The nematode most commonly associated with dry rot disease of yam tubers is Scutellonema bradys. This species is especially important in yam production because it invades tuber tissue and causes damage that appears as dry, brown, necrotic rot. Such injury lowers the quality of the harvested tuber and can seriously reduce storage life and market value.

This is why the name is important to remember in yam pest management. Dry rot is not just a surface defect; it reflects internal tissue damage linked to nematode feeding and associated deterioration. While other nematodes can damage crops, Scutellonema bradys is the species classically associated with yam dry rot. Correct identification matters because prevention relies heavily on clean planting material, rotation, and careful field sanitation. That is why option B is the correct answer.

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The primary symptom of anthracnose disease in yams is black leaf spots and dieback. Anthracnose is mainly recognized as a foliar and stem disease, so the most noticeable signs are dark lesions on leaves and stems, followed by blighting or dieback of affected plant parts. These symptoms reduce the health of the vine canopy and can limit the plant’s ability to support tuber development.

This makes field scouting important. A grower looking for anthracnose focuses on the above-ground parts of the crop, especially dark spotting and dying back of shoots, rather than symptoms like root galls or unusual tuber color. Because anthracnose can seriously weaken vine growth, early recognition matters for management. Since black leaf spots and dieback are the key symptoms listed, option C is the correct answer.

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The virus considered most damaging to yam crops is yam mosaic virus. It is especially important because yams are commonly propagated vegetatively, so infected planting material can carry the virus from one season to the next. Once introduced, the virus can persist in the production system and reduce crop performance repeatedly.

Yam mosaic virus weakens the plant by affecting leaf health and reducing overall vigor, which in turn lowers the crop’s ability to produce and fill tubers. That makes it both a biological and a management problem. Compared with the other virus names listed, yam mosaic virus is the one most closely associated with major economic damage in yam production. Because of its strong impact and ease of carryover in seed tubers, option A is the correct answer.

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The most effective cultural practice for managing yam beetles is crop rotation combined with field sanitation. Crop rotation helps break the pest cycle by removing the beetle’s preferred host from the field for a time, while field sanitation reduces survival by removing crop residues, volunteer plants, and other places where pests may persist.

This is especially useful because yam beetles damage tubers underground, where injury can be severe before the problem is noticed. Preventing pest buildup from one season to the next is therefore a key management goal. The other options in the question are not real pest-control strategies. From both a scientific and practical standpoint, rotation and sanitation are sound cultural controls that reduce beetle pressure in a sustainable way. That is why option D is the correct answer.

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The field pest that can cause major losses by boring into yam tubers underground is the yam beetle, especially Heteroligus species. These beetles are serious pests because they feed directly on the developing tuber, creating holes and internal damage that lower quality, reduce market value, and make the tubers more vulnerable to secondary infection.

Their underground feeding is particularly important because the crop may look acceptable above ground while the tubers are already being damaged below the surface. By the time the problem is discovered, significant losses may already have occurred. Among the options listed, yam beetles are the pest most specifically associated with this kind of subterranean tuber injury in yam cultivation. That is why option B is the correct answer.

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The appropriate management approach for yam nematode prevention is using clean planting material and crop rotation. This works for two reasons. First, clean planting material helps prevent nematodes from being introduced into the field on infected tubers or setts. Second, crop rotation helps reduce nematode populations in the soil by interrupting their life cycle when yams are not continuously grown in the same place.

Because yams are vegetatively propagated, prevention is especially important. Once infested planting material is used, the problem can be carried forward easily. Practices like adding extra nitrogen, increasing field moisture, or trying to change soil alkalinity do not address the main route of spread and persistence. In practical yam production, clean seed and rotation are among the most effective foundations of nematode management. That is why option C is the correct answer.

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The fungal pathogen that causes storage rot, or soft rot, in yam tubers is Lasiodiplodia theobromae, also known by the older name Botryodiplodia theobromae. This fungus is important in postharvest yam losses because it often infects damaged or weakened tubers and causes soft, decaying tissue during storage.

Its importance helps explain why careful harvest and storage practices matter so much. Wounds made during digging, transport, or handling can provide entry points for the fungus, and poor storage conditions can make the problem worse. The other organisms listed are not the standard pathogen associated with yam soft rot. Because Lasiodiplodia theobromae is the recognized fungal cause of this storage disease, option A is the correct answer.

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The integrated pest management technique used for controlling yam diseases is using resistant varieties combined with cultural controls. This is a classic IPM strategy because it does not rely on one method alone. Resistant varieties reduce the crop’s susceptibility, while cultural practices such as clean planting material, rotation, spacing, sanitation, and proper field hygiene reduce the conditions that favor disease development.

This combined approach is more sustainable than routine pesticide use and often works better over time because it lowers disease pressure from several directions at once. By contrast, spraying on a fixed schedule regardless of need is not true IPM, and planting the same crop in the same location repeatedly can increase disease problems. Because effective disease management in yams is built on resistance plus good cultural practice, option D is the correct answer.

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The fungi that cause tuber rot during yam storage are Penicillium, Fusarium, and Aspergillus species. These fungi are common postharvest pathogens that can colonize yam tubers, especially when the tubers have been bruised, cut, or stored under warm, humid, poorly ventilated conditions. Their growth leads to spoilage, quality loss, and reduced storage life.

This is why postharvest management is so important in yam production. Gentle handling, curing where appropriate, and clean, dry, well-ventilated storage conditions help reduce infection. The other options listed are not the typical storage rot fungi for yams. Because Penicillium, Fusarium, and Aspergillus are well-known fungal causes of yam tuber rot in storage, option B is the correct answer.

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The practice that is NOT an effective traditional method for managing yam pests is planting during full moon. Effective pest-management practices usually work through a clear mechanism: they reduce pest survival, discourage attack, or protect the planting material. Intercropping with pest-repellent plants, appropriate crop rotation, and the use of wood ash on planting material all fit that logic better than moon-phase timing.

Planting during a full moon may exist as a traditional belief in some places, but it does not directly control pest populations or protect the crop in a biologically meaningful way. The question asks specifically about effectiveness in pest management, and this option does not meet that standard. Because it lacks a practical pest-control function, option C is the correct answer.

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The most environmentally sustainable approach to yam disease management is integrated disease management using resistant varieties and cultural practices. This approach works by combining plant resistance with preventive field management methods such as crop rotation, sanitation, proper spacing, and the use of clean planting material. Together, these measures reduce disease pressure without depending heavily on repeated chemical treatments.

This is considered sustainable because it protects the crop while reducing unnecessary environmental impact. Frequent broad-spectrum pesticide use can affect non-target organisms, increase costs, and encourage other management problems over time. Complete soil sterilization is also too extreme for normal field production. In contrast, integrated disease management focuses on prevention, resilience, and long-term field health. Because it balances effectiveness with environmental responsibility, option A is the correct answer.

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