**3.1.1 Fungal agent of bottom rot disease**

Bottom rot is caused by a soilborne fungal pathogen *Rhizoctonia solani*. The fungus overwinters in the soil or in crop debris as sclerotia or mycelia. It may survive in alternate hosts and serve as a source of inoculum, sexual spores. It is disseminated by wind or rain splash in the next growing season. *R. Solani* has a wide host range e.g. eggplant, soybean, potato, cotton, alfafa, maize, wheat and several weed species.

#### **3.1.2 Control of bottom rot disease**

Cultural measures includes three year rotations with non-host plants; collecting plant debris and burying it or plowing it deep in the soil; planting varieties that have an upright architecture to reduce contact with the soil; keeping the fields weed free and removing volunteer crops to reduce possible alternate hosts. Since *R. Solani* is able to survive on non decomposed organic matter, it is important to avoid planting lettuce in a field that has high amounts of organic matter that is not decomposed; avoid overhead irrigation during heading of the plants; plant lettuce on ridges which increases aeration and helps avoid plants contact with the soil. Fungicides (Table 2) are the most effective means to control bottom rot disease. However, fungicide control is only satisfactory when used in combination with cultural control strategies. Proper placement and timing of fungicide applications are key elements for effective disease management.

Control of Major Diseases in Horticulture 175

dispersed by wind and water splash from infected to non-infected plants. The disease spreads rapidly at temperatures between 10 and 21°C in combination with high humidity. Several strains of the fungus have been reported and strains recombination increases the chance of having novel strains that are either resistant to fungicides or more tolerant to harsh environmental conditions. *P. infestans* also infects tomatoes and causes mild infections

It is recommended to destroy all volunteer potato and other susceptible plants because *P. infestans* survives on these volunteer plants that represent the primary sources of inoculum during the next season. Potato growers should only use certified seed potatoes and avoid using their own grown tubers as seed in order to contain the devastating effect of late blight disease. It is advisable to make sure that other crops that can also be infected by *P. infestans* are disease free. Cull piles of infected potatoes should be destroyed because they serve as a source of inoculum. The fields should be scouted for late blight on a regular basis, paying close attention to low lying areas, areas under shade, or near water sources. It is important to avoid overhead irrigation in the evening because this provides long periods of leaf wetness that favors disease development. Potato tubers should be harvested after the vines die, which also kills the spores on them and avoids transmission of spores to the tubers. Infected tubers should be removed before storage in order to avoid spreading the disease to the healthy tubers. Planting resistant or moderately resistant potato varieties where available is advisable.

The fungicides recommended for use against late blight disease vary from region to region because strains of *P. infestans* found in one region might not be present in another, and fungicide sensitivity might be different among fungal isolates. Genotypes of *P. infestans* have been reported to recombine to produce new genotypes that are resistant to the recommended

In fields that have already been reported to have late blight, the first application of a protectant fungicide is recommended before row closure and a second application should follow within 7-10 days. Further applications of protectants should be done when the weather conditions are conducive for late blight development. A late blight epidemic is difficult to control, therefore regular applications of protectants during the growing season is important to keep new foliage covered. Applications should be made even late in the season as long as parts of the vines are still green to avoid tuber infections. For a complete list of fungicides recommend in a region, it is advisable to consult the area extension office. However, we highlight in Table 3 some of, the

On potato and tomato foliage early blight appears as brown to black spots, which coalesce to form lesions that are restricted by large veins and therefore having an angular shape (Figure 6 C, D). Occasionally, a chlorotic border may be formed around the lesions. When stems are infected the disease appears as small dark spots. On tubers there are dark sunken lesions that are surrounded by raised margins. The tissue underneath the lesions is dry, reddish

systemic fungicides, but resistance to protectant fungicides has not been reported.

recommended fungicides used to control late blight disease on potatoes.

on eggplants, peppers and related weed species.

**4.1.3 Chemical control of late blight disease** 

**4.2 Early blight disease of potato and tomato** 

brown in color, and leathery in texture.

**4.1.2 Late blight disease management** 


Table 2. Fungicides Recommended for control of bottom rot on lettuce.

