan hasil dan cara

pengukurannya

Ambang ekonomi

Pemantauan Perkembangan OPT

• Pengamatan terhadap kemunculan suatu OPT

di suatu wilayah perlu di monitor dari waktu

ke waktu dengan interval tertentu tergantung

: tingkat tumbuh, jenis tanaman, daur hidup : tingkat tumbuh, jenis tanaman, daur hidup

OPT yang diamati, tujuan pengambilan

sampel, faktor cuaca, dll.

• Pengamatan dilakukan pada sampel tanaman

yang dipilih mengikuti ketentuan secara acak

atau secara sistematik

Pengngambilan sampel

pengamatan

AcakBukan sampel

Sampel pengamatan

Sistematis

Pengambilan sampel secara

Sistematis rbagai bisa mengikuti

Berbagai pola, misalnya sigsaz,

Pola huruf X, pola melingkar dsb

Pengukuran Kerusakan karena OPT

• Tingkat kerusakan tanaman akibat hama

dikenal dengan intensitas serangan atau

intensitas kerusakan,

• Besarnya intensitas serangan dinyatakan • Besarnya intensitas serangan dinyatakan

dengan persen.

• Untuk tanaman yang bernilai ekonomi tinggi

dan kerusakan yang terjadi bersifat fatal atau

sistemik menghancurkan produknya maka

perhitungan kerusakan dilakukan dengan

rumus

• I = n/N x 100• I = n/N x 100

I : intensitas serangan OPT

n : Jumlah tanaman yang terserang

N : jumlah total sampel tanaman yang diamati

Tanaman dengan kerusakan yang dapat diperkiraan

dengan skor atau nilai numerik, contoh:

Skor % Kerusakan Keterangan (misalnya utk bercak daun)

0 0 Tidak ada yg rusak

1 < (=) 10 Luas bercak daun selebar ± 10% dari helaian daun

2 10 - 20 Luas bercak daun selebar 10-20 % dari helaian daun

3 20 - 40 Luas bercak daun selebar 20 - 40 % dari helaian

daun

4 40 - 70 Luas bercak daun selebar 40-70 % dari helaian daun

5 > 70 Luas bercak daun selebar > 70 % dari helaian daun

atau tanaman mati

Contoh Skor

01 2 3 4

5

0% 5 %

10%40% 70% !00 %

Skoring terhadap gejala layu

0 1 2 3 4 5

0 : tdk bergejala 4 : 8 – 15 daun layu

1 : 1-2 daun layu 5 : > 15 daun layu / tanaman mati

2 : 3 -4 daun layu

3 : 5 – 7 daun layu

Pengamatan sampel dengan skoring pada suatu

hamparan lahan

5

43

1

2

35

4

2

1

12

5

3

4

3

• I = nixvi / N Z

ni : jumlah sampel pada katagori kerusakan

Vi : skor pada sampel

N : Jumlah total sampel

Z : skor tertinggi dari katagori serangan

Rumus Perhitungan Intensitas Serangan :

Z : skor tertinggi dari katagori serangan

Berdasarkan tabel di atas (6 katagori)

pengamatan terhadap misalnya 10 sampel

I = 1x1 + 3x2 + 3x3 + 3x5 / 10 x 5 x 100%

I = 31/50 x 100%

Economic damage, economic injury level,

and economic threshold

• Pest management is considered on the

ecological and economical thresholds

• Ecological consideration is decided on the

analysis that the pest control does not harmful analysis that the pest control does not harmful

to the environment

• Economical consideration is decided on the

analysis that the pest control gives economical

benefit

Economic damage, economic injury level, and

economic threshold

• Economic damage : the amount of injury which will

justify the cost of artificial control measures

• Economic Injury Level (EIL) : the lowest population

density that will cause economic damage.

• Economic threshold : The maximum pest population • Economic threshold : The maximum pest population

that can be tolerated at a particular time and place

without a resultant economic crop lost, the

population density at which control action should be

determined (initiated) to prevent an increasing pest

population (injury) from reaching the economic

injury level.

A pest damage curve (thick line) and associated cost of pest control

(thin line) used to estimate at economic injury level (EIL).

This damage curve can take several

forms

1. Tolerance or overcompensation phase no

yield response

2. Positive yield response to injury

3. Linearity phase e.g., yield loss = -a (unit 3. Linearity phase e.g., yield loss = -a (unit

injury) + b),

4. Desensitization and an inherent impunity

phase decreasing

5 No additional yield loss per unit injury.

• The curve can be used with various methods to

determine whether or not any action or pest

management tactic (e.g., pesticide, biological

control, cultural control, etc.) is needed to reduce

the damage associated with this pest.

• This relationship is uniquely characterized by a • This relationship is uniquely characterized by a

critical point, the economic injury level (EIL), or

the point in the agricultural production system

where the costs associated with pest

management equal the benefits from the pest

management actions

• Below the pest population represented by the

EIL there is no need to take pest control

actions because they are not economically actions because they are not economically

justified, but economic damage can occur

when the pest population densities are above

the EIL.

Pedigo et al

EIL = C/VDIK

• C = management cost per production unit,

• V = market value per production unit,

• D = damage per unit injury, • D = damage per unit injury,

• I = injury per pest equivalent, and

• K = proportional reduction in injury with management

• Later combined D+I into a single variable, D‟ = percent yield loss per pest.

Variation formula with the assumption

of 100% control:

EIL = (C x N) / (V x I),

• N = the number of pests causing injury,

• I = the percent yield loss (similar to the D‟ • I = the percent yield loss (similar to the D‟

value above).

• V = market value per production unit

• C = management cost per production unit

Example

• In using the EIL = C/VD‟K formula,

• if a seasonal average of one insect/plant causes a 10% reduction in yield,

• the market value of the crop is $0.4/lb fruit • the market value of the crop is $0.4/lb fruit

• and you expect 5 lb fruit/plant yield, the cost of control is $0.04/plant, and you can count on a 75% reduction in damage with the control tactic used, then:

• EIL = $0.04 cost per plant/($0.4/lb x 0.5 lb/insect x 0.75) = 0.27 insects/plant

• Notice that if you halve the number of insects

required to inflict 10% yield loss, you halve the

EIL value.

• In contrast, if you double the cost of control

you double the EIL value, again balancing the

tradeoff between control costs and benefits.tradeoff between control costs and benefits.

• In reality, the EIL value can be difficult to

calculate exactly because of the temporal and

dynamic nature of pest damage and crop

value

A two-level, fixed economic threshold with treated (narrow line), i.e.,

effectively controlled to stay below the EIL, and untreated (thick line) pest populations

• Example, an early season average of one

insect might result in 15% yield while late

season results in only 5% yield, so the estimate

based on a seasonal mean would not be very

precise for a given period during the season.precise for a given period during the season.

•One way to avoid large seasonal differences is

to calculate an early-season and a late-season

EIL, for example

EIL1 = C/VD1‟K and EIL2 = C/VD2‟K

or

EIL1 = $0.04 cost per plant/($0.4/lb x 0.75

lb/insect x 0.75) = 0.18 insects/plant

EIL2 = $0.04 cost per plant/($0.4/lb x 0.25

lb/insect x 0.75) = 0.53 insects/plant

Delayed response to a biological control tactic