Quiet a number of maladies can plague the tomato fruit. If you have noticed abnormal cavities pitted with scar tissue and swelling, your tomato may be afflicted with cat-facing fruit deformity. Cat-facing refers to a type of physiological damage affecting tomatoes and represented by scarring and cavities near the blossom end.

So called since the abnormal cracking and dimpling on tomatoes looks somewhat akin to a small cat’s face. Basically, it is the abnormal development of plant tissue affecting the ovary or female sex organ which results in the flower, followed by the fruit development to become malformed. In concentric cracking, the fruit develop circular, concentric cracks around the stem end of the fruit.

In radial cracking, the fruit cracks radiate form the stem end. Cat-face is expressed as malformation and cracking of fruit at the blossom end, often exposing the locules.

Conditions favoring disorder development.

The exact cause of cat-facing on tomatoes is uncertain and could be caused by any number of factors but seems to center around unfavorable growing conditions as discussed below:

Possible causes are cold weather with night temperatures of 12 degrees Celsius or lower at flowering time. Other researchers say that temperatures below 16 degrees Celsius for a number of successive days when plants are immature ~ about three weeks prior to blooming appear to coincide with tomato cat-facing fruit deformity. The result is incomplete pollination, which creates the deformity.

Periods of very fast fruit growth with high temperature and moisture levels.

Initial fruit growth during a dry period followed by heavy rain or irrigation during ripening.

Wide differences in day and night temperatures. Cat-face may be caused by abnormally cool or hot weather, or any disturbance to flower parts during blossoming.

High nitrogen levels.

Herbicide injury.

Poor nutrition.

Over-pruning.

Physical damage to the blossom can also cause cat-facing.

Thrips ~ tiny slender insects with fringed wings may also contribute to cat-facing.

Managing the disorder.

Grow varieties that historically have no issues with cat-facing disorder.

Prevent the soil from becoming sodden by irrigation control and well-draining soil.

Avoid the use of hormonal based herbicides and the potential drift that may accompany their use.

Conclusively, manage all the other highlighted factors above such as moisture – have a sound irrigation scheduling, monitor nitrogen levels, careful pruning, control thrips timeously, avoid causing injuries to the fruits when carrying out agronomic activities and have an effective nutrition management regime as determined by soil analysis.

This relatively common problem is not a disease but rather a physiological disorder caused by a calcium imbalances within the plant. A water-soaked spot at the blossom end of the fruits is the classic symptom of this disorder. BER mostly affects: Tomatoes, peppers, eggplants, squash, cucumbers and water melons.

BER is most common when the growing season starts out wet and then becomes too dry prior to or during fruit setting. Damage usually appears when fruits are roughly half their full size. The water-soaked areas enlarge and turn dark brown and eventually begin to rot.

CAUSES:
Low concentration of calcium in the fruit, remember calcium is critical for normal cell growth. When demand for calcium exceeds the supply, tissues break down.

BER occurs when there are wide fluctuations of moisture which reduces uptake and movement of calcium into the plant.
Calcium deficiency during fruit formation can also be caused by too much nitrogen containing fertilizer, high salt levels in the soil, or damage to plant roots when carrying out agronomic activities.
Soil pH – either too high or too low
Cold soil – cold soils limit nutrient uptake.

IDENTIFYING BLOSSOM-END ROT DAMAGE
Usually BER occurs when the fruit is green or ripening. It starts with a small, depressed, water-soaked area on the blossom end of the fruit.

As the spot enlarges, it becomes sunken and turns black or dark leathery brown in color.

PREVENTING BLOSSOM END ROT (BER)

Maintain consistent levels of moisture in the soil throughout the growing season.
Prevent calcium deficiency by supplementing with calcium containing foliar fertilizers or top dress with calcium nitrate.
Maintain soil pH at optimum levels as per specific crop requirements – soil analysis is critical!
Keep records: You may notice that some crop varieties are more susceptible to blossom-end rot than others.
Avoid cultivating or hoeing near the roots of tomato plants, in other words carry out agronomic activities carefully and preferably use herbicides instead of weeding.
Avoid over-fertilizing during early fruiting, when blossom-end rot is more likely to occur.

Symptoms

Unlike with powdery mildew, plants affected by downy mildew are not so easy to recognize. Look out for the following:

• Discolored blotches on the upper leaf surface. These may be pale green, yellow, purple or brown depending on the plant affected. The blotches sometimes have straight edges (e.g. on lettuce) if they are bordered by the leaf veins.
• A mould-like growth on the underside of the leaf, corresponding to the blotch on the upper surface. This growth may be white, grey or purple depending on the species of downy mildew.
• On some plants (e.g. Peas) the growth is easy to see with the naked eye. On others (e.g. Roses) it can be difficult to see, even with a hand lens.
• Severely affected leaves may shrivel and turn brown or turn yellow and fall prematurely.
• Occasionally other plant parts can be affected e.g. Cauliflower curds, Pea pods etc.
• Severely affected plants are often stunted and lack vigor. In some cases the plant may die.