#### **3.2 Fusarium wilt of lettuce**

Lettuce seedlings affected by this disease wilt and ultimately die, while in mature plants the symptoms include red-brown to black discoloration of internal taproot and crown tissue, yellowing of leaves, tipburn of heads (Figure 5 B) and when infection is severe plants are stunted and may fail to form heads.

#### **3.2.1 Fungal pathogen of Fusarium wilt disease of lettuce**

Fusarium wilt of lettuce is caused by a soil-borne fungus, *Fusarium oxysporum* f.sp*. lactucae* forma specialis nov. This pathogen can remain viable in the soil for many years. *Fusarium oxysporum* f.sp*. lactucae* forma specialis nov is host specific to lettuce and therefore only affect/grow on lettuce.

#### **3.2.2 Fusarium wilt disease control**

Recommended cultural practices include clean of farm equipment, avoiding to plant lettuce in infected field and planting resistant/tolerant lettuce varieties.

#### **4. Diseases of potato and tomato**

#### **4.1 Late blight disease**

Late blight is one of the most destructive diseases of potato and tomato. It is found wherever these crops are grown. On potatoes it appears as small light green water soaked spots at the edges of leaves. During favorable weather conditions, cool and moist, the lesions enlarge rapidly, and turn brown to black (Figure 6 A, B). The lesions coalesce to cover entire leaves and even affect the stem. Infected tissue dries up when the weather is dry. The disease spreads rapidly and all the leaves may be killed in a few days. On tubers, the disease appears as irregular, dry, brown depressions. Copper brown, granular lesions are found underneath the skin (Figure 6 A). Potatoes infected with the late blight pathogen are generally susceptible to secondary infection from other fungi and/or bacteria.

#### **4.1.1 Fungal pathogen of late blight disease**

Late blight disease is caused by a fungal pathogen, *Phytophthora infestans*. The primary sources of inoculum are infected seed tubers, volunteer plants and plant debris. Spores are

Action Target site and code Group name Chemical group Common name FRAC

**QoI**-fungicides (**Q**uinone **o**utside **I**nhibitors

Lettuce seedlings affected by this disease wilt and ultimately die, while in mature plants the symptoms include red-brown to black discoloration of internal taproot and crown tissue, yellowing of leaves, tipburn of heads (Figure 5 B) and when infection is severe plants are

Fusarium wilt of lettuce is caused by a soil-borne fungus, *Fusarium oxysporum* f.sp*. lactucae* forma specialis nov. This pathogen can remain viable in the soil for many years. *Fusarium oxysporum* f.sp*. lactucae* forma specialis nov is host specific to lettuce and therefore only

Recommended cultural practices include clean of farm equipment, avoiding to plant lettuce

Late blight is one of the most destructive diseases of potato and tomato. It is found wherever these crops are grown. On potatoes it appears as small light green water soaked spots at the edges of leaves. During favorable weather conditions, cool and moist, the lesions enlarge rapidly, and turn brown to black (Figure 6 A, B). The lesions coalesce to cover entire leaves and even affect the stem. Infected tissue dries up when the weather is dry. The disease spreads rapidly and all the leaves may be killed in a few days. On tubers, the disease appears as irregular, dry, brown depressions. Copper brown, granular lesions are found underneath the skin (Figure 6 A). Potatoes infected with the late blight pathogen are

Late blight disease is caused by a fungal pathogen, *Phytophthora infestans*. The primary sources of inoculum are infected seed tubers, volunteer plants and plant debris. Spores are

generally susceptible to secondary infection from other fungi and/or bacteria.

succinatedehydrogene Carboxamides Pyridine-

Table 2. Fungicides Recommended for control of bottom rot on lettuce.

**3.2.1 Fungal pathogen of Fusarium wilt disease of lettuce** 

in infected field and planting resistant/tolerant lettuce varieties.

