Phytophthora Root Rot

Phytophthora root rot, caused by the pathogen Phytophthora sojae, is a serious disease affecting soybean crops. Here are some key points about this disease:

Symptoms: Infected plants may show stunted growth, yellowing leaves, and wilting. Early in the season, seedlings can be attacked and killed before or shortly after emergence. Later in the season, plants may develop brown lesions on the roots and stems, leading to root rot and plant death.

Conditions Favoring Disease: Phytophthora root rot thrives in warm, saturated soils. It is most common in fields with poor drainage or those that experience heavy rainfall.

Disease Cycle: The pathogen survives in the soil as oospores, which can persist for many years. These oospores germinate in wet conditions, producing spores that infect soybean roots.

Management Strategies:

• Resistant Varieties: Planting soybean varieties with resistance genes (Rps genes) can help manage the disease. However, some races of the pathogen can overcome these resistance genes.
• Crop Rotation: Rotating soybeans with non-host crops can reduce the pathogen population in the soil.
• Improving Drainage: Enhancing field drainage can help prevent the saturated soil conditions that favor the disease.
• Seed Treatments: Using fungicide-treated seeds can protect seedlings from early infection.

Soybean Aphids

Soybean aphids (Aphis glycines) are small, sap-sucking insects that can cause significant damage to soybean crops. Here are some key points about soybean aphids:

Identification: Soybean aphids are small (about 1/16 inch long), yellow to light green, and have a pair of black cornicles (tailpipe-like structures) on their abdomen. They are usually found on the undersides of leaves.

Life Cycle: Soybean aphids have a complex life cycle that includes both sexual and asexual reproduction. They overwinter as eggs on buckthorn plants and migrate to soybeans in the spring. During the growing season, they reproduce asexually, leading to rapid population growth.

Damage: Aphids feed by sucking sap from the plant, which can weaken the plant, reduce pod set, and lower yields. They also excrete honeydew, which can lead to the growth of sooty mold on the plants.

Management:

• Monitoring: Regularly scout fields to monitor aphid populations. Treatment is usually recommended when populations reach the economic threshold of 250 aphids per plant.
• Biological Control: Natural predators like lady beetles, lacewings, and parasitic wasps can help control aphid populations.
• Chemical Control: Insecticides can be used to manage high aphid populations, but it’s important to follow integrated pest management (IPM) practices to avoid resistance.
• Resistant Varieties: Planting aphid-resistant soybean varieties can also help reduce the impact of this pest.

Sclerotina Stem Rot (White Mold)

Sclerotinia stem rot, also known as white mold, is a significant disease in soybeans caused by the fungus Sclerotinia sclerotiorum. Here are some key points about this disease:

Symptoms: Infected plants may show wilting, yellowing, and premature death. White, cottony fungal growth can be seen on stems, and hard, black sclerotia (fungal survival structures) may form inside the stems and pods.

Conditions Favoring Disease: The disease thrives in cool, wet conditions, especially when the canopy is dense and humidity is high. Fields with a history of white mold are at higher risk.

Disease Cycle: The fungus survives in the soil as sclerotia, which can persist for many years. These sclerotia germinate under favorable conditions, producing spores that infect soybean plants.

Management Strategies:

• Crop Rotation: Rotating soybeans with non-host crops like corn or small grains can help reduce the pathogen population in the soil.
• Resistant Varieties: Planting soybean varieties with partial resistance to white mold can help manage the disease.
• Cultural Practices: Practices such as reducing plant density, improving air circulation, and avoiding excessive irrigation can help reduce disease incidence.
• Fungicides: Applying fungicides at the right growth stage can help manage white mold, but timing and coverage are critical for effectiveness.

Sudden Death Syndrome

Sudden Death Syndrome (SDS) is a serious disease affecting soybean crops, caused by the soilborne fungus Fusarium virguliforme. Here are some key points about SDS:

Symptoms: SDS typically manifests in late July or early August. Initial symptoms include yellow spots between the leaf veins, which later turn brown and necrotic. Infected plants may also show root rot and blue fungal growth on the roots in moist conditions.

Conditions Favoring Disease: SDS thrives in cool, wet soils, especially in fields with poor drainage. Early planting and the presence of soybean cyst nematode (SCN) can increase the risk of SDS12.

Disease Cycle: The fungus overwinters in the soil as durable spores (chlamydospores). These spores infect soybean roots early in the season, but foliar symptoms usually appear later.

Management Strategies:

• Resistant Varieties: Planting soybean varieties with high levels of SDS resistance is crucial. Varieties should also be resistant to SCN1.
• Crop Rotation: Rotating soybeans with non-host crops can help reduce the pathogen population in the soil.
• Cultural Practices: Improving soil drainage, minimizing compaction, and staggering planting dates can help manage SDS.
• Fungicides: While fungicides can be part of an integrated management plan, their effectiveness against SDS is limited.

Bean Leaf Beetle

The bean leaf beetle (Cerotoma trifurcata) is a notable pest for soybean crops. Here are some key points about its impact on soybeans:

Identification: Bean leaf beetles are small, about 1/4 inch long, and can be yellow, red, orange, or brown. They have a distinctive black triangle at the top of their wing covers and may have additional black spots.

Life Cycle: These beetles overwinter as adults in the soil and emerge in the spring. They lay eggs in the soil at the base of plants, and the larvae feed on roots and root nodules. The larvae pupate in the soil, and new adults emerge to continue the cycle.

Damage: Adult beetles feed on soybean leaves, creating small, round holes. They can also damage pods, leading to reduced yield and quality. Additionally, they can transmit bean pod mottle virus, which can further impact plant health and productivity.

Management:

• Monitoring: Regular scouting can help detect early infestations. Look for feeding damage on leaves and pods.
• Cultural Practices: Crop rotation and maintaining clean fields can reduce beetle populations. Early planting can sometimes help avoid peak beetle activity.
• Biological Control: Natural predators like lady beetles and parasitic wasps can help control beetle numbers.
• Chemical Control: Insecticides may be used if beetle populations reach economic thresholds. It’s important to follow integrated pest management (IPM) practices to minimize resistance and protect beneficial insects.

Assessing Frost Damage

A number of acres of beans were damaged by the frost over the weekend. If you have population below 110,00 then you should be looking at replanting. It appears the fields that were damaged the most were early planted fields in no till with high residue levels and lower topography. If the beans were frozen below the cotyledon they will not regrow. If the unifoliates were frozen and the cotyledons are still green the bean is still alive and will be okay. Corn is also showing a fair bit of frost injury. If the growing point is green then the plant is still alive. The only problem with this is the growing point has to push through the dead tissue and sometimes this is not possible and the plant still ends up dying or growing distorted.

We have had little rainfall in last few weeks to activate chemical. So please walk your fields to check for week escapes. If you do this approximately 25 days after planting this will give you a good idea if have to respray. Most of the no till ground I have been across looks still very clean for weeds.

A lot of cereal fields both winter wheat and spring crops are taking on a yellow color. This is a result of a manganese deficiency. It is a water soluble nutrient and the drier it gets the more the problem is going to show up. It is very easy to diagnose as field turns yellow except were equipment has driven and these strips will stay green. This is a big issue in the Elmira area most cereal fields have this problem. A foliar application of Manganese or a rain will solve the problem.