Here is a photo of my infected wolfberry. What might have caused the problem and how to treat it ?
Thanks so much for your help.
Thank you for contacting the Toronto Master Gardeners concerning your goji berry plant.
Yellowing leaves can be the sign of numerous environmental factors and or pests or foliar diseases. Goji berries prefer to grow in full sun in slightly alkaline soil with a pH of 6.8-8.0. Abnormal pH levels, whether high or low, can result in nutritional issues in some plants. All plants have an optimal pH range outside of which a plant will struggle to uptake the nutrients it needs. Testing the pH of the soil will tell you if your plant is growing under the right environmental conditions. You can obtain a soil testing kit at your local garden center.
Next, check the undersides of your leaves. Goji berry is susceptible to various sucking insects such as aphids, leaf hoppers, and spider mites. Aphids can be either green, black or yellowish in colour. They feed on the undersides of leaves and leave a sticky residue on the leaves. Spider mites appear like tiny spiders and are either red, black or brown. They suck out the plant juices and chlorophyll and leave tiny white spots. A strong spray of water from your hose can dislodge these insects.
Goji berries are in the nightshade family along with tomaotes and peppers and as a result they could be affected by the same bacterial/fungal disease that affect the members of the nightshade family. One of the common diseases of tomato plant is leaf spot caused by the Septorial fungus. Affected leaves have yellowish spots on them which usually appear on lower leaves.
Septorial fungal spores can linger in the soil or in plant debris and splashing water can carry these spores onto the lower leaves. These spores attach to leaves causing spots which will eventual turn greyish with a brownish edge. This disease usually appears in the spring and can reoccur in the summer.
If it’s in the early stages, you can prune out the affected leaves. Making sure to disinfect your pruners with rubbing alcohol before using them on other plant material and dispose of the infected leaves in the garbage, not in your yard waste.
May 12, 2021