Methoxy acrylates

Dicarboximides Dicarboximies

carboxamides

code

11

2

Azoxystrobin (Amistar) (Quadris Flowable)

(Endura) <sup>7</sup>

Boscalid

Iprodione (Rovral 50 W) Vinclozolin (Ronilan DF)

Mode of

Respiration

Signal transduction

Respiration complex II:

**3.2 Fusarium wilt of lettuce** 

affect/grow on lettuce.

**4.1 Late blight disease** 

stunted and may fail to form heads.

**3.2.2 Fusarium wilt disease control** 

**4. Diseases of potato and tomato** 

**4.1.1 Fungal pathogen of late blight disease** 

complex III: cytochrome bc1 (ubiquinol oxidase) at Qo site *(cyt b gene)*

MAP/Histidine-Kinase in osmotic signal transduction *(os-1, Daf1)*

dispersed by wind and water splash from infected to non-infected plants. The disease spreads rapidly at temperatures between 10 and 21°C in combination with high humidity. Several strains of the fungus have been reported and strains recombination increases the chance of having novel strains that are either resistant to fungicides or more tolerant to harsh environmental conditions. *P. infestans* also infects tomatoes and causes mild infections on eggplants, peppers and related weed species.

#### **4.1.2 Late blight disease management**

It is recommended to destroy all volunteer potato and other susceptible plants because *P. infestans* survives on these volunteer plants that represent the primary sources of inoculum during the next season. Potato growers should only use certified seed potatoes and avoid using their own grown tubers as seed in order to contain the devastating effect of late blight disease. It is advisable to make sure that other crops that can also be infected by *P. infestans* are disease free. Cull piles of infected potatoes should be destroyed because they serve as a source of inoculum. The fields should be scouted for late blight on a regular basis, paying close attention to low lying areas, areas under shade, or near water sources. It is important to avoid overhead irrigation in the evening because this provides long periods of leaf wetness that favors disease development. Potato tubers should be harvested after the vines die, which also kills the spores on them and avoids transmission of spores to the tubers. Infected tubers should be removed before storage in order to avoid spreading the disease to the healthy tubers. Planting resistant or moderately resistant potato varieties where available is advisable.

#### **4.1.3 Chemical control of late blight disease**

The fungicides recommended for use against late blight disease vary from region to region because strains of *P. infestans* found in one region might not be present in another, and fungicide sensitivity might be different among fungal isolates. Genotypes of *P. infestans* have been reported to recombine to produce new genotypes that are resistant to the recommended systemic fungicides, but resistance to protectant fungicides has not been reported.

In fields that have already been reported to have late blight, the first application of a protectant fungicide is recommended before row closure and a second application should follow within 7-10 days. Further applications of protectants should be done when the weather conditions are conducive for late blight development. A late blight epidemic is difficult to control, therefore regular applications of protectants during the growing season is important to keep new foliage covered. Applications should be made even late in the season as long as parts of the vines are still green to avoid tuber infections. For a complete list of fungicides recommend in a region, it is advisable to consult the area extension office. However, we highlight in Table 3 some of, the recommended fungicides used to control late blight disease on potatoes.

#### **4.2 Early blight disease of potato and tomato**

On potato and tomato foliage early blight appears as brown to black spots, which coalesce to form lesions that are restricted by large veins and therefore having an angular shape (Figure 6 C, D). Occasionally, a chlorotic border may be formed around the lesions. When stems are infected the disease appears as small dark spots. On tubers there are dark sunken lesions that are surrounded by raised margins. The tissue underneath the lesions is dry, reddish brown in color, and leathery in texture.

Control of Major Diseases in Horticulture 177

Early blight disease is caused by a fungus, *Alternaria solani*. The fungus overwinters in plant debris, infected tubers, soil and on other host species. Disease development is favored by temperatures between 20°C and 30°C; long periods of leaf wetness, high relative humidity under alternating wet and dry conditions. Spores are dispersed by wind, water splash, insects, machinery and animals. The disease occurs late in the season and increases rapidly during flowering and senescence. Both biotic and abiotic stresses favor disease development. Bruising

