Every year, the Help Desk operated by UC Master Gardeners of Contra Costa County receives numerous inquiries from local residents about sustainable gardening practices. The team at the Help Desk addresses questions on topics such as insect issues, plant diseases, and managing animals that target garden produce.
Recently, the most frequently asked questions were compiled and published online for public reference. The top five questions cover common problems faced by gardeners in the region.
The first question concerns yellowing leaves on citrus trees. This condition, known as chlorosis, can result from several factors including overwatering, improper fertilization, nutrient deficiencies (such as iron, zinc or magnesium), seasonal changes like cold and rain, fungal diseases such as Phytophthora root rot, and pest infestations like mites. Most of these issues can be managed by home gardeners with appropriate care. Additional information on watering is available at https://ipm.ucanr.edu/PMG/GARDEN/FRUIT/CULTURAL/citruswatering.html; details on fertilizing can be found at https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=56049; guidance on fungal diseases is provided at https://ipm.ucanr.edu/home-and-landscape/phytophthora-root-and-crown-rot/#gsc.tab=0; and advice regarding mite pests is offered at https://ipm.ucanr.edu/PMG/GARDEN/FRUIT/PESTS/citrustmite.html.
Another common issue involves tomato plants producing flowers but little to no fruit. Contributing factors include nighttime temperatures below 55°F or daytime temperatures above 90°F, excessive nitrogen fertilizer leading to leafy growth without fruiting, insufficient sunlight (less than six hours per day), poor pollination conditions due to weather extremes, and planting seedlings too early in spring.
Gardeners often inquire about soil testing services. While UC Master Gardeners do not perform soil tests themselves, they direct residents to commercial laboratories that offer a range of soil analysis options for home gardeners. A resource listing these laboratories is available at https://ucanr.edu/sites/default/files/2025-08/405a%20Soil%20and%20Water%20Testing%20Laboratories%20for%20Home%20%20Gardeners%202025_02_28%20Final.pdf.
Aphid infestations are another frequent concern. Aphids are small insects that feed on plant sap and excrete honeydew—a sticky substance often noticed on nearby surfaces. These pests typically do not cause significant harm because natural predators keep their populations in check. If aphid numbers become problematic, gardeners are advised to prune affected areas or use water sprays to remove them. Additionally, controlling ants—which protect aphids in exchange for honeydew—can help manage infestations.
Finally, powdery mildew is identified by white powdery growth on leaves and shoots of various plants. This disease can be managed by selecting resistant varieties and modifying environmental conditions; fungicide treatments may be necessary for particularly susceptible species.
The full list of frequently asked questions with detailed responses is available online at https://ucanr.edu/site/uc-master-gardener-program-contra-costa-county/faq.
Community members seeking further assistance can contact the Help Desk via email at ccmg@ucanr.edu (with photos if needed), call (925) 608-6683 (leaving both phone number and email if calling outside office hours), or schedule an appointment for an in-person consultation at 2380 Bisso Lane in Concord.
“Help Desk of UC Master Gardeners of Contra Costa County (RDH)”