Control

Non-chemical control

• Pick off and dispose of by burying or burning affected leaves as soon as symptoms are seen.
• Remove and destroy severely affected plants.
• Avoid dense planting and control weeds so that there is good air circulation around the plants.
• In glasshouses, try to avoid prolonged leaf wetness or periods of high humidity. Avoid overhead watering where possible. Open the doors and vents when conditions allow encouraging air movement.
• Avoid watering plants in the evening as this can lead to high humidity or leaf wetness that persists throughout the night. Water early in the morning so that leaf surfaces dry out rapidly.
• To avoid infection from soil-borne resting spores, practice crop rotation for vegetables and avoid re-planting with the same host for at least a year where an ornamental plant has been affected.

Resistance: Cultivars with resistance to downy mildew are available for some vegetable crops. However, the disease resistance can break down if the downy mildew mutates to produce a genetically different ‘race’ so growing a resistant cultivar does not always guarantee freedom from infection.

Chemical control

Fungicides applied specifically for downy mildew control may be unnecessary. The following broad spectrum protectant fungicides may be considered as they are at least somewhat effective in protecting against downy mildew infection:

Copper oxychloride 85wp, Dithane M45/Mancozeb, Copper hydroxide 77, Bravo/Chlorothalonil, and Metalaxyl + mancozeb/Chemalaxyl.

Always consult Agricura Agronomists before using any of the stated products as there are a whole lot of unique technical aspects involved of which failure to adhere to these instructions may result in permanent crop or tree damage and significant reduction in yield and quality!

Additional Resources

https://www.rhs.org.uk/advice/profile?pid=683

https://www.google.com/search?rlz=1C1GCEA_enZW788ZW788&tbm=isch&sa=1&ei=JhB5XJnuEIfjUp6rqXg&q=downy+mildew+of+carrots&oq=downy+mildew+of+carrots&gs_l=img.3…18245.21651..22655…0.0..0.449.4086.2-6j5j2……1….1..gws-wiz-img…….0j0i24j35i39.KQ3tHQMx6Qw#imgrc=xlxWef3z3RmxzM:

Powdery mildew can affect numerous plants including fruit, vegetable, and agronomic crops as well as herbaceous ornamentals. This common and widespread disease can occur in commercial and residential plantings. Susceptible plants that are infected early in the season can be seriously damaged, while plant species affected later in the season may not be significantly harmed. Powdery mildew may adversely affect flowering, fruit development, plant vigor and yield. Plants that become stressed by powdery mildew infections may succumb to other abiotic or infectious agents.

Signs and Symptoms

Powdery mildew is easily identified by the presence of white, tan, or gray powdery fungal growth (mycelium and spores) that is present primarily on surfaces of infected plant parts. Immature plant parts are often most susceptible. Affected leaves, stems, buds, flowers and fruit appear as if they have been dusted with white powder. Later in the growing season, tiny, round, black fungal fruiting structures of the overwintering stage may appear.

Powdery mildew may occur as isolated spots or cover entire plant surfaces. When young expanding leaves are infected, they may become distorted and stunted. Leaves may curl at the margins. Discolored, irregular spots and blotches may develop on foliage severely infected leaves drop prematurely. Fruit may be misshapen, fail to color properly, become russetted or split open. Fruit of many vegetables do not become infected but powdery mildews can still reduce yield and quality.

Crops/Plants that are generally affected by powdery mildew in Zimbabwe include: Wheat, Tomatoes, Butternuts, Cucumbers, Peas, Water melons, Roses, Fruit trees etc.

N.B The danger with Powdery Mildew is that it can become problematic even when it is too dry for other diseases to develop.

Disease management

Management options are often determined by the production system e.g. Commercial field, residential landscape and greenhouses as well as by the specific crop. Follow as many of the management options listed below as possible whenever they are applicable.

Cultural Practices

Variety selection

Plant cultivars vary in their susceptibility to powdery mildew. Resistant/tolerant cultivars of apples, grapes, some cucurbits, pepper, rose, wheat and many other crops are available. Whenever possible, select cultivars with known resistance or tolerance to this disease.

Planting site

Do not plant susceptible crops in low areas or sites that are shaded; these are often high humidity areas. Rotate annual crops to reduce pressure from overwintering powdery mildew fungi.