On tomato the disease symptom is characterized by lesions with dark concentric rings. Diseased leaves wither, dry and fall off. Severe defoliation reduces plant vigor and exposes tomato fruits to sunscald. Disease is first observed on the lower leaves and spreads to the upper leaves. Other symptoms include damping-off, collar rot, stem cankers, leaf blight, and

The following cultural practices that promote a healthy crop and therefore hinder early blight disease establishment include: three year crop rotations with non-susceptible crops; removing volunteer crops and keeping the field weed free; planting resistant/tolerant varieties; removing plant debris or burying it in the soil; irrigating in the morning so that the plant have enough time to dry; keeping the plants healthy so that they are less susceptible to disease; having proper spacing between the plants and rows to provide for good air circulation; using certified disease-free tomato seed and transplants; planting potatoes away from previous season potato fields; avoiding bruising and wounding of tubers during

On potatoes it is recommended to apply protectant fungicides at beginning of flowering or at the earliest symptoms of early blight. On tomatoes fungicide application is recommended soon after transplanting or two to three weeks after emergence. In Table 4, the

On underground stems and stolons the disease appears as brown to black sunken lesions that cause the plants to look weak. These lesions may girdle the stolons and cut them off from the rest of the plant. Lesions that girdle the main stem cause the leaves to turn purplish or yellowish and curl upwards. Other symptoms include formation of aerial tubers and formation of whitish mold on the stems at the soil line. On tubers the disease causes tubers to crack or get deformed. Overwintering structures formed on surface of tubers appears as

Black scurf of potatoes is cause by a fungal pathogen, *Rhizoctonia solani* Kuhn. The fungus overwinters in the soil on plant debris or inform of sclerotia. Sclerotia may also survive on

recommended fungicides used in early blight disease control are summarized.

or wounding of tubers during harvest leads to infection with early blight.

**4.2.1 Fungal pathogen of early blight disease** 

**4.2.2 Early blight disease management** 

**4.2.3 Fungicides use in management of early blight** 

**4.3 Black scurf disease of potato** 

dark masses or as netted residues.

**4.3.1 Fungal causal agent of black scurf disease** 

fruit rot.

harvesting.


Table 3. Fungicides listed for control of late blight on potatoes.

Fig. 6. Late blight (A-B) and early blight (C-D) disease symptom on potato (A, D) and tomato plants (B, D) respectively. Late blight disease is depicted on potato (A) and tomato fruit (B), while early blight disease is depicted on potato leaf (C) and tomato leaf (D). Photos: courtesy of B. Millett (A); W. R. Stevenson (B); S. R. Rideout (C); and R. Mulrooney (D).

Dithiocarbamates and relatives

Dithiocarbamates and relatives

Benzamides **Gavel 75 DF**

Fig. 6. Late blight (A-B) and early blight (C-D) disease symptom on potato (A, D) and tomato plants (B, D) respectively. Late blight disease is depicted on potato (A) and tomato fruit (B), while early blight disease is depicted on potato leaf (C) and tomato leaf (D). Photos: courtesy of B. Millett (A); W. R. Stevenson (B); S. R. Rideout (C); and R. Mulrooney (D).

Cyanoacetamide-

**Manebs:** (Maneb 75 DF;Maneb 80; Maneb + Zinc; Manex)

**Mancozebs:** (Dithane M-45; Dithane F-45; Dithane DF; Penncozeb 80 WP; Penncozeb 75

**Chlorothalonil:**(Bravo 500; Terranil Excell; Bravo Ultrex; Terranil 6L; Bravo Weatherstik;

DF)

Methoxy acrylates **Azoxystrobin:**(Quadris)

Bravo Zn)

Cinnamic acid amide **Dimethomorph:**(Acrobat MZ)

oxime **Cymoxanil:** (Curzate 60 DF)

code Mode of action Group name Chemical group Common name

Chloronitriles Chloronitriles

Dithiocarbamates and relatives

Dithiocarbamates and relatives

(**Q**uinone **o**utside **I**nhibitors)

**CAA**-fungicides (**C**arboxylic **A**cid **A**mides)

Cyanoacetamide-

Table 3. Fungicides listed for control of late blight on potatoes.

