How to prevent and control kiwifruit pests and diseases? A full analysis of practical techniques
Kiwifruit, also known as kiwi, fox peach, monkey pear and so on, 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, and the northern foothills of the Qinling Mountains in Shaanxi are the region with the richest kiwifruit resources in China. The history of folk artificial cultivation reaches more than a thousand years. Now let us take a look at kiwifruit pest and disease control techniques!
Fruit ripe rot
[Damage symptoms] When kiwifruit ripens, a mark resembling a thumb pressure indentation appears on one side of the harvested fruit, slightly sunken, brown, dimple-shaped, about 5 mm in diameter. Its skin does not break; when the skin is peeled open, slightly pale yellow flesh is revealed, the edge of the lesion is dark green or water-soaked, and in the middle there is often milky white cone-shaped decay. 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 to 21 days it infects the fruit (that is, it begins infecting young fruit about 3 weeks after flower drop), and symptoms of damage appear at the fruit ripening stage.
[Control methods] ① Begin bagging young fruit one week after flower drop to avoid infecting young fruit. ② From two weeks after flower drop to the fruit expansion stage (May to 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 to 3 times, with a spraying interval of about 20 days. ③ Remove pruned kiwifruit branches and dead branches and fallen leaves to reduce places where the pathogen can parasitize.
Root rot
[Damage symptoms] In the initial stage, a dark brown water-soaked lesion appears at the root crown, and after gradually expanding it produces white silky mycelium. The cortex and xylem of the diseased part gradually rot, with a smell of distiller's grains. After the mycelium develops in large amounts, sclerotia form in 8 to 9 days, resembling rapeseed in size, pale yellow. Afterward the lower roots gradually turn black and rot, thereby causing the entire plant to die.
[Infection process] It overwinters as mycelium in the damaged part. In the Wuhan area, disease begins in April, with July to September being the period of severe occurrence, and it stops developing 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, do a good job of clearing ditches and draining waterlogged areas during the rainy season, do not plant too deep, and do not apply unfermented fertilizer. ② In March and mid-to-late June, use 0.5 kg of zineb plus 200 kg of water to irrigate the roots. ③ When diseased plants are found, dig open the soil at the root crown, carefully scrape away the diseased part and a small amount of the healthy part, disinfect with 0.1% mercuric chloride, then apply Bordeaux paste, and 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 soaking first appears at the fruit stem. Afterward the lesion expands evenly downward, the flesh rots downward from the fruit stem and spreads through the whole fruit, with a slight translucent appearance and a wine smell. On the fruit skin 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 to 40%.
[Infection process] The pathogen overwinters as conidia in the diseased part 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 the flowering stage to the petal-fall stage. 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 sanitation. ② Promptly pick diseased flowers and burn them in a centralized manner. 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 to make the solution adhere to the fruit stem. Within 24 hours after harvest, treat the wound and the whole fruit with a chemical, such as soaking the fruit for 1 minute in 50% carbendazim 1000-fold solution plus "2,4-D" 100 to 200 ppm.
Leafhopper
[Damage symptoms] Adults and nymphs suck the sap of kiwifruit buds, leaves and branch tips. On damaged leaf surfaces, yellow-white spots first appear and gradually expand into patches. In severe cases, the whole leaf becomes pale and falls early, the tree body weakens, and yield drops sharply.
[Infection process] Four generations occur per year, and the fourth-generation adults overwinter in winter green manure crops and grass clumps. In early spring, overwintering adults begin activity, mate and then lay eggs. The egg stage is 7 to 10 days, and the nymph stage is 15 to 20 days. In mid-to-late April, first-generation adults lay eggs. The eggs are laid in the mesophyll near the midvein on the underside of leaves in a strip along the midvein. A small number are laid in the mesophyll near the lateral veins, with 4 to 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 insects per leaf.
[Control methods] ① Choose resistant varieties for cultivation. Delicious kiwifruit (such as the Jinkui variety) suffers less damage than Chinese kiwifruit. ② Choose a suitable trellis type. The occurrence of this pest is related to light intensity. Pergola trellises suffer somewhat more damage, while T-shaped trellises and hedge trellises suffer less. ③ Clear the orchard and disinfect it, remove weeds inside and around the orchard, and promptly plow winter green manure back into the field. ④ During the peak adult occurrence period, spray 40% dimethoate 1:1200 solution, with a control effect of 99.3%; spray 10% trebon 1:2500 solution, with a control effect of 99.6%. You can also spray 25% decamethrin 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 owlet moth
[Damage symptoms] When the fruit is near ripening, 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 skin and suck the juice. The puncture hole is very small and difficult to detect. After about 1 week, the fruit skin at the puncture hole turns yellow and sunken and exudes a gummy liquid. Afterward the area near the wound soft-rots and gradually expands into an oval water-soaked patch, and finally the whole fruit rots.
[Infection process] In the Wuhan area, 3 to 4 generations occur per year. Both larvae and adults can overwinter, and from late May to mid-November there is no interruption. Three occurrence peaks form in mid-to-late June, mid-to-late August, and mid-September to mid-October, and each generation's adult period is about 38 days. The ones harming 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 clearing and disinfection, and uproot Cocculus orbiculatus, Sinomenium acutum and others in and around the orchard together with their roots. 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 trap killing, but pay close attention to the safety of people and livestock. Using the principle that fruit-piercing owlet moths are attracted to the ultraviolet spectrum, blacklight lamps can be placed in the orchard for trap killing. A trap-killing liquid made of 8% sugar and 1% vinegar in water plus 0.2% sodium fluoride can also be hung in bottles for trap 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 owlet moths.
Ghost moth
[Damage symptoms] The larvae damage the cortex and xylem at about 50 cm at the base of the trunk and at the base of the main vine. When boring in, they first spin silk to form a web to conceal the body, then while boring and feeding they send out the gnawed wood shavings, which stick to the silk web and are finally joined into a packet to block the opening. Sometimes the larvae first gnaw a horizontal groove on the branch and then bore into the pith, thus often causing girdling of the bark and making the upper branches wither or break. The larval galleries mostly bore downward from the pith and can sometimes reach deep into the underground roots, and the inner walls of the galleries are smooth. Before pupation, the larval packet enlarges, its color turns brown, and the larva first bites a round hole and blocks the inner opening of the gallery with a silk cover at the hole opening in preparation for pupation.
[Infection process] One generation per year, with a few having two generations every two years. It overwinters as eggs on the ground or as larvae in tunnels at the base of the trunk, and hatches in mid-April of the following year. Early-instar larvae feed on humus, and 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 Insect-eating birds, predatory ground beetles and parasitic flies all have a certain inhibitory effect on the occurrence of ghost moths. ② When insect packets are found at the base of the trunk, tear off the packets, insert a thin wire into the insect hole, 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 enough, and seal the hole opening with wet mud to poison the larvae. ③ Remove miscellaneous trees near the orchard, such as Vitex negundo, Mallotus japonicus and other host plants. ④ In combination with pruning, 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 kill the 2nd and 3rd instar larvae.