Fertility

Avoid excessive applications of nitrogen fertilizer, which stimulate succulent growth that is most susceptible to infection.

Sanitation

Remove and destroy infected plant tissues and debris that may serve as overwintering sources of these fungi. Crop residues can also be incorporated into the soil to reduce sources of overwintering fungi.

Air circulation

Keep plants well-spaced and properly thinned to promote air movement, light penetration, and rapid leaf drying.

Fungicides

Fungicides may be warranted for early season management of powdery mildew on susceptible crops, especially in commercial plantings or where highly valuable plants are grown. Fungicides are most effective when applied as preventatives, before primary infections can occur. Some crops, such as grape, remain susceptible all season and require consistent and prolonged sprays. Fungicide use in residential plantings is generally not recommended, especially when disease occurs late in the season. Late season infections cause minimal damage, even when plants appear severely affected.

The following products are recommended for the prevention and control of this economically important disease:

Always consult Agricura Agronomists before using any of the stated products as there are a whole lot of unique technical aspects involved of which failure to adhere to these instructions may result in permanent crop or tree damage and significant reduction in yield and quality!

Cossan Wettable Sulphur, Agridust/Vegidust, Carbendazim, Propiconazole/Tilt, Orius/ Tebuconazole, Shavit/Triadimenol, Lime Sulphur and Funginex.

Additional Resources

Extension Plant Pathology publications (plant disease fact sheets and spray guides)

http://plantpathology.ca.uky.edu/extension/publications

Stressed weeds

Stressed weeds are harder to kill than healthy actively growing weeds. Stress is caused by lack of moisture, lack of oxygen due to water logging, extremes of temperature, nutrient deficiencies, insect pests, disease, sublethal doses of herbicides from prior applications or residues and mechanical damage from tillage, slashing or grazing.

Once a weed has been subject to stress it will not be adequately controlled by rates of herbicide that would otherwise be sufficient to control an unstressed weed, even after the stressed weed has apparently recovered from the stress. Never apply post emergent herbicides to stressed weeds.

Timing of application

Proper timing is critical for obtaining maximum performance from post-emergent herbicides. The herbicide label defines restrictions regarding application timing and thus is the most important consideration. The impact of application timing on effectiveness and prevention of competitive yield losses also needs to be considered. Post-emergent herbicides generally decrease in effectiveness as weeds increase in size.

The improved control provided by early applications must be balanced against the risk of late emerging weeds becoming established following application. While concerns over late flushes of weeds are valid, weeds that emerge soon after planting are the most competitive with the crop. The control of weeds that emerge soon after crop planting should not be compromised in order to allow later flushes of weeds to become established.

Rainfast period

Herbicide labels include recommendations on how much time must elapse between herbicide application and subsequent rainfall to ensure good herbicide performance. This is known as the rainfast period. Generally, herbicide rainfast ratings are based on good growing conditions. Poor conditions may require a longer interval between application and any rainfall to ensure adequate herbicide translocation within the weed before the herbicide is washed off.

For many herbicides, any amount of rainfall soon after spraying has the potential to reduce absorption, translocation, and subsequent weed control. If you apply herbicide and it rains before its rainfast, herbicide performance will be reduced. Rainfast period generally ranges from 30 minutes to 6 hours depending with the herbicide under consideration among other key factors. Product labels will indicate on the specific rainfast periods.

Effects of temperature on rainfast period

The likelihood of decreased weed control due to cool temperatures will vary, depending upon the target weed, herbicide, and rate applied. For example, glyphosate usually performs well under a wide range of temperatures. When the temperature is lower than 12°C, weed growth slows, resulting in slower herbicide uptake and translocation. This increases the required rainfast period and slows the onset of symptoms and herbicide efficacy.

Water quality

Quality of water used in spray tanks can affect herbicide efficacy. Water is the primary carrier for herbicide applications. In fact, it usually makes up over 99% of the spray solution. Considering that, it should be no surprise that the chemistry of water added to the spray tank greatly impacts herbicide effectiveness.

Turbidity

Turbid water or water containing suspended solids, soil or organic matter can reduce effectiveness of post-emergent herbicides. Water should be clean and clear for all pesticide applications however some pesticides are not as sensitive to turbidity as others.

Hard water

Hard water contains high levels of calcium (Ca), magnesium (Mg), sodium (Na), or iron (Fe). Other cations can cause hard water, but these are the usual suspects. Ca, Mg, Na, and Fe cations (positively charged ions) attach to negatively charged herbicide molecules. Often, the association between herbicides and these cations renders the herbicide ineffective. High pH and hard water act together to reduce herbicide effectiveness. High pH causes more of the herbicide to dissociate while high concentrations of cations bind with the dissociated herbicide to reduce its effectiveness.