oxime

FRAC

40

22

M3 Multi-site inhibitor

M3 Multi-site inhibitor

M5 Multi-site

contact activity

Lipids and membrane synthesis

mode of action

mitosis ß-tubulin assembly

<sup>27</sup>Unknown

11 Respiration **QoI** – fungicides

#### **4.2.1 Fungal pathogen of early blight disease**

Early blight disease is caused by a fungus, *Alternaria solani*. The fungus overwinters in plant debris, infected tubers, soil and on other host species. Disease development is favored by temperatures between 20°C and 30°C; long periods of leaf wetness, high relative humidity under alternating wet and dry conditions. Spores are dispersed by wind, water splash, insects, machinery and animals. The disease occurs late in the season and increases rapidly during flowering and senescence. Both biotic and abiotic stresses favor disease development. Bruising or wounding of tubers during harvest leads to infection with early blight.

On tomato the disease symptom is characterized by lesions with dark concentric rings. Diseased leaves wither, dry and fall off. Severe defoliation reduces plant vigor and exposes tomato fruits to sunscald. Disease is first observed on the lower leaves and spreads to the upper leaves. Other symptoms include damping-off, collar rot, stem cankers, leaf blight, and fruit rot.

#### **4.2.2 Early blight disease management**

The following cultural practices that promote a healthy crop and therefore hinder early blight disease establishment include: three year crop rotations with non-susceptible crops; removing volunteer crops and keeping the field weed free; planting resistant/tolerant varieties; removing plant debris or burying it in the soil; irrigating in the morning so that the plant have enough time to dry; keeping the plants healthy so that they are less susceptible to disease; having proper spacing between the plants and rows to provide for good air circulation; using certified disease-free tomato seed and transplants; planting potatoes away from previous season potato fields; avoiding bruising and wounding of tubers during harvesting.

#### **4.2.3 Fungicides use in management of early blight**

On potatoes it is recommended to apply protectant fungicides at beginning of flowering or at the earliest symptoms of early blight. On tomatoes fungicide application is recommended soon after transplanting or two to three weeks after emergence. In Table 4, the recommended fungicides used in early blight disease control are summarized.

#### **4.3 Black scurf disease of potato**

On underground stems and stolons the disease appears as brown to black sunken lesions that cause the plants to look weak. These lesions may girdle the stolons and cut them off from the rest of the plant. Lesions that girdle the main stem cause the leaves to turn purplish or yellowish and curl upwards. Other symptoms include formation of aerial tubers and formation of whitish mold on the stems at the soil line. On tubers the disease causes tubers to crack or get deformed. Overwintering structures formed on surface of tubers appears as dark masses or as netted residues.

#### **4.3.1 Fungal causal agent of black scurf disease**

Black scurf of potatoes is cause by a fungal pathogen, *Rhizoctonia solani* Kuhn. The fungus overwinters in the soil on plant debris or inform of sclerotia. Sclerotia may also survive on

Control of Major Diseases in Horticulture 179

University of Illinois extension, and Cornell University extension services. In addition, we wish to sincerely apologize to colleagues whose data are not here acknowledged. We wish to thank anonymous reviewers of the manuscript for their valuable and useful comments

Ammermann, E., Lorenz, G., Schelberger, K., Wenderoth, B., Sauter, H. & Rentzea C. (1992).

Behe, B.K., Williams, J.D., Cobb, P., Hagan, A.K. & Stritikus G. (1993). Growing roses.

Bowen, K.L. & Roark, R.S. (2001). Management of black spot of rose with winter fungicide

Ebeling, M., Heimann, K.-G., Schoefer, S. & Sonder K. (2003). The human and environmental safety aspects of trifloxystrobin. *Pflanzenschutz-Nachrichten Bayer* 56: 231-245. Ellis, S.D., Boehm, M.J. & Mitchell, T.K. (2008). Fungal and fungal-like diseases of plants:

Gachomo, E.W. & Kotchoni, S.O. (2007). Detailed description of developmental growth

