Latest Technical Methods and Tutorial for Kiwifruit Pest and Disease Control

Kiwifruit, also known as Chinese gooseberry, fox peach, monkey pear, etc., is a large deciduous woody vine of the genus Actinidia in the family Actinidiaceae. Its place of origin is the Xiangxi region of Hunan Province, China. Shaanxi at the northern foot of the Qinling Mountains is the region with the richest kiwifruit resources in China. The history of folk artificial cultivation reaches more than one thousand years. Now let us take a look together at kiwifruit pest and disease control techniques!

Fruit Ripe Rot

[Damage symptoms] When kiwifruit ripens, on one side of the harvested fruit there appears a spot resembling a thumb pressure mark, slightly sunken, brown, dimple-shaped, about 5 mm in diameter. The skin does not break, but when the skin is peeled back it reveals slightly pale yellow flesh. The edge of the lesion is dark green or water-soaked, and in the middle there is often milky white conical rot. Within a few days it can extend deep into the middle of the flesh and even cause the whole fruit to rot. During storage, the rot rate can reach as high as 30%.

[Infection process] It spreads by wind, rain, and airflow, as well as through branch wounds caused by pruning. Under a temperature condition of 20°C, after a latent period of 14-21 days it infects the fruit (that is, it begins infecting young fruit about 3 weeks after petal fall), and symptoms appear at the fruit ripening stage.

[Control methods] 1. Begin bagging young fruit one week after petal fall to avoid infection of young fruit. 2. From two weeks after petal fall to the fruit enlargement stage (May-August), spray the canopy with 50% carbendazim 800-fold solution or 1:0.5:200 Bordeaux mixture, or 80% thiophanate wettable powder 1000-fold solution 2-3 times, with a spraying interval of about 20 days. 3. Remove pruned kiwifruit branches and fallen dead branches and leaves to reduce places where pathogens can parasitize.

Root Rot

[Damage symptoms] In the early stage, dark brown water-soaked lesions appear at the root crown. After gradually expanding, white silky mycelium grows. The cortex and xylem of the diseased part gradually rot and have a distiller's grains smell. After the mycelium develops in large amounts, sclerotia form after 8-9 days, about the size of rapeseed, pale yellow. Afterward, the roots below gradually turn black and rot, thus causing the entire plant to die.

[Infection process] It overwinters in the diseased part as mycelium. In the Wuhan area, disease begins in April, with severe occurrence from July to September, and development stops after October. It occurs from time to time in orchards with heavy, sticky soil and poor drainage.

[Control methods] 1. When establishing an orchard, choose soil with good drainage. During the rainy season, do a good job of clearing ditches and draining water. Do not plant too deep, and do not apply undecomposed fertilizer. 2. In March and mid-to-late June, use zineb 0.5 kg plus water 200 kg to irrigate the roots. 3. When diseased plants are found, dig away the soil at the root crown, carefully scrape off the diseased part and a small amount of healthy tissue, disinfect with 0.1% mercuric chloride, then apply Bordeaux paste. After half a month, replace with new soil and cover it. If the scraped wound surface is relatively large, apply grafting wax for protection, and additionally apply decomposed liquid manure to restore tree vigor.

Stem-End Rot

[Damage symptoms] On affected fruit, obvious water-soaked symptoms first appear at the fruit stem end. Afterward, the lesion expands evenly downward, the flesh rots downward from the fruit stem end and spreads through the whole fruit, with a slight translucent appearance and an alcoholic smell. On the peel of the diseased part, an uneven layer of downy gray-white mold grows, later turning gray. Because of stem-end rot damage, the fruit rot rate during storage is 20-40%.

[Infection process] The pathogen overwinters in the diseased part as conidia and spreads through airflow. In spring, this fungus first infects flowers and causes flower rot. Fruit infection occurs during harvesting, grading, and packing. In kiwifruit orchards, the period of massive spore formation of the pathogen is from flowering to petal fall. Under cold storage (0°C) conditions, infected kiwifruit show symptoms after about 4 weeks, and fruit that has not developed disease after 12 weeks generally will not develop it again.

[Control methods] 1. Do a good job of winter orchard cleanup. 2. Promptly remove diseased flowers and burn them centrally. Spray a fungicide once in the late flowering stage and once before harvest, such as double-strength Bordeaux mixture or 65% zineb 500-fold solution. 3. For pre-harvest application, try as much as possible to make the solution reach the fruit stem end. Within 24 hours after harvest, treat the wound and the whole fruit with chemicals, such as 50% carbendazim 1000-fold solution plus “2,4-D” 100-200 ppm, soaking the fruit for 1 minute.

Leafhopper

[Damage symptoms] Adults and nymphs suck the sap of kiwifruit buds, leaves, and shoots. On affected leaf surfaces, yellow-white spots first appear and gradually expand into patches. In severe cases, the entire leaf becomes pale and falls early, the tree declines, and yield drops sharply.