Water pH

Water pH is a measure of the H+ ion concentration in water. As water pH decreases, it becomes more acidic and the number of H+ ions increases. Acidic conditions (pH 3 to 6) are generally suitable for mixing post-emergent herbicides classified as weak acids. When water pH exceeds 7, consider adding adjuvants to lower pH.

Weak acids dissociate less under acid conditions where H+ ion concentration is high. Dissociated herbicides are absorbed more slowly across plant cell membranes. Ideally, spray water pH should be low such that herbicides do not dissociate or dissociate at low levels. Avoiding herbicide dissociation is the primary reason water used in pesticide mixing should be acidic.

Role of spray adjuvants

Spray adjuvants are used with post-emergent herbicides to help overcome the barriers that impede movement of the herbicide from the leaf surface to the interior of the cell. An adjuvant is any substance in a herbicide formulation or added to the spray tank to modify herbicidal activity or application characteristics.  Some products are formulated with sufficient additives such that the user usually does not need to add them to the tank whereas other products require addition of adjuvants for all uses.

Adjuvants can enhance herbicide activity in several different ways. The effect of surfactants on the surface tension of spray droplets is well documented. The epicuticular wax on the surface of leaves repels water, resulting in beading of spray droplets as they land on leaves.  In some situations a high percentage of spray droplets may simply bounce off leaves, resulting in the herbicide falling harmlessly to the ground. Surfactants reduce the surface tension of spray droplets, increasing spray retention and allowing the spray droplets to spread over a larger area.  An increase in spray coverage is especially important with contact herbicides that do not move within plants.

1| The annual yield loss in maize as a result of weed problems can reach 50% or more.

2| The crop must have a good head start against weeds and hence must be weed free for the first 10 weeks of the maize crop cycle.

3| If a farmer fails to control weeds in the first 5 weeks of a maize cycle, then 50% of the yield could be lost.

4| If a farmer fails to control shamva grass (Rottboellia cochinchinensis) throughout the maize crop cycle, then 57-80% of the yield can be lost.

5| One year of seeding makes 7 years of weeding. Do not allow weeds to bear seed, lest it will create future weed management problems.

6| There are more than 25 herbicides registered in Zimbabwe, which can be sprayed in maize.

Time to automate agriculture

Hand weeding has no place in commercial agriculture. It is bad and terrible economics and definitely unsustainable. It is expensive, hard and inefficient and it does not guarantee a weed free field. It actually agitates the soil to produce more weeds. Enlightenment of the above startling weed statistics, cost-effective weed management strategies become very critical to the farmer. There is a very important weed management concept in crop productivity called the critical weed free period.

But what is the critical weed free period?

It is the critical point in time during the growing season when weeds cause the largest yield loss.

Weed free period in Maize.

In maize, this period occurs from V1 to V6 (1 to 6 leaf collars). Some sources will mention that it even begins at the VE stage (emergence). During this time the maize crop needs to stay clean. Weeds will definitely affect yield if control is not provided.

Weed free period in Soyabeans.

For soybeans the period is the V1-V3 (1 to 3 trifoliates). If you can control weeds during this time, losses should be assumed to be under 5%.

Why are these periods important?

It is critical to stay weed-free during these periods if a grower wants to maximize yield potential. Maize and soybeans on average can have a yield loss of up to 50 or 60% during this time if control is not provided and even higher depending on the weed spectrum. Timeous and correct use of pre-emergent herbicides can go a long way in as much as weed management options are concerned. Any successful weed management program must include pre-emergent herbicides as these are very critical with quite a number of unique advantages some of which are listed:

Pre-emergent herbicides:

• Offer an alternate mode of action to many post-emergent options; can reduce selection pressure on subsequent post-emergent herbicide applications.
• Remove much of the early season weed competitive pressure on a crop and can protect yield better than post-emergent herbicides.
• Can save costs, especially in the fallow here multiple knockdown applications may be required.
• Can reduce the time pressure on spraying operations, especially in situations when double knocking is a requirement.

Here are some of the effective pre-emergent herbicide combinations/options that a farmer can count on in Soyabeans and Maize.

