Control Technology of Solanaceous Vegetable Diseases in Solar Greenhouse in Shandong Province

Dongwen Sun,Yanchun Gao,Na Li,Yizhe Feng,Tianyi Yang,Jialing Xu*

1.Zibo Digital Agriculture Rural Development Center,Zibo 255000,China;2.Zibo Academy of Agricultural Sciences,Zibo 255000,China

Abstract The occurrence of major diseases of protected solanaceous vegetables in Shandong Province,including tomato Pythium root rot,tomato Phytophthora root rot,tomato Pythium basal stem rot,tomato stem blight,sweet pepper root rot,pepper blight and eggplant stem rot,are studied,and corresponding comprehensive control measures are put forward.

Keywords Solar greenhouse;Solanaceous vegetables;Diseases;Control

Shandong Province is one of the world’s three major horticultural hometowns,with large area and high level of solar greenhouse vegetables.With the prolongation of planting years,vegetable diseases,especially solanaceous vegetable diseases,are aggravating,causing great impact on production.Improper prevention and control of diseases will cause excess pesticide residues in vegetables,directly endangering the health of consumers.

1 Tomato Pythium Root Rot

When there are 1-3 fruits in tomato plants in greenhouse planting,upper leaves begin to wilt.The incidence expands from sporadic strains to spotty areas,and aggravates after watering.The disease has occurred in large area in the main tomato producing areas in recent years.The diseased plant rate is 5%-10%in light cases,generally up to 20%-30%,and more than 50% in severe cases.Plants infected will quickly recover in case of timely prevention and control.

Water-soaked dark green lesions are observed in the stem base 2-3 cm above and below the soil surface,and watersoaked pale brown decay is found on fibrous roots and secondary roots,then spread to taproot and rhizome,forming pale brown epidermis.Pale brown to brown lesions are observed when vascular bundles are longitudinally dissected.The top leaves of aboveground plant are wilted,and the whole plant is wilted under severe cases.

In the initial stage of incidence,50% Genjingbao WP 600 times dilution or OS-oligosaccharin 600 times dilution or Apollo 963 1000 times dilution can be used to irrigate roots,and 3% Zhongshengmycin WP 600 times dilution or OS-oligosaccharin 600 times dilution are sprayed on the aboveground part to control the disease.

2 Tomato Phytophthora Root Rot

The disease mainly occurs in tomato greenhouses with high underground water level or high humidity.When there are 2-3 fruits in tomato plants,upper leaves wilt suddenly,or the whole plant is withered in severe cases.Water-soaked pale brown decay is produced on taproot tip,fibrous roots and secondary roots,and brown epidermis is observed in taproot and rhizome.Dark green or brown lesions appear at stem base in severe cases,causing rapid wilt of apical leaves.When stem base or rhizome is longitudinally dissected,vessels become black brown.The roots are finally rotten,leaving only brown rhizome,without growth of new roots,and the plant wilts rapidly.The disease spread quickly,and will spread to the whole greenhouse when the soil moisture is high,which is the main difference with Pythium root rot.

The prevention and control methods are as follows.(i)The land is leveled,with appropriate watering,while flood irrigation is strictly forbidden.(ii)Tall seedbeds or plots with good drainage should be selected.(iii)The irrigation time is shortened to make water sink rapidly into the soil.(iv)After transplanting,temperature,humidity and ground temperature is well managed;when the humidity rises,the greenhouse is ventilated to exhaust moisture in time;when the ground temperature is low,the soil is loosened for 2-3 times to improve the ground temperature and create normal conditions for the development of roots.(v)In the initial stage of incidence,40% fosetyl-aluminium WP 200 times dilution,58% metalaxyl·mancozeb WP 500 times dilution,70% fosetyl-aluminium·mancozeb WP 500 times dilution,50% metalaxylorganocupric salt WP 600 times dilution are sprayed to control the disease.

3 Tomato Pythium Basal Stem Tot

After transplanting for 7-8 d,the stem base of tomato decays commonly,and the incidence is aggravating year by year.Tomato plants are susceptible to the disease from 7-10 d post autumn transplanting to flowering and fruiting stage of the first cluster.The diseased plant rate is 10%-20%in light cases,and generally 30%-40%.All diseased plants should be removed to transplant the second stubble in severe cases,causing serious threat to tomato production.Water-soaked dark lesions are produced at stem base(mostly 3-5 cm above and below the soil surface).With the growth of plants,lesions extend up and down,and spread around the stem.The stem base is constricted in severe cases,and upper leaves are wilted.After a few days,the plants collapse or die.The disease is severe at high temperatures(32-36℃).

Metalaxyl·hymexazol AS,flumorph·fosetyl-aluminum,metalaxyl-M mancozeb can be used to irrigate roots or spray stem base for the prevention and control of the disease.

