Pest and disease on Water Jasmin trees

[Polanskiman]

Hello,

 

I have these water jasmin trees (10 of them) that I use as a fence to prevent indiscrete views from the outside. They started having lot of yellow leaves. After inspection I saw the leaves were infested with some sort of pest. See picture below:

Lots of black dots as you can see and also some orange dots.

 

Can anyone please recommend what specific product I should use to treat my trees and the course of treatment?

 

Thank you.

[drtreelove]

I think it's the same plant we have Wrightia religiosa, and I know from our experience and from seeing them all over, they are prone to nutrient deficiencies and water deficit/drought stress. Poor growing conditions and inadequate soil and water management sets them up for pest and disease issues.  And they don't respond well to incomplete NPK chemical fertilizers.  

 

You are focusing on the symptoms and not the cause; it is a common mistake.  And your are looking for a quick fix when there may be more complex issues with growing conditions and maintenance.  You show the underside of the leaf surface but not the entire plants and site conditions, so a thorough diagnosis is not possible. 

 

It's hard to see the detail of the spots, even when I download and zoom in, it goes fuzzy. But the black spots appear to be a small scale insect or fungal leaf spot. The orange spots are probably rust fungus. But these issues are secondary to the primary cause of weakened physiology and resistance from possible nutrient deficiencies.  Do you fertilize?  Are they in the ground or in pots?  What have you done to improve soil fertility? Compost, mulch, organic fertilizer. 

 

Mine greened up temporarily last year with a 15-15-15 fertilizer, but soon developed chlorosis again (yellowing). The primary defect was the original soil in the pots was poor, so I am re-potting them one by one with better soil.  They don't really come around until I do this and apply a complete organic fertilizer, mulch with real compost, and drench with a soil biology innoculant and micro-nutrient solution.  And I use a soil moisture meter to take the guess work out of watering frequency.  

 

I spray regularly with an Azadirachtin (neem) solution for pest prevention, and a biological fungicide.  

[Polanskiman]

Thanks.

 

I do fertilise the plants every two weeks or so with some fertiliser given to us by the shop where I bought the plants. The plants have been with us for around 2 months now and they started developing those symptoms not long after. Our place is just in front a another house with all kind of fruit trees, palms and whatnot and I can see they are all infested with some kind of disease/pest so I guess our plants just got exposed to those.

 

Our water jasmin trees are planted in some mix of soil and coconut husk chips. Plants are doing better perhaps because I recently fertilised them but I think the problem will come back again.

 

 

 

[drtreelove]

While the foliage appears reasonably good at this time, it's going to be difficult to keep these plants healthy for a long period of time due to the limited soil volume in the containers and the over-planting. Your regular fertilization will help. Compost mulch will be good. 

For a fast acting pesticide for ornamental plants, not food plants, Starkle G with active ingredient of dinotefuran, is a systemic insecticide that can be applied as a soil drench (therefore no spraying). It is highly mobile in the plant tissues for fast uptake and translocation and rapid control of sucking insect pests (one week or two at most if irrigated to facilitate uptake). Your plants don't appear to be flowering at this time, so there should be no pollinators foraging. It will get knock down but won't have more than two or three months residual effectiveness.  In spring you can treat with another systemic, imidacloprid, which will last in effectiveness the entire season with one application in late February or early march. 

These are neonicotinoids, controversial insecticides because of hazards for pollinators like honey bees. Imidacloprid less so than dinotefuran. They are low toxicity for mammals, deadly for fish.  Read and follow label instructions for safe an effective use. 

Organic program materials are not systemic; contact sprays have limited effectiveness on scale insects unless the timing is specific for the nymph/crawler stage.  Regular, every two weeks spraying with neem extract or wood vinegar or other bio-pesticide is possible, but better for prevention than control of an active infestation. Trichoderma is a biological fungicide for foliar spray. 

[Thian]

Right now i'm culling ours which isn't easy.

 

But since i hate pruning i never ever watered them but they don't care and always grow well.

 

Plants which get a lot of fertilizers attract pests, maybe you treated them too well?

[Polanskiman]

9 minutes ago, Thian said:

Right now i'm culling ours which isn't easy.

 

But since i hate pruning i never ever watered them but they don't care and always grow well.

 

Plants which get a lot of fertilizers attract pests, maybe you treated them too well?

Not really. They are actually doing fine now. Perhaps it was an adaptation period they were going through after being potted and became susceptible to pest/disease. I will watch them over for the next couple of weeks see how they go along and treat them with the above mentioned chemicals if it happens again.