Soyabeans pre-emergent herbicide combinations:

• Metolachlor 1.5 Litres/ha + Metribuzine 0.6 -1 Litres/ha. Mix these two herbicides in 200 litres of water and apply immediately after planting or within three days after planting when the soil is relatively moist.
• Metolachlor 1.5 Litres/ha + Strongarm 30grams/ha. Mix these two herbicides in 200 litres of water and apply immediately after planting or within three days after planting when the soil is relatively moist.
• Metolachlor 1.5 Litres/ha + Terbutryn 1.8 – 2.4 Litres/ha. Mix these two herbicides in 200 litres of water and apply immediately after planting or within three days after planting when the soil is relatively moist.

1. You can alternatively use Kalif/Clomazone/Command in place of Metolachlor.

Maize pre-emergent herbicide combinations:

• Metolachlor 1.5 Litres/ha + Atrazine 3 -5 Litres/ha. Mix these two herbicides in 200 litres of water and apply immediately after planting or within three days after planting when the soil is relatively moist. However note that Atrazine is both a pre-emergent herbicide as well as an early post emergent herbicide. This combination is suitable for those growers who intend to repeat growing maize in the next season, bearing in mind that Atrazine has a residual period of up to 18 months from point of application upon which NO any other crop other than maize or sorghum can be grown. Failure to appreciate this critical piece of information is the very reason why there is a misconception by some farmers that herbicides affect soil fertility and productivity “Mishonga yesora inouraya ivhu”, ichi hachizi chokwadi what is important is to appreciate the residual period and plan accordingly. Farming is a business and therefore planning remains an essential tool in the equation.
• Metolachlor 1.5 Litres/ha + MCPA 3 -5 Litres/ha. Mix these two herbicides in 200 litres of water and apply immediately after planting or within three days after planting when the soil is relatively moist. However note that MCPA is both a pre-emergent herbicide as well as a post emergent herbicide. This combination is very suitable to growers who are into rotations for example those growers who rotate maize with soyabeans, tobacco and other broad leaf crops in the following season.
• Metolachlor 1.5 Litres/ha + Terbutryn 2.5 Litres/ha. Mix these two herbicides in 200 litres of water and apply immediately after planting or within three days after planting when the soil is relatively moist.

1. You can alternatively use Acetochlor/Relay/Harness or S-Metolachlor/Dual Magnum or Alachlor/Laso in place of Metolachlor.

Acknowledgements:

John Basera – SeedCo Head of Agronomy Services.

Bongayi Gokoma – Agricura Sales Manager.

Onias Tawananyasha Mlambo – Agricura Technical Agronomist.

Critical weed-free period

Chemical crop protection products commonly referred to as pesticides or agrochemicals play a vital role in controlling the pests and diseases that threaten our food security.

Food crops must compete with 30,000 species of weeds, 3,000 species of nematodes and 10,000 species of plant-eating insects. We know that despite the use of modern crop protection products 20-40% of potential food production is still lost every year to pests. These losses can occur while the crop is growing in the field, when it is in storage and in the home. In short, an adequate, reliable food supply cannot be guaranteed without the use of crop protection products.

• In underdeveloped countries Agriculture employs more people than any other industry.

• Women provides an average of 43 percent of the agricultural labour force in developing countries.

• In most underdeveloped parts of the world reliance is based on agriculture for a big portion of GDP.

• The global value of Agriculture adds up to $2.4 trillion.

Every winter, rodents invade homes looking for a warm place to harbor and nest. As we say goodbye to winter and welcome summer, rats continue to invade homes in search of food. Rats do not make good house guests regardless of the season due to their destructive behavior like gnawing furniture, food packaging or clothes and they can transmit diseases through their droppings and biting. In Zimbabwe the most common rat types that invade homes are the black rat and the brown rat. Once in your home, rats breed and multiply swiftly. 

Here are some tips to help reduce chances of rats invading your home this summer

• Thoroughly inspect the exterior and interior of your home. If you identify any openings or cracks, you can seal the cracks or openings with steel wool or any ideal substance. This will help prevent rats from squeezing or gnawing through the spaces.
• Keep your garage and other storage areas well organized. For instance, store boxes on shelves and not on the floors.
• Install door sweeps on all exterior doors
• Dispose of garbage promptly, and keep garbage cans as far away from your home as possible.
• Store firewood at least 20 feet away from your home, rats like to nest in wood piles therefore moving firewood further from your home makes it harder for rats to get inside your house.

Have rats already invaded your home and you are in dire need of professional help? Thankfully homeowners no longer need to worry about rats’ invasion and infestations because as Agricura we offer professional rodent control services that are designed to control rats’ infestations no matter what time of the year. Our prices are affordable and the service is prompt and can be customized to better meet your needs. We have been in the business for over 51 years and over this time we have built a formidable wealth of experience. We are well equipped with latest technology and well trained staff. When it comes to pest management, we strongly believe no one is better than us. Get in touch with us today.