Gachomo, E.W. (2005). Study of the Life cycle of Diplocarpon rosae Wolf and the Effects of Fungicides on Pathogenesis. Goettingen, Germany: Cuvillier Verlag. Gachomo, E.W., Dehne, H.-W. & Steiner, U. (2006). Microscopic evidence for the

Gachomo, E.W., Dehne, H-W. & Steiner, U. (2009). Efficacy of triazoles and strobilurins in

Gachomo, E.W., Manfredo, J., Seufferheld, M.J. & Kotchoni S.O. (2010). Melanization of

Haverkort, A.J., Boonekamp, P.M., Hutten, R., Jacobsen, E., Lotz, L.A.P., Kessel, G.J.T.,

Killian, M. & Steiner, U. (2003). Bactericides and fungicides. In Encyclopaedia of Rose

Kuck, K.H., Scheinpflug, H. & Pontzen, R. (1996). DMI fungicides. In Modern Selective

stages of *Diplocarpon rosae* Wolf: a core building block for efficient disease

hemibiotrophic nature of Diplocarpon rosae, cause of black spot disease of rose.

controlling black spot disease of roses caused by *Diplocarpon rosae*. *Annals of Applied* 

appressoria is critical for the pathogenicity of *Diplocarpon rosae*. *Molecular Bioliology* 

Visser, R.G.F. & van der Vossen, E.A.G. (2008). Societal costs of late blight in potato and prospects of durable resistance through cisgenic modification. *Potato Research*

Science, pp. 190-198. Eds A.V. Roberts, T. Debener and S. Gudin. Amsterdam, the

Fungicides; Properties, Applications, Mechanisms of Action. 2nd revised and enlarged edn, pp. 205–258. Ed. H. Lyr. Stuttgart, Germany: Gustav Fisher Verlag. Margot, P., Huggenberger, F., Amrein, J. & Weiss B. (1998). CGA279202: a new broad-

spectrum strobilurin fungicide. Proceedings of the Brighton Crop Protection

Alabama Cooperative Extension Service, Circular ANR-157.

management. *Annals of Applied Biology* 151: 233-243.

*Physiological and Molecular Plant Pathology* 69: 86-92.

BCPC. Surrey, UK: BCPC Publications.

treatment. *Plant Disease* 85: 393-398.

Ohio State University Extension.

*Biology* 154: 259-267.

*Reports* 37: 3583-3591.

Netherlands: Elsevier Academic Press.

Conference-Pest and Diseases, 2, 375-382.

51: 47-57.

BAS 490F: A broad spectrum-fungicide with a new mode of action. In Proceedings of the Brighton Crop Protection Conference-Pest and Diseases. pp. 403-410. Eds

and suggestions.

**6. References** 

tubers. Initial infection occurs when sclerotia germinate to infect stem and sprouts. Tubers are most susceptible to infection when left in the soil after the vines die. Infection is favored by cool (12-16°C) moist soils.


Table 4. Fungicides for early blight control in tomato

#### **4.3.2 Disease management**

Recommended cultural practices in management of black scurf of potatoes include planting certified disease free seed, planting in warm soils (16°C); warming the seed before planting; rotation with non-host plants such as grasses; avoiding field with a history of disease because the fungal population builds in the soil when potatoes are grown in the same field.

#### **5. Acknowledgement**

We gratefully acknowledge data availability by colleagues from Research units and Extension services from the University of Maine, Idaho, Pennsylvania State University, University of Illinois extension, and Cornell University extension services. In addition, we wish to sincerely apologize to colleagues whose data are not here acknowledged. We wish to thank anonymous reviewers of the manuscript for their valuable and useful comments and suggestions.

#### **6. References**

178 Fungicides for Plant and Animal Diseases

tubers. Initial infection occurs when sclerotia germinate to infect stem and sprouts. Tubers are most susceptible to infection when left in the soil after the vines die. Infection is favored

group

Methoxy-

Methoxy-

Dithio carbamates and relatives

Recommended cultural practices in management of black scurf of potatoes include planting certified disease free seed, planting in warm soils (16°C); warming the seed before planting; rotation with non-host plants such as grasses; avoiding field with a history of disease because the fungal population builds in the soil when potatoes are grown in the same field.

