tomato

Cause

Aphids (light green, sap-sucking insects) and spider mites (grey/black) cause leaf distortion and sooty mold by excreting honeydew. Ants farm aphid colonies for this honeydew. Fruit flies lay eggs in developing tomato and capsicum fruit, creating internal maggot damage visible as skin blemishes.

Solutions

• 1. Identify pest: aphids cluster on new growth; spider mites create fine webbing on leaf undersides; fruit fly damage appears as skin soft spots
• 2. For aphids/mites: spray plants with hard hose jet to dislodge insects, then apply soapy water (1 tbsp dish soap per litre water) to leaf undersides
• 3. For fruit fly: hang proprietary fruit fly traps with pheromone lure near affected plants; cover developing fruit with fine-net bags before color change
• 4. For caterpillars: inspect leaf undersides for raised egg clusters (rub off); spray with Bacillus thuringiensis (Bt) biological spray for active caterpillars
• 5. Apply molasses spray (1 tbsp molasses + 1 tsp dish soap per litre water) weekly as deterrent — reapply after rain

Cause

Azadirachtin (C35H44O16) from neem oil acts as antifeedant and growth regulator against Tetranychus urticae. Neem oil LC50: 33.99 ppm vs aqueous extract LC50: 260.30 ppm — neem oil is 7.7x more effective due to higher azadirachtin concentration.

Solutions

• 1. Mix neem oil at 50-300 ppm concentration with 0.1% Tween 80 emulsifier in distilled water
• 2. Shake vigorously before each application to ensure emulsification
• 3. Spray directly on leaf undersides where spider mites congregate
• 4. Wait 7 days then assess mortality using Abbott's formula
• 5. Repeat application if mortality < 90%

Cause

Soil pH outside 6.5-7.5 range causes nutrient lockout — even when nitrogen, phosphorous, and potassium are present in the soil, they become chemically unavailable to plant roots. Acidic soil (pH < 6.5) causes aluminium and manganese toxicity while binding calcium and magnesium. Alkaline soil (pH > 7.5) precipitates iron, zinc, and phosphorus into insoluble compounds that roots cannot absorb.

Solutions

• 1. Insert pH probe into moist soil, wait 60 seconds — record reading
• 2. If below 6.5: apply agricultural lime at 50g per square meter, rake into top 2 inches, water lightly
• 3. If above 7.5: apply elemental sulfur at 30g per square meter OR add 2-inch layer of composted pine needles
• 4. Wait 2-3 weeks for pH to stabilize, then retest with fresh reading
• 5. Add trace minerals: 1-2 handfuls rock dust per 3 sq ft (1m2) each season

Cause

Seedling damping-off (Pythium spp., Rhizoctonia solani, Fusarium spp.) occurs when pathogenic fungi infect seedlings at or below soil line. Fungi colonize root cortex and vascular tissue, producing phytotoxins and enzyme cocktails (cellulases, pectinases) that degrade cell walls, causing water transport collapse leading to sudden wilting and death.

Solutions

• 1. Sterile medium: Use commercially sterilized seed-starting mix or amend garden soil with 50% perlite:50% peat for drainage; do not reuse old seed-starting mix without sterilization (steam at 82°C for 30 min)
• 2. Spacing: Sow seeds thinly to avoid dense seedling clusters that trap humidity; ideal density is 60-80 seedlings per 10x10cm tray
• 3. Water management: Apply water from below (tray bottom-watering) rather than overhead; keep substrate moisture at field capacity (50-60%), not saturation; water in morning to allow surface drying
• 4. Biocontrol: Incorporate Trichoderma harzianum at 5g/L medium or drench at 1x10^6 CFU/mL at seed emergence to competitively exclude damping-off pathogens
• 5. Fungicide treatment: For high-risk conditions, apply metalaxyl or mefenoxam as drench at 0.5mL/L at first true leaf stage; organic alternative: copper octanoate at 2mL/L

Cause

Tomato grafting failure occurs when union formation is incomplete due to incompatible cambium alignment, leading to poor water/nutrient conductance at the graft interface. Incompatible rootstock-scion combinations show necrotic tissue at the graft union by day 10-14, with stunted growth, leaf chlorosis, and eventual collapse by week 4-6.

Solutions

• 1. Rootstock preparation: Sow Solanum habrochaites seeds 5-7 days before tomato scion to synchronize stem diameter (4-5mm); grow at 24-26°C with 16hr photoperiod for vigorous seedlings
• 2. Scion preparation: Grow tomato scion seedlings at slightly cooler (20-22°C) to slow growth; prepare 1.5-2cm single bevel cut at 30° angle using sharp blade
• 3. Grafting technique: Use tube grafting method with 2mm silicone clip to hold union; ensure at least 2-3mm cambial contact on one side minimum
• 4. Healing environment: Place in darkness at 25-28°C and 95% RH for 3-4 days (high humidity prevents scion dehydration before union forms); then gradually reduce RH to 80% over 3 days
• 5. Gradual acclimation: After 7-10 days post-graft, move to normal conditions over 3 days; transplant when scion leaves show no wilting symptoms at 60% RH ambient

Cause

Sexual propagation involves the union of pollen (male) with the egg (female) to produce a seed containing an embryo. Germination begins when water penetrates the seed coat, activating enzymes that convert stored endosperm into energy for radicle emergence.

Solutions

• Start with high-quality seed from a reliable dealer suited to your climate zone
• Sow at depth equal to 2-3x the seed diameter in pre-moistened sterile mix
• Maintain consistent moisture (not saturation) and temperatures of 65-75°F for most vegetable seeds
• Provide light for fine seeds; bury larger seeds in darkness
• Allow 65-80% germination rate expectation; expect 60-75% of germinated seeds to produce vigorous seedlings

Cause

Repeating the same crops or crops from the same botanical family in the same location year after year causes pest and disease populations to build up in the soil, while specific nutrients become depleted from the same soil depth. Pathogens like Fusarium and Pythium persist in soil for years without rotation.

Solutions

• 1. Map your garden beds and record what was planted where each year
• 2. Group vegetables by botanical family: Solanaceae, Brassicas, Fabaceae, Alliums, Cucurbits, Chenopodiaceae
• 3. Create a 3-4 year rotation plan ensuring no family returns to same bed within 3 years
• 4. In year 4, return to year 1 bed positions — the soil pathogen load will have declined
• 5. For container gardens: replace all soil and wash containers every 2 years to achieve same effect