The 2013 tomato taste tests at the Adelaide Botanic Garden brought out throngs of tomato connoisseurs, but among the tomato tips and chat about favourites was a reoccurring theme of poor yields and crop failure.
Yields from field grown tomatoes vary with season and region and, as we were experiencing a pretty good crop at Heronswood, we were left wondering what was occurring in South Australia, and if their problems were unique to the area. Although not everyone has the same problems as Adelaide we can use it as a case study to highlight how to diagnose problems in your own patch.
Jan, from our Adelaide Garden Shop, points to heat and low humidity as the culprits. Heat stresses tomatoes; they typically wilt as they struggle to balance water uptake with water loss during very hot days. However a less understood impact is that flowers drop and fruit set aborts when temperatures exceed the ideal growing range for extended periods (e.g. days above 29°C and nights above 21°C).
Humidity also plays a two part role. Tomatoes like 40-70% humidity, for although we tend to think of high humidity as bad (it facilitates the spread of moisture borne diseases such as fungi), it can also be problematic when it is too low.
Air moisture is required to help pollen stick to the stigma and to allow flowers to pollinate, while some major pests, such as two-spotted mites, thrive and become a serious problem in drier conditions. So climate and season play a significant role in vegetable production, but how does knowing this help you?
If you can identify the issues you are dealing with you may be able to either prevent or treat resulting problems.
♦ Observe your plants for symptoms and/or pathogens. Photos or notes may help ensure you remember exactly what you observed.
♦ Online searches or an Australian specific disease reference book will help identify most common issues. We've also provided some tips below. Think plant and soil, and consider diseases, nutrient levels and pests.
♦ Identify the conditions that support the problem.
Can you change these or do you treat the symptoms?