4 Tomato Stem Blight

Tomato stem blight occurs from seedling stage to adult stage,but it is more common in the middle and late growth stage.The disease mainly harms stems and fruits,as well as leaves and petioles.Lesions at base initially are elliptic,brown,depressed,ulcer-shaped,and then gradually spread to the whole plant along the stem.Small gray-white spots on infected fruits gradually extend to dark brown sunken patches,and black mold layer is produced,causing fruit rot.Alternaric acid produced by the strain will transfer to the upper part of plant and kill leaf veins on both sides of leaf tissue,so that the leaf surface is covered with irregular brown spots,and petiole of tender leaves or leaflets are dark brown and soft.Finally,leaves are dried or the whole plant is dead.The disease is aggravating in recent years.

10%Score WG 2000 times dilution and 70% thiophanate-methyl WP 600 times dilution can be sprayed alternatively to control the disease.

5 Sweet Pepper Root Rot

Sweet pepper root rot mainly harms pepper root and rhizome,as well as aerial stem base.The disease initially occurs in middle and late April when fruit branches begin to blossom and bear fruit.It enters peak incidence period in early and middle May,which may be slightly earlier or later depending on the time of planting.Greenhouse pepper plants in continuous cropping field are easily infected at seedling stage due to excessive watering and heavy humidity after transplanting.The infected plants begin to wilt during the daytime,and recover from the evening to the next morning.The whole plant will die after a few days.The roots and stems of diseased plants are light brown to dark brown,rust rot,which are peeled off once touched,exposing dark xylem.The above are the main features of the disease.

50%Compound benzodiazepine WP 800 times dilution,50% carbendazim SC 500 times dilution,or 40% carbendazim·sulfur 600 times dilution are sprayed when primary infection focus appear in the field.

6 Pepper Blight

Pepper blight occurs from seedling stage to adult stage.The stem base of seedlings is dark green,water-soaked soft rot or damping off.Due to special climatic conditions of solar greenhouse,such as high relative humidity and appropriate temperature,plants grow vigorously.Watersoaked lesions first appear at stem base or 3-6 cm above stem base or the stem of the first branch,and then spread around the stem epidermis,showing black brown or black water-soaked lesions.The situation is severe especially in continuous cropping field.The infected part of blight is conspicuously constricted,and stem,branches,leaves above the infected part or the whole plant wither and collapse rapidly.The disease has become a destructive disease in hot pepper production in solar greenhouse.

The prevention and control methods are as follows.(i)Seed infection:seeds are soaked in 52℃warm water for 30 min or preimmersed in water for 10-12 h,then soaked in 1%copper sulfate for 5 min;subsequently,the seeds are mixed with a small amount of plant ash,or soaked in 70% ofurace 600 times dilution or 25% metalaxyl 400 times dilution for 10 min;finally,seeds are washed and dried for accelerating germination.(ii)Spraying or root irrigation after transplanting:in the early stage,agents are sprayed at stem base and ground surface before incidence to prevent and control primary infection;in the middle and late stage,root irrigation is the main method to control secondary infection;when infection center is found in the field,root irrigation and stem spraying should be performed;50% metalaxyl-organocupric salt WP 800 times dilution or 70% ofurace WP 600-800 times dilution or 72%curzate WP 800 times dilution are sprayed for continuous 3-4 times.

7 Eggplant Stem Rot

The disease used to be a sporadic disease in some areas and plots in Shandong Province.In recent years,it has gradually become one of the most important soil-borne diseases of eggplant in solar greenhouse in the province.In the process of control,the control strategy of prevention first,comprehensive prevention and control should be adopted.The aboveground parts show the symptoms of bacterial wilt;brown depressed spots are produced 3 cm above the ground,which gradually spread around;the lesions may form a pitting lesion around the base of the whole stem.The diseased part is dried and shrunk,and the cortex decay when the humidity is large,exposing xylem.The leaves of heavily infected plants are wilted,like exsiccosis.The plants are wilted at noon,and recover to normal in the morning and evening in the initial stage,but will no longer restore after several days.Thereafter,the whole plants die,different from eggplant blight caused by Fusarium oxysporum.The disease is caused by two species of fungi,F.oxysporum and Phytophthora nicotianae.The pathogens survive the winter as residues in the soil.The pathogens invade from root collar or wounds,causing the disease.The greenhouses with much ground water,extensive management and close planting easily suffer heavy incidence.Before planting,high temperature tightly greenhouse is developed by lime nitrogen(calcium cyanamide)+cow dung or chicken dung in continuous cropping field.77%Donin WP 600 times dilution is used for root irrigation;60%pyraclostrobin·metiram WG 1500 times dilution is used for root irrigation or spraying;72%curzate WP 800 times dilution is used for root irrigation or spraying;and 70%thiophanate-methyl WP 1000 times dilution is used for root irrigation.