[Infection process] Four generations occur per year, and the fourth-generation adults overwinter among winter green manure crops and weeds. In early spring, overwintering adults begin activity, mate, and then lay eggs. The egg stage is 7-10 days, and the nymph stage is 15-20 days. In mid-to-late April, first-generation adults lay eggs. The eggs are laid in the leaf mesophyll near the main vein on the underside of leaves in a strip along the main vein. A small number are laid in the mesophyll near the lateral veins, with 4-10 eggs laid at a time. Second-generation adults occur from mid-June to mid-July, which is the peak occurrence period of the whole year, averaging 13.9 per leaf.

[Control methods] 1. Choose resistant cultivars for cultivation. Delicious kiwifruit (such as the Jinkui cultivar) suffers less damage than Chinese kiwifruit. 2. Choose a suitable trellis system. The occurrence of this pest is related to light intensity. Pergola trellises suffer heavier damage, while T-bar and hedgerow trellises suffer lighter damage. 3. Clean the orchard and disinfect it, remove weeds in and around the orchard, and plow winter green manure back into the field in time. 4. During the peak adult occurrence period, spray 40% dimethoate 1:1200 solution, with a control effect reaching 99.3%, or spray 10% trebon 1:2500 solution, with a control effect reaching 99.6%. You can also spray 25% deltamethrin 3000-fold solution or 50% pirimicarb wettable powder 4000-fold solution and other pyrethroid pesticides, all of which can achieve relatively good control effects.

Fruit-Piercing Noctuid

[Damage symptoms] When the fruit is near maturity, adults use their siphoning mouthparts (with thick and sharp mouthparts, and the tip and both sides of the proboscis having many small spines) to pierce the kiwifruit peel and suck the juice. The puncture holes are very small and hard to notice. After about 1 week, the peel at the puncture hole turns yellow, sinks, and exudes a glue-like liquid. Afterward, the area near the wound softens and rots and gradually expands into an elliptical water-soaked patch, and finally the entire fruit rots.

[Infection process] In the Wuhan area, 3-4 generations occur per year. Both larvae and adults can overwinter. It is continuous from late May to mid-November, and forms three occurrence peaks in mid-to-late June, mid-to-late August, and mid-September to mid-October, with each adult stage lasting about 38 days. The adults that damage kiwifruit are mostly third-generation adults. The larvae of each generation mostly feed on Cocculus orbiculatus and Sinomenium acutum.

[Control methods] 1. Do a good job of orchard cleanup and disinfection, and dig out Cocculus orbiculatus, Sinomenium acutum, and other plants together with their roots in and around the orchard. 2. Begin bagging kiwifruit from the young fruit stage. 3. Before adult damage, soak melons and fruits in a 15-fold solution of the highly toxic pesticide sodium fluoroacetate for 1 minute, take them out, and hang them in the orchard for trapping and killing, but pay close attention to human and livestock safety. Using the principle that fruit-piercing noctuids are attracted to the ultraviolet spectrum, blacklight lamps can be placed in the orchard for trapping and killing. A trapping and killing liquid made of 8% sugar and 1% vinegar in water plus 0.2% sodium fluoride can also be hung in bottles for trapping and killing. 4. In a 10-mu kiwifruit orchard, set up 6 40-watt golden-yellow fluorescent lamps, which can reduce the amount of damage by fruit-piercing noctuids.

Bat Moth

[Damage symptoms] The larvae damage the cortex and xylem at about 50 cm from the tree trunk base and at the base of the main vine. When boring in, they first spin silk and form a web to conceal the body, then while boring and feeding they send out the bitten wood fragments, which stick to the silk web and finally are joined into a packet that covers the opening. Sometimes the larvae first gnaw a horizontal groove on the branch or trunk and then bore into the pith, thus often causing girdling of the bark and causing the upper branches or trunk to wither or break. The larval tunnels mostly bore downward from the pith and sometimes can reach as deep as the underground roots, and the inner walls of the tunnels are smooth. Before pupation, the larval packet enlarges, its color becomes brown, and the larva first bites a round hole and uses silk to block the inner opening of the tunnel in preparation for pupation.

[Infection process] One generation per year, with a few having one generation every two years. It overwinters as eggs on the ground or as larvae in tunnels at the tree trunk base, and hatches in mid-April of the following year. Early-instar larvae feed on humus. After the 2nd and 3rd instars, they turn to boring and feeding inside the root crown. Adults appear from late August to September.

[Control methods] 1. Insectivorous birds, predatory ground beetles, and parasitic flies all have a certain inhibitory effect on bat moth populations. 2. When insect packets are found at the tree trunk base, tear off the packets, insert fine iron wire into the insect holes, and stab the larvae to death. Or drip in 50% dichlorvos 50-fold solution, or use a cotton ball dipped in the pesticide solution and plug it into the boring hole. Or use aluminum phosphide tablets, 0.1 g per hole is sufficient, and seal the hole opening with wet mud to poison the larvae. 3. Remove miscellaneous trees near the orchard, such as Vitex negundo and Mallotus apelta and other host plants. 4. Combine with pruning to cut off damaged vines and burn them. 5. During the period when early-instar larvae are active on the ground, spray 10% cypermethrin 2000-fold solution under the canopy and at the trunk base to eliminate 2nd and 3rd instar larvae.