We gratefully acknowledge data availability by colleagues from Research units and Extension services from the University of Maine, Idaho, Pennsylvania State University,

Common name FRAC

acrylates azoxystrobin, 11

carbamates pyraclostrobin 11

Fungonil)

Copper

Chlorothalonil (Daconil, Bravo, Echo,

(Bordeaux Mixture, Kocide, Tenn-Cop,Liqui-cop, Basicop, Camelot)

mancozeb maneb Ziram M3

Mineral oils, organic oils,potassium bicarbonate (Armicarb 100, Firststep), hydrogen dioxide (Oxidate) material of biological origin (*Bacillus subtilis*).

code

M5

M1

NC

code Group name Chemical

**QoI**-fungicides (**Q**uinone **o**utside **I**nhibitors

**QoI**-fungicides (**Q**uinone **o**utside **I**nhibitors

activity Chloronitriles Chloronitriles

activity Inorganic Inorganic

Dithio carbamates and relatives

by cool (12-16°C) moist soils.

Target site and

complex III: cytochrome bc1 (ubiquinol oxidase) at Qo site *(cyt b gene)*

complex III: cytochrome bc1 (ubiquinol oxidase) at Qo site *(cyt b gene)*

Multi-site contact

Multi-site contact

Multi-site contact

not classified unknown diverse diverse

Table 4. Fungicides for early blight control in tomato

activity

**4.3.2 Disease management** 

**5. Acknowledgement** 

Mode of Action

Respiration

Respiration

Multi-site contact activity

Multi-site contact activity

Multi-site contact activity


**9** 

*Mexico* 

**Target-Site-Specific Screening** 

*Centro de Investigación en Alimentación y Desarrollo, A.C.* 

Consuelo Corrales–Maldonado,

**System for Antifungal Compounds** 

Miguel Ángel Martínez-Téllez and Irasema Vargas-Arispuro

The rapid emergence of fungicide resistance has brought a strong demand for crop protection agents with a new mode of action. One of the challenges for modern plant pathology research is the discovery of new modes of action that provide improved activity of fungicides against commercially important target, combined with assures environmental and public safety, is a critical step in safeguarding food security. This chapter reviews biochemical and molecular biological approaches that have revealed new insights into fungal growth and morphogenesis and offer potential target sites for the development of new fungicides. It also discusses prospects for exploiting these modern technologies for the

Agriculture will always face crop losses caused by microorganisms. Since bible the first pages talk about pest, nowadays, in the XXI century must be added to pest, the losses caused by the effect of global climate change (Gustafson, 2011). Particularly, fungal plant pathogen that comprises an important group of microorganisms that causes significant economic losses in agriculture around the world. They are able to infect any tissue at any stage of plant growth (Garrido *et al*., 2010). Control of plant diseases typically depends upon the application of chemical fungicides, despite their potentially toxic effects on non-target organisms and the environment (Santos *et al,* 2008; Ferrer-Alcón, *et al*, 2009). Although effective, their extensive use for several decades has disrupted biological control by natural enemies and has led to new pathogen races that are resistant to fungicides (Fernandez-Acero *et al.,* 2006). In spite of the incredible amount of biological information about fungal plant pathogens, there is a scarce commercial fungicide developed from a new knowledge approach. The absence of fungicides that are capable of acting in more than one site of action is a direct consequence of resistance to fungicides, which is common among currently used agrochemicals (Brent & Hollomon, 2007). For example, chlorhexidine, quaternary ammonium compounds, organic acids, esters and alcohols that acts by interfering with the structure or permeability of the cell membrane, subsequently altering its barrier function (Russell, 2003). Pyribencarb cause an inhibition of the electron transport system in fungi, it has been suggested that pyribencarb inhibited succinate-cytocrome C reductase in *Botrytis cinerea* and *Corynespora cassicola* and decylubiquinol-cytocrome C reductase in *B. cinerea* in the same way as strobilurin fungicides . Benzimidazole fungicides, such as benomyl, act

**1. Introduction** 

development of fungicides.

